Educational goal: to study the organization of labor, learn how to rationally perform installation operations, as well as acquire skills in operational quality control when installing columns of the basement and master safe labor techniques.
Preparation for work and conditions for its implementation. Before the installation of columns begins, the installation of prefabricated foundations and the construction of monolithic foundations (if provided for in the project) must be completed; verified
Organization of the workplace when installing reinforced concrete columns in foundation glasses:
1 - tower crane; 2 - installed columns; 3 - mounting crowbars;4 - tool box; 5 - foundation glass;6 - linings
If the footing is completed. or filling the bottom of a glass with a solution, it is necessary to establish its correspondence with the marks of the bottom of the glass marked on the walls of the foundation.
Instructions for self-control.Before starting to lay the mortar on the bottom of the glass, it is necessary to check the presence of marks on the internal walls of the foundation that determine the level of laying the concrete mixture. If there are no marks, then they must be applied using the installation and as-built diagrams for installing the foundation blocks.
2. Preparing the column for installation.
Performed by assembler-slinger M 3 using a semi-automatic gripper and meter.
The installer-slinger MZ checks the markings of the column, determines its suitability for installation, determines the presence of axial marks and, if necessary, restores them. Then he gives the command to the crane operator to bring the gripper to the slinging point, accepts it and rigs the column, threading a steel pin through the hole in the head of the column and the jaws of the gripper. Next, he attaches the rope to the cable on the gripping finger and gives the command to the crane operator to pull the branches of the sling.
Instructions for self-control.First, you need to make a test lift 30-40 cm from the base and check the reliability of the sling, move to a safe distance, and then give a command to continue lifting.
3. Lifting and moving the column to the installation site.
Performed by the crane operator independently or with the help of an assembler-slinger M 3 .
The crane operator, having raised the column to a height of 50-80 cm above the level of the installed foundations, moves it along the shortest distance to the prepared foundation (unless there are instructions for another movement of the column).
Instructions for self-control.To speed up the installation of the column into the foundation shell and ensure installation accuracy, it is recommended to stop the column at a distance of 30-50 cm above the foundation shell so that the marks on the edges* of the foundation and column are approximately oriented to each other.
4. Reception and installation of the column. Performed by M installers 5 them 4 using mounting crowbars.
Installers M 5 them 4 , being at the installation site of the column, take it with your hands by the side edges, stop and orient it above the foundation shell, combining the risks of the column with the axial marks on the foundation shell. Installer Me installs a crowbar into the foundation so that the column slides along it to the installation site, and installer M 4 gives a command to the crane operator to smoothly lower the column. After the column touches the bottom of the glass, installer M 3 takes out the crowbar.
Instructions for self-control.If the marks do not match, it is necessary to command the crane operator to tighten the slings and, using crowbars, straighten the bottom of the column to align the axial marks.
5. Alignment and fastening of the column.
Performed by installers Mb and M 4 using mounting crowbars, a sledgehammer, steel wedges and two theodolites.
InstallersMbthem 4 carefully center the column in the direction of two mutually intersecting planes. Then, based on the surveyor’s signals, the column is aligned using two theodolites. The MB installer signals the crane operator to move the top of the column to one side or the other to the design position. After this, installers drive steel wedges into the gap between the bottom of the column and the walls (Fig. 59).
Instructions for Self-Control.Maximum deviations from the alignment of landmarks when installing columns of the basement from the design position should not exceed the following values:
deviations from alignment of landmarks (marks of geometric axes, edges) in the lower section of installed elements with installation landmarks (marks of geometric axes or edges of underlying elements, marks of alignment axes) 8 mm;
deviations from alignment of landmarks (marks of geometric axes) in the upper section of columns with marks of alignment axes of 15 mm;
the difference in elevations of the top of the columns of each tier of the building within the verified area when installing contacts is 12 + 2p, when installing along beacons 10 mm(P- serial number of the tier of columns).
6. Column slinging.
Performed by M installers 5 them 4 .
Installers check the reliability of the temporary fastening of the column. Then installer M5 commands the crane operator to loosen the slings, and installer M 4 releases the gripper by pulling the pin out of the gripper and the column. The crane operator moves the grip away from the column and delivers it for slinging the next column.
Instructions for self-control.You should pay attention to the tight fit of the wedges to the edges of the column and the walls of the foundation. During the process of bridging the column, there should be no displacement of the alignment axes of the column and foundations relative to each other and no deviation of the top of the column from the design position.
Instructional and technological map 3. Installation of reinforced concrete floor columns.
Scope of application: installation of frame building structures from prefabricated reinforced concrete elements.
Educational goal: to study the organization of labor, learn how to rationally perform installation operations, and also acquire skills in operational quality control when installing columns on lower columns.
Preparation for work and conditions for its implementation. Before the installation of the columns begins, all work on the installation of the structures of the underlying floor must be completed, the alignment axes must be placed on the installation horizon, the conductor must be placed on the floor, and delivered to the place of work
installation equipment. fixtures and tools. The columns must be delivered to the on-site warehouse within the range of the installation crane.
Building structures and materials. Cantilever-type reinforced concrete columns weighing up to 1.5 tons are installed on lower columns. Permissible deviations from the main design dimensions, mm, with a column length of up to
4.5 m: length ±5; in size from the lower end of the column to the supporting plane of the console ±4; according to the cross-sectional dimensions of the columns and the dimensions of the consoles ±5.
Equipment, devices and tools: conductor, semi-automatic gripper, two hammers, two chisels, four-leg sling, mounting crowbar, sledgehammer, steel meter, tape measure, hemp rope, trowel, theodolite, steel brush, plumb line.
Work performed and performers. A team of structure installersVcategoryMB,IVcategory M 4 and assembler-slingerIIIcategory M 3 carries out installation of building structures, stropping and geodetic work.
Workplace organization
Organization and execution of installation operations. Performers and tools. Instructions and explanations.
1. Preparation of the column head.
Performed by installersMB andM 4 using hammers,chisel, steel brush, meter.
The installers, being on the ceiling, clean the head of the underlying column from the influx of concrete and mortar, and the embedded parts from rust. Then check for the presence of axial marking marks and, if necessary, restore them. Check the compliance of the column head marks with the design ones. If necessary, installers select a metal backing and place it on the head to ensure the design level.
Instructions for self-control.To ensure the design installation of the column, it is necessary to analyze the as-built installation diagram of the lower floor columns and the installation diagram of the building frame.
2. Installation of the conductor in the working position.
Performed by M installers 5 them 4 .
Installer M 5 The conductor inspects it to determine its serviceability. Then, using a four-leg sling, he slings the conductor and gives a command to the crane operator to tension the slings. Having made sure that the sling is secure, the installer leaves the danger zone and gives the command to the crane operator to move the conductor to the installation horizon.
Installers M 5 them 4 are located on the ceiling, take the conductor at a height of 30-40 cm from the head.
Then the installer M 5 gives a command to the crane driver to lower the conductor onto the head, together with the installer M 4 holding him.
Instructions for self-control.Installation of the conductor in the design position is carried out in accordance with the technological map.
3. Preparing the column for installation. Performed by assembler-slinger MZ with the help
hammer, chisel, column lifting grip, rope, steel brush.
Installer-slinger M 3 inspects the column, establishing its suitability for installation, checks for axial scratches and, if necessary, restores them. Then, with a hammer and chisel, he knocks down the concrete sagging and cleans the embedded parts and the head of the column with a steel brush. Next, he instructs the crane operator to move the semi-automatic grab to the column, points it at the column and threads a steel pin through the holes in the column head and the jaws of the grab. After inserting the steel pin into the column hole, installer-slinger M 3 attaches the rope to the cable attached to the gripping pin, and gives the command to the crane operator to tighten the branches of the sling.
Instructions for self-control.Based on the column markings and installation diagram, it is necessary to determine the compliance of the prepared column with the project.
4. Lifting and moving the column to the installation site.
Performed by assembler-slinger MZ. First, the crane operator lifts the column by 30-. 40 cm from the base, and the installer-slinger M 3 checks the reliability and correctness of the sling. Then he moves to a safe distance and gives the command to the crane operator to lift the column and move it to the installation site.
5. Reception and installation of the column. Performed by M installers 5 them 4 .
Installer M 4 rises to the conductor's platform and receives the column at a height of 30-40 cm from the conductor. InstallerMBgives a command to the crane driver to install the column on the head and together with the installer M 4 hold it in an oriented position. Having installed the column on the head, installers use crowbars to straighten the bottom of the column until the marks of the column coincide with the marks of the head.
Instructions for self-control.Bringing the columns into the conductor barely blows smoothly, avoiding blows.
6. Temporary fastening and alignment of the column.
Performed by installers Mb and M 4 using a plumb line.
After straightening the bottom of the column, installer M 5 Plumb sets the deviation of the column from the vertical and gives a command to the crane operator to tilt it in the required direction. Installer M 4 using the screws of the upper chords of the conductor, fixes the column in a position close to vertical
Instructions for self-control.Before straightening the column, you should check the reliability of fastening of the conductor and the column.
7. Unslinging the column.
Performed by M installers 5 them 4 using a semi-automatic gripper and rope,
Having made sure that the thrust screws of the upper chords of the conductor are tightly fitted, installer M 5 gives a command to the crane operator to loosen the branches of the sling, and the installer M 4 takes the hanging rope attached to the gripper pin and moves the gripper pin downwards out of the column hole. After this, the M5 installer gives the command to the crane operator to move the grip away from the column and apply the hook for slinging the next column.
Instructions for self-control.When unslinging and retracting the sling, it is necessary to pay attention to the possibility of accidental snagging of the sling branches on the conductor structure.
8. Column alignment.
Performed by MB and M4 installers.
At the command of the surveyor, who is aligning the column with a theodolite, the installers use the thrust screws of the upper chords of the conductor to bring the column into a vertical position. When the column reaches a vertical position, the surveyor signals this to the installers. Alignment of the column in another plane is done in the same way. Each time after alignment, you should check the tightness of the thrust screws to the column.
Instructions for self-control.Maximum deviations from the alignment of landmarks when installing floor columns from the design position should not exceed the following values:
deviations from alignment of landmarks (marks of geometric axes, edges) in the lower section of installed elements with installation landmarks (marks of geometric axes or edges of underlying elements, marks of alignment axes) 8 mm;
deviations from alignment of landmarks (marks of geometric axes) in the upper section of columns with marks of alignment axes of 15 mm;
the difference in elevations of the top of the columns of each tier of the building within the verified area when installing contacts is 12+2p, when installing along beacons 10 mm (i is the serial number of the tier of columns).
Safety measures when installing construction designs. Building structures must be installed in strict accordance with safety regulations under the guidance of experienced engineers and foremen. In the area where installation work is being carried out, other work and unauthorized persons are not allowed.
The main condition for ensuring work safety is the proper organization of the workplace. If necessary, it is fenced and protective safety devices and devices are installed. Workplaces located above the ground or ceiling at a distance of 1 m or higher should be fenced with railings at least 1.2 m high from the working floor. If it is impossible or impractical to install fencing, workers are provided with safety belts. The places where the safety belt carabiner is attached are indicated in advance by the master or foreman and are brightly colored.
Installation scaffolds, cradles, and ladders are inspected daily by the foreman and workers before the start of the shift. The base on which the devices are installed or rested is leveled and compacted. When supported on the structure, the scaffolding means are finally and securely fixed. The width of the flooring of scaffolds and platforms must be at least 1 m and have a flat surface with gaps of no more than 5 mm between the boards. When the flooring is located at a height of more than 1.3 m, the scaffolding means are protected. Near driveways, scaffolding must be installed at a distance of at least 0.6 m from the vehicle dimensions.
Portable stairs without working platforms are used only for transition between individual tiers of a building and for performing work that does not require the performers to support the structure of the building. The dimensions of a portable ladder must ensure the ability to work while standing on a step located at a distance of at least 1 m from the upper end of the ladder. When working on a portable ladder at a height of more than 1.3 m, a safety belt should be used. The supporting part of the portable ladder must have stops in the form of sharp metal spikes or rubber tips. The upper ends of the ladder must be attached to securely fastened structures.
During the construction of a building, it is prohibited to carry out work related to the presence of people in one section (occupancy, area) on the floors (tiers) above which the structures are moved, installed and temporarily secured. Simultaneous execution of installation and other construction work on different floors (tiers) is allowed if there are reliable interfloor ceilings between them with the written permission of the chief engineer.
The danger zone during the installation of structures is indicated by warning signs. When moving structures, installers must be outside the contour of the structure being installed on the side opposite to their supply by the crane. It is prohibited for workers to remain on structures during their lifting, moving and installation, and it is also forbidden to leave the raised structure suspended. People are not allowed to be under the mounted structures until they are installed in the design position and secured. During the installation of building structures, installers must be on previously installed and securely fastened structures or scaffolding means.
Special safety measures must be observed when installing long and heavy structures. They are slinged according to pre-developed schemes. The columns are mounted, having previously equipped them with stairs, cradles, and platforms.
The greatest danger when installing steel structures are trusses, which must be mounted with special traverses. To make assembly connections at the level of assembly units, assembly cradles, scaffoldings, and ladders are used, and for installers to move from one structure to another, ladders, walkways, and ladders are used. Crossing a truss, crossbar or beam is permitted only with a steel rope securely fastened and tightly stretched along them at a height of 1.2 m, intended for securing the safety belt carabiner. It is not allowed for installers to cross installed structures that do not have fencing and steel rope. Workers can move along suspended stairs only within two floors. It is strictly forbidden to move people using cargo cranes and lifts.
Constructions of the subsequent floor of a multi-storey buildingbuildinginstalled only after reliableconsolidationall structures of the previous floor. After installation of the floor and covering structures, it is necessaryinstallfencing before subsequent work begins. Openings in ceilings and openings to which people can access must be covered with solid solid flooring or have fences with side boards around the entire perimeter.
