The standard "Code for Construction of Steel Structure Engineering" (hereinafter referred to as the Code), approved and edited by the Ministry of Housing and Urban-Rural Development and numbered GB50755-2012, will be implemented from August 1.

Our country is in the period of rapid development of steel structure industry, however, the domestic construction process and construction technology standards are very few, the standard issue, filled in the gap of domestic steel structure construction in the field of technical standards. The specification is China's ****** approved construction technology standard, which is jointly prepared by China State Construction Corporation Limited and China Construction Steel Construction Co., LTD., together with 14 related units.

One of the key chapters: steel

Steel structure is an engineering structure composed of steel processed, connected and installed. There is no doubt that the quality of steel determines the life of steel structure buildings.

The code consists of 16 chapters, including general principles, terms and symbols, construction survey, construction monitoring, construction safety and environmental protection. In the specification "Materials", it is not only proposed that "when ordering steel, its variety, specification and performance should meet the requirements of the design document and the current steel standards", but also listed 30 common steel product standards such as "High Quality Carbon Structural Steel" (GB/T699) and "Carbon Structural steel" (GB/T700). Code requirements, steel acceptance in addition to meet the provisions of the code, but also in accordance with the current standard "steel structure Engineering construction quality acceptance Code" (GB50205) relevant provisions. Specification requirements, the following 6 cases of steel samples should be reinspected. First, imported steel from abroad; Second, mixed batch of steel; Three is the plate thickness is equal to or greater than 40 mm and the design of Z direction performance requirements of the thick plate; Fourth, the safety level of the building structure is one level, the steel used by the main force members in the long-span steel structure; Five is the design of reinspection requirements of steel; Six is the quality of suspicious steel.

According to the specification, the reinspection of steel shall include mechanical property test and chemical composition analysis. The sampling, sample preparation and test methods shall be carried out in accordance with seven steel test standards, including "Sampling Location and sample Preparation for Mechanical Property Test of Steel and Steel Products" (GB/T2975) and "Tensile Test of Metallic Materials Part 1: Test Method at room Temperature" (GB/T228.1). In addition, the specification of Q235, Q345 and other commonly used steel in the steel structure engineering sampling reinspection of the inspection batch carried out in detail.

Key section two: Welding

Yao Bing, president of China Building Metal Structure Association, pointed out, "Life ****** is an important criterion for construction. Safety construction is a key area that construction enterprises must pay great attention to, especially for the steel structure industry."

It is well known that a beautiful dress is made by a tailor stitch and thread. Whether a garment fits well depends not only on the skill of tailoring but also on the skill of sewing. In the same way, the steel structure building is composed of countless components, through the welding of the building, its quality is good or bad, the length of life depends on the quality of the welding. Dai Weizhi, deputy secretary-general of China Engineering Construction Welding Association, emphasized the importance of welders by saying, "Three years can train a college student, but 10 years may not necessarily train a ****** welder."

Specification for welding professionals, including welding technicians (welding engineers), welding quality inspection, weld NDT personnel did clear rules, welder qualification, and especially important to responsible for large-scale steel structure engineering of welding technical personnel's technical level and ability to put forward more requirements, in order to guarantee the quality of welding. Welding process evaluation is one of the prerequisites to ensure the quality of welding, therefore, the specification of welding process evaluation and program, welding working conditions, positioning welding, arc starting plate, leading plate and liner plate, preheating and channel temperature control, welding deformation control, post welding ****** stress treatment of 7 welding process for more detailed requirements. Specification requirements, construction units used steel, welding materials, welding method, joint form, welding position, post-welding heat treatment and other parameters and the combination of parameters, should be in the steel structure production and installation before the welding process evaluation test. The test methods and requirements for welding process evaluation and the restrictions exempted from process evaluation shall comply with the relevant provisions of the current standard "Code for Welding of Steel Structures" (GB50661). Prior to the welding construction, the construction unit shall compile the welding method or the combination of welding methods based on the qualified welding process evaluation results or the use of qualified welding process evaluation conditions. Specification, grade, thickness and coverage of base metal; Specification, class and type of filler metal; Welding joint form, groove form, size and allowable deviation; Welding position; Type and polarity of welding power supply; Root removal treatment; Welding process parameters (welding current, welding voltage, welding speed, welding layer and weld pass distribution); Preheating temperature and inter-channel temperature range; Post welding ****** stress treatment technology; Other necessary welding process documents stipulating 11 items. The specification emphasizes that the dimension deviation, appearance quality and internal quality of welds should be inspected in accordance with the relevant provisions of the current standard "Code for Acceptance of Construction Quality of Steel Structures" GB50205 and "Code for Welding of Steel Structures" GB50661.

Key Section Three: Steel structure Installation

Steel structure buildings with its light weight, good seismic performance, fast construction speed, high degree of industrialization, beautiful appearance and other advantages more and more become or regional landmark buildings, from the current trend, the building is getting higher and higher, personalized characteristics are more and more obvious, therefore, also bring great challenges for the installation of steel structure.

Two mandatory provisions of the code appear in the "steel structure installation", one is that the steel structure lifting work must be carried out within the rated lifting range of the lifting equipment; Second, the steel wire rope, hoisting belt, shackles, hooks and other spindles used for hoisting should be inspected and qualified, and should be used within the rated allowable load range. It is well known that mandatory regulations are legally binding, characterized by "mandatory enforcement, must be adopted". Therefore, the importance of steel structure installation is obvious. The description of the two mandatory provisions emphasizes the importance of safety everywhere. The code states that the lifting equipment for lifting steel structures must be lifted within its rated lifting weight range to ensure the safety of lifting. If the lifting operation exceeds the rated lifting weight, it will easily lead to production safety accidents. The hoisting spreader, such as steel wire rope, hoisting belt, shackle and hoisting hook, may have local wear and tear and other defects in the process of use. The user shall conduct a full inspection of the spreader to ensure that the quality meets the requirements, prevent accidents, and operate within the rated allowable load to ensure the safety of hoisting.

The code puts forward constructive suggestions on the installation of single-layer steel structure, multi-high-rise steel structure, long-span space structure and towering steel structure engineering, and makes clear provisions on the installation site of steel structure.

It is reported, in the process of preparation of specification, drafting group has carried on the extensive investigation and study, summarizes the construction experience of decades of steel structure engineering in our country, draw lessons from the foreign related to steel structure technology standard, has carried out a number of studies, and in many ways solicit opinions from the relevant units and experts, and explains the main problems discussed repeatedly, coordination and modification, and was finalized after examination. The promulgation and implementation of this standard is of great significance to standardize the construction of steel structure and ensure the engineering quality.