With the development of spatial structure, the span of structure is becoming larger and larger, and the forms are also increasing accordingly. With the continuous emergence of new structural systems, the joint connection forms between components in the structure are becoming more and more complex. In addition to the traditional welded ball joints, steel tubular joints and other joint forms, cast steel joints have been widely used abroad, especially in developed countries such as Germany and Japan.
In China, cast steel joints have gradually been concerned and understood by the engineering community, and triggered an upsurge of engineering application. Cast steel joints have successively appeared in the National Stadium “bird’s nest”, Nantong Sports Exhibition Center, Chongqing Jiangbei Airport terminal, Nanjing Olympic Sports Center and other construction projects, and have also achieved good technical and economic benefits in steel structure bridges and offshore platforms.
The technical specification for cast steel structures (2017) regards cast steel as an ideal continuous homogeneous material to calculate its bearing capacity, but in fact, due to the limitation of casting process level and the influence of environmental factors, cast steel joints will inevitably have internal or external casting defects such as cracks, inclusions, air holes, shrinkage porosity and so on, The existence of casting defects will affect the mechanical properties of cast steel joints and even the overall structure to a certain extent, and may even threaten the structural safety.
Therefore, as the key stress part of engineering structure, the research on the distribution law and evaluation method of casting defects of cast steel joints and the accuracy of nondestructive testing method have important practical significance.