考虑应变率效应的钢框架梁柱组合节点抗倒塌性能研究

The progressive collapse resistance of steel-frame structures mainly depends on the catenary capacity of the upper steel beams bridging over the bottom failed area in accidental events. The catenary action is dominated by the material strain rate sensitivity, the stiffness and plastic deformation capacity of beam-column connections, the tie capacity of reinforcing bars in concrete slabs, the tensile capacity of steel decks, and so on. Nowadays, the related researches mainly focused on the progressive collapse resistance of the remaining structure by the Alternate Path method, in which the basic assumption is that beam-column connections will not fail earlier than the corresponding beams. However, little research focused on the influence of beam-column connections on the progressive collapse resistance of the global structural system. In this project, the multi-scale finite element model considering the beam-column connection details and the composite action of concreter slabs will be developed to research its micro failure mode and the mechanical behavior of the global structure under the different loading rate. The influence of different connection constructions, concrete slab thickness, reinforcing bars and steel deck thickness on the beam-column connection behavior is considered respectively. The different loading rate is applied to research the strain rate effect on the progressive collapse resistance under the interaction of an axial tensile force and a bending moment. The behavior of beam-column connections will be further validated by ultimate bearing capacity experiments of typical beam-column connections. The simplified numerical simulation model considering the influence of beam-column connections and concrete slabs will be developed and some design suggestions will be given for the progressive collapse analysis of actual projects.

框架结构抗连续倒塌能力主要取决于失效柱上方钢梁能否发挥悬链作用跨越局部破坏区域，这种跨越能力受材料应变率效应、梁柱节点刚度和塑性变形能力、混凝土板内钢筋以及组合楼板中压型钢板拉结作用等多种因素的影响。目前相关研究成果主要集中在采用备用荷载路径法、假定梁柱节点不会先于构件破坏，分析局部柱失效后剩余结构的反应，对整体结构抗连续倒塌分析中梁柱节点的影响尚缺乏深入研究。申请者拟建立考虑节点构造细节和楼板作用的多尺度数值分析模型，研究倒塌分析中梁柱节点在拉力和弯矩共同作用下的微观破坏过程和框架结构整体受力特征；分析不同节点构造、楼板厚度、楼板内钢筋和压型钢板等对梁柱节点性能的影响；通过不同加载速率研究应变率效应对梁柱节点性能影响；通过不同加载速率下无楼板和有楼板的梁柱节点承载力试验验证多尺度数值模型；建立考虑梁柱节点刚度和楼板组合作用的简化杆系分析模型并提出设计建议。

框架结构抗连续倒塌能力主要取决于失效柱上方钢梁能否发挥悬链作用跨越局部破坏区域，这种跨越能力受材料应变率效应、梁柱节点刚度和塑性变形能力、混凝土板内钢筋以及组合楼板中压型钢板拉结作用等多种因素的影响。目前已有的相关研究成果主要集中在采用备用荷载路径法、假定梁柱节点不会先于构件破坏，分析局部柱失效后剩余结构的反应，对整体结构抗连续倒塌分析中梁柱节点的影响尚缺乏深入研究。本项目在已有研究基础上，对四种典型的钢框架节点的抗连续倒塌性能以及应变率效应和组合楼板对结构抗连续倒塌性能的影响开展了深入研究。.本项目开展了Q235、Q345、Q420钢材不同应变率下的单轴拉伸试验，并通过试验与仿真相结合的方式获得了钢材在不同应变率下的真实应力应变曲线，提出了能准确反映钢材应变率效应和应变硬化效应的修正Johnson-cook模型和修正H/V-R模型；利用经过验证的精细化有限元模拟方法，建模分析了典型钢框架节点的梁柱子结构在连续倒塌中的失效过程，提出并验证了其简化数值模型；采用钢材动本构模型的研究成果，研究了应变率在典型钢框架节点连续倒塌中的影响；完成了组合楼板各成分的抗连续倒塌性能的参数化分析；开展了考虑楼板作用以及四种节点形式的八个梁柱子结构足尺静力加载试验。