Use of 3-Dimensional Nonlinear Response to Multi-Directional Ground Motions in Earthquake Resistant Design of Reinforced Concrete Frames

为了分析双向弯曲的共同作用效应，建立了钢筋混凝土柱的分析模型，该模型的两端有两组多个转动弹塑性弹簧。单层框架模型在双向强地震动作用下的三维反应分析结果表明，柱的双向弯曲作用可以增加柱的损伤和框架的层间反应。为了研究柱的时变轴向荷载对建筑地震反应的影响，分析了一个简化的单自由度模型，该模型等效于八层钢筋混凝土建筑的纵向框架，一层柱采用纤维片模型，考虑了横向框架的倾覆力矩引起的柱内轴向荷载的时变性。分析表明，轴向荷载的高度变化会导致柱的损伤增加和抗侧强度降低。采用考虑构件的弹塑性特征的方法分析了一座11层钢筋混凝土结构的三维地震反应。研究了框架侧向强度分布与框架损伤分布之间的关系。结果表明，根据静力或动态线性分析得到的框架剪力分布来确定框架的强度分布，可以得到均匀的损伤分布。

An analytical model of a reinforced concrete column, which has two sets of multiple rotational inelastic springs at the both ends of an elastic flexural rod, is newly developed to analyze the interaction effect of bi-axial bending. The results of 3-dimensional response analysis of one-story frame models subjected to bi-directional strong ground motions show that the damage to columns and the story response of the frames can be increased by the interaction effect of the bi-axial bending of columns.To investigate the effect of time-varying axial load in columns on the earthquake response of a building, a simplified SDOF model, which is equivalent to longitudinal frames of a eight-story reinforced concrete building and has fiber-slice models for columns in the first story, is analysed considering the time-varying axial load in columns induced by the overturning moment of the transverse frame. It is illustrated that the high level of variation of axial load may cause the increase in the damage and the reduction of the lateral strength of the columns.Three dimensional earthquake response of an eleven-story reinforced concrete building with a setback is analysed by the method considering the inelastic characteristics of the constituent member. The relationship of the distribution of the lateral strength of frames and the distribution of the damage to frames is investigate. It is shown that the strength distribution of frames based on the distribution of the shear forces of the frames by the static or dynamic linear analysis may lead to the uniform damage distribution.