Approved by the Ministry of Housing and Urban-Rural Development, editor, code GB50755--2012 national standard "Steel Construction Project Code" (hereinafter referred to as the standard) on August 1 come into operation.
China is in a period of rapid development of the steel structure industry. However, there are few norms in the domestic construction technology and construction technology. The release of the norms has filled in the blank of the technical standards in the field of domestic steel structure construction. The norm is the first batch of national standards for construction technology in China. It is jointly compiled by China State Construction Engineering Co., Ltd. and China National Steel Construction Co., Ltd. with 14 related units.
One of the key chapters: steel
Steel structure is made of steel after processing, connecting, installing the composition of the project structure, no doubt, the quality of steel determines the life of steel structures. The Code consists of 16 general chapters, terms and symbols, construction surveys, construction monitoring, construction safety and environmental protection. In the specification "material" not only put forward PCB design: "When ordering steel, its varieties, specifications, performance, etc. should be consistent with the design documents and the provisions of the current state of the relevant steel standards," the requirements are also listed "high-quality carbon structural steel "(GB / T699)," carbon structural steel "(GB / T700), 30 commonly used steel product standards. According to the normative requirements, in addition to complying with the normative provisions, the inspection and acceptance of steel products shall comply with the relevant provisions of the current national standard "Acceptance of Construction Quality of Steel Structure Engineering" (GB50205). Specification requirements, the following six conditions of the steel should be sampled reinspection. One is steel imported from abroad; the other is mixed batch of steel; the other is thick slab with plate thickness equal to or greater than 40 mm and designed with Z-direction performance requirements; the fourth is safety rating of building structure is Grade 1; The steel used by the components; the fifth is designed steel reinspection requirements; the sixth is the steel of doubtful quality.
Specification requirements, the reinspection of steel should include mechanical properties and chemical composition analysis, sampling, sample preparation and test methods in accordance with "steel and steel products mechanical properties test sampling location and sample preparation" (GB / T2975), "metal materials Tensile test Part 1: room temperature test method "(GB / T228.1) and other seven kinds of steel test standards. In addition, the vector frequency changer specification carries on the detailed stipulation to the steel-making project Q235, Q345 and so on commonly used steel sample reinspection examination batch to carry on the detailed regulation.
The key chapter two: welding
Yao Bing, president of China Construction Metal Structure Association, pointed out: "Life first is an important criterion for construction, and safety construction is a key area that construction enterprises must attach great importance to, especially for the steel structure industry."
People know that a beautiful dress is stitched through the tailor's stitches, and whether or not the garments fit together depends not only on the tailoring technique but also on the sewing skill. By the same token, steel structures consist of numerous components made of welded structures of good or bad quality whose life depends on the quality of the welding. Dai Weizhi, deputy secretary general of China Construction Welding Society, stressed the importance of welders with "three years to train a college student, but 10 years may not be able to train a good welder."
Specification of the welding practitioners, including welding technicians (welding engineers), welding quality inspectors, non-destructive testing of welders, qualified welders made a clear rule, and in particular, is responsible for large and important steel structure engineering, welding technicians technical level And ability to put forward more requirements, in order to ensure the quality of welding. Welding process qualification is one of the preconditions to ensure the quality of welding seam. Therefore, the standardization of welding procedure qualification and scheme, welding operation conditions, positioning welding, arc plate, lead plate and liner plate, preheating and interpass temperature control, welding Deformation control, stress relief after welding seven welding process carried out more detailed requirements. For the first time, the combination of various parameters and parameters such as steel, welding material, welding method, joint form, welding position and post-weld heat treatment adopted by the construction unit should be subject to the welding procedure qualification test before the steel structure is manufactured and installed. Welding procedure qualification test methods and requirements and to be exempted from the process of assessment of the qualification conditions should be consistent with the existing national standards, "Steel Welding Code" (GB50661) of the relevant provisions. Before the welding construction, the construction unit shall formulate the combination including the welding method or the welding method based on the qualified welding procedure qualification results or the application of the qualification test in compliance with the exemption craft; the specification, grade, thickness and coverage of the parent metal; the specification of the filler metal , Type and type of welding joint; form of bevel, size of bevel and its permissible deviation; location of welding; type and polarity of welding power source; clearance root treatment; welding process parameters (welding current, welding voltage, welding speed, Weld distribution); preheat temperature and the temperature range between the road; after welding to eliminate stress treatment process; other necessary provisions of the 11 content of the welding process documents. The norms emphasize that dimensional deviation, appearance quality and internal quality of welded seams should be inspected according to the relevant national standards GB50205 of "Acceptance of Construction Quality of Steel Structure Engineering" and "GB50661 of Welding Code of Steel Structure" according to the current national standard.
The third key chapter: steel structure installation
Due to its light weight, good seismic performance, fast construction speed, high degree of industrialization and beautiful appearance, steel structure buildings are increasingly becoming the landmarks of countries or regions. From the current trend, the buildings are getting taller and taller , More and more obvious personalized features, therefore, also pose a great challenge for the installation of steel structures.
Two mandatory provisions of the norms appear in the "steel structure installation", one hoisting operation of steel structures must be carried out within the rated lifting range of lifting equipment; the second is used for lifting the rope, lifting belt, shackle, Hanging slings and other spreaders should be checked and should be within the rated allowable load range. People all know that the mandatory provisions are legally binding and their characteristics are "mandatory and must be adopted." Therefore, the importance of steel installation is obvious. The explanations of the two mandatory provisions all emphasize the importance of safety. The code states that lifting equipment for hoisting steel structures must be hoisted within the rated lifting capacity to ensure hoisting safety. If the hoisting operation beyond the rated capacity, easily lead to production safety accidents. Mitsubishi air conditioning maintenance lifting wire rope, lifting belt, shackles, hooks and other spreaders in the course of the existence of local wear and tear, damage and other defects, the user should check all the spreaders in order to ensure the quality of qualified requirements to prevent accidents , And in the rated allowable load within the scope of operations, to ensure the hoisting safety.
The norms set forth constructive suggestions on the installation of single-story steel structures, multi-high-rise steel structures, long-span space structures and towering steel structures, and specified the site for the installation of steel structures at the same time.
It is reported that in the process of compiling norms, the compilation team conducted a wide range of investigations and studies, summarized the construction experience of China's steel structures over the past decades, borrowed the relevant technical standards of foreign steel structures, and conducted many special studies, Ways and means Widely solicited the opinions of relevant units and experts, repeatedly discussed, coordinated and revised the major issues and finalized the draft for examination and approval. The promulgation and implementation of the standard, to regulate the construction of steel structures, to ensure the quality of the project is of great significance