There are many kinds of steel products with different resistance. The connection design is usually restricted by the following factors:

1. Source of components: in theory, steel structure components or connecting components have arbitrary processing, but in each specific project, structural components and connecting components are always restricted by the actual conditions. Experienced designers usually choose section steel which is easy to obtain and easy to install, and design simple and effective connection methods and connection components.

2. Limitation of connection means: one of the construction features of steel structure is factory processing and field assembly. This is different from the traditional masonry method and produces a large number of nodes. There are three main methods for the connection between various sections: riveting, welding and bolting. Riveting is often used in the early steel structure construction, which is simple in construction, but it needs to dig out holes in the components, which reduces the section performance and easily produces concentrated stress at the joints. The welded joints have simple appearance and continuous load transfer efficiency, but the construction requirements are high. The high-strength bolt connection in the later stage can also meet the strength requirements of similar welding, which is widely used in modern steel structures.

3. Connecting members are hierarchical: there is a complex and logical hierarchical relationship between the structural systems of steel buildings. At the connection level, this hierarchical relationship is reflected in the differences between the size and installation sequence of members. The purpose of connection is to achieve hierarchical transformation, and it is also the key to realize the transformation of force from three-dimensional to two-dimensional, and finally to one-dimensional components. Complex connection is usually completed by the combination of three-dimensional connection components and plane connection components.

4. Plane of connecting member: two linear structural members are always in the same plane, which is the plane where the stress occurs. In order to effectively resist the stress, bending moment or shear force in this plane, the connecting member is often designed in this plane, such as the welding plate of steel pipe and cable is always in the plane formed by the two; in the case of multiple members' connection, the combined plane is the same The surface component can correspond to the stress of the solid.