多维地震下钢管混凝土柱-组合梁框架结构体系抗震性能分析

Analysis on Seismic Performance of Concrete-Filled Steel Tubular Columns-Composite Beam Frame Structural System Under Multi-Dimensional Earthquake

基于柱端拉筋对钢管混凝土柱、钢管混凝土柱-组合梁节点和钢管混凝土柱-组合梁平面框架结构抗震性能影响的试验研究成果,建立了钢管混凝土柱-组合梁空间框架结构动力时程分析的三维实体-壳单元模型,探讨了柱端拉筋和主梁加高等增强约束措施、削减钢梁跨中腹板高度的变截面组合梁以及多维地震波对结构抗震性能的影响规律,分析了不同地震波强度作用下该类组合框架结构的位移响应、轴压比时程曲线、应力-应变等曲线,以及结构塑性耗能分配机制、塑性铰形成与发展规律和结构刚度损伤演化规律等抗震性能指标。有限元计算结果表明:1)柱端拉筋和主梁加高等增强约束措施均能有效提升组合框架结构抗震性能而减小结构刚度损伤,且地震波强度越大作用效果越明显;相同地震波作用时,柱端拉筋增强约束措施比主梁加高增强约束措施更有效,而两种增强约束措施共同作用则能进一步提升组合结构的极限抗震能力。2)柱端拉筋增强约束措施能够降低钢管壁与混凝土间界面滑移,增强混凝土的耗能能力,降低钢管混凝土柱塑性耗能占比,提升钢梁塑性耗能占比,提升结构总塑性耗能;此外,柱端拉筋增强约束措施还可减少组合框架柱端塑性铰并增加梁端塑性铰的数量,延缓柱端“压铰”的出现,延长“压铰”向“拉铰”转变的过程。3)降低钢梁跨中腹板高度的变截面组合梁对框架结构抗震性能没有影响,采用该变截面组合梁的框架模型不仅能够满足结构基本功能要求,还可节省结构耗材、降低造价,进一步扩大建筑实用空间。4)与单向地震波作用相比,多维地震波作用下组合框架结构的极限抗震能力大幅下降,结构失效模式由剪切破坏转变为剪扭破坏。另外,三维地震波中竖向加速度对框架结构柱端轴压比有放大作用,而对楼层最大位移、层间位移角、塑性耗能和刚度损伤等方面则无明显影响。柱端拉筋增强约束措施对组合框架结构抗震性能仍有提升作用。

Based on pseudo-static tests of column end stirrup-confined on CFST columns,CFST column-composite beam joints,and CFST column-composite beam planar frame structures,a three-dimensional solid and shell element model of CFST column-composite beam spatial frame structures was established for dynamic time-history analysis.The influence of the column end stirrup-confined,the main beam heightening,the variable cross-section composite beams with the height of the mid span web reduced,and multidimensional earthquake on the seismic performance of composite structures were discussed.The displacement response,axial compression ratio time history curve,stress-strain curve of composite frame structure under various seismic wave were discussed,as well as the distribution mechanism of plastic energy dissipation,the formation and development law of plastic hinge,the evolution law of structural stiffness damage and other seismic performance indicators.The finite element analysis results indicate that:1)the strengthened restraint measures,such as the column end stirrup-confined and the main beam heightening,can effectively improve the seismic performance of composite frame structures and reduce the structural stiffness damage,and the greater of the seismic wave is,the better the effects of the enhanced constraint measures are.Under the same seismic wave,the strengthened restraint measure of column end stirrup-confined has more advantages than the main beam heightening,and the combined effect of two measures can further enhance the ultimate seismic capacity of the composite structure;2)the strengthened restraint measure of column end stirrup-confined can reduce the interface slip between steel tube and infilled-concrete,enhance the energy dissipation capacity of concrete,reduce the proportion of plastic energy dissipation of CFST columns,increase the proportion of plastic energy dissipation of steel beams,and increase the total plastic energy dissipation of the structure.At the same time,the strengthened restraint measure of column end stirrup-confined can also reduce the number of plastic hinges at column ends and increase plastic hinges at beam ends,delay the emergence of“compression hinges”at the column ends,and extend the transition from“compression hinges”to“tension hinges”;3)the variable cross-section composite beam with the height of the mid span web reduced has no effect on the seismic performance of composite frames.Using this variable cross-section composite beam not only meets the basic functional requirements of the structure,but also saves structural materials,reduces costs,and further expands the space of the building;4)compared with the horizontal seismic wave,the ultimate seismic capacity of composite frame structure decreases significantly under the multi-dimensional seismic wave,and the failure mode of composite frame structure changes from shear failure to shear torsional failure.In addition,vertical acceleration in three-dimensional seismic wave has an amplification effect on axial compression ratio,while it has no significant impact on maximum displacement,interlayer displacement angle,plastic energy dissipation and stiffness damage.The strengthened restraint measure of column end stirrup-confined still has an improvement effect on the seismic performance of composite frame structures.