The building facilities that make concrete shape are called templates.
Its structure includes a panel system and a support system.
The panel system includes panels and related ribs; The supporting system includes vertical and horizontal banks, supporting beams, supporting trusses, cantilever beams, cantilever trusses, pillars and supports.
Wood formwork was widely used in the early days.
After 1950s, steel, plywood, reinforced concrete, or the mixture of steel, wood, concrete and other materials gradually developed.
There are also shaped combined steel templates with a certain proportion of thin steel modulus, which are assembled into templates of various shapes and different areas with U-shaped cards, L-shaped pins, hook bolts, butterfly fasteners and other accessories.
Since 1970s, the sliding mode technology has made great progress.
Using slip form can greatly save raw materials and costs, and significantly improve the engineering quality and construction speed.
Therefore, it is not only used in civil buildings, but also widely used in hydraulic structures such as lock chambers, holes, pier walls, shafts, tunnels, spillways and overflow surfaces of dams. The construction of dams and inclined shafts has started on a trial basis.
Although formwork is an auxiliary structure, it is very important in concrete construction.
In water conservancy projects, the cost of formwork works accounts for 15 ~ 30% of the cost of reinforced concrete structures, accounting for less than 5 ~ 15% of the cost of reinforced concrete, and the labor cost of formwork installation accounts for about 28 ~ 45% of the total consumption of concrete projects.
For projects with complex structures, the time of formwork support and steel binding is much longer than that of concrete pouring, so the design and technology of formwork is an important link that cannot be ignored in concrete construction.
The formwork of powerhouse and lock chamber of hydropower station is mostly plate, beam, wall and column structure, and the design and construction of formwork are basically similar to those of industrial and civil buildings.
However, under the bottom plate of the turbine, because the shape of the volute and draft tube are all kinds of curves, it is necessary to design the template specially.
Generally, it is made into a bent frame according to the shape of each section, and then the formwork is laid outside after the bent frame.
Sometimes the bent frame can be segmented in different places, and it will be hoisted to the site for assembly after the floor of the factory building is poured, so as to strive for the construction period.
When the workshop is too high to support the formwork of the roof structure, the structural reinforcement of the roof can also be used to design the load-bearing skeleton, and the formwork can be hung outside to bear the weight of concrete and play a supporting role.
Small wooden formwork is often used in the early stage of dam formwork. For the convenience of manpower, the general area is 1m2.
About, low efficiency, large wood loss, has been phased out.
With the improvement of construction mechanization, larger and larger formwork is gradually developed.
For example, the hydropower station project in Hunan Town, China adopts 6m×9m steel-wood concrete mixed formwork, which is hoisted by crane, and the work efficiency is improved by 8 times.
Some also use reinforced concrete formwork or concrete gravity formwork as a part of the dam body, which will not be removed and can play the role of surface protection.
1980 In order to save wood, steel formwork is widely used instead of wood formwork in our country, and shaped composite steel formwork supported by steel cantilever beam or steel cantilever truss can improve work efficiency and reduce interference in warehouse.
Slipform technology has also developed in dam construction, and is widely used in overflow surface or spillway construction (see color map) because it is easy to ensure the flatness of shape and surface.
China Hongshi Hydropower Station adopts vacuum slipform with soft sucker, which not only reduces the cracks on the overflow surface, but also increases the slipform speed and enhances the durability and wear resistance of the overflow surface.
The shaft wall formwork project is similar to the wall formwork of industrial and civil buildings.
There are round shafts, such as surge shafts, and square shafts, such as gate shafts.
Since 1970s, many shafts have been constructed by slip form, and the work efficiency and quality are far better than that of vertical formwork casting.
In the past, tunnel formwork concrete lining was mostly poured in sections. First, set up the bottom formwork, pour the bottom slab or arch, then set up the side wall formwork, pour the side wall, and finally set up the top formwork, pour the top slab or arch.
This construction method has many procedures, many columns in the tunnel and great construction interference.
In 1950s, special formwork equipment was used for concrete lining of moving tunnel, which was called steel formwork trolley.
Its main structure consists of steel frame and formwork installed on the steel frame.
The formwork can be disassembled and assembled by jacks and screws on the frame, and the frame can run on the poured bottom arch, with or without rails.
When the formwork itself can bear external force, the frame can be separated from the formwork and driven to the section to be poured in front.
The template can be removed and reused in about four days.
Another kind of tunnel lining equipment, called pin beam formwork, is suitable for full-face lining of tunnels.
Its characteristic is that there is no need to lay a track, and the expansion and movement of the template depend on an extended needle beam.
This kind of construction equipment was adopted for the lining of diversion tunnel with an inner diameter of 8m in Lubuge Hydropower Station in China (see color map).
It consists of 10 segments.
1.5m template,
* * * Length 15m.
Each section consists of four formwork (bottom arch, top arch and formwork on both sides). The needle beam is 2.4m wide, 2.39m high and 38m long.
Slipform construction is also used in tunnel lining, which is mostly confined to tunnel bottom arch, and some small inclined shafts are constructed by full-face slipform method, but it is not common.
Although the action template is an auxiliary structure, it is very important in concrete construction.
In water conservancy projects, the cost of formwork works accounts for 15 ~ 30% of the cost of reinforced concrete structures, accounting for less than 5 ~ 15% of the cost of reinforced concrete, and the labor cost of formwork installation accounts for about 28 ~ 45% of the total consumption of concrete projects.
For projects with complex structures, the time of formwork support and steel binding is much longer than that of concrete pouring, so the design and technology of formwork is an important link that cannot be ignored in concrete construction.
