Mechanism and Experimental Validation of Frictional Steel Truss Coupling Beams

Abstract

Coupling beams in shear wall and frame–shear wall systems are structural fuses that undergo significant inelastic deformation and absorb earthquake input energy. However, severe damage to coupling beams can disrupt building functions and have substantial repair costs. This study proposes frictional steel truss coupling beams (FTCBs) that aim to resolve these issues. The truss configuration is advantageous because it decouples shear and bending demands and facilitates pipeline layout. Shear-critical FTCBs (SFTCBs) adopt a smaller span-to-height ratio and place friction dampers in the diagonal webs, while bending-critical FTCBs (BFTCBs) adopt a larger span-to-height ratio and place friction dampers in the bottom chords. Quasi-static tests were conducted to validate the seismic performance of the FTCBs. A traditional reinforced-concrete coupling beam (RCCB) specimen was also tested for comparison. Results showed that FTCBs can realize damage control by concentrating inelastic deformation in friction dampers while keeping the main body of the steel truss and wall piers elastic. The FTCBs exhibited full and stable hysteretic behavior and enhanced energy dissipation capacity and replicability, which is difficult to achieve in RCCBs. Therefore, the FTCBs provide resilient alternatives to coupling beams over a range of span-to-height ratios.