冷轧圆端椭圆钢管压弯构件滞回性能研究

Hysteretic Behavior of Cold-Formed Round-Ended Elliptical Hollow Section(REHS)Beam-Columns

对不同轴压比和压弯方向的5个冷轧圆端椭圆钢管试件进行拟静力试验研究,得到各试件的滞回曲线并讨论了其破坏模式、屈服/极限荷载、延性和耗能能力。基于试验结果,建立1 080个圆端椭圆钢管压弯构件有限元模型,并开展参数分析,提出实用抗震设计方法。研究表明:柱脚的局部屈曲导致了试件的破坏,不同压弯方向的试件的局部屈曲破坏形态不同。试验中钢管截面的平直板段最先屈曲,且具有稳定的屈曲后性能。更大的轴压比会造成更早的局部失稳和更严重的柱底破坏,从而导致试件延性降低。绕强轴压弯试件的截面塑性弯矩可以得到更充分的发展。对有限元模型数据进行最小二乘和下边界曲线拟合,得到基于延性和基于承载力的实用设计方法。

Quasi-static tests are conducted on five REHS beam-column specimens with different axial load ratios and bending directions. The failure mode,yield/ultimate strength,ductility,and energy dissipation-related quantities are discussed.A numerical study is then conducted on a total of 1 080 REHS beam-column models,and the cross section and material parameters are further studied. Finally,the practical seismic design method for REHS beam-columns is proposed. Based on this study,the local buckling at the fixed base governs the failure mode of REHS beam-columns,although different failure mechanisms are observed under different bending directions. The flat plate section of the REHS is more prone to local buckling,and has stable post buckling performance. When the axial load ratio increases,an earlier local buckling and more severe damage to the column base could occur,hence the ductility is compromised.When the beam-column is under major axis bending,the plastic moment resistance is better mobilized. Based on the finite element model data,practical ductility-oriented and strength-oriented design approaches are finally proposed,and both least-square regression and lower-bound solutions are provided.