Installation of flights of stairs and building platforms must be carried out simultaneously with the installation of building structures. Fences should be immediately installed on installed flights of stairs.
When working on a roof with a slope of more than 20°, workers must use safety belts
(the places where they are secured are indicated by the foreman or foreman). During breaks in work, technological devices, tools and materials must be secured or removed from the roof. Placement of materials on the roof is allowed only in the places specified in the PPR, with measures taken to prevent their collapse.
It is not allowed to carry out installation work at height in open areas if the wind speed is 15 m/s or more, as well as during icy conditions, heavy snowfall, rain and thunderstorms. Installation of vertical blind panels and similar structures is stopped when the wind speed is 10 m/s or more.
U 
construction of linoleum floor covering
DEVICE COATINGS FROM LINOLEUM
Allowed
- drawdown coatings under concentrated load 50 kg -1 mm
- deviation surfaces screed from plane -2 mm
- deviation surfaces coatings from plane -2 mm
- deviation surfaces coatings from horizontal plane - 0,2 %-50 mm
- deviation thickness elements gender from design - 1 0%
- thickness interlayers from mastics -0,8 mm
Installation of foundations begins with laying out the axes of the structure and tying them to the terrain. The layout of axes on the ground is carried out by surveyors. The design level of the base of the foundation is determined by a level. After this, the axes of the structure are transferred to the bottom of the pit. The axles are secured to cast-offs.
For strip foundations, mainly two structural elements are used: a trapezoidal or rectangular-shaped cushion block placed at the base of the foundation, and wall blocks or panels from which the foundation wall is erected. The basis for strip foundations is a sand bedding, which is laid on protected or compacted crushed stone soil at the bottom of a pit or trench. The installation of strip foundations begins with the laying of lighthouse blocks, which are verified and installed in strict accordance with the axes of the walls of the structure. Lighthouse blocks are installed at a distance of no more than 20 m from each other. Corner blocks and intersection blocks are always lighthouse blocks. A mooring cord is secured along the inner and sometimes along the outer edge of the lighthouse blocks. At a height of 20-30 cm from the installation site, the block is oriented and lowered into the design position. Permissible deviations from the design position when installing strip foundations from prefabricated reinforced concrete blocks should be no more than (mm):
Pillow blocks are laid one against the other or (if the base has good load-bearing capacity) with gaps that can reach up to 40-50 cm. Pillow blocks are laid along the entire perimeter of the building or within one section. For the passage of pipelines and cable entries when continuously laying pillow blocks, special mounting holes are left.
Blocks or panels of foundation walls are installed at the design marks, filling the joints with cement mortar. Basement panels are usually welded to embedded elements in cushion blocks. During the installation process, wall elements are aligned both relative to the longitudinal and vertical axis. After installing all the blocks, a leveling layer (mounting horizon) of cement mortar is arranged along the upper edge of the wall, the surface of which is brought to the design level. The installation work of the zero cycle is completed by installing the plinth and ceiling above the basement or underground. Strip foundations are usually installed with a crane standing at the planning level, and not in the pit.
Installation of precast concrete foundations begins with a slab
Installation of precast concrete foundations begins with a slab. After installing it in the design position, a bed of cement mortar is arranged on the slab, on which a glass block is installed. To connect the glass to the plate, embedded parts are used. After welding the embedded parts, they are protected with an anti-corrosion coating. Installation of the foundations of industrial buildings, made in the form of a single block, is carried out using a crane. The foundation blocks are aligned to the design position by weight, after which the block is lowered onto the prepared site and verified against the axle marks, aligning them with the pins or marks that secure the position of the axes on the base. If the installation is incorrect, the block is lifted, the base is corrected and the installation procedure is repeated again. The correct installation of foundations vertically is checked with a level.
Reinforced concrete columns are mounted as follows
Before installation, check the position of the transverse and longitudinal axes of the foundations and the marks of the supporting surfaces of the foundations, the bottom of the glasses, the dimensions and position of the anchor bolts. Before installation, axial marks are applied to the columns on four edges at the top and at the level of the top of the foundations, and for columns intended for laying crane beams along them, in addition, the marks of the beam axes are applied to the consoles. Columns of industrial buildings are installed by first laying them out at the installation site, or directly from vehicles. The columns are laid out in such a way that during the installation process it is necessary to do a minimum of movements and various auxiliary work and there is free access for inspection, mounting of equipment and slinging. Columns in the installation area are laid out according to various patterns. With a linear layout, the columns are laid out in one line parallel to the axes of the building and the movement of the crane. This layout is carried out provided that the length of the column is less than the pitch of the foundation. When laying out with ledges, the columns are placed parallel to the axis of the structure being mounted and the axis of the crane's penetration. An inclined layout is used when the layout area is limited in size; The centered layout scheme is characterized by the fact that the rotation trajectory of the crane boom during the installation operation is a one-way arc. The columns are not laid out flat, but so that during the lifting process the bending moment from the weight of the column and equipment acts in the plane of greatest rigidity of the column. This is especially important to consider when installing two-branch columns. When laying out, you should take into account the method in which the installation will be carried out. It is more convenient to lift rectangular and two-branch columns from an edge position. Since the column can arrive at the site in a flat position, the first operation during installation is tilting it onto the edge. After laying out, the columns are inspected, checking their integrity and dimensions. At the same time, check the dimensions and depth of the glass under the column. Then the column is constructed with ladders, fixtures, braces, etc.
The conditions for ensuring the correct position of the column during installation are provided for in the installation project. When lifting columns by turning, the lower end of the column is usually secured in a special hinge fixed to the foundation. When lifting columns by turning with sliding, the lower end of the column is hingedly attached to a special trolley, to a slide, or equipped with a spacer and a roller. Columns are slung with various friction grips, pin grips with local or remote bridging, and when installation is carried out from vehicles - with balancing traverses. You should strive to ensure that the column hangs on the crane hook in a vertical position and does not have to go up to unsling it. Friction grips are put on the column with the beam removed. After installing and securing the beam, the column is raised. The grip holds the column due to the friction that occurs between the beams and the surface of the column when the cables are tensioned.
Holes for pin grips must be provided during the manufacturing process of the columns. A cable is used to unfasten pin grips used for lifting light columns; To unfasten heavy columns, the grippers are equipped with electric motors. Columns are mounted from vehicles by rotating in weight. To reduce the length of the crane boom during mass installation of columns, booms equipped with a forked head are used. Lifting a column (transferring it from a horizontal to a vertical position) consists of three sequential operations:
transferring the column from horizontal to vertical position; feeding the column to the foundation in a raised position; lowering the column onto the foundation.
The column is lifted in one of the following ways:
the crane moves from the top of the column to its base and simultaneously lifts the hook. The column gradually rotates around the supporting rib. To prevent slipping, the shoe is reinforced with a guy rope. The movement of the crane and the lifting of the hook are carried out in such a way that the cargo pulley is in a vertical position at all times; the crane is stationary. Simultaneously with the lifting of the hook, the column shoe mounted on the trolley or the guide rail track lubricated with grease moves towards the vertical. These two methods are used primarily when lifting heavy columns and using cranes that cannot move with a suspended load; the crane is installed in such a way that the slinging point and the lower end of the column are at equal boom radii. The column is lifted by turning the boom while simultaneously operating the cargo pulley, which must always be vertical. The top of the column and the place of slinging describe spatial curves. This lifting method is used mainly when installing light and medium-sized columns with jib cranes.
After lifting and installing the column in place, without releasing the crane hook, they begin to align their position. Lightweight reinforced concrete columns are aligned using mounting crowbars and wedges placed in the foundation glass, and special mechanical wedges. The correct position of the columns in plan is achieved by combining the axial marks on the column with the axial marks on the foundation. The position of the columns is checked with a theodolite and a level.
Immediately before the installation of columns in glass-type foundations, a leveling layer is laid to fill the gap between the bottom of the glass and the lower end of the column. The preparation is made of rigid concrete, laid in a layer, the thickness of which is determined by measuring in situ the mark of the bottom of the glass and the length of the column. After installation, the column compresses the fresh preparation with its weight; This ensures uniform pressure transfer to the bottom of the glass. Another way to secure columns is as follows. On the foundation, the bottom of which is not concreted to the design level by 5-6 cm, a support frame is installed, verified and securely fastened. To create the base surface, a forming device is used that has special stamps and a vibrator. Then concrete is placed at the bottom of the glass and the forming device is lowered, directing its bushings onto the fingers of the support frame, then the vibrator is turned on. Lowering under its own weight until it stops, the stamp of the forming device squeezes out imprints of a certain shape in the concrete at the required level, strictly oriented relative to the axes of the foundation; the excess concrete is squeezed upward, after which the forming device is removed and transferred to the next foundations. The use of this method requires the manufacture of columns with increased accuracy.
Short columns of multi-story buildings can be raftered close to their top. As a rule, it is impossible to sling reinforced concrete columns of one-story buildings at the upper end, since its resistance to bending may be insufficient. In most cases, slinging of such columns is carried out at the level of the crane console. In this case, during the turn, the lower end of the column rests on the ground and bends like a single-cantilever beam. The raised column must be vertical. To do this, you need to hang it from a point located on a vertical line that passes through the center of gravity of the column. For lifting, a traverse with grips or slings covering the column on both sides is used. If the bending strength of the column is insufficient, increase the number of suspension points.
Methods for temporarily securing columns
Methods for temporarily securing columns after installation in the design position depend on the design of the support of the columns and their dimensions. Columns installed on glass-type foundations must be cemented immediately after installation. Until the concrete has acquired 70% of the design strength, subsequent elements cannot be installed on the columns, except for mounting ties and spacers that ensure the stability of the columns along the row. Columns up to 12 m high in foundation cups are temporarily secured using wedges and jigs. Wooden (hardwood), concrete and welded wedges are used; depending on the depth of the foundation glass, the wedges should be 25-30 cm long with a slope of no more than 1/10 (the length of the wedges is approximately taken to be half the depth of the glass). One wedge is placed at the edges of columns up to 400 mm wide, and at least two wedges are installed at edges with a larger width. Wooden wedges should be used only for small volumes of work, as they make it difficult to seal joints and are difficult to remove. Wedges are used not only to clamp the column in the glass, but also to slightly shift it or rotate it in plan if it is necessary to point it at the alignment axes. Rigid conductors are used to temporarily secure columns. Temporary fastening of columns with a height of more than 12 m with conductors is not enough; they are additionally secured with braces in the plane of greatest flexibility of the columns. Columns over 18 m high are braced with four braces. These devices must simultaneously provide stability along and across the row. The first two columns are braced crosswise with braces, the subsequent ones - with crane beams. Reinforced concrete columns of frame buildings are secured by welding, as a rule, after installing the crossbars and welding the embedded parts of the columns and crossbars. Installation of crane beams is carried out after installation, alignment and final fastening of the columns. Installation begins after the concrete at the joint between the column and the foundation walls reaches at least 70% of the design strength (exceptions to this rule are specifically stipulated in the work project, which simultaneously indicates measures to ensure the stability of the columns during the installation of crane beams and other elements). Before installation on the ground, the condition of the structures is inspected and the joints are prepared. The beams are slung with ordinary slings using mounting loops or in two places “on a noose” with universal strapping slings and suspended from them to a traverse, the size of which is selected depending on the length of the beams. Lifting of crane beams due to their large length (6-12 m) is most often carried out using special or universal traverses or two-leg slings equipped with safety corners. When choosing a grip for a particular structure, you should pay attention to the nature of the reinforcement of the beam flange and the installation conditions. Thus, it is impossible to use pincer grips for the installation of crane beams, the shelves of which are not capable of withstanding the bending moment from the installation load. It is advisable to install crane beams with crane rails attached to them before lifting (with a beam length of 12 m). The rails are fixed temporarily; final fastening is carried out after installing the beams and aligning the position of the rail. When aligning, check the position of the beams along the longitudinal axes and the mark of the top flange. To install beams along the longitudinal axes, marks are applied to the column supports, and marks in the middle of the wall are placed on the upper planks and ends of the beams.
During the reconciliation process, the risks are aligned. The position of the crane beams during their installation is adjusted using a conventional installation tool, and after they are laid out on the support consoles, without resorting to the installation mechanism, using special devices. After alignment, the embedded parts are welded and the beam is unfastened. When installing beams, the following deviations are allowed; displacement of the longitudinal axis of the crane beam from the alignment axis on the supporting surface of the column ±5 mm; marks of the upper flanges of beams on two adjacent columns along a row and on two columns in one cross section of the span ±15 mm.
Rice. 38. Installation of beams and trusses covering industrial buildings
The installation of beams and roof trusses in industrial buildings is carried out separately or combined with the installation of roof slabs (Fig. 38). When preparing trusses for lifting, the heads of the columns and support platforms of the truss trusses are cleaned and aligned, and axle marks are applied. To align and temporarily secure the trusses, scaffolding is arranged and the necessary devices are installed on the columns. The process of installing trusses includes delivering structures to the installation site, preparing for lifting trusses, slinging, lifting and installation on supports, temporary fastening, alignment and final fastening in the design position. The trusses are installed in the design position in a sequence that ensures the stability and geometric immutability of the assembled part of the building. Installation is usually carried out “on a crane”, which sequentially retreats from parking lot to parking lot. Slinging of trusses is carried out using traverses, the slings of which are equipped with locks with remote control for unslinging (slinging of reinforced concrete trusses in order to avoid loss of stability is carried out at two, three or four points). To ensure stability and geometric immutability, the first installed truss is braced with steel rope braces, and subsequent ones with braces attached with clamps to the upper chords of the trusses, or with jigs. For trusses with a span of 18 m, one spacer is used; for spans of 24 and 30 m, two spacers are used, which are installed at 1/3 of the span. With a truss pitch of 6 m, the spacer is made of pipes, with a pitch of 12 m - in the form of a lattice girder made of light alloys. The spacers are attached to the truss before lifting begins. A hemp rope is tied to the free end of the pipe, with the help of which the spacer is lifted to the previously installed truss for connection to the clamps installed there. The spacers are removed only after the trusses are finally secured and the covering slabs are laid. The first trusses in the span are secured with cables. When installing lanterns, their structures are attached to the trusses before installation and lifted together with the truss in one step.
