Steel structure design

Excerpt from Zhulong Web: In steel structures, the connection between beams and columns typically adopts three forms: flexible connections (also known as hinges), semi-rigid connections, and rigid connections. In engineering practice, to determine whether a joint is rigid, semi-rigid, or hinged, one mainly considers its rotational stiffness. A rigid joint should not exhibit significant deformation of the joint angle; that is, the reduction in the structural resistance due to joint angle deformation should not exceed 5%. Semi-rigid connections lie between the two. The semi-rigid connection of beams and columns can be achieved by welding end plates to the beam ends and connecting them with high-strength bolts, or by using upper and lower angle steels attached to the flanges along with high-strength bolts. As a supplementary note, our usual approach for joining hinges is to use bolts with single-sided connection plates; in cases where rigid connections are required, we employ bolts with double-sided connection plates, along with gussets welded to each of the upper and lower flanges, or we use double-sided connection plates that are welded around all four sides. As for semi-rigid connections, they are currently still in the research phase. The approach you mentioned is indeed used in practice, but since there isn’t much research available on this topic, it isn’t reflected in design standards. In other words, the theoretical basis for using semi-rigid connections in construction isn’t yet well-established, and experts have not reached a consensus; therefore, I would advise using them with caution.