Throughout the present situation and development trend of building steel structure engineering, it has more and more architectural features of modern architectural style and high scientific and technological content. Its main characteristics are as follows:
1. Novel and unique shapes, various structural systems, complex joints and various forms of welded joints make the welding technology more and more difficult in component fabrication and field installation. For example, the National Stadium's Bird's Nest steel structure project has a large number of complex truss columns, main truss, sub-structure welded joints, and the welds are crisscrossed, so the construction is very difficult.
2. Building height is high, structure span is large, seismic performance design requires high welding quality of main steel structures. For example, the joints of frame beams and columns, shear plates and columns, web and column joints and column splicing welds are the main parts of the structure, basically the groove penetration first-class welds, 100% ultrasonic flaw detection, the welding quality requirements are very high.
3. There are many kinds and specifications of steel used, and more and more tend to use low-alloy high-strength structural steel and large-thickness steel. With the continuous improvement of steel production technology, cast steel, austenitic stainless steel and composite steel plate have also been more and more applied. Therefore, it is necessary to conduct real-time weldability tests of new steel grades, explore scientific welding process parameters and formulate corresponding welding process measures according to the delivery status of the steel used before site construction.
4. There are many links between factory production and site installation, and there are many crossover operations among different types of work, which makes site installation more difficult.