- Sliding gate foundation configuration
- Active loads
- How easy it is to carry out earthworks
- Assembling the reinforcement cage
- Installation of mortgages for fastening the gate
- Pouring the foundation
For the installation of sliding gates, a reliable base is required, made taking into account several specific requirements. We propose to consider the main questions regarding the degree of deepening of such a foundation, the location of the embedded elements, the reinforcement scheme and the stages of work.
Sliding gate foundation configuration
Due to the considerable length of the sash overhang, the base of the sliding gate experiences significant loads in the form of longitudinal roll. To counteract them, the foundation must have a sufficient area of contact with the ground, a correct distribution of impacts and high structural strength. At the same time, it is important to ensure the minimum consumption of materials – reinforcement and concrete mixture.
As practice has shown, the most advantageous form factor of the foundation for sliding gates is a U-shaped structure consisting of two pillars and an upper belt connecting them together. The first pillar is located parallel to the pillar that limits the door opening from the side of the drive mechanism. The second pillar is removed from the opening exactly at the distance of the departure of the lower beam, connected to the sash by a brace. In general, manufacturers of sliding gates make the beam overhang with a length of at least half the width of the main sash..
1 – channel # 20; 2 —reinforcement frame; 3 – electric drive; 4 – roller bearings; 5 – supporting rollers; 6 – gate leaf; 7 – toothed rack; 8 – end roller; 9 – bottom catcher; 10 – upper catcher
The upper connecting belt should contain embedded anchoring elements intended for fastening the support rollers and the drive mechanism. In some cases, it is possible to recommend laying in the upper face of a steel channel numbered from 16 to 20. With such a foundation design, it is much easier to position the drive with support roller blocks and fix them by welding, but such a device has its drawbacks. The main risk factor is considered to be corrosion processes arising from the absence of a protective layer of concrete, while the structure of not only the upper belt, but also the entire foundation, may be destroyed. Also, the smooth surface of the channel does not provide a sufficiently high adhesion to the concrete mass, therefore, reinforcement must be present in any case..
If a set of drive mechanisms for sliding gates was purchased before the start of the foundation construction, it will be much easier to get by with anchoring, which is installed in the thickness of the concrete product. If you do not know the exact mounting dimensions for the drive, a universal mounting plane must be provided. In the most reliable version of the device, it is represented by a wide metal plate with multiple attachment points to the foundation reinforcement.
To build a foundation for a sliding gate with minimal material and labor costs, one should understand the mechanics of its operation. Here the fact that the structure has a limited number of concentrated loads plays into the hands.
Since the main impact on the foundation from the sash is carried out in its closed position, the load distribution scheme can be calculated quite simply. The foundation pillar, located closer to the opening, serves as a fulcrum and receives the bulk of the gate, directed along the vertical axis. Since in the closed position the extreme free part of the sash rests on the trap, the bending moment and wind loads can be neglected..
The second post, located at a distance from the opening, is loaded in the opposite direction. The stability of the foundation is largely determined by the strength of the connecting belt and the shape of the second pillar. To counteract pull-out loads, its inward-facing edge is beveled at an angle of 10-15 °. In this case, the strength of the upper belt can be calculated from the bending resistance of an ordinary concrete beam: the force acting vertically upwards will be equal to the mass of the gate multiplied by the ratio of the lengths of the lever arms, that is, the ratio of the main leaf width to the overhang of the lower beam.
Temporary loads should not be neglected either. The U-shaped form of the foundation is not particularly beneficial for counteracting the forces of frost heaving, therefore, the pillars must either have a length exceeding the freezing depth, or be surrounded by a hygroscopic incompressible shell.
How easy it is to carry out earthworks
Excavation begins with digging a trench under the upper armored belt. It adjoins the base of the fence without a rigid connection with it, has a width of at least 40 cm and a depth corresponding to the current class of loads. To be sure of the strength of the connecting belt, you can follow a simple scheme: the depth of the underground part is 25 cm with a sash weight of up to 1000 kg and 35–40 cm with a sash weight of over 1000 kg and its length no more than 5 meters.
At the second stage, holes are dug for concreting the pillars. The pit walls can be used as ready-made formwork only if the soil is not too loose. If the walls are crumbling heavily, holes should be dug 10–15 cm wide on each side for the panel formwork. The cross section of the pillars is a square, the side of which is equal to the width of the upper connecting belt.
