How are wooden formwork supports held in place?

Guidelines for Wooden Formwork Construction I. Material requirements for formwork 1. Pine boards are used for foundation formwork, with the side panels of the floor beams having a thickness of 20 mm. 　　2. The formwork for the bottom of the main beams is made of pine boards, with a thickness of 40 mm; the formwork for columns and floors is made of manufactured wood panels (plywood), with a thickness of 12 mm. 　　3. The support system uses cedar logs, with a minimum diameter at the smaller end of 70 mm; tie rods are made from small square timber sized 400×500 mm, while the lower layer of the support system is composed of steel pipe supports. 　　4. Brittle wood, severely distorted wood, or wood that has deformed due to moisture should not be used for wooden formwork and support systems. 　　II. Formwork construction method for strip foundations (with ground beams) 1. Ensure the accuracy of the shape, dimensions, and relative positions of all parts of the concrete structure and components. 　　a. Fix 40×60 mm wooden strips vertically and horizontally on the side forms; the length of these strips should be consistent, while the spacing between them should be 1000 mm. In addition, supports should be placed on the outside of the short wooden strips and secured to the walls of the foundation trench, in order to ensure the accuracy of the shape, size, and position of the components. 　　b. Fixed internal dimensions of the component are achieved by using regularly sized wooden strips on the inside of the side formwork, with a spacing of 1000 mm. When the height of the foundation beam exceeds 700 mm, double-strand lead wire is stretched across the middle of the side formwork at intervals of 1000 mm to prevent the formwork from expanding. 　　2. It is necessary to meet the requirements regarding the strength, stability, and stiffness of the formwork: a) Use formwork pieces measuring 400×500 mm at the points where the inner wall of the foundation trench meets the supports, to ensure that the formwork has sufficient strength. 　　b. Fix the upper part of the foundation beam with 60×80 mm wooden strips to ensure sufficient stability of the formwork. 　　c. Fix wooden footings under the side formwork at intervals of 1000 mm (remove them after pouring) to ensure sufficient stiffness of the formwork. 　　3. It is necessary to ensure a simple structure that is easy to assemble and disassemble, facilitating steel bar binding and installation as well as concrete pouring and curing. 　　4. Ensure that the joints of the formwork are tight to prevent grout leakage. 　　III. Construction method for column formwork 　　1. Marking and leveling: Prepare a cement mortar leveling layer according to the elevation, place the fixing pier bases along the position lines, and mark out the edges of the columns. 　　2. Install the column formwork (insert rebar for binding and install embedded parts in the middle). 　　3. Install braces and clamps to correct the cross-sectional dimensions, and temporarily fix the position and elevation. 　　4. After adjusting the verticality of the formwork using a plumb bob, thetheodolite, etc., fix it firmly to the load-bearing frame and support system, and ensure that the entire formwork support system meets the required strength and stiffness standards. 　　5. Clean the column formwork thoroughly, seal the cleaning openings, and conduct a technical review and acceptance of the column formwork. 　　6. The frame slab of the short rectangular column consists of four side panels, column stirrups, and supports. Both the column and the surrounding side formwork use longitudinal formwork (nine-ply boards), and small square timbers are nailed at the bottom of the column formwork to serve as a fixing mechanism for it. 　　7. At the junction of the column top and the beam, a notch should be created; the dimensions of this notch are its height and width. Shims should be fixed on both sides of the notch as well as at its bottom. The distance between these shims and the edges of the notch corresponds to the thickness of the side panels and the bottom plate of the beam. To prevent the formwork from bulging or deforming during concrete pouring, wooden braces should be installed around the column formwork. The distance between these braces should be determined based on the spacing of the column formwork itself, typically ranging from 400 to 600 mm. The spacing should be smaller near the bottom of the column formwork, and it can gradually increase as one moves upward along the column. 　　IV. Construction Method for Formwork 　　1. Selection of slabs and supports: Slabs are made of nine-ply plywood, while the studs are 60×80 dimension lumber. The supports are wooden, with a minimum diameter of 70 mm. Horizontal supports are made of 400×500 dimension lumber, and the bottom part of these supports is covered with 20 mm thick plywood. 　　2. Load calculation: 　　① The self-weight of the formwork is 0.3 KN per meter ； 　　②, concrete weight 2.4KN ； 　　③, rebar weight 0.2KN ； 　　④, the construction load is 1 KN per meter ； 　　⑤The load generated by vibrating concrete is 0.2 KN ； 　　⑥The load generated by pouring concrete is 0.5 KN ； 　　⑦The cumulative load is 4.6 KN/m. 　　The support is made of round logs with a diameter of 70 mm, spaced 800 mm apart; the vertical columns used for support are square timbers measuring 60×80 mm, designed to bear the vertical loads transmitted from the formwork between the two support columns. 　　a. Strength verification formula: 　　After calculation, the support area is 3848 mm2, which is greater than 3050 mm2, satisfying the requirements. 　　b. Stability check formula: It is not considered for floor heights of 4m or less. 　　3. Floor formwork erection 　　①、Construct the load-bearing frames and support systems of the required height based on the floor elevation; once it has been confirmed that the elevations of these frames and support systems are correct and that they are stable, lay down the grating and the bottom formwork. 　　②The axis of the spring, the edges of walls or columns, as well as the crosshairs indicating the locations of embedded components – if any errors are found after verification, formwork is set up, rebar is tied in place and embedded (or pre-embedded), followed by assembly, fixation, and final inspection. 　　③Conduct technical reviews and inspections of concealed works. 　　V. Construction Method for Beam Formwork 　　1. Selection of beam formwork and supports: The formwork for the bottom of the beam is made of nine-ply plywood, while the studs are 60×80-sized timber pieces. Wooden supports are used, with a minimum diameter of 70 mm at the smaller end; horizontal supports are made from 400×500-sized timber pieces, and the bottom of these supports is covered with 20 mm thick wooden planks. 　　2. Load calculation: 　　① The self-weight of the formwork is 0.35 KN per meter ； 　　②, concrete weight 3.6KN ； 　　③, rebar weight 0.4KN ； 　　④, the construction load is 1 KN per meter ； 　　⑤The load generated by vibrating concrete is 0.2 KN ； 　　⑥The load generated by pouring concrete is 0.5 KN ； 　　⑦The cumulative load is 5.6 KN/m. 　　The support is made of log supports with a diameter of 70 mm, and the spacing between them is 900

