端部设肋方钢管混凝土柱抗震构造措施及塑性铰

Seismic Structural Measures and Plastic Hinges for Square Steel Tube Concrete Columns with Stiffeners at the Ends

为深入分析端部带肋方钢管混凝土柱的抗震构造措施及柱端部塑性铰形成机制,通过建立三维实体有限元模型并与试验结果验证,有限元结果与试验结果符合较好,在此基础之上进一步建立30个足尺模型,分析轴压比、含肋率以及加劲肋高度等参数对柱的承载力、延性、塑性耗能的影响,提出了不同轴压比下柱的合理含肋率和加劲肋高度等抗震构造措施以及塑性铰判定方法。结果表明:①当含肋率增大,柱的承载力、延性、总塑性耗能值显著提高,加劲肋的塑性耗能占比增大而混凝土的塑性耗能占比减小,对钢管影响较小;②当轴压比为0.2时,柱的承载力下降不明显,延性较好,故可不布置加劲肋,轴压比为0.5、0.8时,合理含肋率分别为0.2、0.4,加劲肋高度分别为1000、1500 mm;③当钢管纵向受压应变达到4倍屈服应变时,柱端出现塑性铰,进一步提出了考虑轴压比和含肋率的塑性铰长度公式,公式计算结果与有限元结果离散性较小。

In order to deeply analyze the seismic structural measures and the formation mechanism of plastic hinge at the end of concrete-filled square steel tubular columns with stiffeners,a three-dimensional solid finite element model was established and verified with the test results.The finite element(FE)results were in good agreement with the test results.On this basis,30 full-scale models were further established to analyze the influence of parameters such as axial compression ratio,stiffener ratio and stiffener height on column bearing capacity,ductility and plastic energy consumption.Seismic structural measures such as reasonable stiffener ratio and stiffener height of columns under different axial compression ratios and the determination method of plastic hinge were proposed these as follows.The results show.When the stiffener ratio increases,the bearing capacity,ductility and total plastic energy consumption of the column increase significantly,the plastic energy consumption of stiffeners increases,while the plastic energy consumption of concrete decreases,which has little effect on the steel tube.When the axial compression ratio is 0.2,the bearing capacity of the column is not significantly reduced and the ductility is better,so stiffeners can be omitted,when the axial compression ratio is 0.5 and 0.8,the reasonable stiffener ratio is 0.2 and 0.4,respectively,and the stiffener height is respectively 1000 mm,1500 mm.When the longitudinal compressive strain of the steel tube reaches 4 times the yield strain,plastic hinges appear at the end of the column,a plastic hinge length formula considering the axial compression ratio and stiffener ratio is further proposed,the calculation results of the formula and the FE results are less discrete.