Design principle: Practical principle: Formwork shall ensure that the shapes, sizes and mutual positions of components are correct, with simple structure, convenient support and disassembly, smooth surface, tight joints and no slurry leakage. Safety principle: it has sufficient strength, rigidity and stability to ensure no deformation, damage or collapse during construction. Economic principle: on the premise of ensuring the quality and safety of the construction period, try to reduce one-time investment, increase formwork turnover, reduce support and demolition labor, and realize civilized construction.
1. Design of steel formwork and its support The design of steel formwork and its support shall conform to the current national standard Code for Design of Steel Structures (GB 500 1 7-2001), and the plastic development coefficient of its section shall be1.
2. Design of wooden formwork and its support The design of wooden formwork and its support shall comply with the current national standard Code for Design of Timber Structures (GB50005——2003), in which the diameter of the tip of the compression upright post shall not be less than 60mm except for meeting the calculation needs.
Safety technology (1) before work, you should wear a safety helmet and check whether the tools used are firm. Tools such as wrenches must be hung on the body with ropes to prevent people from falling.
Concentrate on your thoughts when you are working, and avoid the nail sticking your feet and falling into the air.
(2) Scaffolding shall be provided for the installation and removal of formwork more than 5m, and protective railings shall be provided to prevent the same vertical plane.
Fasten your seat belt when working at height.
(3) A large number of templates and other materials shall not be piled up on the scaffold.
(4) Installation and removal of formwork with high and complex structure shall be carried out with practical safety measures in advance.
When the formwork is dismantled at high places, there should be a special person to command, and the operation area should be marked below.
When assembling and disassembling the composite steel formwork, someone should meet up and down, and it should be transported with the disassembly. It is forbidden to throw from a height.
(5) Brackets, poles, etc. Do not put it on the door window frame and scaffolding.
The diagonal brace and tie rod in the middle of the passage should be located at a height above1.8m. ..
In the process of formwork support, if it is necessary to stop halfway, the support, lap and stigma plate should be nailed firmly.
Intermittent form removal, moving formwork, tie rod, support, etc. Should be transported away or properly stacked.
6. Generally, a long crowbar is used to dismantle the formwork.
No one is allowed to stand on the template being demolished.
When dismantling the formwork, the whole formwork shall be prevented from falling off to avoid personal injury.
⑦ If there are reserved holes in the template, cover the holes after installation.
The reserved holes on the concrete slab shall be covered immediately after formwork removal.
⑧ Erect wires and use electric tools on composite steel formwork, use safe voltage below 36V or take other effective safety measures.
It is not allowed to require the formwork engineering support safety card to control the "seven prohibitions" 1. No construction shall be carried out without the preparation of special safety plans or the examination and approval according to regulations.
2. The supporting system foundation cannot meet the requirements of the scheme, and construction is not allowed.
3. The formwork and supporting system with unqualified materials shall not be constructed.
4. Formwork and supporting system shall not be constructed without acceptance or unqualified acceptance.
5. No construction is allowed without technical training or unqualified training.
6. The deformation of formwork support system must be monitored by special personnel on site, otherwise the construction may not be carried out.
7. According to the principle of hierarchical management, no construction is allowed without management personnel on site.
Safety requirements: 1. When the working height of formwork works is 2m or above, it shall be protected according to the requirements of Technical Specification for Safety in Working at Heights. Safety nets and protective railings should be set around or on two or more floors.
2. The shuttering shall be carried out according to the prescribed operating procedures, and the next working procedure shall not be carried out before the template is fixed.
It is forbidden to climb up and down on the connectors and brackets, and it is forbidden to install and dismantle the formwork on the same vertical plane.
3. The column formwork with a height of more than 3m shall be surrounded by diagonal braces and a platform shall be erected; if it is less than 3m, a horse stool can be used.
4. For the form of cantilever formwork, there should be a stable foothold.
Scaffolding should be installed when the airport structure formwork is installed.
There are reserved holes on the template, which should be covered after installation.
The edges or holes formed on the concrete slab after formwork removal shall be protected as required.
5. People are not allowed to climb the formwork or scaffolding when going up and down, and are not allowed to walk on the narrow formwork surface without fence such as wall top and independent beam.
6. Formwork supports cannot be fixed on scaffolding or doors and windows to avoid collapse or template displacement.
7. When constructing on the formwork, it is not advisable to pile up too much and concentrate in one place, and the pile of large formwork should have anti-dumping measures.
8. In winter construction, the ice and snow on the construction site and pedestrian passage should be cleared in advance; During construction in rainy season, lightning protection facilities shall be installed for formwork work of high-rise structures; It is not suitable for assembling and hoisting large formwork in windy weather above level 5.
Safety requirements for formwork removal 1. Before the formwork support is dismantled, the concrete strength must meet the design requirements, and it can only be carried out after application and approval by the technical director.
2. The dismantling sequence and method of all kinds of templates shall be carried out in accordance with the provisions of template design. Unless otherwise specified, dismantle the formwork first, then dismantle the non-bearing formwork, and then dismantle the bearing formwork and support.
3. The cordon must be set when ripping, and send someone to monitor.
Demolition must be clean and thorough, and there can be no suspended templates.
4. When the formwork is dismantled for aerial work, it should be equipped with climbing equipment or erection support, and fasten your seat belt when necessary.
5. Remove the template are not allowed to throw down at will, should be cleaned up in time.
The temporary stacking place shall be not less than 1m from the floor edge, and the stacking height shall not exceed1m. It is forbidden to pile up any dismantled objects on the edge of the floor, the opening of the passage and the edge of the scaffold.
6. Move the formwork, support, support, etc. during the clearance of formwork removal. Should be transported away or properly stacked to prevent falling due to stepping on the air or holding the air.