How to construct combined formwork?

Construction process of installation and dismantling of stereotyped composite steel formwork. This process standard is applicable to cast-in-place concrete frame and cast-in-situ concrete shear wall formwork projects for industrial and civil buildings. 1. Construction preparation 1. Materials ⑴ The composite steel formwork material consists of steel formwork and accessories. 　　1) Flat template specification length: 450mm, 600mm, 750mm, 900mm, 1200mm, 1500mm width: 100mm, 150mm, 200mm, 250mm, 300mm 2) Shaped steel angle mold: Yin and yang angle molds, joint angle molds. 　　3) Link attachments: U-shaped clips, L-shaped pins, type 3 fasteners, disc fasteners, hook bolts, wall bolts, and fastening bolts. 　　4) Support system: Column hoops, steel flower beams, wooden beams, wall hoops, steel pipe portal scaffolding, adjustable steel support tops, adjustable upper brackets, steel trusses, and wood. 　　5) Release agent. 　　⑵SP─Formwork series materials (i.e. steel frame plywood surface formwork) 1) Formwork specification length: 900mm, 1200mm, 1500mm width: 200, 300mm, 600mm thickness: 55mm, 70mm 2) Shaped steel angle mold: Movable hinge formwork, connection angle formwork, modified connection angle formwork, fixed yin and yang angle formwork. 　　3) Link attachments: Steel pipe clamps, square steel clamps, wedge-shaped latches, wall bolts, connecting bolts. 　　4) Support system: Column hoops, square steel wall hoops, steel pipes, portal scaffolding, adjustable steel supports, adjustable upper brackets, steel trusses, wooden beams, and timber. 　　5) Release agent. 　　2. Working conditions ⑴ Template design: Design the formwork according to the form and characteristics of the engineering structure and on-site construction conditions, determine the formwork layout, vertical and horizontal keel specifications, arrangement dimensions and the location of wall bolts, determine the form, spacing and arrangement of the support system, check the strength, stiffness and stability of the keel and support system according to the specifications, and draw a full set of formwork design drawings (including formwork layout plans, elevations, assembly drawings, node drawings, parts processing drawings, material lists, etc.) The number of formwork should be combined with the division of construction flow sections during formwork design, and a comprehensive study should be conducted to reasonably determine the number of formwork preparations. 　　⑵The formwork is numbered according to sections, coated with release agent, and stacked according to the locations specified in the construction floor plan. 　　⑶According to the formwork design drawing, place the axis and formwork edges, determine the opening position and horizontal control elevation, and cement mortar leveling layer should be made at the bottom of the wall and column formwork. 　　⑷The wall column steel bars have been tied, the water and electricity pipelines and pre-embedding have been installed, the steel protective layer pads have been tied, and the concealed acceptance procedures for the previous process of divisions or sub-projects have been completed. 　　⑸The supporting points or steel anchor rings of the diagonal supports are firm and reliable. 　　⑹Before installing the formwork, provide safety and technical explanations to the team based on the formwork plan, drawing requirements and operating process standards.

