1. 1 The core problem in the construction of assembled concrete structures. The core difficulty in the construction of assembled concrete structures lies in the on-site assembly construction. There are many uncertain factors in site construction, and there are many kinds of precast concrete structural members. In order to successfully complete the established quality, safety and construction period, it is necessary to effectively manage the construction site, especially the core technology management of on-site construction. 1. 1. 1 It is difficult to manage the transportation and stacking of assembled concrete structural members, which is one of the difficulties in the construction of assembled concrete structures. On-site stacking supports for walls, beams, plates, etc. Safety calculation and analysis are needed to ensure the stability and safety during stacking. 1. 1.2 The hoisting risk of assembled concrete structural members is high, and a large number of hoisting machines are needed in the construction process of assembled concrete structural members. Because the hoisting height and weight are relatively large, and the shapes of some components are complex, higher requirements are put forward for hoisting construction. Unreasonable selection of hoisting position may affect the construction of the project and the safety of workers' operation. 1. 1.3 It is risky to install temporary supports on the site of assembled concrete structural members. After temporary hoisting, the assembled concrete members are in a dangerous stress state before pouring concrete at the joints. In order to ensure the safety of the whole construction process and reduce the abnormal stress and deformation of the members, it is necessary to set up temporary supports before the concrete pouring of the joints. However, if the support is not firm, it will bring great security risks to the workers' operation and serious consequences to the engineering construction. 1. 1.4 it is difficult to waterproof the external wall panel of assembled concrete structure. The flat joint external wall panel of assembled concrete structure is an important waterproof weakness of assembled building. If the construction quality here can't be guaranteed, the problem of external wall leakage will occur. 1. 1.5 It is difficult to assemble and locate the members of precast concrete structures. For prefabricated buildings with high prefabrication rate, there are many kinds of on-site components, and whether the components can be positioned and installed well will affect the appearance and mechanical properties of the structure. It is very difficult for mechanical equipment to install and locate various prefabricated components in engineering. 1. 1.6 On-site construction safety risks There are many mechanical equipment in the construction site, and there are great personal safety risks in the process of tower crane operation, temporary scaffolding and component installation, so it is of great significance to formulate effective management and measures for safe and civilized construction. 1.2 On-site construction supervision control points The main risks of the construction site are construction quality and safety. The risk sources of construction safety exist in various construction processes and non-construction processes, such as the use safety of water and electricity, the protection safety of various holes, and the construction safety of large mechanical equipment. These risks can generally be effectively controlled by taking measures and strengthening management. The following will focus on the analysis of supervision and control points related to the construction of assembled concrete structural members. 1.2. 1 The stacking of precast concrete structural members on the construction site has a great influence on the construction progress. If the components are stacked reasonably, the tower crane construction is simple and the components are easy to assemble, the construction progress can be greatly accelerated. In addition, the reasonable stacking of components is also conducive to the safety management of on-site construction. 1.2.2 the hoisting of hoisting components of assembled concrete structures requires professional hoisting personnel and strict construction procedures to locate the components, so as to avoid the long stagnation time of the components in the hoisting process and pose a threat to the safety of construction personnel and the construction period of the structure. In addition, when hoisting components, the selection of hoisting points is extremely important, and the wrong selection of hoisting points will cause damage and overturning of components during hoisting. 1.2.3 temporary support members cannot be installed at one time after hoisting in place, so temporary support fixed structures need to be set up, and temporary construction scaffolding needs to be set up for the cast-in-place section of prefabricated buildings. These structures belong to the lifeline of construction, involving casualties and construction quality, and the stability and strength of temporary supports must be guaranteed. 1.2.4 During the installation of positioning members of assembled concrete structural members, due to different sizes of members or different hoisting schemes, it may be difficult to accurately install the installation positions and connection gaps of each member, and it is difficult to operate auxiliary positioning installation tools or instruments. 1.2.5 After construction, prefabricated external walls of prefabricated buildings with waterproof and impervious structures basically adopt prefabricated components. However, the positioning and installation of prefabricated components on site are uncertain, and inaccurate positioning will lead to cracks in the structure. It is technically difficult to try to deal with the connection with relevant construction methods. 2 Precast concrete structure construction supervision countermeasures 2. 1 personal safety management measures 2. 1. 1 Applicability and regular maintenance of machinery and equipment In order to ensure the safe operation of large-scale machinery and equipment, in the construction process, the construction unit should first ensure that the machinery and equipment used in the construction site are in good condition. Large-scale machinery and equipment in a "sick" state, such as the lack or failure of safety devices, shall not enter the construction site. After the large-scale mechanical equipment comes into play, the construction unit shall make a written disclosure of the construction tasks and safety technical measures to the mechanical equipment operators. 2. 1.2 The hoisting of hoisting components is the main construction process of prefabricated buildings, and the hoisting construction belongs to a partial project with greater danger. According to past experience, the following technical measures can be taken. (1) In order to ensure the safety of hoisting, the position of lifting point and the safety of spreader should be designed and checked. The lifting point must have sufficient strength and rigidity, and the spreader such as sling must also meet the relevant hoisting strength requirements. (2) The crane driver must be experienced. During the hoisting process, there must be at least one hoisting commander at the site to conduct hoisting command, and all personnel must hold relevant certificates. (3) The area affected by hoisting must be temporarily isolated from other areas. Non-operators are forbidden to enter the lifting operation area, and lifting operators must wear safety protection articles according to regulations. 