Column formwork is the most important part of a concrete structure, because the columns are connected to the ground and bear a lot of pressure to transfer the forces on the building and structures. Being careful in implementing the details of the concrete column formwork will increase the resistance of the building during an earthquake, which includes reinforcement, molding and concreting. The column concrete formwork consists of two parts, which include the wall of the formwork and the coil, and it is important to use a combination of rebar and concrete formwork to increase the strength of the formworks. Usually, the operation related to the column formwork is done after the reinforcement stage. In the column form, the general attitude is based on the highest part of a column, which is called the head form, and this form is also called the concrete head form.
The design of each side of the column template in the final section is required to support the column itself. The three main forms of capitals that exist in all ancient capitals are that they may be convex, concave and can also be scrolled. Column molding can be implemented using metal column formwork, metal concrete formwork, planking, plywood and other models, and it is better that the height of the corners and modular in a cylindrical formwork is not the same, for example, the height of the panel is less or more than The height of the corner is to prevent the columns from twisting. Of course, warping is one of the results of the column formwork, and to fix this defect, the sides of the clamps must be changed one at a time, or tension must be applied to the clamps in opposite directions.
This type of column formwork has a wide range and variety, which is used for the purpose of concreting light and semi-heavy prefabricated objects in larger circulations. It is also possible to build colonies and perform several of its types with the provision of moving chassis and also CLC packs. All of these structures include types of table, canyon, flower box, waffle, prefabricated block, tetrapod, reinforced prefabricated bases and foundations, which, despite the modern methods of machine injection in some of the above types, still have the advantages of using the formwork. The concrete box leads many to prepare and use them. For columns with a circular cross-section, a round metal formwork is used, and for columns with a large diameter, an arched column formwork is used.
Formwork is used in different parts of concrete construction. Walls, foundation, stairs, columns are some parts of the building that are made using different formworks. Molding of columns is usually done through wooden or metal formworks.
Various types of wooden formworks made of sawdust, timber and boards are less used today and are usually used in small jobs with little importance. The wooden headboard formwork has a shorter lifespan than metal formworks, but they are very flexible in cases where molding is difficult. Wooden planks are typically 2.5 to 3 cm. The number of nails used in molding work is usually 28 and 65, that is, the diameter is 2.8 mm and the length is 65 mm, and 25 and 50 nails can also be used for narrow and small diameter boards.
The reasons for using wood to formwork concrete columns as a wooden column formwork include the following:
Excellent speed in execution, the possibility of multiple use, durability and fire resistance are among the advantages of using this type. If the panels are distorted, it causes instability and due to the chemical reaction of the inner surface of the aluminum tubes with cement, they produce hydrogen gas and reduce the quality of cement, which can reduce the strength of concrete by 50%. Column formwork with a width of 10-15-20-50 cm and the standard length of these formworks is 1 meter, 1.5 meter and 2 meter. Column moldings are often prepared in the dimensions of (5*5) – (5*10) and (10*10) cm, and the length of the corners is usually 1.5 meters because the corners do not fall in front of the seams of the formworks.
Types of molding with concrete metal column formwork:
In the implementation of double-sided wall molding, the speed of molding increases 1.5 times compared to one-sided wall (that is, 15 square meters of professional molding per person per day), and in molding the head of the column by the column formwork, this figure reaches up to 1.5 square meters per day. In addition, the time spent for disassembly is almost half of the assembly time. All the mentioned cases are in the case of using the modular form, which in case of using the large panel form, the execution speed is high (per person about 25 square meters per day) and the quality of the executed concrete will be much higher than the modular form.
In addition to the type of molding, the location and location of the building and having facilities including tower cranes and cranes are also effective at the time of molding. Each expert formwork can perform 20 square meters daily, formwork of foundation and columns with column formwork. This amount will increase by 1.5 times the speed of molding for molding one-sided and two-sided walls and will reach up to 1.5 square meters per day.
After the implementation of the foundation with the reinforcement of the columns, they start the implementation of the concrete skeleton. Concrete columns are specially executed in square, rectangular and sometimes circular sections by the column formwork. Reinforcements play an effective role in guiding concrete structures, absorbing energy, increasing tensile strength and ductility, and preventing the increase of cracks. Naturally, the structure changes its shape with the application of lateral and gravity forces, which in areas with tensile stress, the role of reinforcements can be very sensitive and effective. Each reinforcement is designed according to its shape and location to deal with bending, shearing, tensile stresses or their combination.
Molding of the columns is done with a wooden or metal formwork up to the size of the ceiling. Today, the use of metal column formworks is more common due to the speed of implementation, greater strength and quality. Wooden formwork is used in small and low importance projects where after lubrication with diesel or burnt oil, metal forms are regularly installed in place according to the desired column width and locked together by steel pins and wedges. be.
The important factor in column formatting is that due to the possibility of the floor not being level, the final level of the columns must be determined using a leveling hose.