Study on the Bending Performance of Connection Joints in a New Type of Modular Steel Structure Emergency Repair Pier

The pier-type repair equipment for bridges is a crucial branch of bridge emergency repair. However, the existing bridge pier repair equipment predominantly utilizes rod systems, which require substantial assembly work, hindering the rapid restoration of damaged bridges. Modular steel structure buildings, as a highly integrated form of prefabricated construction, can play a significant role in emergency rescue operations. Based on the modular architectural design concept, this paper proposes a new type of modular steel structure emergency repair pier joint that facilitates rapid assembly and connection between modular units. Using ABAQUS 2022 software to establish a finite element model of the joint, the bending performance under lateral displacement loads perpendicular to the joint opening direction (X-direction in the model coordinate system) and parallel to the joint opening direction (Z-direction in the model coordinate system) is analyzed. The influence of the width-to-thickness ratio of the upper corner piece base plate D/t1 (where D is the width of the upper corner piece base plate and t1 is the thickness of the upper corner plate), the height-to-thickness ratio of the lower corner piece top plate h/t2 (where h is the height of the protrusion of the lower corner piece and t2 is the thickness of the lower corner piece top plate), the height of the protrusion of the lower corner piece (h), and the bolt diameter (d) on the bending performance of the joint is investigated. Recommendations for the design values of the joint are provided. Then, the flexural behavior of the joint under 0.1, 0.2, and 0.3 axial compression ratios is studied, respectively. The results show that with the increase of axial compression ratio, the yield rotation angle and ultimate rotation angle of the joint decrease, and the bearing capacity decreases faster after the joint reaches the ultimate bearing capacity. When the joint is subjected to the X-direction horizontal lateral displacement load, the initial flexural stiffness and flexural capacity of the joint increase with an increase in the axial compression ratio. When subjected to the horizontal lateral displacement load in the Z-direction, the initial bending stiffness of the joint increases with an increase in the axial compression ratio, and the bending capacity does not change much. In addition, the joint is classified; from the perspective of load-bearing capacity, it is a partially resistant joint, and from the perspective of stiffness, it is a semi-rigid joint. Finally, a simplified calculation model for the joint is proposed based on the component method.