After temporary fastening, the lantern is installed in the design position. Trusses are verified according to the risks present on the supporting platforms of the trusses and columns, combining them during the installation process. To secure the trusses in the design position, the embedded parts in each support unit are welded to the base plate, which in turn is welded to the embedded parts of the column head. The anchor bolt washers are welded along the contour. The first two trusses in the span must have a fence or special scaffolding for the period of installation of the covering slabs. Rafter beams and trusses are unfastened only after they are finally secured.
The installation of the covering slabs is carried out in parallel with the installation of the trusses or after it. Installation of the coating can be carried out according to two schemes:
longitudinal, when the slabs are mounted by a crane moving along the span; transverse, when the crane moves across the spans. In this case, when selecting cranes, it is necessary to check whether the cranes can pass under the mounted trusses or crane beams.
When installing roof slabs on tall buildings, it is advisable to equip cranes with special mounting jib. Sometimes, during the installation of covering slabs, which is carried out after the installation of trusses, it is advisable to use special roof cranes that move along the mounted slabs. Before installation, the coating slabs are placed in stacks located between the columns, or they are delivered on vehicles directly for installation. The order and direction of installation of the slabs is indicated in the work project. The sequence of installation of the slabs should ensure the stability of the structure and the possibility of free access for welding the slabs. The location of the first slab must be marked on the truss. In clerestory coverings, the slabs are usually laid from the edge of the roof to the clerestory. For slinging coating slabs, four-legged slings and balancing crossbeams are used, and when using heavy-duty cranes, crossbeams with daisy-chained suspension of the slabs are used. The laid covering slabs are welded in the corners to the steel parts of the rafter structures. The plates located between the first two mounted trusses are welded at four corners; located between the second and third trusses, as well as subsequent ones: the first during installation - in four corners, the rest - only in three, since one of the corners of each slab (adjacent to previously installed slabs) is inaccessible for welding. It is recommended to install the slabs:
along reinforced concrete trusses with a roofless covering - from one edge to the other; along reinforced concrete trusses with a lantern - from the edges of the covering to the lantern, and on the lantern - from one edge to the other.
Installation of the first slab at the edge of the covering is carried out from suspended scaffolding, and subsequent slabs - from previously installed ones. The joints between the coating slabs can be sealed simultaneously with installation or after it, unless there are special instructions in the work design.
Installation of floor panels in multi-storey buildings is carried out using the main installation mechanism, and in brick buildings - using a crane, which provides the supply of materials for masonry. To lift floor slabs, balancer-type slings or traverses are used, which make it possible to impart a slight slope to the panel suspended on the crane hook. Floor panels in multi-storey frame buildings are laid in the same flow with the rest of the structures or upon completion of the installation of columns, crossbars and purlins within a floor or section on a floor. The installation of floor panels begins after the walls have been erected in frameless buildings and spacer plates have been laid and secured, as well as purlins or crossbars in frame buildings. Installation begins from one of the end walls after checking the mark of the supporting plane of the top of the walls or crossbars (if necessary, they are leveled with a layer of cement mortar). The panels are lifted with a four-leg sling or a universal traverse. Panels the size of a room are slung using all mounting loops. If the panels were stored in a vertical position, then before slinging they are transferred to a horizontal position on the tilter. Using a universal sling, the slab is lifted from a panel carrier or from a pyramid without a tilter. The first one or two slabs are installed from mounting scaffolding tables, and the subsequent ones are installed from previously laid slabs. If the panels are laid on a surface leveled with a screed, then the bed is made of plastic mortar 2-3 mm thick. When laying panels directly on parts, the bed is made of ordinary mortar. If necessary, the panels are upset by squeezing out the solution during their horizontal movements. When installing the panel on the mortar, special attention is paid to the width of the supporting platform, since it is prohibited to move the laid panels in the direction perpendicular to the supporting structures.
The sagging panels are reinstalled, increasing the thickness of the mortar bed. The thickness of the seams between adjacent panels is determined by sighting along the seam. If the plane of the panel is curved, it is laid at the junction with walls or partitions so that the free edge is horizontal. A panel with a sagging middle is installed on a thick bed so that the sag is divided in half between adjacent slabs. In multi-storey frame industrial buildings, first of all, so-called “spacer” slabs are installed, located along the longitudinal axes of the building, and panels located along the walls. The order of installation of the remaining slabs can be arbitrary if it is not dictated by the project. Strapping is carried out immediately after installing the panel in the design position.
Installation of wall panels is a separate stage of installation work in industrial construction. It begins only after completion of the installation of load-bearing structures in the structural block of the building. In frame buildings, the middle of the frame columns is most often taken as the position of the building axes. When installing an internal wall panel between columns, from their middle, a distance equal to half the thickness of the panel plus the length of the template (usually 20-30 cm) is laid on the ceiling using a meter; this is done so as not to accidentally destroy the risk, for example, when making a bed. If the panels do not fit with the columns, then a mooring is pulled along the plane of adjacent columns, the required size is laid out along it, and the position of the panel plane is fixed with two marks on the ceiling, taking into account the length of the template. For panels adjacent to columns, for example, shear walls, marks that fix the position of the panel surfaces are applied to the column at a distance of 20-30 cm from the floor and ceiling. To install panels of external walls adjacent to columns, for example in one-story industrial buildings or multi-story buildings with blank walls in several tiers, the height marks of the seams of each tier are marked on the columns using a tape measure along the entire height of the column. In large-block and large-panel buildings, in which the walls bear vertical constants (from the weight of the building, equipment) and operational loads, markings are carried out using geodetic instruments. First, the main axes are transferred to the installation horizon; For basement walls, cast-off is used; for subsequent floors, the method of inclined or vertical sighting is used.
Installation of wall panels in frame buildings is carried out in a certain sequence. Internal wall panels are installed during the installation of the building before installing the ceiling of the overlying floor. The shear walls are secured immediately after installation in accordance with the design. External wall panels, which ensure the stability of the frame structures, are also installed during installation with a lag of no more than one floor. Wall panels that do not affect the stability of the frame are most often mounted vertically in single-story buildings and horizontally in multi-story buildings. In heavily framed industrial buildings, exterior wall panels are usually installed in vertical strips. In multi-storey civil buildings, external wall panels are supplied during installation by the same crane as the frame elements. In industrial one-story and multi-story buildings with a heavy frame, external walls are mounted in a separate flow using self-propelled cranes. Wall panels of all types are usually slung with a two-leg sling. When installing multi-story frame buildings, the length of the sling branches must be such that the hook and lower block of the crane pulley when installing the panel are higher than the ceiling of the next floor. The supply of wall panels to the installation site in frame buildings is complicated by previously installed frame structures, therefore, when lifted, the wall panels are kept from turning around and hitting the structure with two hemp rope guys. The panel is installed on the bed vertically or with a slight slope towards the outside of the building to ensure that the panel rests tightly on the bed solution. External strip panels are attached to the columns with two corner clamps; wall and blind area panel - with struts to the floor slabs. The same devices are used to bring the panel to the vertical in the plane of the wall. To check the verticality of the panels, a plumb line is most often used. Before removing the slings, the bottom of the panel is secured by welding. The panels are finally secured by welding them to the frame elements.
If the panels are mounted before installing the purlin or crossbar, when slinging, two guys from hemp rope are tied to the panel of such a length that when the panel is fed 1.5 m above the top of the columns, the end of the guy is on the ceiling. The panel is lowered between the columns, rotated 90 degrees from the design position, and temporarily secured with a tray clamp or a clamp to the column. The verticality of the panel is checked using a plumb line and the marks on the column. If the crossbar is installed, the strapped partition cannot be placed under the crossbar, so the top of the panel is reattached during its installation. To do this, holding the panel by the guys, it is lowered next to the crossbar and stopped at a height of 10-15 cm from the ceiling. Pressing the bottom of the panel, install it on the mortar bed. If necessary, correct the position of the bottom of the panel. The top of the panel is temporarily secured with a chain or clamp. The chain is passed through the mounting loops of the panel and wrapped around the crossbar, the open ends are connected. Window panels are installed during the installation of wall panels or after their installation. Window panels are installed one above the other, resting them on support consoles made of large profile corners (150-200 mm), welded to columns or to embedded parts. Window panels are often mounted in large blocks. Sometimes they are enlarged together with half-timbered structures and imposts. To do this, the bindings are assembled and attached below to the half-timbered elements. Lantern top-hung frames are mounted from the covering slabs manually or using blocks and winches, and secured from ladders or leaning ladders.
Installation of walls of large-block buildings is carried out within the area after completion of installation of all structures of the underlying tier. Blocks, as a rule, are slung with a two-legged sling using two mounting loops. Tall wall blocks, if they are stored in a stack in a horizontal position, are first transferred in the same position to the site, where they are transferred to a vertical position.
It is impossible to tilt blocks directly in a stack, since if the lower edge of the block slips, the jerk of the crane boom can lead to an accident. If, when installing the upper floors of a building, light blocks are slung with a four-branch sling, supplying two blocks per floor at a time, then while the first block is being installed, the second one is temporarily placed on the floor above one of the internal load-bearing walls. If two textured blocks of external walls are lifted, then the inner edges of the blocks must touch each other during lifting. The mortar bed is arranged on the cleaned base. The beacons are placed near the outer edge of the block at a distance of 8-10 cm from the side edges. The correct installation of the top of the block is checked by the mooring and by sighting on previously installed blocks. The horizontality of the top of the block in the longitudinal direction is controlled by a rule with a level and sighting on previously installed blocks. The correct installation of the top of the lintel block is checked by measuring the distance from the mark of the top of the block to the supporting quarter of the lintel with a meter or template, and the lighthouse blocks of the internal walls - to the top of the block. The top of the gable blocks is checked using a mooring stretched along the gable slope.
Minor deviations in the position of the block along the pediment are corrected by shifting it along the longitudinal axis of the wall. It is impossible to move jumper blocks along the walls, as this may cause displacement of the blocks of the lower tier. Installation of external wall panels of large-panel buildings begins:
basement walls - after installation of foundations; walls of the first floor - after completion of work on the underground part of the building; on the second and subsequent floors - after the final fastening of all structures of the underlying floor.
On the installation horizon, two beacons are installed for each side panel at a distance of 15-20 cm from the side edges. For external wall panels, beacons are located near the outer plane of the building. The panel supplied by the crane is stopped above the installation site at a height of 30 cm from the ceiling, after which the panel is directed to the installation site, while ensuring that the panel is lowered correctly into place. The correct installation of the external wall panels in place is checked along the cut line of the walls of the underlying floor.
Installation of load-bearing panels of internal walls is carried out in the same way as external ones, with the installation of two beacons. Non-load-bearing panels and partitions are installed directly on the solution. When installing gypsum concrete partitions, before installing the bed, a strip of roofing felt, roofing felt or other waterproofing material 30 cm wide is placed on the base; The edges of the strips, bent upward when installing floors, protect the partition from moisture. Installation of cross-wall panels on the mortar and alignment are greatly facilitated if the design provides for inserting the panel into the groove at the junction of the outer panels. The end ribs of the outer panels in this case serve as guides. To temporarily fasten the end of the panel adjacent to the outer wall, it is wedged; The free end of the panels and partitions is secured with a triangular stand; a screw device at the top of the stand makes it easier to adjust the panel into the plane of the wall. If the panel only adjoins the panels of the internal walls, the adjacent end is temporarily secured with a spacer or corner clamp.
Installation of reinforced concrete shells for public buildings
Installation of reinforced concrete shells for public buildings (transport, sports, entertainment, shopping facilities, etc.) is carried out using two main technologies for installing prefabricated monolithic shells:
at ground level - on the conductor with subsequent lifting of the fully assembled shell to the design mark using installation cranes; at design marks.
The main method is the installation of prefabricated shells at design marks, which is carried out on mounting supporting devices or with the support of enlarged shell elements on the supporting structures of the building - walls, contour trusses, etc.
A long cylindrical shell measuring 12x24 m is assembled from side elements in the form of gable pre-stressed beams and curved slabs measuring 3x12 m. Installation of the building frame begins with the installation of columns. Depending on the parameters of the installation crane, two options for organizing the installation are used: in the first case, the crane beams are installed immediately after the installation of the columns in a separate stream, and the installation of the shell is carried out by a crane located outside the span of the shell being mounted; in the second, the assembly is carried out by a crane moving inside the span of the building being assembled. After laying the side elements, temporary tubular supports are installed under the side elements, since before the joints are grouted they are not able to absorb bending forces from the weight of the separately lying shell elements. The enlargement of end plates with tightening is carried out on enlargement stands. After installing all the elements, the fittings are welded and the joints are sealed. Spinning is carried out after the concrete in the joints reaches 70% of the design strength.
