Construction of Long-span Steel Space Frame Membrane Structure (Part 2)

4.2 Implementation plan for large-span steel space frame membrane structure

4.2.1 Construction flow and procedures

After the working environment and working conditions at the construction site meet the requirements, the owner unit must coordinate and manage the installation and construction, actively organize all units to participate in it, and carry out the construction of each construction area according to the key points and characteristics of the tool project during construction. Reasonable division, and at the same time, independent and parallel construction operations should be carried out under the unified management and deployment of the project. The fundamental purpose of this is to avoid more energy and resource consumption. The construction procedure is in accordance with the process of detailed design, procurement of materials, in-plant processing, construction site installation operations and final completion acceptance.

4.2.2 Division of different construction sections

In the early stage of construction, a series of preparatory work must be done in advance, enter the construction site to determine the site, and ensure that all preparatory work is implemented, especially in terms of surveying and laying out, construction personnel and equipment arrangements. It is well configured in advance to lay a good foundation for the orderly development of subsequent construction. The quality control of measurement and setting-out has always been the top priority in this link. It is necessary to carry out unified coordination and management at the construction site. After the basic positioning of the axis is determined, it is directly handed over to the person in charge for confirmation and management. In the installation process of embedded parts, the bolts are positioned in advance in strict accordance with the requirements in the drawings, and the installation process is carried out according to the requirements of the axis to ensure parallelism and flatness and reduce errors as much as possible. At the same time, positioning bolts and fixing parts must be processed, installed in strict accordance with the size requirements, and reinforcement measures must be taken to ensure parallel, flat and firm effects. During the actual construction, attention should also be paid to the construction process of the purlins. On the channel steel purlins, the construction personnel must ensure the fixing of the lap bolts of the membrane cloth, and then weld the edges. When installing the membrane structure, it is necessary to strictly follow the current standardization requirements of the entire industry, put the requirements in the drawings in the first place, effectively promote according to different steps, and strengthen the control of the installation quality. In the final acceptance process, the protection of the finished product must be done well.

4.2.3 Application of membrane body processing and production scheme

Inspection materials: All materials entering the construction site must be carefully inspected, and the inspection results must also be documented. During the inspection process, it is necessary to inspect any material in contact with the membrane material, including non-contact materials if necessary. Usually these materials include membrane materials, joint buried ropes, clamp splints, tension steel cables, various auxiliary parts, such as sewing threads, wear-resistant liners, cable straps, etc. In the material inspection process, it is usually composed of appearance, size, material performance and data inspection. It strictly follows the prescribed standard requirements and rules and regulations to ensure the orderly development of inspection work and provide guarantee for material quality.

Cutting design : Combined with the construction requirements of this project, mainly membrane materials, so the loss of membrane materials is generally relatively large. In order to achieve reasonable cost control, we must be aware of the importance of controlling the loss of membrane materials. The loss of the material will be directly affected by the cutting plan, so it is necessary to ensure the pertinence and effectiveness of the cutting plan when it is compiled and applied. Combined with the requirements put forward in the design of the membrane body of the current engineering project, properly refer to the past processing experience, and try to choose and optimize the layout of the weld seam of the membrane body.

Membrane material blanking : Combined with the requirements of the design documents, design a 1 : 1 planar model of the membrane in the professional processing software, and typesetting and cutting each membrane on the rolled membrane material in the software. Transfer the design file to the self-cutting machine, automatically cut the diaphragm, and perform retesting after cutting to ensure the accuracy and reliability of the retesting results.

Diaphragm pre-positioning : Only the diaphragms that have passed the inspection of the quality inspection department can enter the pre-positioning process—this is the first step of inspection that must be carried out before pre-positioning. There are three types of pre-positioning : connection pre-positioning, hemming pre-positioning and local cutting enhancement. Before pre-positioning, use an alcohol knife to overheat the diaphragm and the back-adhesive border to ensure that there are no burrs and roughness on the border. The pre-positioning work is the preparation stage for the connection process. Pre-positioning uses a portable welding machine for pre-positioning “false welding”. When pre-positioning, the start point and end point of the two parts of the diaphragm must be consistent at the same time. During the pre-positioning, the stress of the two parts of the diaphragm should be ensured to be uniform, so as to ensure that no one diaphragm is pulled or a certain film is pulled. The phenomenon that the sheet is bent. If the continuous pre-positioning length is very long, the middle positioning starting point should be set on the two parts of the diaphragm at the same time to ensure uniform positioning. In principle, a positioning starting point must be set every 3m. In addition, the 3S glue used in the pre-positioning process is a dangerous product, so the relevant operating procedures must be followed to avoid hidden dangers.

Diaphragm connection : When the diaphragm is connected, it is usually composed of different types of welding, bonding, mechanical connection and seaming. In the construction of this project, the welding process is used. Before the film is connected, the welding test must be done in advance, and the test results must be carefully recorded. Strictly follow the basic operation process and determine the number of the membrane plate and parameters such as corners and corners according to the processing procedures. During the welding process of the membrane material, the welding temperature on the thermometer should be paid attention to at all times and recorded well, and the stability of the welding temperature must be ensured. When the temperature setting is not suitable, the operation should be stopped immediately, report to the equipment management to repair the defective part, and reconfirm the welding quality after the repair is completed. In addition, during the welding process, the pressure on the welding cloth knife directly determines the strength of the membrane body after welding, and it must be ensured that the pressure is stable and meets the requirements ; if any pressure changes are found during the operation, the welding must be stopped immediately and Report to the equipment management for maintenance, and reconfirm the welding quality after the maintenance is completed.

Membrane packaging: When the membrane is packaged, in order to ensure the treatment effect, it must be operated in accordance with the basic requirements of packaging. When packing the film body, the width of the film body after packing should not exceed 2.5m required for road transportation. After the packing process, it can be easily opened on site. The stacking height of the membrane units after packing is preferably controlled within the range of 1.5m. After packing, the relevant staff can directly use relevant measures to protect the outside of the film, and at the same time paste the corresponding number on the surface as a mark. Combined with the actual situation of the project, when packing, it is necessary to carry out proper bending according to the requirements of different directions such as length and width, which can provide convenience for subsequent installation. Starting from the center position, the packaging process is gradually carried out to both sides, so as to avoid adverse effects on the surface of the membrane material during packaging, and in terms of outer packaging, it is packaged with flexible materials.

Membrane surface placement and installation : According to the installation position of the membrane surface, combined with the membrane packaging diagram in the box and the on-site construction drawing, confirm the membrane cloth with the same number; the outer layer of the membrane cloth is wrapped with a thick packaging bag, and the entire membrane body Wrap it with a packaging bag and tie it with a wire rope, and then use a crane to put the membrane cloth in place on the platform. The connection between the membrane surface and the structure of this project adopts a fixed boundary form. During installation, the requirements for the stretching process of the membrane surface are relatively high, and considering the local stability of the structure and the uniform tension of the membrane body, the membrane body must be installed from the center of the overall structure. At the beginning, it spreads from the inside to the outside and installs them symmetrically. During the installation, temporary steel supports should be set according to the specific tensioning conditions for the tensioning and fixing of the membrane body to ensure that the rope tensioner has an operable tensioning distance.

When the construction technology of large-span steel space frame membrane structure is applied, it must strictly follow the requirements of the existing quality assurance system, reasonably construct and utilize the quality assurance system that meets the requirements, and follow the basic principles of “quality management”, to ensure that all aspects of the construction of the large-span steel space frame membrane structure can be carried out in an orderly manner, so as to provide a guarantee for the construction quality.