2. Operation process 1. Basic template installation ⑴ The installation sequence is the same as the installation sequence ⑴ in Section 1 (2) Operation process. 　　⑵Nail the presser foot plate according to the basic ink line, and fasten the shaping template with U-shaped cards or connecting pins. 　　⑶Install the surrounding keels and supports, fix the position of the steel bars, and check that they are correct. 　　2. The column formwork installation ⑴ formwork procedure is the same as the ⑴ formwork procedure in the operation process of Section 1 (2). 　　⑵According to the position of the formwork in the column formwork design, install the formwork from bottom to top. Use wedge-shaped latches between the formwork to connect the two formworks at the corner position. 　　⑶Install post hoops: Column hoops can be made of steel pipes, shaped steel, etc. The column hoops should be designed and selected based on the column mold size, lateral pressure and other factors. Wall bolts can be added if necessary. 　　⑷Install tie rods or diagonal braces for column formwork: The tie rods or ejector rods on each side of the column formwork are fixed on the steel rings pre-embedded in the floor slab. Use blue bolts or adjustable bolts to adjust and correct the verticality of the formwork. The support points of the tie rods or ejector rods must be firm and reliable, and the angle with the ground should not be greater than 45 degrees. 　　3. Installation of shear wall formwork ⑴ Formwork setting and positioning → Place embedded parts in the formwork → Install (hoist) the formwork on one side → Install supports → Install door and window hole formwork → Bind steel bars and concrete (mortar) pads, insert wall bolts and casings, etc. → Install (hoist) the other side formwork and support in place → Adjust the position of the formwork → Fasten the wall bolts → Fix the support → Check and correct → Connect the adjacent formwork. 　　⑵Nail the presser foot plate according to the laying-out position, then assemble the formwork, and insert wall bolts and casings while installing. The specifications and spacing of the wall bolts should be clearly specified in the formwork design. 　　⑶For walls with door and window openings, it is advisable to install the formwork on one side first, and then install the formwork on the other side after the position line of the door and window opening is set. Before installing the formwork on the other side, the debris in the wall should be cleaned. 　　⑷Install the tie rods or diagonal braces of the wall formwork according to the formwork design requirements. Generally, diagonal braces can be added on both sides of the interior wall. If it is an exterior wall, tie rods and diagonal braces should be installed on the inside at the same time, and the flatness and verticality should be corrected while installing. 　　⑸After the formwork is installed, you should check whether the fasteners, bolts, and top braces are firm, whether the formwork joints and the bottom edge are tight, especially whether the formwork supports around the door and window openings are firm. 　　4. Installation of beam formwork (1) The installation procedure is the same as (1) in the operating process of Section 1 (2) of this chapter. 　　⑵Pop up axis lines, beam position lines and horizontal lines on the columns. 　　⑶The arrangement and spacing of beam supports must comply with the requirements of the formwork design and construction plan. Generally speaking, the spacing of adjustable steel supports ranges from 400 to 1000mm, depending on the keel arrangement. ； When using an adjustable mast support, the spacing is 600, 900, 1800mm, etc. 　　⑷Adjust the elevation of the pillars according to the design elevation, then install wooden beams or steel keels, lay the beam bottom plate, and pull wires for leveling. When the span of the beam bottom plate is equal to or greater than 4m, the beam bottom should be arched according to the design requirements. If there is no design requirement, the arching height should be 1‰ to 3‰ of the beam span. 　　⑸Horizontal tie rods and scissor braces should be installed between the support tops, and their vertical spacing should not be greater than 2m. If mast supports are used, cross rods should be used to connect the masts. If the floor height exceeds 3.8m, a separate roof rack erection plan must be formulated in accordance with the company's relevant regulations. 　　⑹If the support roof is supported on the base soil, the base soil should be flat and compacted to meet the bearing capacity requirements, and effective measures such as wooden pads or concrete pads should be added to ensure that the support roof will not sink during the pouring process of concrete. 　　⑺The formwork on both sides of the beam is connected to the bottom with a U-shape or pin through the connecting mold. 　　⑻When the beam height exceeds 700mm, beam-piercing bolts are added to the side formwork. 　　⑼The formwork structure of beam and column heads should be designed and processed according to the characteristics of the project. 　　5. The installation procedure for floor panel installation ⑴ is the same as the installation procedure ⑴ in Section 1 (2) of this chapter. 　　⑵The subfloor should be compacted and the baseboards should be laid. When using multi-layer support formwork, the support top should be vertical, the upper and lower support tops should be on the same vertical center line, and the vertical and horizontal stability between multi-layer supports should be ensured. 　　⑶The arrangement and spacing between the support tops and keels should be determined in the formwork design based on the concrete weight of the floor slab and the construction load. Generally, the support top spacing is 800~1200mm, the large keel spacing is 600~1200mm, and the small keel spacing is 400~600mm. Construction channels should be considered for the support top arrangement. 　　⑷Use the wire to adjust the height of the support top and level the large keel. 　　⑸When laying the formwork, you can start from one side, and use U-shaped clips to connect the side ribs between each two boards. The opening plate position can be connected with L-shaped pins. The distance between U-shaped clips should not be greater than 300mm. The clamping direction should be positive and negative, not the same direction. For joints less than 50mm, wooden boards can be used instead. If the SP─ formwork series is used, except that the formwork ribs laid along the periphery of the beam are connected with wedge-shaped latches, the formwork laid in the middle does not need to be connected with latches. The junction with the beam formwork can be connected with a bolt through a fixed angle form. The closing seam can be replaced by a wooden formwork or a special ruler formwork, but the seams must be tight. 　　⑹After the floor formwork is laid, you should check whether the pillars are firm and whether the U-shaped cards or pins connected between the formwork have fallen off or been missed, and then clean the floor. 　　6. Formwork removal ⑴ Column formwork removal: First remove the diagonal tie rods or diagonal supports, then remove the column hoops and pull bolts, then remove the U-shaped clips or pins connecting the formwork, and then use a crowbar to gently pry the formwork to separate the formwork from the concrete. 　　⑵Wall formwork removal: First remove the diagonal tie rods or diagonal supports, then remove the wall bolts and vertical and horizontal keels or steel pipe clips, then remove the U-shaped clips or bolts and other accessories, then use a crowbar to gently pry the formwork away from the wall, and pass the formwork down piece by piece for stacking. 　　⑶Removal of floor slab and beam formwork 1) First remove the adjustable upper brackets on the pillars * * , separate the generation dragon from the formwork, and lower the keel to the horizontal tie rod. Then remove all U-shaped cards or pins and accessories connecting the formwork, and then use a steel drill to pry the formwork so that the formwork block is lowered and supported by the generation dragon. Remove the formwork and generation dragon, and then remove the horizontal tie rods, scissor supports and pillars. 　　2) When removing the formwork, the operator should stand in a safe place. 　　3) When removing the lower support of a beam with a larger span, you should start from the middle of the span and remove it to both ends. 　　4) When the floor is high and double-layer racking is used for support, the upper layer of racks should be removed first so that the keel and formwork fall on the bottom layer of racks. After all the upper layer formwork has been shipped out, the upper layer of racks can be removed. 　　5) If an early-detachable formwork support system is used, the top support should be removed only when the concrete strength level reaches 100% of the design. 　　6) The removed formwork should be cleaned of adhesive materials in a timely manner, painted with release agent, and neatly stacked in categories. The removed fasteners should be managed in a centralized and unified manner in a timely manner. 　　3. Quality standards 1. Ensure that the project template and its brackets must have sufficient strength, stiffness and stability ； The supporting part should have sufficient supporting area. If it is installed on the base soil, the base soil must be solid and have drainage measures. 　　2. The width of the template joints in basic projects shall not be greater than 1.5mm. The surface of the template shall be cleaned and measures to prevent adhesion shall be taken. The cumulative area of ​​glue and missing isolation agent on the template shall be: Walls and boards should not be larger than 1000c ； Columns and beams should be no larger than 400c. 　　3. Allowable deviations. The allowable deviations for the installation of stereotyped combined steel formwork are shown in Table 4-1. 4. Construction precautions 1. Avoid common project quality problems ⑴ problems easily caused by column formwork: Column displacement and cross-sectional dimensions are inaccurate, the concrete protective layer is too large, the column body is twisted, and the beam-column joints have large deviations. Prevention methods: Before setting up the formwork, correct the position of the steel bars according to the ink line and nail the presser foot plate. ； Corner parts should use joint angle molds to ensure accurate angles ； The form, specification, and spacing of column hoops should be designed and determined based on the size and height of the column carrying surface. ； The beam-column joint formwork must be installed according to the large drawings and the connection must be firm. 　　