Study on Reinforcement Mode and Corrosion of Reinforced Concrete Primary and Secondary Beam Joints

In reinforced concrete structures, the primary and secondary beam joints are capable of transferring concentrated loads through additional transverse reinforcement, such as additional stirrups or additional hanging reinforcement. Ensuring the structural safety of these joints under situations such as small height differences between the primary and secondary beams, large secondary beam loads, or marine environments is crucial. Current research mainly focuses on the structural safety of individual structural members or conventional frame joints. Studies on primary and secondary beam joints are limited, and the performance of additional hanging reinforcement under special situations has been neglected. This study identifies two special situations at primary and secondary beam joints—the “small height difference” and the “large load”—and verifies their rationality through numerical simulations. Furthermore, an ultimate bearing capacity degradation ratio is introduced to quantify the effect of reinforcement corrosion on the mechanical performance of these joints. The results demonstrate that, without considering reinforcement corrosion, beams with additional stirrups fail to satisfy the ultimate bearing capacity requirements under the “small height difference” and “large load” situations. In such cases, additional hanging reinforcement should be adopted as the reinforcement mode. When reinforcement corrosion is considered, the ultimate bearing capacity degradation ratio of the beam with additional stirrups drops to approximately 0.65 after 30 years of service, whereas that of the beam with additional hanging reinforcement remains above 0.95. Under these situations, additional hanging reinforcement is even more preferable. This study clarifies the selection principle for primary and secondary beam joint additional transverse reinforcement under the two special situations and corrosion environments. The research findings provide guidance and reference for the structural design of reinforced concrete primary and secondary beam joints.