2. 1.3 Safety of construction electricity, strengthening the management of standardized safety boxes; Effectively implement repeated grounding and protective grounding (zero) measures; Standardization of lighting facilities in construction site; Standardization of cable laying in construction site; Strengthen the education and training of welders, electricians and other special operators; Educate all construction personnel on safe use of electricity, and be familiar with the basic common sense of safe use of electricity. 2. 1.4 limb protection and stair setting (1) railings are set on the edge of the structure with foot pipes, and the enclosure is made of safety green net, and the corresponding warning signs are made of red and white paint. (2) Protective railings should be set on both sides of the ladder climbing passage, and the erection height and spacing should comply with relevant codes and standards. (3) The channel shall be laid with scaffolding and firmly fixed. (4) Stair protection conforms to safety protection standards, scaffolding is proposed, and the gradient of stairs should meet relevant requirements. It is forbidden to build steep stairs when conditions permit. 2.2 construction technology risk management measures 2.2. 1 temporary support system layout The temporary support system can adopt special portal support, and the upper part of the support adopts section steel as the stress piece, and sleepers are prohibited. Support spacing and step distance should be calculated safely and reported to the supervision unit for review before implementation. All supports must be accepted when they enter the site, mainly the corresponding quality assurance documents, component wall thickness and appearance quality. The temporary support frame at the lower part of the fabricated concrete structural members shall be arranged in strict accordance with the scheme, and the support frame shall be tightened in time after the members are hoisted in place. As the supporting point, the steel beam at the upper part of the support frame needs to be reliably connected with the support frame. The removal of the support frame should be carried out after the strength of the cast-in-place concrete in the upper overlapping part meets the design requirements. In the process of erection, the support frame must be operated in strict accordance with the specifications, and barbaric operation and illegal operation are strictly prohibited. 2.2.2 Stacking management of assembled concrete structural members In order to avoid the secondary handling of the components entering the site affecting the construction progress, it is necessary to manage the stacking of solid components, improve the numbering rules of components, and track and manage the components; For the components entering the site, they should be numbered in time according to the pre-established numbering rules, and the stacking area should be reasonably divided according to the construction progress plan, so that the stacking of components is consistent with the relevant hoisting plan. Assembled concrete structural members should not be in direct contact with the ground when stacked, but should be placed on wood or soft materials. When precast columns are stacked, the height shall not exceed two floors, and the ends shall be padded with wood between 0.2L and 0.25L.. Before lifting, the upper column should be translated to the ground. When large and small beams are stacked, the height shall not exceed two floors. Solid beams need to be padded at a distance of 0.2L~0.25L from both ends, and thin-shell beams need to be padded at the solid part of the beam to avoid the stress on the thin-shell end. The stacking of KT boards should not be tilted, and should not exceed 4 pieces. When stacking, the wood should be padded between 0.2L and 0.25L from both ends, and the floor should have sufficient strength. The stacking of external wall panels adopts the principle of A-frame, and it must be bound with safety plastic belts or fixed with steel cables when stored for a long time. When the wallboard is stored vertically, it must be considered whether it can not shake up and down and whether it is stable during the earthquake. 2.2.3 Waterproof and seepage control technology management Waterproof and seepage control of prefabricated buildings is a control difficulty in the construction process. In order to ensure the overall waterproof performance of the structure, waterproof joints should be designed reasonably in the design stage. Usually, the joints can be filled with waterproof modified silica gel on the outside, embedded with waterproof rubber strips on the inside, and a polyurethane waterproof joint is added on the inside of the cross joint of wallboard. At the same time, it is necessary to further optimize the detailed structure of wallboard, for example, water guide and drainage measures can be set at the flat-fell seam, or tongue-and-groove structures can be set at the flat-fell seam of upper and lower plates to prevent water from entering the interior from the outside. Secondly, the quality control of waterproof construction should be strengthened in the construction process to ensure that the quality of waterproof construction meets the relevant requirements of design documents. 2.2.4 Safety management of component hoisting Before hoisting prefabricated concrete structural components, the construction unit must prepare a special hoisting safety plan and report it to the supervision unit for approval. During hoisting, all relevant operators must hold relevant certificates, and all equipment has been tested and is within the validity period. After the components enter the site, the supervisor shall timely check and accept them, focusing on the location of lifting points to ensure that the lifting points meet the lifting requirements. During the whole hoisting process of components, the supervisor shall regularly check the steel wire rope for hoisting. If damage or wear is found, the construction unit shall be required to replace it in time. When hoisting the component, the operator may consider setting a pull rope to control the direction of the component during hoisting. In addition, the supervisor needs to require the construction unit to carry out special disclosure before hoisting operation and special disclosure before daily operation to ensure that the technical level and safety ability of on-site construction personnel meet the requirements. Conclusion The above is an introduction to the key points and countermeasures of construction supervision and control of assembled concrete structures. If you want to know more about it, please visit Zhong Da Consulting.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd