Concreting purlins
Concreting of purlins, beams and slabs should begin 1...2 hours after concreting the columns and the initial settlement of concrete in them.
Purlins and beams with a height of more than 50 cm are concreted in layers of 30...40 cm, with each layer individually compacted with deep vibrators. Densely reinforced purlins and beams are compacted using vibrators with special nozzles. Last layer concrete mixture not brought to the bottom plane of the slab by 3...4 cm.
The floor slabs are concreted over the entire width at once and compacted with surface vibrators.
Arches and vaults with a span of less than 15 m are concreted continuously simultaneously on both sides from the heel to the castle. Vaults with a span of more than 15 m are concreted in separate sections. In this case, the concrete mixture is laid in strips simultaneously in three areas in the castle and at the heels. After this, individual strips are concreted, between which shrinkage gaps of 20...30 cm are left, which are sealed with a low-flow concrete mixture 5...7 days after concreting the strips. Tightening of vaults and arches is tightened before concreting.
On steep sections of arches or vaults, in order to prevent the concrete mixture from slipping during vibration, concreting is carried out in double-sided formwork, the outer panels of which are built up during the concreting process.
The start of concreting must be preceded by thorough check(with drawing up an act) of the geometric dimensions, stability and strength of the formwork.
Technology of construction of residential and civil buildings from monolithic reinforced concrete. Along with fully prefabricated factory housing construction, the construction of buildings made of monolithic reinforced concrete is gaining some momentum in the country. This type of construction turns out to be advisable:
- if it is necessary to solve urban planning problems through the construction of atypical buildings of a tower composition;
- during construction in areas of high seismicity or in mining areas, where increased requirements are placed on the spatial rigidity of buildings;
- when constructing buildings in areas significantly removed from house-building enterprises.
K category: Home remodeling and renovation
Working techniques for installing precast concrete parts in brick buildings
Moving heavy parts manually using mounting crowbars is carried out in three main ways: “with your paw away from you,” for which the pulled end of the crowbar is inserted under the part and the crowbar is pressed away from you onto the part (shown by the arrow). At the same time, the part rises somewhat and, sliding off the paw, moves forward.
If there is a large gap between the part and the base, the “sharp end away from you” technique is used, which is performed in the same way as the “paw away from you”, but the sharp end of a crowbar is placed under the part.
To move to the sides, use the “paw to the side” technique, in which the pulled end of the crowbar is brought under the part at an angle to the nearest vertical edge. By pressing the crowbar in the direction shown by the thick arrow, they lift and move the part, turning the crowbar on the heel of the paw. During the reverse movement, the crowbar is lifted upward and the end of the paw is moved to the initial position, but already at some distance from the first point.
The “paw-on” technique is used to move parts installed in upper tiers. To perform this technique, place the paw of the crowbar under the part and press the second end of the crowbar down. At the same time, the part is lifted and moved towards the worker.
Rice. 1. Techniques for moving the detail with a mounting crowbar: a - “with your paw away from you”; b - with the sharp end away from you"; c - “paw to the side”; g - “paw on yourself.”
When checking the position of an installed part and correcting it, follow the following procedure:
- install the base (supporting parts of the part) in place;
— check and correct, if necessary, the mark of the top of the part;
- bring the side edges of the part to the vertical.
Installation of beams, purlins and lintels over openings.
The installation of purlins (beams, crossbars) begins after the walls are erected. Installation is carried out from scaffolding or from mobile assembly tables. For safety reasons, ladders should not be used.
To mark the position of the purlin (crossbar) in the plan, place the position of the intersection axes on the walls with a theodolite, use a steel tape measure to mark the position of the axes of the remaining purlins (crossbars) and fix them with marks on the wall. Using a meter, an auxiliary mark is applied on the wall near the supporting platform at a distance equal to half the width of the purlin, or crossbar.
The mark of the top of the beam purlin (crossbar) from the alignment is transferred with a mooring or a level to the place of support of each purlin (crossbar) and fixed with a mark on the wall near the socket. For ridge girder you need to mark and fix with marks on the brick pillar a conventional mark 100 mm below its supporting plane.