You can dig holes under the pillars just with an ordinary bayonet shovel. After notching at the edges and loosening the bottom, the soil is excavated with a plastering bucket. When the depth of the pits becomes too large and the excavation cannot be done by hand, the bucket handle should be lengthened with a steel pipe and the loosened soil should be scooped out, pressing the bucket against the wall of the pit.
When digging a hole for the second post, it is necessary to increase its width from the inside by about 1/5 of the depth of the foundation. Another option is to deepen the second post at least 1/3 more than the length of the first. To ensure the slope of the inner edge, a piece of foam plastic plate is laid in the pit.
After the pits have been dug, an ASG is poured onto their bottom with a layer of about 20 cm and the pillow is tamped with a deck. Further, bags of polyethylene film are placed in the formwork, corresponding to the dimensions of the “legs” of the foundation. The upper edges of the bags must be cut and wrapped to the bottom of the trench under the armored belt. The above-ground part of the foundation is formed by formwork from boards 200–250 mm wide, the upper edge of which is brought out into the common horizon. Waterproofing is also laid in the formwork and the trench – a polyethylene sleeve, the upper edges of which are turned outward and fastened with brackets to the outer sides of the decks. Inside, the overlaps of the film are fixed with ordinary tape.
Assembling the reinforcement cage
Reinforcement of the foundation for sliding gates is represented by three rectangular frames, each of which has four rows of working reinforcement about 14 mm thick. Two frames are assembled for the pillars so that protective layers of concrete of at least 60 mm are formed on all sides, and the release of the rods upwards is about 30–35 cm.
Reinforcement of the foundation for sliding gates: 1 – working reinforcement Ø14 mm; 2 – sand and gravel mixture; 3 – concrete B15; 4 – structural reinforcement Ø10 mm; 5 – working fittings O 16 mm; 6 – embedded anchors
The reinforcement of the tie strap must provide sufficient strength to support the weight of the gate. Due to the direction of action of the loads, reinforced reinforcement is installed in the upper part of the belt – these are two threads of corrugated reinforcement with a diameter of 16–18 mm. The bottom row of two rods, 12-14 mm thick, is designed to ensure the overall stability of the concrete structure and resist temporary loads. The working reinforcement is connected to each other by rectangular clamps made of structural smooth reinforcement with a thickness of 8-10 mm.
After laying the upper reinforcing cage, it is associated with the reinforcement of the pillars. The rods located on the inside are bent at the level of the lower row of the belt reinforcement, the outer ones at the level of the upper one. The ligation of rods of different frames should be carried out with at least two wire clamps, the length of the overlap should be at least 20 diameters of the reinforcement used.
Installation of mortgages for fastening the gate
Embedded anchors for fastening the drive are installed in groups in three places: in the center of each pillar, where the support rollers will be installed, and in an arbitrary place between them, where the drive mechanism itself is planned.
Studs with threaded ends are used as embedded elements. The opposite ends of the studs are bent in the form of a semicircular hook with a length of about 150 mm, and the thread is protected with adhesive tape. Contrary to popular belief, mortgages of this type should not be tied to the rods of the working reinforcement so as not to exert a bending effect on them. In general, the hooks are located inside the upper reinforcement cage and are directed towards the center of the concrete product..
To ensure the correct alignment of the embeds with the bases of the rollers and the drive mechanism, an installation template is made for them. This can be a metal plate, an OSB sheet, or a frame made of wooden slats. In the template, according to the marking scheme, holes are drilled into which the straight parts of the embedded hooks are threaded and counter with nuts on both sides. The resulting assembly is immersed in the foundation immediately after the concrete is poured and leveled along the planned door installation plane.
Pouring the foundation
If the depth of the pits for the foundation pillars reaches 2 meters, there is a risk of delamination when the concrete mixture is dropped. In this case, pouring is carried out with the frame installed and the concrete is carefully compacted by pinning in layers of 40-50 cm. Concrete will not delaminate when dropped from a height of up to 1.5 meters, in this case it is recommended to first fill the holes 1 meter from the bottom, and then immerse they have a frame of pillars.
For the foundation for sliding gates, concrete with a strength class of at least B15 with a filler fraction 4–5 times less than the distance between the closest reinforcement elements should be used. To increase the mobility of the mixture, it makes sense to prepare it in a weak soap solution..
After pouring the mixture, the upper plane is smoothed and the foundation is covered with plastic wrap. After 3-4 days, the aboveground formwork can be removed and the collapsed edges can be plastered if necessary. It is recommended to start installation of drive technology for gates no earlier than the middle of the total holding period, that is, two weeks after pouring.