SELF-CENTERING KNEE-BRACED STEEL FRAMES WITH BUCKLING-RESTRAINED NITI SMA BARS: COMPONENT TEST AND STRUCTURAL BEHAVIOR

Knee braces are often installed at locations near the beam-to-column connections in frames. In comparison with concentrical braces, knee braces have advantages of using less space, generating less impact to architecture view and being installed more conveniently. Super-elastic shape memory alloys (SMA) exhibit flag-shape hysteresis at room temperature, which indicates energy-dissipating capacity and self-centering (SC) capability. Accordingly, SMAs gained wide attention among the community of earthquake engineering. Combining NiTi SMA bar with buckling-restrained device, a novel knee brace, i.e., SC knee brace (SCKB) was proposed. Further, a new seismically resilient steel structure was developed , which is named as SCKB frame (SCKBF). And the reduced scale specimen of SCKB was tested. The testing results show that, SCKB has stable flag-shape hysteresis under both tension and compression. To evaluate the seismic performance of SCKBF, two frames with 3 and 6 stories were designed by equivalent base shear method and subjected to a suite of earthquake ground motions. The nonlinear time history analysis indicates that SCKBF can well meet the drift target prescribed by the code. Besides, the structures have minimal residual inter-story drift ratios, implying good seismic resilience. It also sheds light on further experimental work and design method.