Installation of free-standing shells
Installation of free-standing shells (free-standing shells mean shells measuring 36x36 and 24x24 m from slabs measuring 3x3 m, the shell of which is supported by four diaphragm trusses that are not structurally connected to adjacent shells) is carried out using conventional installation cranes. Such shells are assembled on special devices - inventory mobile conductors. The conductor moves along railway tracks installed on a solid base - concrete preparation, prefabricated slabs, a layer of ballast. When constructing a building with several shells, the complete assembly of the conductor is performed once, and then the conductor is moved to the next cell. The installation of the shell begins with the installation of a diaphragm truss located at the end of the span, then a second truss is installed along the outer wall. The trusses are secured together with spacers and secured with guy ropes. After this, the conductor is assembled, installing support trolleys, racks, two load-bearing trusses and lattice girders. After alignment and temporary fastening of the conductor with rigid connections between the trolleys (guys - behind the columns and spacers - to the trusses), part of the purlins is removed and a third contour truss is mounted, which, after alignment, is attached to the conductor with spacers. After this, the crane is moved into the span and installation of the corner slabs of the shell and then the remaining slabs in the established sequence begins. The slabs are laid on the support tables of the conductor’s pre-calibrated lattice purlins. After installing half of the shell slabs, the crane exits the cell, replaces the previously removed purlins and then installs the fourth contour truss. The remaining slabs are mounted in a similar mirror sequence.
During the construction of multi-span industrial buildings covered with double-curvature shells measuring 36x38 or 24*24 m, inventory conductors are used that move from position to position on rails. In a span or simultaneously in several spans, conductors are installed and then raised to the design marks, which are mesh circular structures that repeat the contours of the shell. Contour shell trusses are installed on the columns using assembly cranes. After laying the prefabricated slabs, which is done from the contours of the shell to the center, and adjusting their position, the butt joints are welded and the seams are sealed. After the concrete at the joints reaches 70% of the design strength, the shell is turned around, the conductor is lowered into the transport position and moved along the rails to an adjacent position.
The installation of multi-wave shells measuring 18x24 m from 3x6 m slabs has the peculiarity that adjacent shells rest on a common contour truss 24 m long, and along the upper belt of 18-meter contour trusses, adjacent shells are monolithic. When constructing a two- or three-bay building, installation is carried out on two or three conductors. The procedure for assembling and installing conductors is the same as for free-standing shells, but the assembly order is different: first the first conductor is installed, then two 18-meter diaphragm trusses are placed and attached to it - one extreme and one middle (in a single-span building - both extreme) and a 24-meter extreme truss. Walking scaffolding and elements of steel inventory formwork are installed on 18-meter trusses before lifting. After installation, alignment and fastening of the trusses, the corner zones are welded and the shell elements begin to be assembled. When constructing a multi-span building, after securing the trusses of the first shell, trusses of adjacent shells are installed. To avoid tipping over, they are secured together with rigid spacers, welded in the corner areas to the embedded parts of the upper chords. Thus, it is possible to install conductors in the remaining spans. The installation of the shell begins with laying the corner slabs, then installing the contour slabs of the far row and the middle one. Row slabs are laid on the conductor beams. After installing the middle row of slabs, a 24-meter truss is installed, and then the last row of slabs is laid, which are mounted through the installed truss. After this, the outlets of the reinforcement and embedded parts are welded. Before grouting the joints, the first row of slabs must be installed in the adjacent shell. The grouting of joints begins from the corner zones and the junction of the slabs with 18-meter trusses, and the remaining joints are grouted in the direction from the 24-meter trusses to the vault shelya.
Shells of double positive curvature with dimensions of 18x24, 24x24, 12x36 and 18x36 m are mounted in enlarged blocks assembled on stands from 3x6 or 3x12 m panels. The panels are assembled into an assembly block on a stand by welding embedded parts and fastening with temporary mounting ties. The length of the enlarged block corresponds to the span of the shell. After this, the block is installed by crane in the design position on the pre-assembled side elements.
Byte suspended coverings are a type of reinforced concrete shells. They consist of a reinforced concrete contour with a mesh of steel ropes (cable cables) stretched over it and prefabricated reinforced concrete slabs laid over them. The byte network consists of longitudinal and transverse steel ropes located along the main directions of the shell surface at right angles to each other. The ends of the cables are anchored using special sleeves in the supporting reinforced concrete contour of the shell. When installing suspended coverings, a cable-stayed network of steel ropes is stretched onto the reinforced concrete contour, ensuring the design curvature of the shell. Then prefabricated reinforced concrete covering slabs are laid along the ropes and their temporary loading is in the form of uniform filling of the shell with a piece load, the weight of which is taken equal to the weight of the roof and the temporary load. After this, the seams between the prefabricated shell slabs are sealed. After the concrete reaches its design strength, the temporary load is removed. Thus, prestress is created in reinforced concrete slabs, and they are included in the overall work of the coating, which reduces the deformability of the suspended structure.
Installation processes of reinforced concrete structures
Preparation of foundations for columns
The accuracy, labor intensity and duration of installation of columns and other frame elements of industrial structures depends primarily on the correct arrangement of foundations for columns and the accuracy of preparation of supporting surfaces.
In the case of using reinforced concrete glass-type foundations of small height, their features should be taken into account. The upper level of these foundations is significantly lower than the edge of the pit. Columns on such foundations should be installed in open pits.
Higher foundations, the upper level of which is located approximately 0.15 m below the floor level, make it possible to lay foundation beams, backfill pits, plan the site and prepare floors before installing columns to ensure favorable conditions for the operation of transport and installation equipment. In order to improve transportation and installation conditions, foundations with pillars are also used.
To ensure accuracy and speed up the installation of columns, it is necessary to correctly position the foundation glasses in plan (the displacement of the axes is allowed no more than ±10 mm); ensure accurate design marks of the bottom of the glasses (tolerance ±20 mm); maintain the specified gap between the design position of the column faces and the walls of the glass. It is advisable to install a shallow pit in the bottom of the glass (Fig. 2), corresponding to the outlines of the end of the column, located along the alignment axes and ensuring a fixed installation of the column along the design axes. To form a pit in the bottom of the glass, metal molds are used.
One type of mold is used to construct pits when installing columns on the surface of the bottom of the foundation shell, which has been previously poured to the design level. The design of this form, 7.5 cm high, is equipped with fastening screws for installing it relative to the alignment axes. Another type of form is used when foundations are not poured to the design level. Unlike the first type, the mold is equipped with screws for installation not only along the design axes, but also at the design mark. The process of grouting and formation of pits consists of the following operations: installation by a team of two installers of the 3rd, 4th category, headed by a surveyor, of forms of the first type on previously poured surfaces of foundations or forms of the second type in cases where the foundations are accepted without grouting at the design elevation; lubrication of established forms with technical oil; feeding fine concrete to the bottom of the glass and leveling it with a plaster trowel; curing the concrete for 2-3 hours of dismantling the molds.
After removing the forms, a pit remains at the bottom of the foundation shell with the outline of the supporting end of the column. Thanks to pinching in the pit, the lower part of the columns does not shift from the design axes when aligning verticality, which often occurs and significantly delays installation carried out using conventional technology. The entire process of filling the bottom of the foundation, from installing the form to disassembling it. According to experience, it takes 20-30 minutes.
Rice. 1. Scheme of supporting prefabricated reinforced concrete columns in glass-type foundations: 1 - prefabricated reinforced concrete column; 2 - pit in the gravy bottom of the glass; 3 - foundation
Checking the condition of structures
The condition of structures is checked to ensure their correct and quick installation, connection in the design position and reliability of their operation in the structure. By checking prefabricated reinforced concrete structures, it is established: the presence of quality control marks and stamps on them; availability of passports; compliance of the geometric dimensions of structures with working drawings; presence on the structure of a mark indicating its mass; absence of cracks, potholes and surface cavities in the concrete that exceed the permissible dimensions; no deviations from the geometric shape (straightness, horizontality of supporting surfaces); the presence and correct location of embedded parts, the absence of sagging on them; presence of anti-corrosion coating on embedded parts; the presence of design and installation holes and their diameter; cleanliness of the holes (no concrete in them); compliance with the design of the reinforcement outlets and the absence of cracks and unacceptable deformations in them; compliance with the design of the mounting loops and the absence of deformations and cracks in them; the presence of axial marks on those elements that do not have other landmarks that ensure the possibility of their correct mutual installation; the presence on one-sided reinforced elements of signs indicating the correct position of the element during unloading and installation.
In terms of geometric dimensions and shape, prefabricated reinforced concrete structures for buildings should not have deviations from the design dimensions more than those given in SNiP I-B.5-62.
Integrated assembly of structures
Elements of columns along the length, columns with crossbars, roof trusses with spans of 30-36 m, delivered in the form of two halves, wall panels, manholes, bunkers and other structures are enlarged into assembly blocks. Enlargement is carried out on special stands or in conductors. Elements to be enlarged are delivered by crane from the warehouse and placed on the stand supports so that their longitudinal axes coincide. Then the ends or outlets of the reinforcement are adjusted to achieve alignment of the elements or individual rods. After installing additional clamps and welding the rods, the formwork is installed and the joint is concreted. The grade of concrete used to concrete the joint and its strength after hardening are established by the design. Usually the brand is the same as that of the elements being connected, or one brand higher.
Slinging of structures
Slinging of prefabricated structures is carried out using slings, grips or traverses. Gripping devices for slinging must provide convenient, quick and safe gripping, lifting and installation of structures in the design position and their unslinging. One of the important requirements for gripping devices is the ability to lift from the ground or directly from the crane cabin. This requirement is best met by semi-automatic gripping devices.
Slings (Fig. 2, a, b) are made of steel ropes; They come in two main types - universal and lightweight. Universal slings are made in the form of a closed loop, while lightweight slings are made from a piece of rope with hooks attached to both ends, loops on thimbles or carabiners. Slings can be made with one, two, four or more branches, depending on the type and weight of the element being lifted.
Rice. 2. Slings: a - universal; b - lightweight with hook and loop; c - cable with two branches; g - the same, with four branches
Since as the angle a increases, the forces in the sling branches increase, which can cause rupture or pulling out of the mounting loops, as well as increase the compressive forces in the lifted element, the angle a is taken to be no more than 50-60°.
For installation work, slings made of steel ropes with a diameter of 12 to 30 mm with permissible loads per branch are most often used: universal slings from 2.15 (19.5 mm in diameter) to 5.25 tf (30 mm in diameter); lightweight slings from 0.65 (diameter 12 mm) to 5.25 tf (diameter 30 mm). When making slings with more than three branches, their equality in length must be observed, otherwise the load in the branches will be uneven. Uniform distribution of the load on each of the sling branches is ensured in a four-leg sling and in a balance sling. The balance sling consists of a roller fixed between two cheeks, through which a lightweight sling is passed. The presence of a roller ensures uniform distribution of the load on both ends of the sling, regardless of the position of the load.
Rice. 3. Scheme of forces in the sling branches
Rice. 4. Slinging columns with a universal sling: 1 - column; 2 - wooden linings; 3 - sling
During operation, the slings wear out from crushing, abrasion at the nodes, rubbing of wires on the corners of structures, twisting and impacts. The service life of slings, usually from 2 to 3 months, can be increased subject to their careful operation: the use of wooden or steel spacers between the slings and the structure being lifted, etc.
In many cases, slinging of prefabricated reinforced concrete elements is carried out using loops (staples) embedded in the concrete during the manufacture of products. The disadvantage of this method is the need to spend reinforcing steel to install hinges.
Grips allow lifting of many reinforced concrete elements (columns, beams, trusses, slabs) without installing hinges. For this purpose, traverse slings, sling grips, semi-automatic finger friction, pincer, cantilever, wedge and other grips are used.
Traverses, in the form of beams or triangular trusses with suspended slings, allow you to suspend the element being lifted from several points. When lifting loads with traverses, the compressive forces in the lifted elements arising from their own weight when using inclined slings are eliminated or reduced. Slinging of prefabricated reinforced concrete foundations for columns is carried out using loops embedded in concrete, using a two-legged or four-legged sling. Slinging of columns is carried out using universal (Fig. 4) and traverse slings (Fig. 5), sling grips or semi-automatic grips. Slinging of columns with universal slings and sling-grabs is carried out in girth. Traverse slings and grips are secured using a round rod (finger) passed through a hole left in the column during its manufacture. Disadvantage of slinging using universal and traverse slings (conventional grips): when slinging, the installer must climb onto the column being installed. To avoid this, sling grips or semi-automatic grips are used.
Rice. 5. Slinging columns with a traverse sling
Rice. 6. Sling-grab for installation of columns: 1 - long cable loop; 2 - lifting cable pin; 3 - for the lamb press; 4, 5 - earrings; 6 - lifting bracket; 7 - glass with a spring locking pin; 8 - cable for bridging; 9 - gaskets
The sling grip (Fig. 6) ensures a strictly vertical position of the column during installation, ease of slinging and unslinging. For columns measuring 40X40X600 cm and weighing 3 tons, the gripping loops are made of cable with a diameter of 16 mm, the lifting bracket and earrings are made of strip and sheet steel, the gaskets are made of pipes with a diameter of 2” cut lengthwise. Turned fingers with a diameter of 25-30 mm. The gripper sling is put on the column, stacked on spacers, the lifting loop is placed on the crane hook, the column is tightened and the wings are secured. Upon completion of installation and fastening of the column, the locking pin opens and the gripper freely leaves the column.
The semi-automatic gripper (Fig. 7) for the installation of columns is a U-shaped frame with a box rigidly welded to it, on which an electric motor with a gearbox is placed, driving the screw. The nut, moving along the screw, moves the locking pin along the frame, which then enters or exits the space between the side edges of the frame. The frame is attached by cable rods to the beam traverse. The electric motor of the gripping device is activated from the crane operator's cabin, where the cable is pulled, or from duplicate control buttons installed on the gripping device. To allow quick disconnection of the gripping device from the tap, a plug connector is built into the cable. The gripping device has a set of locking pins of various diameters, which can be easily changed at the installation site depending on changes in the mass of the column being lifted. The process of slinging and unslinging columns using gripping devices with remote control is carried out as follows.