Purlins (beams, crossbars) are slung with a two-legged sling. If there is a special crossbeam and sufficient lifting capacity of the crane, several girders are lifted simultaneously.
As a rule, for better distribution of force in a brick wall, a reinforced concrete slab (cushion) whose dimensions are larger than the support platform of the purlin (beam) is laid under the purlin on the butt row of the inner mile. The pillow is placed on the mortar so that the top of the pillow is 8-10 mm below the mark of the bottom edge of the purlin. A mortar bed is arranged under the run, leveling the mortar with a trowel. The top of the bed should be located slightly above the level of the supporting plane of the purlins (crossbars). The area of the bed should be such that after lowering the purlin, the solution is not squeezed out.
Purlins (crossbars) in frame buildings and buildings with an incomplete frame are installed, starting with the lighthouses, along the intersectional axes. The installation of these purlins should be checked especially carefully.
Rice. 2. Control over the installation of the sighting run on the auxiliary line: 1 - run; 2 - mortar bed; 3 - reinforced concrete pad; 4 - auxiliary risk.
The correctness of lowering the purlin (crossbar) into place is controlled by sighting along the lateral plane at the auxiliary line (Fig. 100), as well as along the length of the supporting platform. It should be remembered that longitudinal movement of the purlin (crossbar) is prohibited by safety rules.
The correct installation of the purlin (crossbar) is checked along the length of the supporting platform with a meter. An incorrectly installed purlin should be lifted, the mortar bed replaced and reinstalled.
The correct installation of the purlins in height is checked by matching the top of the purlin with the previously applied mark. When aligning purlins (crossbars) installed directly on brick pillars(ridge girder), measure with a meter the distance from the upper plane of the girder (crossbar) to the auxiliary line.
A slight settling of the purlin (crossbar) can be achieved by squeezing out the solution when moving the purlin (crossbar) with a mounting crowbar in a horizontal plane across the axis.
The position of the longitudinal axis of the purlin (crossbar) is checked by the coincidence of the middle of the purlin and the axial mark on the wall or column. Possible deviations are eliminated by moving the purlin using a mounting crowbar.
The verticality of the side edges of the purlin is checked with a plumb line “by hand”; deviations are eliminated using a mounting crowbar or a special lever from the ceiling.
In addition, the position of the installed purlin must be additionally controlled by sighting along the top edge at the beacon and previously installed purlins (crossbars) and checked with a template for the distance between the purlins and crossbars. High beams of large spans are temporarily secured with wedges in space with the walls of the nest.
The installation of rafter beams begins after installing the attic floor, laying the cornice and installing the ridge girder, if it is provided for in the project. Installation begins with laying lighthouse beams located along the intersectional axes and carried out in pairs on both slopes.
The beams are slung with a special two-legged sling having branches of different lengths, or by lengthening one of the branches of the two-legged sling with a short sling so that the slope of the beam slightly exceeds the design one.
The beams are laid into place using a crane, starting with the lower end of the beam being placed in place.
If necessary, transverse movements of the beam are carried out using a mounting crowbar in a “paw away” manner, holding the other end of the beam with the crowbar.
Installation of reinforced concrete beam lintels over the openings (Fig. 101) is carried out along the course of the masonry in accordance with the instructions
a mark in order. Lightweight lintels are laid manually or using a crane. When laying lintels, pay attention to the order in which regular and reinforced lintels are laid, the horizontal and vertical sides, the sufficient size of the support area in accordance with the design, and that the side surface of the lintel does not extend beyond the plane of the wall.
The installation of floor slabs (flooring) begins after the walls have been erected and the purlins have been laid on the grip. Installation begins from the end walls.
Before laying hollow-core slabs, the voids at their ends are sealed with concrete liners (if they are not sealed at the factory).
The slabs (panels) are slung with a four-leg sling or a universal traverse. Panels “for a room” must be strapped using all mounting loops.
