钢桁架约束混凝土组合柱约束机理及截面曲率分析

钢桁架(ST)约束混凝土组合柱具有良好的力学性能及抗震性能，且其截面形式能够有效提高内部钢材的利用率。基于已进行的轴向力学性能试验，对ST约束混凝土的约束机理进行详细分析，建立有效约束力计算模型、承载力计算模型以及本构模型。进行ST约束混凝土组合柱低周反复荷载试验研究，在试验研究的基础上，建立组合柱的截面弯矩-曲率分析模型。基于所提出截面分析模型，分析轴压比、混凝土强度等级、角钢含钢率、缀板宽度与角钢间距之比、缀板净距与角钢间距之比、角钢间距与缀板厚度之比对柱截面屈服曲率和极限曲率的影响。建立组合柱截面屈服曲率和极限曲率的计算公式，进一步推导截面曲率延性系数和位移延性系数的计算公式，并与试验结果进行对比，验证公式的准确性与适用性。所提出公式基于大量计算数值，所考虑的因素较为全面，可为后续组合柱的变形能力计算以及基于位移的抗震设计提供一定依据。

Confining mechanism and section curvature analysis #br# of steel truss confined concrete composite columns

Steel truss (ST) confined concrete composite columns have good mechanical and seismic behaviors and the section form can improve material utilization of inner steel section. Based on the existing axial compression experiment, the confining mechanism of ST confined concrete was analyzed. The corresponding models were established, including the lateral confining stress model, bearing capacity model and constitutive model. The low cyclic reversed loading experiment was conducted, based on which the section analysis model was proposed. The influence factors of section yield curvature and section ultimate curvature were analyzed, including the axial compression ratio, concrete strength, angle steel ratio, ratio of batten width to angle steel spacing, ratio of batten spacing to angle steel spacing and ratio of angle steel spacing to batten thickness. Then the calculation formulas of section yield curvature and section ultimate curvature were established. Furthermore, the calculation formulas for the section curvature ductility coefficient and displacement ductility coefficient were proposed and were validated by the tests. The proposed formulas are based on a large number of calculated values and verified by experiment results can consider comprehensive influence factors, which can lay good foundation for the deformation capacity calculation and the displacement-based seismic design.