The frame of the gripping device is placed on the column prepared for installation so that the locking pin is located opposite the sling hole in the column. Then press the button that turns on the electric motor, the locking pin is set in motion, enters the hole in the column, reaches the opposite side edge and stops using
limit switch. After lifting, installing and securing the column, the load is removed from the gripping device and the crane operator, pressing a button in the cabin, removes the locking pin from the column hole, thus releasing the gripping device without the help of an installer.
To lift columns weighing up to 10 g, a friction grip is used (Fig. 8), which holds the mounted element by friction against the column’s own weight. The grab is unslinged by lowering the crane hook after securing the column to the foundation; in this case, the gripper opens somewhat and descends down the column.
Slinging of beams is done with universal slings in the girth (Fig. 9), two-legged slings or traverses (Fig. 10) by loops, or through holes left in the concrete. To sling heavy beams and crossbars, the balancing beam is suspended by means of two clamps and four sling branches to a ring placed on the crane hook. At the ends of the traverse, support clamps with carabiners are secured with adjustable bolts. Slinging of coating trusses is carried out using lattice or beam traverses with universal slings, slings with semi-automatic mechanical grippers (Fig. 11) or electric gripping devices. More advanced is the slinging of trusses using semi-automatic gripping devices. Slinging is carried out around the girth or through holes in the upper chord of the truss.
A semi-automatic gripping device for lifting trusses (Fig. 12) consists of a rigid traverse from which grippers with a cable are suspended, similar to those described above, but with non-replaceable locking pins. When slinging a truss, the fingers of the gripping devices pointed at it pass under its upper chord. After installing and securing the truss, the pins are withdrawn back into the gripper boxes, freeing them and the supporting crossbeam for subsequent operations.
Slinging of reinforced concrete wall panels, which are in a vertical position before lifting, is usually performed with two-leg slings or traverses, hooking them onto loops embedded in the upper end of the panel. Slinging of floor slabs and coverings is carried out using four-legged slings or traverses using loops, or through mounting holes in concrete, or using cantilever grips.
Rice. 7. Semi-automatic grip for installation of columns: 1 - frame; 2 - cable rods; 3 - beam traverse; 4 - plug connector; 5 - cable; 6 - electric motor; 7 - box; 8 - nut; 9 - duplicate control button; 10 - screw; 11 - locking pin
Rice. 8. Friction grip: 1 - traverse; 2 - butts; 3 - fork ties; 4 - thrust strips; 5 - latches
Rice. 9. Slinging of crane beams with universal slings: 1 - beam; 2 - steel linings; 3 - slings
Rice. 10. Slinging of reinforced concrete beams, purlins and crossbars: a - light beams; b - heavy beams, purlins and crossbars; 1 - clamp; 2 - adjustable bolts; 3 - support clamps; 4-slings; 5 - balancing beam; 6 - carbine
Slinging of the slabs is carried out at four (Fig. 13, a) or more points. For slinging large-sized reinforced concrete slabs, three-traverse and three-block gripping devices with an increased number of suspension points are used, thereby reducing installation stresses in the lifted elements (Fig. 13, b). The three-beam jig can also be used to lift wall panels, staircases, beams, columns and other prefabricated elements by gripping them with three, two or one crossbeam. However, this device is metal-intensive, cumbersome and requires great effort from the worker when tensioning the suspensions with the traverse while engaging the structure with the mounting loops. The three-block device does not have the above disadvantages (Fig. 13, c), but it requires a higher lifting height of the crane hook (about 2 m), which can make it difficult to select an assembly crane for lifting floor slabs on the upper floors of buildings. Large slabs are also lifted using universal (Fig. 14) or spatial (Fig. 15) traverses, or universal balanced slings (Fig. 16). The universal traverse (Fig. 14) consists of load-bearing beams made of two channels, each of which has guide rollers mounted. A rope is attached to the end rings of each beam, which carries three blocks with hooks. The load-bearing beams are connected to each other by two pipes with holes for installing a bolt, which fixes one or another distance between the load-bearing beams, depending on the width of the panel being lifted.
Universal balancing slings, also called balancing traverses (Fig. 16), consist of two five-ton blocks connected to each other by a common ring, which is suspended on the crane hook.
Rice. 11. Slinging schemes for reinforced concrete trusses: 7 - truss; 2 - traverse; 3 - semi-automatic mechanical grip; 4 - finger; 5 - upper chord of the truss
Rice. 12. Semi-automatic gripping device for installation of reinforced concrete trusses: 1 - grippers; 2 - rigid traverse; 3 - cable
Rice. 13. Slinging slabs and floor panels: a - with a four-legged sling; b - three-traverse device e - three-block device
Ropes with a thickness of 19.5 mm are thrown through each of the blocks; carabiners are suspended from the ends of the ropes, and two-ton blocks with 13 mm thick ropes thrown through them, also ending with carabiners, are suspended from the ends of the ropes. The blocks are freely put on the axles, which ensures uniform tension of the ropes hanging from them and uniform distribution of loads on all six carabiners of the gripping device. Using this device, floor panels can be tilted into a horizontal position if they were transported vertically. Turning is done by weight. This device is also used for lifting wall panels.
Plates with mounting holes are slung using wedges or other grips. The wedge grip (Fig. 17) has the form of a bracket with branches connected to each other by steel rods in three places; used for slinging floor panels. An unequal-armed piece of square steel is mounted on the lower rod, like an axis, which can rotate. In the folded position, the axis of the segment (Fig. 17, a) coincides with the axis of the staple, and in the unfolded position it occupies a position perpendicular to the axis of the staple (Fig. 17, b). When used to lift a panel, a rolled-up grip is inserted into its mounting hole, and the section, due to the different weights of the arms, will tend to rotate 180°; to prevent this, the gripper is raised until the segment touches the panel and secured with a wedge.
Slinging reinforced concrete floor slabs using cantilever grips suspended from a crossbeam (Fig. 18) does not require installation of mounting loops in the concrete. To better use the lifting capacity of assembly cranes, it is advisable to use spatial crossbeams, with the help of which a package of several slabs is lifted simultaneously. This type of traverse (Fig. 19) consists of a steel triangular shape, at the ends of which two transverse traverse beams are attached with slings suspended from them to grip each slab. Design
The traverse allows you to sequentially hook three plates onto the mounting loops. With this lifting method, the use of the assembly crane is significantly improved. Panels of precast reinforced concrete shells are lifted using traverses (Fig. 20). For installation of structures outside the operating area of cranes, special cantilever traverses are used (Fig. 21).
Lifting, erection and installation on supports, alignment and temporary fastening of structures
During the installation process, it is necessary to pay special attention to compliance with the required sequence of installation of structures, temporary and permanent connections and their reliable fastening. Installation of each overlying tier of structures (crane beams, roof beams, trusses, columns, crossbars, floor slabs) can begin only after the elements of the underlying tier have been finalized and after the concrete at the joints of the load-bearing structures has reached 70% of the design strength. In construction practice, there are known cases of collapse of structures due to the fact that some bracing elements were not installed, not all bracing elements were securely fastened, the sequence of installation of elements was violated, and other applicable norms and rules for the installation of structures were not observed.
Rice. 14. Universal cross beam for installation of large-size slabs: 1 - load-bearing beams; 2 guide rollers; 3 - single-roll block - 4 - rope; 5 - end ring; 6 - pipe
Rice. 15. Spatial cross-section for installation of large-size slabs
Rice. 16. Universal balancing slings: 1 - carabiners; 2 - ropes 13 mm thick; L - blocks with a load capacity of 2 g; 4, 7 - ropes with a thickness of 19.5 mm\ 5 - blocks with a load capacity of 5 g; c - ring
Rice. 17. Wedge grip for slabs: a - in a folded position; b - in an expanded position; 1 - lower rod; 2 - steel piece; 3 - wedge; c - thickness of the floor panel
Rice. 18. Cantilever grips for lifting flooring slabs: 1 - clamp; 2 - loop
Rice. 19. Spatial crossbeam for lifting slabs in batches
Rice. 22. Crossbeam for lifting heavy structures with two cranes of different lifting capacities
Prefabricated structures for lifting to a facility under construction should be fed in the required sequence directly under the hook of the erection crane. Preliminary layout of structures at lifting points is allowed only in certain cases, since it is always associated with unproductive rigging operations, clutters up the construction site and complicates the work of the installation crane.
Reinforced concrete columns, depending on their weight and length, supply conditions, characteristics of cranes, are lifted in the following ways: translational movement of the column by a crane, rotation of the column around the base, rotation of the column around the base and translational movement of the crane, rotation of the column and crane boom.
Heavy and tall reinforced concrete columns are lifted by moving the lower end on a trolley (Fig. 23) or rotating around the base (Fig. 24). In the latter case, a rotary shoe is used. Such methods of lifting columns make it possible to transfer part of the load to a trolley or shoe, which makes it possible for the crane to operate at the beginning of the lift at a larger boom reach, at which the crane’s lifting capacity is less than the weight of the column. Reinforced concrete frames of industrial and other buildings and structures, made at installation sites or enlarged from individual racks and crossbars, are lifted by turning from a horizontal to a vertical position.
Rice. 23. Lifting a heavy and high reinforced concrete column: a - the position of the column during lifting; b - capture of the column; 1 - traverse; 2 steel roller (finger)
Rice. 24. Scheme of lifting a heavy reinforced concrete column with an increased boom reach: 1 - traverse sling; 2 - column-3 - log spacer; 4 - rotating steel shoe; 5 - rotary shoe pipe; 6 - gusset - 7 - channel; 8 - corner
Rice. 25. Guidelines for the correct installation of a reinforced concrete column: a - on a glass foundation; b - on a column; c - elevation marks; 1 - risks on the foundation; 2 - marks on the column; 3 - axes of crane beams; E - thickness of the glass gravy layer
The rotation is carried out around the bases of the racks located above the foundation glasses. To avoid movement of the bases of the racks, the frame, strapped to the brackets in the upper edge of the crossbar or to the girth, is lifted with a gradual change in the position of the assembly crane hook in the plan. After bringing the column or frame into a vertical position, it is pointed and lowered onto the foundation or onto the joining surface of the lower column. To monitor correct installation, guidelines are placed on the foundation and column. Such landmarks are marks applied with a core to steel plates embedded in the upper faces of the foundation (Fig. 25, a) or grooves left on these faces during the manufacture of foundations, and marks on columns (Fig. 25, b). The column is installed in such a way that the risks on it coincide with the risks on the foundation. Holding the column with a crane, it is verified to be vertical and temporarily fastened. In the case of using special conductors, the final alignment is carried out after temporarily securing the column with a conductor.
Rice. 20. Cross-beams for mounting panels and shells: 1 - cross-beam; 2 - slings; 3 - pendants; 4 - crane hook; 5 - carbine
Rice. 21. Cross-beams for installation of structures outside the range of cranes: 1 - counterweight; 2 - sling; 3 - beam; Q - mass of the lifted load: G - mass of the counterweight
To ensure the accuracy of the installation of columns and the entire building frame, it is necessary to prepare the supporting surfaces of the foundations in advance by filling them with mortar to the design level or by installing fixed pits in combination with manufacturing the supporting ends of the column with an accuracy of +5 mm, or use special equipment that does not require preparation of the supporting surfaces.
One of such solutions that ensures the fixed installation of reinforced concrete columns in foundation glasses can be the use of equipment consisting of a metal frame with four fixing fingers installed on the foundation, and mounting angles secured with tie bolts on the column. When using such equipment, the column is fixed to the frame using fingers inserted into the holes of the mounting tables and corners.
The sequence of work when installing columns using equipment, tested experimentally so far, is as follows.
The frame is aligned on the foundation. Its risks lead to the position of the alignment axes, the plane - to the horizontal level. The base surface is the surface in which the upper points of the fingers are located, inserted into the holes of the support tables. First, one fixing finger (adopted as a beacon) is brought to the required level. Then the rest are brought to the same level. The frame is aligned with jacks using a triangle laid on the surface of three fingers, including the beacon, and a water level. The jacks are rotated with special socket wrenches included in the equipment kit. The frame is brought into a horizontal position by two jacks. In this case, the first - lighthouse - remains motionless, the fourth - free - should not touch the surface of the foundation. After bringing the pin surfaces to a horizontal position, this last jack is screwed in until it rests on the foundation. The frame is fixed in the correct position with hooks. The nuts on the hooks are screwed in with force. Mounting angles are placed on the column and secured with coupling bolts. The nuts on the bolts are screwed in with force. The fixing fingers are removed from the holes of the support tables. The column is inserted into the frame by crane. At the moment of alignment of the holes of the mounting angles with the holes of the mounting tables, the fixing fingers are inserted. Fingers should be inserted in pairs, along one side of the column, not allowing them to be installed diagonally. One of the mounting angles should be pressed against the cheeks of the tables. Wedge washers are inserted into the gap between the other corner and the cheeks of the tables. The location of their installation is determined by a special sign on the tables.
Rice. 26. Frame alignment diagrams: a - on the foundation; b - columns; 1 - conductor risks; 2 - supporting lighthouse jack; 3 - lighthouse shaft; 4 - unscrewed jack; 5 - jacks that set the shafts to the required level; 6 - shafts brought to the level of the lighthouse shaft; 7 - column
If, after installing the column, the solution poured into a glass and squeezed out by the column does not reach the upper edge of the foundation, the solution is added to the gaps between the column and the foundation. After the mortar (concrete) acquires a strength of 25 kgf/cm2, the equipment is removed for reuse. Mounting equipment (frame, mounting angles, fixing means), made and installed with the precision specified by the design, ensures the column's design position without additional alignment. The correct installation of the mounted columns is checked by control measurements: relative to the alignment axes of the building - one measurement for every five columns; regarding the marks of the supporting surfaces - one measurement for every 50 m2 of structure area; vertically - one measurement for every 200 m2 of structure area. Deviations of assembled reinforced concrete structures from their design position should not exceed the tolerances given in SNiP III-B. 3-62*.