The slabs that are laid first at a distance of at least 2-2.5 m from the wall must be taken and laid from the mounting tables, and the rest - from the previously installed floor.
Special attention pay attention not to knock down brickwork a quarter of the wall, and the width of the supporting platform, remembering that moving the laid slabs in the direction perpendicular to the supporting structures is not allowed.
Rice. 3. Installation of block lintels: a - bed arrangement; b - manual laying; at the same time, with a crane.
The discrepancy between the width of the supporting platform and the base of the slab is eliminated by re-laying the slab.
When installing narrow slabs of hollow-core flooring, the discrepancy in the size of the mounting sags is determined by sighting along the plane of the ceiling or using a rule. If necessary, settlement of the slab can be achieved by squeezing out the solution during horizontal movements of the slab. The sagging slabs are reinstalled, increasing the thickness of the mortar bed.
Discrepancy in size assembly seams between adjacent slabs is determined by sighting along the seam; Deviations are eliminated by moving the slab using a mounting crowbar.
If the plane of the slab has a curvature, it is laid in places where it adjoins walls or partitions so that the free edge is horizontal.
A slab with a sagging middle is laid on a thick bed so that adjacent slabs divide the sag in half.
Slabs (panels) can be unslinged only after the alignment has been completed.
The seams between the slabs immediately after laying the slabs are sealed with mortar, feeding it with a shovel and compacting it with a trowel.
A temporary inventory fence is installed around the mounted part of the ceiling.
To install the coating attic roofs begin after laying the cornice and installing at least 4-6 pairs of rafter beams.
Before installing the coating slabs (panels) on attic floor must be supplied hydro- and thermal insulation materials provided for by the project.
Installation begins with the laying of lighthouse slabs and is carried out alternately on one or the other roof slope. The end of the slab outer wall accepts the linkman, standing on the ceiling, and the installer accepts the slab at the ridge from the assembly table.
When covering the roof with ribbed slabs, the marks of intersectional axes on the eaves are used. Using a steel tape measure, the joints between the slabs are marked on the cornice and purlin, and after laying the lighthouse slabs, the mooring is pulled at the level of the top of the end rib of the end of the slab resting on the cornice.
When covering with rolled panels (shells), marks mark the middle of the rafter beams.
Slabs and rolled panels of attic roofs are slung with a universal traverse or a special four-leg sling and supplied for installation with an inclination slightly greater than the design one, so that the slab (panel) rests first with its lower end.
The correctness of lowering the slabs (panels) into place is controlled by risks, the size of the installation gap between the laid and previously laid slabs (panels) and the mooring (for ribbed slabs). Particular attention should be paid to the width of the support area, since moving laid ribbed slabs along and shells across the slope is not allowed.
The installation of balcony slabs along the entire length of the grip begins only after the walls have been erected and the ceiling has been laid above the underlying floor. Installation should begin with the installation of beacon plates along the edges of the grip.
For balconies on the second floor, use a meter to mark and mark the position of the balcony slab with marks. On subsequent floors, the position of the marks is additionally controlled along the balcony of the underlying floor, using a plumb line for this.
After installing the lighthouse slabs, it is necessary to pull the wire mooring along their outer upper edge along the length of the entire grip.
The slabs are slung with a four-legged sling or served in a traverse container.
The mortar bed is made by leveling it with a trowel and not bringing the bed 2-3 cm to the edge of the wall.
The correct lowering of the slab is controlled by risks and mooring.
The slab should be laid horizontally or with a slight slope towards the free end. Temporary fastenings should be installed immediately after laying the slab.
When positioned laterally balcony door For temporary fastening, it is necessary to use racks installed on the balcony or masonry of the underlying floor. If the door is located in the middle of the panel, then the slab is secured using a stand with guy wires. To do this, the rack is installed on the ceiling, the guy ropes are secured to the mounting loops of the slabs, they are put on the side of the balcony slab, the rod is secured with a pin and, by rotating the nut, the rod is tightened.
Rice. 3. Lifting balcony slabs with a container traverse.
