بررسی تجربی و تحلیلی اتصالات فولادی گذرا در ساختمان های سنتی

This article examines experimentally the behavior of transition steel connections between smaller rectangular and larger circular tubes in traditional-style Chinese buildings. The steel connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four 2/3 scale connections extracted from a prototype with two upper column lengths (or slenderness) and two levels of axial force. The influence of axial compression ratio and slenderness ratio on the mechanical behavior of the connections was assessed by looking at hysteretic performance, backbone curves, characteristic loads and corresponding displacements, ductility, energy dissipation capacity, and stiffness degradation. Test results showed that the primary failure modes were cracking of welds or base metal around the welds, and local buckling of the flange at the base of the rectangular steel tube column. The hysteresis loops were full and showed moderate degradation, indicating very good seismic performance for these steel connections. When failure occurred, the interstory displacement angle was between 2.2% and 2.8%, and the equivalent viscous damping coefficient was about 0.26–0.29. Based on the experimental research, an idealized bilinear backbone curve model was developed considering both stiffness degradation and second order effects. This simplified model provides both a yield and an ultimate strength and deformation capacity that can be used in design.