Temporary fastening of columns. The column installed in the foundation shell is aligned and temporarily secured using wedges, adjustable wedges, wedge liners, braces or struts, and conductors. Reinforced concrete columns up to 12 m high can be temporarily secured by driving concrete, reinforced concrete, steel or oak wedges into the gaps between the side faces of the column and the walls of the glass. It is most advisable to use concrete or reinforced concrete wedges, which are left in the foundation cups. However, it is impossible to straighten columns with such wedges; therefore, they are used after installing the column in the design position, and when straightening, they use inventory metal wedges. Wooden wedges must be dry, otherwise when they dry out, the column may deviate from the vertical. Wooden wedges should also not be left in glasses for a long time to avoid their swelling from atmospheric influences and possible damage to the structure. The length of the wedges is taken to be at least 250 mm with one edge beveled by 1/10; after driving, their upper part should protrude from the glass by approximately 120 mm. To secure a column, one wedge must be installed at each edge up to 400 mm wide, and two wedges at larger edges. At the bottom between the edges of the column and the walls of the glass there should be a gap of at least 2-3 cm to be able to fill it with concrete mixture. It is more effective to use inventory adjustable wedges or wedge inserts.
The adjustable wedge consists of cheeks hingedly connected to each other at one end; the cheek is flat, the cheek has the shape of an equal-block prism. At the other end, the cheeks are connected by means of an adjustable screw that passes through the nut in the cheek and connects to the cheek with a head. The latter fits into the slot of the channel welded to the flat cheek. A hinged bracket with a lock is attached to the cheek, with the help of which the device is attached to the wall of the foundation glass using a clamping screw.
Before installing the column, marks are applied to the edge of the foundation to indicate the position of the column faces. Then, two adjustable wedges are installed on two adjacent sides of the glass so that the cheek rests with its edge against the wall of the foundation glass, and the flat cheek runs along the plane of the future position of the column edge. The wedges are installed using a duralumin corner ruler. After installing a pair of adjustable wedges, the column is inserted into the glass so that its edges are pressed against the outer edges of the flat jaws secured by the wedges. Next, two more adjustable wedges are installed along the free edges of the column and the column is straightened and temporarily secured. When the pressure screw rotates, the jaw rotates around the support rib and with its lower end presses the column against the previously installed adjustable wedges, which ensures alignment of the position of the column in plan. By rotating the adjustable screws, the column is straightened and aligned vertically. The action of the wedge screws pinches the column using flat jaws at the level of the adjustable screws.
Rice. 27. Adjustable wedge for straightening and temporarily securing columns in the foundation glass: 7.2 - cheeks; 3 - channel; 4 - nut; 5 - adjustable screw; 6 - hinged bracket; 7 - clamping screw
Rice. 28. Diagram of a wedge liner: 1 - body; 2 - faces of the column; 3 - screw; 4 - handle; 5 - wall of the glass; 6 - wedge; 7-gasket; 8 - boss; 9 - support for removing the wedge liner; 10-nut; 11- ratchet wrench
The height of the adjustable wedge is taken equal to a third of the depth of the foundation glass, so that it is possible to seal the joint of the column with the foundation with a concrete mixture in two steps; first to the bottom of the wedges, then after removing them from the glass when the concrete reaches 25% of the design strength. The wedge liner (Fig. 28) consists of an L-shaped steel body 250 mm high and 55 mm wide, a steel wedge, a screw and a boss. The wedge is hinged to the horizontal arm of the body. The hinge axis rotates freely and moves in the longitudinal grooves located on the inner edges of the horizontal arm of the body. The screw rotates along a sleeve with a screw thread welded to the body. A boss is movably attached to the lower end of the screw. When the screw is screwed in, the boss moves down along the vertical part of the body and presses out the wedge. For ease of carrying and installation, the insert is equipped with a handle. The wedge liner weighs 6.4 kg. Inventory wedge liners are installed during alignment in the gaps between the walls of the foundation glass and the column. In this case, the screw must be unscrewed so much that the liner fits freely into the gap. The wedge liner rests with its horizontal shoulder on the wall of the glass. After installing the device, rotate the screw with a ratchet wrench, the boss is lowered, pressing the wedge towards the wall of the glass, and the body towards the edge of the column. At the same time, two wedge liners are fixed, placing them on opposite faces of the column.
According to TsNIIOMTP, when using liners, the installation time of columns and crane operation is reduced by approximately 15%, steel consumption is reduced, and installation accuracy is increased compared to driven steel wedges.
Heavy columns of great length for stability must, in addition to wedges, be strengthened with braces or rigid struts. The upper elements of prefabricated reinforced concrete columns are temporarily attached to the lower ones by installation welding. To ensure the stability of the upper element of the column, reinforcement outlets or linings located at the corners of the column are welded, and then the element is unstrapped. In the same way, temporary fastening of columns on foundations at joints with a pipe or reinforced concrete tooth is carried out. Single and group conductors have been developed and used for installation and alignment of reinforced concrete columns. Single conductors can be divided into two types: freely supported on the foundation and fixed to the foundation.
Conductors of the first type do not take the load from the mass of the column. They are designed to expand the base of the column to a size that ensures its stability from tipping over when freely resting on the foundation. When using such jigs, it is impossible to verify the position of the column in plan, and to straighten it it is necessary to use horizontal jacks fixed to the top of the foundation shell. Such conductors can only be used for installing light columns (weighing up to 5 g). Conductors of the second type are fixed in the foundations with screws, support the mass of the columns and are equipped with devices for alignment. The jig-fixer of this type of Uralstalkonstrukdia trust is fixed to the foundation with four stop screws and takes the weight of the column through the support axles of two vertical screws, for which purpose a steel roller is placed into the column during its manufacture in a precisely adjusted position. The pins and ends of the roller are located in the cuts between the stops. Having installed the column at the bottom of the foundation glass, raise it by 10-15 mm so that it can easily rotate in the axles. Then its vertical position is verified using ratchet bars in the transverse direction and screws in the longitudinal direction. With the help of such a conductor, reinforced concrete columns weighing 15-20 g were installed. For temporary fastening and alignment of high columns, group conductors are used, attached to the foundations with screws. These conductors ensure the stability of two columns simultaneously along and across the row. The general disadvantages of conductors are the complexity of their design, large weight and significant time spent on installation and alignment of columns (up to 1 hour). Improving conductors is possible by using aluminum alloys for their manufacture, improving the quality of node connections and alignment devices, and simplifying structures. Multi-tiered prefabricated reinforced concrete columns of large frame buildings are joined together by welding steel embedded parts and grouting the joints. Their temporary fastening within each floor or tier is carried out by installation welding (tack welding) of linings or outlets of reinforcement, braces with tension couplings or conductors. The upper ends of the braces are secured to clamps placed on the columns approximately in the middle, the lower ends to the hinges of the floor panels over which the column is mounted.
Temporary fastening of the first raised frame is carried out with braces or struts (Fig. 31), and the subsequent ones are connected to the previously installed ones by means of two inclined guys and two horizontal struts. Frame posts are temporarily secured with wedges, single jigs or installation welding. Temporary fastening of frames is also carried out using spatial conductors.
Rice. 29. Temporary fastening, alignment of reinforced concrete columns using a jig-fixer 1 - stop screw; 2 - cremalier; 3 - limiter; 4 - support pin; 5 - mounted column; 6- steel roller; 7 - column foundation 8 - screw
Rice. 30. Temporary fastening of reinforced concrete frames during their installation: 1 - strut; 2- inclined guy; 3 - horizontal strut
For temporary fastening and alignment of multi-tiered columns of multi-story industrial buildings, single conductors are used. The jig (Fig. 32) has corner posts, clamping and adjusting devices. The lower clamping device is used to attach the jig to the head of the previously installed column. Adjustment devices are located in the middle and upper parts of the racks. The adjusting device consists of four beams, adjusting screws and hinges. Three beams have one screw each, and the fourth has two screws, which makes it possible to rotate the column around its vertical axis.
A jig with automatic lever grips, designed for temporary fastening and alignment of reinforced concrete columns of multi-story buildings, has a more advanced design. The conductor is installed on a previously mounted column of the lower tier. Before installing the mounted column into the clamping carriages, automatic lever grips are moved apart by springs. When lowering, the column moves apart the levers, which together with the pressure carriages ensure centering and reliable grip of the column. The conductor is equipped with two horizontal screw jacks installed on the upper chord. Horizontal screws are connected to automatic grippers by bearing supports. The upper chord is attached to the upper ends of four screw vertical jacks. At the moment of gripping the column, the hinge supports of the lower belt, which is a frame-frame, are automatically activated. Support-grippers of the lower belt are hingedly attached to it, on which vertical jacks are installed. The hinged solution of the lower belt using a lock and hooks ensures that preliminary fixation of the conductor on the lower column, its installation in height and in the horizontal plane are carried out simply and quickly, without special alignment.
The column is verified in height and vertical using three vertical jacks, the rods of which can rise to the same height (search for the elevation mark) or to different heights (search for the verticality of the column). Then the column is aligned in the plane of the narrow edge by rotating horizontal screw jacks.
After final alignment and fastening of the mating parts of the column, the conductor is moved by crane to the next prefabricated element.
In addition to single conductors, conductors are used for the installation of prefabricated reinforced concrete structures of multi-story buildings: group conductors with two columns; group spatial for installation of four columns; spatial for mounting frames; volumetric (frame-hinged indicators) and others. A group spatial jig is used in conjunction with two single jigs for fastening and aligning columns of industrial buildings. In this case, the process of installing four columns is carried out in the following sequence. Single conductors are attached to the heads of two columns. Columns are installed in them and verified using these conductors and a theodolite. Then, using single conductors, the next two columns are temporarily secured. To align them, a group spatial conductor is installed on the tops of the four columns. The latter is a rigid metal welded frame made of angle and gas pipes. The frame in plan corresponds to the dimensions of one cell of the columns 6X6 m. In the corners there are caps-columns welded from sheet steel. Each cap is equipped with four adjusting clamping screws. In the upper walls of the columns there are holes - windows with built-in sighting axes. At the level of the lower belt of the frame there is a wooden flooring on which the installers work. There is a cable fence along the perimeter of the frame. Four sling loops are welded to the upper chords of the braced trusses for moving the conductor with a tower crane. The mass of the group conductor is 900-1000 kg. For temporary fastening of columns, a single conductor is used, which is a rigid spatial structure - a U-shaped frame with a hinged door, with fastening and adjusting screws. The jig is secured with fastening screws to the head of a previously installed column. Using adjusting screws, it is placed in a vertical position, after which the column is accepted.
Rice. 31. Conductor for installation and alignment of columns of multi-story industrial buildings: a - section; b - conductor installation diagram; c - adjusting device; g - clamping device; 1 - column; 2- corner stand; 3 - junction of columns; 4 - previously installed column; 5 - mounted column; 6 - conductor; 7 - interfloor ceilings; 8 - beam; 9- hinge; 10 - adjusting screw
Rice. 32. Conductor diagram: 1 - pressure carriage; 2 - automatic lever grip; 3 - springs; 4 - horizontal screw jack; 5-top belt; 6 - bearing support; 7 - vertical screw jack; 8 - hinged support of the lower belt; 9- lock; 10- hooks; 11 - column
Rice. 33. Conductor diagram for mounting frames: a - top view; 6 - front view; c - side view
The column to be mounted is inserted into the jig not from the top, as usual, but into the side door, and thus the structure weighing about 5 g is not located above the installer’s head during installation, which ensures operational safety and faster installation of the column in the design position.
Rice. 34. Sequence of installation of the conductor and prefabricated elements: 1, 2 - crane parking; 3, 4 - position of the conductor; 5-10, I-16 - sequence of installation of elements
The group conductor ensures the accuracy of installation of two columns simultaneously into the design position, which determines the quality of further installation of the frame - crossbars, floor slabs and coverings. As a result of using this installation method, the time required to align columns is reduced by one-third and labor costs are reduced by almost 3 times.
Using spatial conductors, several frames are installed. One of these conductors is a spatial structure measuring 12x5.50x3.6 m and weighing about 2 tons, welded from angle steel (Fig. 33). The length of the conductor can be reduced to 9 or 6 m. The upper working platform of the conductor is covered with boardwalk for the work of installers. Clamps are attached to the jig for temporary fastening of four frames from one position. During installation, the frames are held in a vertical plane by one clamp attached to the crossbar. After aligning and securing the frames, the conductor is moved by crane to a new workplace (Fig. 34). Frame-hinged indicators (RSI), proposed by S. Ya. Deych, are a complex device consisting of spatial lattice scaffolding on which a hinged (floating) frame with corner stops is arranged for fastening four columns, retractable and rotary cradles in the upper position for installers and welders.
Rice. 35. Sections of the frame-hinged indicator: a - transverse; b-longitudinal; 1 - wooden lining; 2-dimensional ring scaffolds; 3, 7 - retractable rotary cradles; 4 - hinged indicator; 5 - fence; 5-ball bearings; S - detachable flange joint; 9 - stairs
RSHI can be made for one (4 columns), two (8 columns) or three (12 columns) cells, one or two floors in height. The RSHI is installed through the building cell and connected with calibration rods. The mass of the RSHI per cell is 4-5 tons, the cost is 2-3 thousand rubles.
The RSHI is installed with a crane and verified with a theodolite. After alignment (about 1 hour per two cells), columns are installed, each of which is secured with corner stops.