The correct laying of the slab is checked by risks and mooring, as well as by sighting on lighthouses and earlier installed slabs. Deviations are eliminated by moving the slab using a mounting crowbar.
The horizontal installation of the slab is checked by laying a straight line with a level in two perpendicular directions. If there is a slope in the longitudinal direction, it is necessary to lay the slab again, changing the thickness of the mortar bed. The slope towards the building is eliminated by rotating the nut of the posts.
Temporary fastenings can only be removed after laying the walls of the next floor.
For installation landings they begin after erecting the walls of the staircase to the level of the landings and carry it out as the walls are erected.
The platform is slung with a four-leg sling or a universal traverse and delivered to the laying site in a horizontal position.
The mortar bed is arranged by feeding the mortar with a shovel and leveling it with a trowel. The surface of the bed should be 3-5 mm above the design level of the bottom of the platform.
The platform at the floor level must be laid in place from the ceiling, and the intermediate platform must be laid from scaffolding installed in the rooms adjacent to the staircase.
Rice. 4. Temporary fastenings of the balcony slab: a - resting on the masonry of the lower floor; b - stand on guys.
The correct height of the platform is controlled by risks, and horizontality is controlled by setting a level with a level in two mutually perpendicular directions. Possible deviations are eliminated by changing the thickness of the mortar bed and re-laying the platform.
The correct laying of the platform should also be monitored by the size of the installation gap with the adjacent wall and a special template in two places (at the support points of the flight stringers).
If necessary, the platform is moved using a mounting crowbar.
Flights of stairs are slung with a special sling and delivered to the laying site in a position close to the design one, with slight (up to 10 cm) excesses of the upper end of the flight, thereby ensuring that the lower end of the flight is first supported, and then the upper. In the absence of embedded mounting loops, loops made from a cable or clamp are used for slinging.
For reception flight of stairs The team member is located on the lower platform, and the installer is located on the ceiling or upper platform.
When laying the march in place, lower the lower end of the march onto the platform and press the march against the wall; lower the upper end of the march and loosen the slings. After this, the position of the march and the platform is checked.
If necessary, you should raise the upper end of the flight and, using the “paw away” technique, move the flight or platform slightly, increasing or decreasing the mounting clearance with the wall.
After alignment, the installer seals the march with mortar, first thoroughly clearing the seam of debris, snow, etc. Using a shovel bucket, lay a bed of mortar along the length of the joint and thoroughly compact it with a trowel.
After completing the installation of the march and platform, temporary or permanent fences are immediately installed.
Rice. 5. Scheme of installation of a flight of stairs using a special traverse: 1- traverse; 2 - installed march; 3 - previously established march.
- Working techniques for installing precast concrete parts in brick buildings
Strength building structures help provide reinforced concrete products. Their shapes and sizes are varied. Some are produced directly on the construction site, others are prepared in production. No construction is complete without reinforced concrete purlins.
Definition
The appearance and structure of the purlin are almost no different from a reinforced concrete pillar. Outwardly they look like frozen concrete mortar with a metal frame inside. What is the difference between the runs? Designs differ large mass, long and reinforced with strength. The production of structures is not on stream; their production is associated with the need for the element to withstand a certain load.
Purpose
Reinforced concrete purlins are used in construction to solve an important problem. For example, not a single opening can be made without using a purlin. Only after its installation are the floor slabs attached. And reinforced products made under the influence heat treatment, withstand heavy loads. They are used in the construction of public and industrial buildings with brick and reinforced concrete walls. Most often they are used in the construction of openings, supports on which floor slabs are attached.
Installation of the purlin: a) view of the support on the wall; b) on a pole; 1. reinforced concrete pad; 2. runs. Reinforced concrete purlins prepared exclusively in an industrial way, in accordance with state construction standards. For their production, only heavy concrete is used, most often M200 and M300, with the use of reinforcement for reinforcement. The use of structures in favorable conditions increases the service life of buildings.