⑵Common problems with wall formwork: The concrete thickness of the wall is inconsistent, the upper opening is too large, the wall is rotten, and the wall is not vertical. Preventive measures: The U-shaped clips or pins used to connect the formwork should not be too sparse. The specifications and spacing of wall bolts should be determined according to the design. Wall bolt sleeves should be installed on all walls except the outer walls of the basement. ； The keel should not be made of steel flower beams ； The diameter, spacing and spacer specifications of wall bolts must meet the design requirements ； Ties should be provided at the junction of wall beams and the top of the wall. ； The pull and top supports on the exterior walls must be strong and reliable, and the spacing and location of the supports should be determined by the formwork design. Before installing the formwork, a leveling layer of cement mortar should be applied to the bottom edge of the formwork to prevent leakage. 　　⑶Problems easily caused by formwork of beams and floor slabs: The beam body is not straight, the bottom of the beam is uneven, the sides of the beam are bulging, the size of the top of the beam is enlarged, the middle part of the board is bent downward, and honeycomb pockmarks appear. Preventive measures: There should be at least two connecting pins between the formwork below the beam height of 700mm. The beam bottom and beam side plates should be connected with connecting angle formwork. For side plates with a beam height greater than 700mm, wall bolts should be added. The size and spacing of the formwork supports should be arranged to ensure sufficient stiffness of the system. The bottom of the formwork supports should be on solid ground. If the beam span is greater than 4m, if there is no requirement in the design, it will be arched according to the specifications. 　　2. Main safety technical measures (1) Waste and rotten wooden beams cannot be used as keels. 　　⑵When installing and removing exterior wall formwork, you must confirm that the exterior scaffolding meets safety requirements. 　　⑶When the installation height of the inner formwork exceeds 2.5m, temporary scaffolding should be erected. 　　⑷When dismantling the formwork at an altitude of more than 4m, the formwork and materials must not be allowed to fall freely, nor must they be pried off in a large area at the same time. During the operation, attention must be paid to the movements of people below. ⑸ The roof of the floor below the floor slab that is being poured under construction is not allowed to be removed. 　　⑹When installing formwork for peripheral walls, columns and beams on the second floor and above, scaffolding or safety nets should be erected first. 　　⑺Horizontal pull rods are not allowed to be nailed to unstable objects such as scaffolding or springboards. 　　3. Product protection ⑴ When installing the formwork, holes must not be opened at will. The wall bolts should pass through the steel rings of the steel stiffeners or add wooden strips in the seams of the boards to install the wall bolts. One end of the reserved steel bar can be bent at 90° to be welded or tied firmly with the concrete wall steel bar, and the other end can be tied firmly with an iron wire. Pull it tightly from the seam of the board to the inside of the formwork, and then pull it out after removing the formwork. 　　⑵When the formwork is installed vertically, the concave surface of the stiffener must be installed downward. 　　⑶When removing the formwork, do not smash it hard with a sledgehammer or pry it hard with a crowbar to avoid damaging the formwork frame. 　　⑷During operation and transportation, the formwork must not be thrown. 　　⑸After each formwork is dismantled, it must be cleaned, coated with release agent, and sorted and stacked. 　　⑹When welding steel bars and other work on the formwork surface, it must be isolated with asbestos plates or thin steel plates. ； Effective measures such as pads should be added to the feet of the distribution frame for pumping concrete and the feet of the concrete pipe frame. 　　⑺If the removed template is found to be desoldered, deformed, etc., it should be repaired in time. Disassembled scattered accessories should be collected in boxes or bags.

Combined formwork foundation formwork and demolition column formwork. Combination formwork is a tool formwork, which is the most commonly used formwork in engineering construction. It consists of several types of plates, corner formwork, supports and connectors with a certain modulus (Figure 3-19). It can be used to create a variety of sizes and geometric shapes to adapt to the construction needs of beams, columns, slabs, walls, foundations and equipment foundations of various types of buildings. It can also be used to create large formwork, tunnel formwork and table formwork. It can be assembled directly on site during construction, or it can be pre-assembled into large block formwork or component formwork and then lifted and installed by a crane. The panels of the combined formwork are either steel or steel-framed wood (bamboo) plywood. Combined formwork is not only used in construction projects, bridge projects, and underground projects, but is also widely used. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-19.GIF a) b) Figure 3-19 Combined steel formwork a) plate ； b) Assembled pilaster formwork 1. Plate and corner formwork Block is the main component of the fixed combination formwork, which consists of frame, panel and vertical and horizontal ribs. Steel formwork users in my country mostly use 2.75-3.0mm thick steel plates as panels, 55mm or 70mm high, 3mm thick flat steel as vertical and horizontal ribs, and the frame height is the same as the vertical and horizontal ribs. The steel frame wood (bamboo) plywood formwork (Figure 3-20) consists of steel frame with replaceable wood plywood or bamboo plywood. The plywood is plastic-coated on both sides and treated with resin coating. All edges and holes are treated with effective sealing materials to prevent moisture absorption and deformation. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/PIC/3.2.2.jpg 　Shaped combined steel formwork http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-20.GIF Figure 3-20 In order to form the same series as the combined steel formwork, the steel-framed wood (bamboo) plywood formwork can be used simultaneously. The model and size of the steel-framed wood (bamboo) plywood formwork are basically the same as those of the combined steel formwork. However, due to the light weight of the steel-framed wood (bamboo) plywood formwork, the maximum length of the flat formwork can be up to 2400mm, and the maximum width can be up to 1200mm. Due to the large size of the slabs and few formwork joints, assembly and disassembly are efficient and the surface of the poured concrete is flat and smooth. The corner formwork and special-shaped formwork of steel frame wood (bamboo) plywood are formed by pressing steel. Its accessories are the same as those of combined steel formwork. The module size of the plate is related to the scope of use of the formwork, and is one of the basic issues in designing the final combination formwork. When determining, mathematical statistics should be used to determine the frequency of use of various sizes of the structure, fully considering my country's modular system, and making the weight of the largest size plate easy for workers to install. The lengths of combined steel formwork panels currently used in our country are 1500mm, 1200mm, 900mm, etc. The width of the plates is 600mm, 300mm, 250mm, 200mm, 150mm, 100mm, etc. Templates vary for each model. When designing the panels, if there is a gap of less than 50mm, use wooden squares to fill the gaps, and use nails or bolts to connect the wooden squares to the holes in the board frame. Since the panels and ribs of the combined steel formwork are welded, they are generally calculated as four-sided support plates. ； Depending on the welding condition of the vertical and horizontal ribs with the panel, determine whether they can be considered to work together with the panel. ； If the frame and panel are rolled at one time, the frame can be calculated as working together with the panel. In order to facilitate the connection between the panels, there are connection holes on the frame. The hole distance of the frame is 150mm in both the long and short directions, so that it can be spliced ​​horizontally and vertically. The hole shape depends on the connection piece. The connecting parts of the plate include hook bolts, U-shaped clips, L-shaped pins, and fastening bolts (tie rods). Angle formwork is divided into female and male angle formwork and connecting angle formwork. It is used to form the male and female angles of the concrete structure. It is also a connecting piece for two plates to be assembled into a 90° angle. Although the stereotype combination template has greater flexibility, it cannot adapt to every situation. For this reason, a small amount of wooden boards still need to be prepared on site to fill special parts. 2. Supporting parts The supporting parts include supporting beams (multipurpose steel pipes and cold-formed thin-walled steel) and diagonal braces that support the wall formwork. ； Support beams, support trusses and top braces of plate formwork, etc. Beams and plates are supported by beam brackets, support trusses and top supports (Figure 3-21). They can also be supported by multi-functional portal scaffolding. In bridge engineering, due to the large height, tool-type supports are often used for support. Beam brackets can be made of steel pipes or angle steel. There are many types of support trusses. Generally, whole-frame trusses welded by angle steel, flat iron and steel pipes or assembled trusses composed of two half-frame trusses are used. There are also telescopic trusses with adjustable span, which are more convenient to use. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-21.GIF Figure 3-21 Support of finalized combined formwork a) Support truss ； b)Steel pipe support ； c) Beam bracket 1—truss telescopic pin hole ； 2—Inner casing steel pipe ； 3—Sheath steel pipe ； 4—Latch hole ； 5—The adjusting bolt jack supports are made of steel casings of different diameters, which can be adjusted to various heights by pulling the casings. In recent years, a formwork quick-release system has been developed. Early-release column heads are set on the top of the top supports (Figure 3-22), so that the formwork can be removed early after the floor concrete is poured, while the top supports are still supported on the bottom of the floor. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/PIC/3.2.3.jpg 　Quick release formwork support system　 http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-22.GIF Figure 3-22 Early removal of stigma a) Wedge shape ； b) Bolt shape For monolithic multi-story houses, when supporting formwork in layers, the upper support should be aligned with the lower support and the pad should be laid. When using stereotyped combination templates, panel design is required. Since the formwork of the same area can be composed of various panel plans using plates and corner moldings of different specifications, panel design is to find the best combination plan. Before carrying out the panel design, first draw the expansion diagram of the structural components, and make the panel diagram of the component based on this. The specifications, location and quantity of the panels and corner molds to be matched should be indicated on the panel drawing.