Rice. 36. Scheme of frame-joint indicator (plan): 1 - longitudinal rod; 2- clamp cable; 3- clamp tensioner; 4 - rotary housing; 5 - transverse thrust; 6, 15 - brake frame mounting units; 7, 14 - longitudinal beams; 8, 10, 13 - mechanisms of movement; 9 - folding clamp; 11 - brake frame mounting units; 12, 16 - cross beams
Temporary fastening of beams. Reinforced concrete beams with a height to width ratio of up to 4:1 are laid on horizontal supports without temporary fastening; with a larger height to width ratio, the mounted beams are fastened with spacers and ties to other firmly installed structures. For temporary fastening of covering beams installed on columns, a special device is proposed, shown in Fig. 37. Rods with towbars tighten the grip, attached to the top end of the beam, with a bolt passed through the hole at the top of the column, and steel brackets fix the position of the bolt.
Rice. 37. Device for installing covering beams on columns: 1 - bolt; 2 - steel brackets; 3 - rods with towbars; 4 - capture
In column structures, permanent anchors are installed on supports, which greatly simplifies the attachment of roof beams to them. Temporary fastening of trusses. When installing reinforced concrete trusses, their axes are aligned with the marks on the columns and secured with anchor bolts. The first truss is secured with braces, tying the nodes of the upper chord adjacent to the ridge to fixed parts of the structure or to special anchors; subsequent trusses are fastened along the ridge with an inventory screw spacer with previously installed spacers at the junction points of the braces to the upper chord. Temporary truss fastenings are removed after creating a rigid system from a group of trusses and the covering elements laid on them. Dismantling temporary fastenings. Temporary fastenings of prefabricated reinforced concrete structures (wedges, struts, braces, struts, conductors, etc.) are allowed to be removed after the concrete at the joints has acquired 70% of the design strength.
Permanent fastening of structures
Permanent (design) fastening of structures is carried out by welding reinforcement at the joints and then embedding them. Before embedding the joints, anti-corrosion protection of welded joints is performed. Welding of reinforcement at joints of reinforced concrete structures, depending on the spatial position of the rods or seams, the diameter of the welded rods and the type of joints, can be of several types: semi-automatic submerged arc bath (butt horizontal and vertical joints), manual bath (butt horizontal joints), semi-automatic arc and manual arc (butt, lap and cross vertical and horizontal connections). It is possible to weld joints from low-carbon steels (class A-I, grade St.Z) at an air temperature not lower than -30°C, and from medium-carbon steels (class A-II, grade St.5 and 18G2S) and low-alloy steels not lower - 20 °C. At lower temperatures, measures are taken to maintain the air temperature at the welder’s workplace not lower than the specified limits.
In order to reduce the influence of welding stresses on the strength of reinforced concrete structures, reinforcement outlets are welded in a certain sequence (Fig. 39). Welding quality control includes: preliminary control, during the welding process, quality control of welded joints. They preliminarily check the compliance of basic and welding materials with the requirements of technical specifications, the quality of preparation of joined elements for welding, and the adjustment of equipment to a given mode. During the welding process, ensure that the required welding mode and technology are maintained. Quality control of welded joints includes external inspection, strength testing of samples, gamma ray examination, etc. Permissible deviations in the dimensions of welded joints are given in SNiP III-B. 3-62*.
Anti-corrosion protection of welded joints of prefabricated reinforced concrete structures is carried out by applying metallization, polymer or combined coatings: metallization-polymer or metallization-paint and varnish to steel embedded parts, connections of reinforcement at joints and fastening parts of enclosing structures. Zinc is mainly used for metallization coatings. Metallization-polymer coatings consist of zinc or zinc-coaluminum alloy and polymers (polyethylene, polypropylene, etc.). In metallization and paint coatings, zinc, primers (phenolic, polyvinylbutyryl, epoxy), paints (ethylene), and varnishes (bitumen-resin, perchlorovinyl, epoxy, silicone, pentophthalic) are used. The anti-corrosion coating is applied twice: in the factory, before installing embedded parts in the structure, and after installing the structures on welds and on individual coating areas damaged during welding of parts.
At a construction site, various coatings are applied in several ways: zinc - by flame spraying or electroplating; zinc-polymer and polymer - by flame spraying; paint and varnish - by applying a zinc sublayer, over which paint and varnish materials are applied with paint spray guns or manually.
Rice. 38. Sequence of welding joints: a - columns with foundation by two welders; b - the same, with one welder; c - crossbar with column; g - longitudinal connections
Zinc coatings are applied by flame spraying in one layer, by electroplating in 2-3 layers (with a thickness of 0.1-0.15 mm) and 3-4 layers (with a coating thickness of 0.15-0.2 mm). Zinc-polymer coating in two layers - first a zinc sublayer, then a polymer layer. The polymer can be applied immediately after the application of zinc. The polymer coating is also formed in two layers. In combined zinc-paint and varnish coatings, a zinc sublayer is first applied, and then paint and varnish materials are applied in 2-3 layers. Each layer of paintwork must be dried at a positive temperature for several hours and even days (depending on the type of material), which is a disadvantage under installation conditions. Therefore, instead of paints in combined coatings, it is better to use polymers.
Anti-corrosion coatings are applied immediately after welding elements and preparing surfaces, avoiding breaks lasting more than 4 hours.
The surface should be free of grease stains, traces of moisture and rust. After applying the coating, check the strength of its adhesion to the base, the thickness of the coating, the presence or absence of swelling and cracks. Sealing of joints. Sealing of joints and seams with mortar or concrete mixture is carried out only after verification of the correct installation of structural elements, acceptance of welded joints and anti-corrosion protection of metal embedded parts. When grouting, it is necessary to take into account that the concrete (mortar) at the joints of reinforced concrete structures does or does not accept the design loads. Thus, in the joints of columns with foundations that do not have embedded parts, as well as in joints in which the connection of prefabricated elements is carried out by welding the releases of reinforcing bars, concrete monolithically connects the elements and takes the load.
At joints with embedded steel parts, the concrete (mortar) seal is a filling between prefabricated elements, protects the embedded parts from corrosion, but does not take the loads acting on the structure.
The strength and stability of prefabricated structures with joints in which concrete carries design loads depend on the strength of the concrete in the embedment and on the adhesion of the embedding concrete to the strength of the prefabricated structure; the roughness of the joining surface significantly increases the adhesion of concrete at the joint. When embedding reinforced concrete columns in foundation shells, as well as other monolithic joints that bear design loads, rigid concrete mixtures of a higher grade than the concrete of the main structure (20% or more) are used to accelerate hardening and ensure joint strength. It is advisable to use a concrete mixture based on expanding cement, which is characterized by rapid setting and hardening and does not shrink, which is very important for the density of the embedment, or prestressing cement. Portland cement of a grade of at least 400 is used. Medium- or coarse-grained quartz sand is used. Crushed stone for the concrete mixture is chosen to be fine granite in order to ensure better filling of joints, with a particle size of up to 20 mm. To increase the plasticity of the concrete mixture at a low water-cement ratio (0.4-0.45), sulfite-alcohol stillage is added to the composition, and aluminum powder is added to increase the density of concrete.
The most commonly used compositions of dry mortar or concrete mixtures (by weight): 1:1.5; 1:3; 1:3.5; 1:1.5:1.5; 1:1.5:2. In order to activate the hardening of the solution (concrete), additives are added to the compositions: 3% semi-aqueous gypsum, 2% sodium chloride, up to 10% sodium nitrite, 10-15% potash by weight of cement, or use concrete mixtures preheated by electric current. Potash should be added at temperatures up to + 15°, since its use is ineffective at higher temperatures. To embed joints of prefabricated reinforced concrete structures, high-strength polymer solutions and plastic concrete are also used, which harden at a temperature not lower than +16°C. Therefore, if they are used at lower temperatures, the solution (concrete) in the joint area is heated with electric heaters. The joints of the columns are concreted in steel formwork. It consists of four steel panels 1.5 mm thick, connected to each other with bolts. At the top of each shield there are pockets for filling and compacting the concrete mixture. The formwork is held on the joined columns using wooden stops resting on the ceiling. The labor intensity of assembling such formwork is 0.16 man-hours, concreting one joint is 0.75 man-hours. The formwork is removed 4 hours after concreting, and in the case of using fast-hardening concrete, it is removed earlier. Similar formwork is used for concreting the joints of crossbars with columns. The joints are filled with mortar (concrete) mechanically using mortar pumps, pneumatic blowers, cement guns, syringing machines and other equipment. Pneumatic blowers and syringe machines are suitable for sealing joints with both concrete mixture and mortar; mortar pumps and cement guns - only with mortar. To create a wet hardening mode for concrete, the cemented joints are covered with burlap, sawdust and systematically moistened for 3 days.
Sealing joints in winter conditions. In winter conditions, when cementing joints with concrete that can withstand design forces, it is necessary to: warm the joining surfaces to a positive temperature (+ 5-8 ° C); lay the concrete mixture heated to 30-40 °C; maintain or heat the laid mixture at a temperature of up to 45°C until the concrete acquires at least 70% of its design strength.
The interface between the column and the foundation can be heated in various ways: low-pressure steam; water (the joint cavity is filled with water and then heated with steam supplied through a hose); rod electrodes at low voltage current; electric heating devices. When heating with water, it is necessary to ensure that after heating the water is completely removed from the joint cavity.
Rice. 39. Graph for determining the strength of concrete depending on temperature and heating time. Portland cement concrete
The concrete mixture placed in the joint is prepared by heating the components or heated in bunkers with electric current to 60-80°. Along with warming up and electrical heating, at outside air temperatures down to -15 °C, antifreeze additives can be introduced into the concrete mixture to seal joints. Joints, the concrete of which does not withstand the design forces, at an outside air temperature of up to -15 ° C can be monolithed with a concrete mixture (mortar) only with anti-frost additives, since such a mixture hardens even at subzero temperatures; in this case, after laying in the joint, the mixture does not need to be heated; in the event of a sharp drop in outside air temperature, it is sufficient to use insulated formwork. Solutions of calcium chloride salts CaC12 are recommended as antifreeze additives; calcium chloride CaCL with table salt NaCl; calcium chloride CaC12 with table salt NaCl and ammonium chloride NH4C1; sodium nitrite NaN02, etc.
Rice. 40. Consolidation of the joint between the column and the foundation in winter conditions: a - diagram of electrical heating of the concrete joint with electrodes; b - heating of the joint surface with electric cylinders; c - heating the cemented joint with electric furnaces; g - the same. using a heater; 1 - foundation; 2 - column; 3 - electrode; 4 - transformer; 5 - switch; 6 - soffits; 7 - electrodes
The use of antifreeze chemical additives such as chloride salts is prohibited when sealing joints with metal embedded parts and fittings.
To increase the plasticity and water resistance of concrete at the joint, sulfite-alcohol stillage is added to the concrete mixture with anti-frost additives in an amount of up to 0.15% by weight of cement.
If it is necessary to obtain high strength embedding in a short time (one day or less), concrete prepared with antifreeze additives can be subjected to artificial heating.
When cementing joints with a concrete mixture without anti-frost additives, it is necessary to pre-heat the mating elements of the joint and warm up the concrete until it acquires the required strength; design joints loaded with the design load in winter must be heated until 100% of the design strength of the concrete in the joint is obtained and until 70% strength is obtained in other cases. The strength of concrete prepared with Portland cement, depending on the temperature and heating time, can be approximately determined according to the schedule.
Rice. 41. Heating and warming up the joints of multi-tiered columns and the joints of floor slabs with purlins during monolithic installation in winter conditions: a - using thermoactive formwork; b - through heating elements; 1, 2 - steel sheets; 3- thermal insulation layer; 4 - three layers of electrical insulating fabric with nichrome wire in the middle; 5 - spiral in a layer of sawdust wetted with a solution of table salt; 6- layer of sand; 7-tubular electric heater; 8 - tarpaulin; 9 - clamp
Most often, heating is carried out by electric current, as well as steam. For electrical heating, electrodes are used (Fig. 40, a), tubular electric heaters or electric cylinders with tips inserted into the joint cavity (Fig. 40, b), thermoactive formwork, heating cassettes, reverberatory electric furnaces (Fig. 40, c) or electric heaters (Fig. . 40, d), electrode panels. It is advisable to warm up and warm up the joints of multi-tiered columns, as well as beams, using thermoactive formwork (Fig. 41). In the cavity of a double formwork consisting of inner and outer steel sheets, either three layers of electrical insulating fabric with nichrome wire on the middle layer, or a layer of mortar with embedded steel wire and a thermal insulating layer of mineral wool are placed. This formwork is made in accordance with the dimensions of the joined elements and is held on them using a clamp. Concrete mixture with a cone draft of 10-12 cm is loaded into the joint through a funnel built into the formwork. Tubular electric heaters (TEH) can be used to heat many joints, both directly (Fig. 41, b) and as heating elements of cassettes (thermal shields) (Fig. 42), reverberatory furnaces and other devices. A tubular electric heating element is a hollow metal tube into which a spiral of nichrome wire is pressed. The filler is fused magnesium oxide or quartz sand. The filler acts as electrical insulation.
Rice. 42. Heating cassettes: a - diagram of a set of cassettes for heating the column joint; b - cassette diagram; c - tubular electric heater; 1 - tubular electric heater; 2 - reflector; 3 - body; 4 - insulating sleeve; 5 - filler; 6 - spiral; 7 - filling
In Fig. 41, b shows the heating of the junction of the floor slab with the purlin (or beam) using a tubular electric heater, which is covered with a tarpaulin.
After heating, which lasts about 4-5 hours, remove the tarpaulin and heating element, concrete the joint, cover it with slag or sand and lay the heating element again.
