Experimental Investigation and Restoring Force Model of Steel Archaizing Building Joints with Viscous Dampers

To enhance the seismic performance of steel archaizing buildings without altering their traditional architectural appearance, viscous dampers were installed in the Que-ti bracket regions of beam–column joints. Dynamic cyclic loading tests were conducted on four viscous damper-equipped joint specimens with single-beam and double-beam configurations. The failure modes, hysteretic behavior, skeleton curves, and stiffness degradation characteristics were investigated, and a restoring force model was subsequently developed. The results showed that damage was primarily concentrated in the beam-end plastic hinge regions, where local buckling and base-metal cracking progressively developed with increasing displacement. The columns, upper columns, joint core regions, and complete-joint-penetration welds remained essentially intact, indicating a beam-controlled failure mechanism. All specimens exhibited stable spindle-shaped hysteretic loops without obvious pinching. The displacement ductility coefficients ranged from 1.77 to 2.05, while the ultimate loads ranged from 59.88 to 104.55 kN. After normalization, the skeleton curves exhibited consistent elastic, post-yield strengthening, and post-peak degradation stages. Based on these characteristics, a restoring force model incorporating a trilinear skeleton curve, unloading and reloading stiffness degradation relationships, and hysteretic rules was established. The predicted backbone curves agreed well with the experimental results, indicating that the proposed model can reasonably represent the nonlinear response of viscous damper-equipped joints in steel archaizing buildings.