Seismic-Resistant Weld-Free Steel Frame Buildings with Mechanical Joints and Hysteretic Dampers

This paper presents an innovative structural system, named weld-free system, developed to overcome the difficulty in the quality assurance encountered in construction of steel moment resisting frames with conventional welded connections. The proposed structural system adopts a mechanical joint equipped with metallic-yielding damper as beam-to-column connection, wherein slip-critical joints are made by recently developed super high-strength bolts. The structural configuration and load-carrying mechanism of weld-free steel structures are described herein. Key features of the super high-strength bolts are also introduced. Furthermore, an experimental verification is presented. Cyclic tests were conducted on full-scale models of weld-free beam–column subassemblies and one base-line specimen with conventional welded connection. The test results clearly reveal the efficiency of the weld-free system in enhancing large and stable hysteresis loops while maintaining the beams and columns virtually in the elastic range until the ultimate state of the structure. It is also verified that the load-carrying mechanism of weld-free systems can be predicted very well by the presented theoretical solutions.