Kinds
Reinforced concrete purlins are divided into types, which are formed according to the shape of the product and the grade of concrete. The purlins are assigned the following types
T-section
Channels and I-beams are used in production. This type is divided into two types:
- The first group includes products with metal located perpendicular to the rib of the purlin. They are suitable for the construction of buildings that have a roof slope of approximately 25%. 1PR rod frame, 2PR pre-stressed, 3PR is used when the roof slope is no more than 5% - varieties of the first group.
- The second group includes products that can withstand a roof slope of 25%. It includes products 4PR stressed and 5PR artificially created tension.
These designs can be used for unheated room. Used in temperature conditions from - 40 to 50 degrees and exposure to gas. Characteristic feature is the ability to use products in the construction of structures in hazardous, seismically active zones.
The difference is the presence of special holes, through which the gripping devices are inserted, making it easier to lift and install the elements. T-section elements are suitable for the construction of buildings:
- unheated with a roof made of cement and asbestos fibers;
- heated with lightweight ceilings;
- heated with cement roof.
Rectangular section
This type of purlin has an I-beam division. The rectangular cross-section of the purlins can be solid or lattice. The lattice type is lighter, the spacing of products is 6 meters, so it is used in construction much more often. To produce a continuous type, bent channels are used. Products with a rectangular cross-section have thin walls, but excellent height. The strength of the products is ensured by specially created fastening bends.
Marking
Example of marking runs. The manufacture of building structures is approached in compliance with state standards and technology. You can get maximum information about products by studying the product series. An inexperienced builder will not be able to obtain complete information on markings without knowledge. It is worth focusing on the transcript data.
For ease of use, a special classification in letters and numbers is used. They encrypt information about length, height, width, and support load. The first letters encrypt information about the series of runs:
- P - one-piece product.
- PR - the presence of a side located parallel or at an angle to the axis of the element.
- PRG — rectangular section.
The second group of signs contains information about the load and type of reinforcement. The third signs indicate the specific purpose of the material, including the features of the use of concrete composition.
For example: PRG 28-1-3-4t. PRG - rectangular section. The following series of numbers indicates the dimensions of the structure: 2800 mm long, 100 mm wide, 300 mm high. The 4t indicator indicates the ability to withstand a load of 4 tons per meter.
In brick buildings interfloor ceilings stacked from reinforced concrete slabs along walls and crossbars.
Crossbars (purlins)(Fig. 1, a, b) rest on reinforced concrete pads, which are laid in brick walls during the laying process. The difference in the marks of the top of the pillows within a section of the house should be no more than 10 mm.
Figure 1. Installation of the crossbar (purlin): a - view of the support on the wall; b - on a pole; 1 - reinforced concrete pad; 2 – runs
Before installing crossbars (purlins) Use a level to check the horizontality of the support pads. The crossbars are slung using two loops, brought to the installation site and lowered onto a bed of mortar spread on the supports. The crossbars are brought to the design position using mounting crowbars. The crossbar can only be moved perpendicular to the longitudinal axis, working with the paw of a crowbar. Otherwise, the stability of the walls or pillars on which the crossbar rests may be compromised. Installers work from inventory scaffolds. After checking the horizontal position (by level and sighting on previously installed crossbars), verticality (by plumb line), the crossbar is attached to the previously installed structures (the method of fastening is indicated in the project) and then the slings are removed.
Before installation floors check the position of the upper supporting parts of the masonry under the floor structure, which must be in the same plane (the difference in marks within the floor should not exceed 15 mm).
To ensure the horizontality of the ceiling formed by the ceiling, use the following techniques. Within an occupation (section) of the building along the perimeter of the top of the walls or purlins, using a level or flexible level, marks are applied (on pre-fixed slats) that correspond to the installation horizon, i.e. the mark at which the bottom of the floor structures will be located. A leveling layer of mortar (screed) is laid along the leveling marks (along the mooring cord), leveled with the rule, and after the screed has acquired 50% strength, the floor slabs (panels) are mounted, spreading a layer of fresh mortar 3-4 mm thick on the supporting surfaces .