To embed vertical joints of columns, universal heating formwork with automatic control of the heat treatment mode is used. It consists of a metal case, heating cassettes, power supply and control. The formwork body is used for laying concrete in a joint and is made of two halves, bolted together. Each half is made of sheet steel and has guide plates for attaching the heating cassettes and the power and control unit. The halves are interchangeable and each has a loading window. Heating cassettes are flat metal heat-insulating boxes with built-in tubular electric heaters with a power of 0.5 kW and a voltage of 220 V. The operating temperature of the heater surface is 600-700 °C. There is an air gap between the heating element and the wall adjacent to the concrete. A reflective plate made of tinplate is installed under the heater. According to experience, the use of heating elements instead of spirals increases the reliability of the heating device, increasing its service life to 5000 hours, and also allows for infrared heating. Three types of heating cassettes in various combinations provide heat treatment of the joint of any column section. A set of heating cassettes is inserted along the guides of the metal formwork and covers the joint on four sides.
Installation of the heating formwork at the joint of the column is done manually from halves with heating cassettes installed on them or element by element. The mass of an individual element of the heating cassette is 5.5-9 kg; the mass of the entire formwork for a column with a cross section of 250X500 mm is 70 kg.
The cassettes are connected to the network before the joint is concreted. After preliminary heating of the joint cavity for two hours, the cassettes are turned off for laying concrete. Subsequent heat treatment of the joint concrete is heating to 50°C and isothermal heating at this temperature by periodically turning on and off the current. Electricity consumption with automatic control and outside air temperature down to -15 °C is 35 kWh per joint. With manual regulation, it is equal to 50 kWh per junction.
The design of the joint between the crossbar and the floor slabs allows for only one-sided peripheral heating. Reverberatory furnaces are used for this purpose. The stove is an inventory box 1300 mm long, made of two rolled metal sheets, between which thermal insulation made of mineral wool 50 mm thick is laid. The inner sheet is also a parabolic reflector, along the focal axis of which there are two tubular electric heaters with a power of 0.8 kW each and a network voltage of 220 V. Each box has a cable outlet ending with a three-phase plug connector, one of the pins of which is grounding. Box weight 50 kg. To reduce heat and moisture loss, the perimeter of the box is filled with sawdust. Electricity consumption at an outside air temperature of -15°, a heating temperature of + 50° and its automatic regulation is 25 kWh per junction.
To automatically maintain a given constant temperature for concrete processing, a power and control unit is used. It consists of a power cable, a thermostat and a control box. The following are mounted in the metal box of the control box: a magnetic starter, a switch, a signal lamp and a terminal block for connecting the leads of the heating cassettes. The control box is inserted into the guides of the metal formwork of the joint. The thermostat has one pair of normally closed contacts, which open when the temperature rises above the set point. The thermostat is connected to a network with a voltage of 220 V. Using it allows you to automate all types of heat treatment of concrete during installation.
Rice. 43. Diagrams of a reverberatory furnace (a) and an electrode panel (b): 1 - housing; 2 - tubular heater; 3 - cable outlet with plug connector; 4 - protective strip; 5-vapor barrier; 6 - terminals; 7 - conical pins; 8 - steel tires
Electrode panels are also used to heat the joined elements. Three steel bars serving as electrodes are mounted on the panel, with conical pins that improve the contact of the electrodes with the concrete.
TO category: - Installation of building structures
The installation of glass-type foundations and, in general, the construction of structures of the underground part of the building are considered zero-cycle works and are carried out as an independent installation flow. The above-ground part of the building is usually assembled using a mixed method, when columns are mounted independently and wall panels are hung, and crane, sub-rafter and rafter trusses are installed in a comprehensive manner, and covering panels are laid.
For one-story industrial buildings, a range of prefabricated reinforced concrete columns with a height of up to 19.35 m and a weight of up to 26.4 tons, mounted in glass-type foundations, has been developed.
Before installing the columns you must:
- - fill the sinuses of the foundations;
- - mark installation axes along four edges at the level of the upper plane of the foundations;
- - cover the foundation glasses with shields to protect against contamination;
- - arrange roads for the passage of the installation crane and cars;
- - prepare sites for storing columns at the place of their installation;
- - deliver the necessary installation equipment, fixtures and tools to the installation area;
- - check the position of all embedded parts of the columns;
- - apply the marks of the installation axes on the side faces of the columns.
The columns are preliminarily laid out at the installation sites on wooden pads with a thickness of at least 25 mm. The columns are laid out in such a way that a crane from the assembly stand can install them in the design position without changing the boom radius. Before installation, each column must be inspected to ensure that it does not have deformations, damage, cracks, cavities, chips, exposed reinforcement, or concrete sagging. It is necessary to check the geometric dimensions of the column, the presence of a mounting hole, and the correct installation of steel embedded parts.
Before or simultaneously with slinging, a column with a height of more than 12 m is equipped with ladders, hanging cradles, and braces.
Column slinging carried out by mounting loops, by a mounting rod passed into a special hole in the column. Friction grips or various self-balancing traverses are widely used, allowing the column to be lowered vertically onto the foundation. All of them must provide remote slinging, eliminating the need to lift a worker to the slinging site after installing the column in the foundation shell. Using an assembly crane, the columns are lowered into the foundation glass onto reinforced concrete pads or onto a leveling layer of concrete mixture.
Reconciliation and temporary fixing columns installed in the foundations are carried out using a set of installation equipment. The design position of the bottom of the column at the bottom of the foundation shell, temporary fastening and vertical alignment of the columns are carried out using wedge liners. The stability of the columns after installation is ensured by temporary fastenings, most often by conductors or wedge liners. Vertical alignment and correction of columns is carried out using jacks; in this case, the deviation from the vertical and the displacement of the axes of the columns in the lower section should not exceed standard values.
Columns up to 12 m high are usually secured in foundation cups only with the help of wedge liners; for taller columns, jigs and braces are additionally used. Unslinging of installed columns should be done after they are securely fastened in the foundation glasses with wedge liners, and, if necessary, with braces.
The stock wedge insert consists of a body with a nut and handle, a screw with a boss and a wedge suspended on a hinge. Wedge liners are installed in the gaps between the edges of the column and the walls of the foundation shell. For gaps greater than 90 mm, additional inserts are used. When the screw is rotated with a wrench under the action of the boss, the wedge moves in the body on a hinge, as a result a thrust force is created between the wedge and the cup body. Before sealing the joint between the column and the foundation with a concrete mixture, a fence is installed on the wedge liner, which is removed from the glass immediately after compaction of the rigid concrete mixture or after the start of setting with ordinary mixtures.
Various types of conductors are used to temporarily secure columns. The conditions for using different types of conductors, the procedure for performing work on installation and alignment of columns with their use are stipulated by the work project.
After alignment of the columns, they are secured in the design position by concreting the joints with a concrete mixture using fast-hardening non-shrinking cement using a pneumatic blower. Wedge liners are removed only after the concrete joint has acquired the strength specified in the work plan or when the concrete reaches 50% of the design strength.
When installing columns, it is necessary to check the mark of the bottom of the foundation glass, the alignment of the marks on the edge at the bottom of the column with the alignment mark on the upper face of the foundation, the verticality of the columns, the marks of the crane console and the head of the column. The alignment of the column axes and the alignment axes must be controlled along two axes; the verticality of the column must be ensured using one or two theodolites along two alignment axes or with an zenith device using the vertical design method. The marks of the supporting platforms for crane beams and trusses are controlled by the method of geometric leveling.
Installation of columns
Metal columns installed on solid concrete foundations can be supported:
- - on anchor bolts pre-embedded in the foundations with grout at the joints of the cement mortar after alignment of the installed column along two mutually perpendicular axes;
- - directly on the surface of foundations erected to the design level of the milled base of the column without subsequent grouting with cement mortar;
- - on pre-installed, calibrated (with a layer of cement mortar if necessary) steel base plates with a top planed surface (no-calibration installation).
When preparing columns for installation, the following marks are applied to them: the longitudinal axis of the column at the level of the bottom of the column and the top of the foundation.
Columns installed on foundations are provided only with anchor bolts if the column has wide shoes and their height is up to 10 m. Higher columns with narrow shoes, in addition to being bolted, are braced in the plane of least rigidity on both sides. The braces are secured to the top of the column before it is raised and, during installation, are secured to anchors or adjacent foundations. After tensioning the braces, the slings can be removed from the column.
The braces can be removed only after the columns have been secured with permanent elements. The stability of the columns in the direction of the building axis is ensured by crane beams and connections installed after the installation of the first pair of columns and the crane beam connecting them.
Metal columns installed on foundations are secured with anchor bolts during installation. If metal gaskets are placed under the base of the column, they must be welded. The columns of the upper tiers (for example, in a built-in shelf) are secured with high-strength bolts or welded.
Alignment of frame structures, especially columns, requires a lot of labor. Application non-calibration installation method allows you to improve the quality of work while reducing the construction time of the structure.
For non-calibration installation, appropriate preparation of structures is required at the manufacturing plant and at the construction site. Increased precision in manufacturing structures is ensured by the following:
- - the structures of the column shoe and the shoe base plate are manufactured and delivered to the site separately;
- - the ends of the two branches of the columns must be milled;
- - base plates are made planed.
Each base plate must be welded to 4 strips with threaded holes for installing bolts; Axial marks must be applied to the branches of the columns.
With the non-alignment method of installation, steel columns rest on a steel plate. In this case, the surface of the foundations is concreted below the design mark by 50...60 mm and, after precise installation, the slabs are topped with cement mortar. The base plate is installed with adjusting bolts on the support strips, which must be concreted into the foundation flush with its surface as embedded parts. The reference plane of the slab is set by adjusting the nuts of the set screws using a level. The actual elevation of the base plate should not differ from the design one by more than 1.5 mm.
When installing a column, the axial marks on its branches are combined with the marks marked on the base plates, which ensures the design position of the column, and it can be secured with anchor bolts. In this case, additional displacement of the column for alignment along the axes and height is not required. After installing the braces to the mounted column structures and their tension, the crane beams begin to be installed. Crane beams installed along axial risks do not require additional alignment. After they are secured to the bolts, the braces are removed.
Reinforced concrete columns of one-story industrial buildings are installed in glass-type foundations, and of multi-story buildings - at the ends of the columns of the lower floors.
Before installing the column, marks on the upper surfaces of the foundations are marked with marks of the column axes and the mark of the bottom of the glass is verified. To accurately install a column, several methods are used: cement mortar is poured into the bottom of the glass in advance to the required level, taking into account the length of the column; at the bottom of the glass in the refilled solution, an imprint of the base of the column is created using a stamp using a jig; a pin is installed and poured in the center of the column at the bottom of the glass, onto which a hole is then placed in the base of the column; Asbestos concrete pads of the required thickness are placed on the bottom of the glass.
The layout, lifting and installation of reinforced concrete columns is carried out in the same way as stable ones.
Columns with crane consoles are usually transported in the “flat” position, and due to the strength conditions when lifting columns of great height and for ease of slinging, in some cases they have to be turned to the “edge” position, which requires tilting the column before lifting. To distribute the forces in the branches of the column when lifting, a spacer jack is placed at the bottom of the support before lifting. Reinforced concrete columns are raftered in the same way as steel ones, above the center of gravity. If there are crane consoles, the slings are secured under them. The slings must ensure the verticality of the column when installing it in the design position, minimal labor intensity and safety of slinging. For slinging, a universal sling with a traverse and a collapsible frame is used, which is placed under the consoles. The pin securing the joint of the frame can be pulled out with a thin cable or hemp rope tied to the end of the pin. In this case, unslinging does not require climbing onto the column. In some cases, a hole is provided at the bottom of the column into which a shaft is inserted to secure the ends of the slings. It is also possible to sling with two universal (loop) slings, which are tightened on the column with a “boa constrictor”, and they are held in place due to friction. For safety, the slings are tied below the sling loop of the column.
After securing the column to the foundation, the hook is lowered and the weakened slings slide down. When installing a column in a glass-type foundation, the axes of the raised column are aligned with the axes of the marks on the surface of the glass, the verticality is verified and temporarily secured in the glass, after which the slinging is carried out.
For temporary fastening of the column, wedges, wooden, concrete and metal, wedge inventory liners, single and group conductors are used. The most commonly used are wooden and steel wedges. It is advisable to use concrete wedges that do not need to be removed, but they are not widely used. For column widths up to 500 mm, wedges are placed on one side, and for wider columns, two wedges per side.
The glasses are concreted in two stages: first to the bottom of the wedges, so that they can be removed after the concrete reaches 25% strength, and then to the top. Alignment of the column should be performed before slinging, until the column is easily placed in the correct position. Columns above 12 m, in addition to being secured in a glass, should be braced along the row.
Columns of multi-storey buildings are temporarily fixed in single or group conductors attached to the underlying structures. The columns are attached to the jig with horizontal adjusting screws - stops, which can be used to align and secure the installed column (Fig. 5.19). Conductors are used for one, two and less often four columns. The four-column conductor allows for calibration-free installation of structures.
The position of the columns is fixed with clamps located at two levels. The screws of the clamps ensure the vertical position of the columns. The presence of a flooring on the top of the conductor ensures the safety of the installation of crossbars (see Fig. 5.19).
Columns of multi-storey buildings can also be secured using struts or spacers with screw ties. In some cases, temporary fastening of installation joints of reinforced concrete columns is carried out by welding to the extent determined by the work plans. Such fastening increases the operating time of the assembly crane, since unslinging can only be done after the temporary fastening by welding has been completed. Final fastening of the column joint is recommended after installing and fastening the crossbars and slabs securing it. Installation of structures on columns is allowed only after the design fastening of the column and achievement of 70% of the strength of the embedment concrete. Column installation work should be carried out in accordance with operational control charts. Deviations from the design position of the columns should not exceed the tolerances specified in table. 5.3.