Traditional formwork construction methods generally use large steel formworks to support and dismantle the whole structure, or use small steel formworks to support and dismantle the structure. When using large steel formworks for construction, because today’s houses pay great attention to the shape and decorative effects of the exterior walls, the facades are more varied, which makes the processing of large steel formworks time-consuming, labor-intensive and material-intensive, and the construction cost rises sharply. In addition, large steel formworks cannot be separated from tower cranes during installation, correction and removal. In addition, large steel formworks need to occupy a large construction site during turnover, which makes it difficult to use large steel formworks for projects with narrow construction sites. When using small steel formworks to support large walls, not only is the labor intensity high, but also the surface flatness of the concrete wall does not meet the specified requirements due to the difficulty in correction and reinforcement. This article introduces a new method for the construction of fully cast-in-place frame-shear structure formworks that is economical, practical and highly operable – the construction method of film faced plywood, through an engineering example.
1.Project Overview
This project is the Qingdao North Locomotive Depot Operation and Maintenance Complex Building Project, with a construction area of 2784㎡. The project adopts a frame-shear structure, with a total building height of 21.62m, a standard floor height of 3.3m, a total of five floors, a total length of 42.5m, and a width of 13.1m. The foundation form is reinforced concrete precast piles; the foundation burial depth is 2.2m. The filling wall uses aerated concrete blocks, and the masonry mortar grade uses M5 mixed mortar; the foundation masonry is MU10 sintered ordinary bricks, and the masonry mortar grade uses M5 cement mortar; the frame column and beam concrete strength grades are C35 and C30, and the rest are C30; the interior walls are painted with cement and mixed mortar spray paint; the exterior walls are painted with latex paint; the roof is a high polymer modified asphalt waterproof membrane roof, the windows are plastic steel sliding windows, and the doors are wooden doors. The floor is terrazzo. The service life of this project is 50 years. The building safety level is level 2, the seismic fortification crack degree is six degrees, and the frame seismic level is level 4. This project is adjacent to Qingdao Port Station, with existing railway traffic on the south side and existing factory roads of Qingdao North Locomotive Depot on the north side. Due to the narrow construction site, after the arm tower crane is arranged in the north-south length direction, it will seriously affect the safety of the existing traffic line and the operation and production of the factory area during operation. Through the active coordination of the construction unit, the locomotive depot agreed to the construction unit to set up a tower crane on the east side of the building. Due to the unsatisfactory position of the tower crane, it is difficult to use a large steel formwork for hoisting. After many considerations, it was decided to adopt the construction method of light-weight and efficient laminated bamboo plywood formwork.
2.Materials and equipment
The formwork is made of coated bamboo plywood, and the support system uses tool-type quick-detachable steel pillars. The rest of the materials and equipment are the same as general formwork projects.
The coated bamboo plywood has moderate density, a smooth surface, low water absorption, and is not easy to deform. It can be used in engineering projects that have high requirements for the wear resistance and turnover of the formwork. It is an economical and practical building formwork. The coated bamboo plywood has a large format and few joints. The basic size is 2440mm×1220mm, which is equivalent to 6.5 pieces of P3015 steel formwork. It can reduce the labor for installation, and the formwork is quickly removed, the concrete surface has a good appearance quality, and it can be poured with plain concrete, eliminating the plastering work on the concrete surface, shortening the decoration construction time, and speeding up the construction progress.
The coated bamboo plywood is light in weight and easy to install. Its adsorption force on concrete is only 1/7-1/8 of that of steel formwork, making it easy to demould. It has good thermal insulation performance. The thermal conductivity of the coated bamboo plywood is 0.17W/(m.K), which is 1/360 of that of steel formwork, much smaller than that of steel formwork, which is beneficial to the thermal insulation of concrete during winter construction. The coated bamboo plywood can be used on both sides. Under the current management level in my country, it can be reused more than 30 times, with obvious economic benefits.
3.Construction technology
3.1 Principles of panel matching
According to the specific size requirements of the construction drawings, the top plate template uses a 2440×1220mm whole board as the panel matching unit, and the unfitted parts are supplemented with laminated bamboo plywood of appropriate size.
3.2 Joint treatment
The size deviation of the template that does not conform to the basic size modulus should be controlled within +0, -2mm to ensure that the template can be assembled correctly. In order to ensure that the joints between the templates are tight and do not leak, sponge strips with self-adhesive glue should be attached to the gaps.
3.3 Construction Methods
At the intersection of formworks in different planes, sealing construction methods are adopted according to different situations to ensure that the lines and angles of the nodes of the concrete are clear, neat and beautiful after the formwork is removed.
3.4 Formwork splicing method at beam-column joints
The beam-column joint splicing method is: the beam side formwork and beam bottom formwork are inserted into the column formwork by one formwork thickness, and lining square wood is nailed at the intersection of the beam side formwork and beam bottom formwork with the column formwork.
4.Process flow
Laying out the lines, screeding the bottom and leveling the layer, supporting the template on one side of the inner horizontal wall, fixing the template for doors and windows, and pre-embedded parts for water and electricity, laying of wire pipes and wire boxes, etc., concealed acceptance, and the template on the other side of the horizontal wall, the template for the inner vertical wall, the template for the inner side of the outer wall, the template for doors and windows, and pre-embedded parts, etc., fixed, concealed acceptance, supporting the outer side of the outer wall, pre-inspection of the wall template, supporting the top plate template, pre-inspection of the template, lower process
5.Several Discussions on the Construction Method of Film faced Plywood
The above uses a project example to illustrate the specific method of using film-coated bamboo plywood for the construction of a fully cast-in-place frame-shear structure. Film-coated bamboo plywood has been widely used in the engineering practice of concrete top slabs in recent years, but it is rarely used in fully cast-in-place frame-shear structures, and there are still some areas for discussion.
5.1 The rigidity of the coated bamboo plywood is poor, which leads to the use of more steel pipes and matching tension bolts and butterfly clips when reinforcing the formwork, and more turnover materials are used.
Advantages of bamboo plywood over wooden formwork 1. High strength and good toughness. The static bending strength of bamboo plywood is equivalent to 8-10 times the strength of wood and 4-5 times the strength of wood plywood, which can reduce the number of formwork supports used. 2. Wide format and few joints. A bamboo plywood is about 3 square meters, and a commonly used wooden formwork small board is about 1.67 square meters. Fast demolding speed, simple installation and easy maintenance. 3. Smooth surface and easy demolding. The adsorption force of the surface of the coated bamboo plywood on concrete is only one-eighth of that of the steel formwork. After demolding, the concrete surface is flat and smooth, and the plastering operation can be cancelled, shortening the construction period of the decoration operation. 4. Good water resistance, anti-corrosion and anti-insect. The bamboo plywood will not debond after being boiled in water for 3 hours, and will not deform when exposed to water and moisture during the concrete curing process.
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