Figure 2. Laying floor slabs: 1 - box with solution; 2 - shovel; 3 - tool box; 4 - crowbar; 5 - plate
The installation of the ceiling is carried out by a team of four people: a crane operator, two installers (4th and 3rd categories) and a rigger (3rd category). The rigger slings the slabs with a four-legged sling. Two installers are on the floor (initially on scaffolding), one at each support of the slab being mounted (Fig. 2). They receive the supplied slab, unfold it and guide it when lowering it to the design position.
After alignment, the floor slabs are secured by welding the mounting loops to the anchors embedded in the walls during laying; adjacent slabs are fastened with anchors using the mounting loops.
The connections between the floor and the walls are sealed after the installation of the floor. In hollow core floorings, when they are supported on external walls for the purpose of insulation, the voids are filled lightweight concrete or ready-made concrete plugs to a depth of at least 120 mm. Voids in slabs resting on internal load-bearing walls, sealed with heavy concrete or liners. This is necessary to protect the supporting parts of the floor slabs from destruction under the pressure of the overlying structures.
Jumpers. Load-bearing lintels in brick buildings, like purlins, are installed by lifting them by mounting loops and laying them on a prepared mortar bed, while ordinary lintels are laid manually. During installation, ensure the accuracy of their installation along vertical marks, horizontality and the size of the supporting area.
Staircases and landings. The elements are installed as the walls of the building are erected. Before installing landings and flights, their dimensions are checked. Then the installation sites for the platforms are marked, a layer of mortar is applied and the platform is installed. The intermediate platform and the first march are installed along the course of the masonry interior walls the staircase, the second (floor) landing and the second flight - upon completion of the floor laying.
The flight of stairs is slung with a four-legged sling with two shortened branches, which give the lifted element a slope slightly greater than the design one. When installing a flight of stairs, it is first supported on the lower platform, and then on the upper one. If the landing of the march on the support platforms is carried out in the opposite way, then it may fall off the upper platform or it may get jammed between the upper and lower platforms.
Before installing the flight, installers make a bed of mortar on the supporting places of the landings, spreading it and leveling it with trowels. When installing flights, one installer is on the lower platform, the other is on the overlying ceiling or on scaffolding next to the staircase. Accepting the march, the installer directs it into the stairwell, moving simultaneously to the upper landing. At a height of 30-40 cm from the landing site of the flight, both installers press it against the wall, give the crane driver a signal and install first the lower end of the flight, then the upper one. Installation inaccuracies are corrected with a mounting crowbar, after which the sling is unhooked and the joints between the march and the platforms are sealed. cement mortar and install inventory barriers.
Flights of stairs without mounting loops are lifted using a fork.
Balcony slabs . The installation of balcony slabs begins along the entire length of the grip after laying the floor. First, beacon slabs are installed along the edges of the grip, marked on the ceiling and the position of the balcony slab is recorded with marks. On subsequent floors, the position of the marks is additionally controlled along the balcony of the underlying floor, using a plumb line for this. After installing the lighthouse slabs, a wire mooring cord is pulled along their outer upper edge to the length of the entire grip and the remaining slabs are installed along it. The slabs are usually slung with a four-leg sling. The mortar bed is leveled with a trowel, not bringing it 2-3 cm to the edge of the wall. Balcony slabs are laid by two installers, monitoring the correct lowering of the slab along the risks and the mooring cord. The slab should be laid horizontally or with a slight slope towards the free end. The horizontal installation of the slab is checked by laying the rule with a level in two perpendicular directions. When sloped in the longitudinal direction, the slab is raised and lowered again, replacing the mortar bed. The slope towards the building is eliminated when installing temporary racks or rods.
Temporary fastenings are installed immediately after laying the slab. To do this, the racks are placed on the balcony of the underlying floor and, using a screw spacer, they support the mounted slab.
The slab remains suspended on the crane hook until the temporary fastening is installed, the position of the slab is adjusted and the embedded parts are welded to the anchors. Balcony slabs are secured by welding steel rods to the mounting hinges of the floor and balcony slabs.