Wooden formwork: Wooden formwork and plywood formwork are still widely used in some construction projects. Such templates are generally in a loose, disassemblable form; some are also manufactured as basic components (panel assemblies) that are assembled on-site, and can be reused after being dismantled. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/PIC/3.2.1.JPG Wooden formwork: The panels are assembled from various strips fastened together with screws (while plywood formwork uses solid pieces of plywood). The thickness of these strips is generally between 25 and 50 mm, and their width should not exceed 200 mm, in order to ensure uniform gaps during drying and to facilitate tight sealing after watering. However, the width of the slats on the bottom slab of the beam is not restricted in order to reduce grout leakage. The spacing of the strips (small ribs) in the laminated slab depends on the lateral pressure of the freshly poured concrete and the thickness of the slats, usually ranging from 400 to 500 mm. The structure and support methods for wooden formwork used in civil engineering construction are as follows: 1. Foundation formwork – When installing the foundation formwork, it is necessary to ensure that there is no relative displacement between the upper and lower formworks (Figure 3-14). If there is a cup mouth, a cup mouth template also needs to be placed inside it. http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-14.GIF Figure 3-14 Trapezoidal foundation template 1—Panel assembly ； 2—Diagonal bracing ； 3—Pile ； 4—Wire; 2—Column formwork. The panels of the column formwork are connected using joints, with two panels facing each other to form a rectangle. To withstand the lateral pressure of the concrete, column stirrups must be installed outside the paneling; their spacing depends on the lateral pressure of the concrete and the thickness of the paneling, which is why the stirrups at the bottom of the column formwork are more densely spaced. The bottom of the column formwork is equipped with cleaning holes, and pouring holes are provided every approximately 2 meters along its height. A wooden frame is generally provided on the concrete at the base of the column to fix the position of the column formwork. Notches for connecting to the beam formwork can be provided at the top of the column formwork as required (see Figure 3-15). http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-15.GIF Figure 3-15 Column template 1—Inner panel ； 2—Outer paneling ； 3—Column hoop ； 4—Beam notch ； 5—Cleaning hole ； 6—Bottom wooden frame ； 7—Cover plate ； 8—Tighten the bolt ； 9—Splicing strips 3. Beam and floor formwork: The beam formwork consists of a bottom formwork and side formworks. The bottom formwork bears vertical loads; it is generally thick and supported by supports (or trusses) beneath it. The supports are usually telescopic and adjustable in height; they should be placed on solid ground or a floor surface, with wooden wedges under them. If the ground is soft, wooden planks should be placed under it. In the construction of multi-story buildings, the supports of upper and lower floors should be on the same vertical line; otherwise, measures must be taken to ensure that the load from the upper supports can be transferred to the lower supports. Horizontal and diagonal tie rods should be used to secure the supports together, in order to enhance overall stability. When the height between layers is greater than 5m, truss formwork or multi-layer formwork is recommended. When the beam span is 4m or more, the bottom formwork should be arched. If there are no specific specifications in the design, a value of 1/1000 to 3/1000 of the structural span can generally be used; a larger value can be adopted for wooden formwork, while a smaller value is suitable for steel formwork. The formwork on the sides of the beam bears the lateral pressure from the concrete; it is held at the bottom by strips nailed to the top of the supports, while the top can be supported by the grid of the formwork for the floor slab, or by diagonal braces. Floor formwork is usually made of prefabricated forms or plywood; it is placed on a grid, which in turn is supported by crossbeams outside the side formwork of the beams (Figure 3-16). http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-16.GIF 　　　　　　　　　　　　　　　　Figure 3-16 Beam and floor formwork 1—Floor formwork ； 2—Side formwork of beam ； 3—Grid ； 4—Transverse rib ； 5—Clamp strip ； 6—Minor rib ； 7—Supporting the laying of floor formwork: http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/REAL.JPG The wooden formwork for bridge piers and abutments is shown in Figure 3-17. Piers and abutments generally taper upwards; their formwork consists of inclined surfaces and inclined conical surfaces, and is made up of paneling, struts, columns, supports, tie rods, etc. The uprights are placed on the foundation pillow beams, and steel tie rods are used at both ends to keep them tight, thereby ensuring the stiffness of the formwork and preventing any displacement. Struts (linear or arch-shaped) are fixed to the uprights, while the wooden panels are arranged vertically on top of these struts. If the bridge piers are tall, diagonal braces, cross braces, and cables must be added (Figure 3-18). http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-17.GIF Figure 3-17 Bridge pier formwork 1—Arch ribs ； 2—Pillar ； 3—Panel ； 4—Horizontal crossbeam ； 5—Tie rod: http://www.scutde.net/t14courses/1412-efmdljiaif/hunningtu/3.2/IMAGE/%CD%BC3-18.GIF Figure 3-18 Measures for stabilizing the pier formwork 1—Temporary braces ； 2—Cable