【摘要】 双向水平地震动的耦合作用将使塑性变形更多集中于柱端,框架结构在双向地震下的塑性铰分布明显较单向地震作用下更差。严格按中国规范设计了8度0.2g区二级抗震规则空间框架结构,并采用上部各层柱端"强柱弱梁"措施与底层柱下端弯矩增大系数不同取值的多种组合,形成了共7个算例框架。在OpenSees平台上,采用基于柔度法的纤维模型从而更加真实地模拟柱在双向弯曲和变化轴力作用下的非线性反应,对各空间框架进行了罕遇地震下的非线性反应分析。结果表明,在双向水平地震作用下,抗震规范给出的8度二级抗震的"强柱弱梁"措施取值明显偏低,框架部分楼层形成了层侧移柱铰屈服机制。基于梁端实际配筋∑Mbua对上部各柱端进行"强柱弱梁"调整的塑性铰控制效果较好,但底层柱下端非线性损伤过大。将底层柱下端的弯矩增大系数提高为1.8,上部各柱端按∑Mc=1.25∑Mb进行增强可形成较为优化的塑性铰控制效果。更多还原

【Abstract】 More plastic deformation will concentrate on the column ends due to the coupling effects of bi-directional horizontal seismic action,and the plastic hinges distributions of spatial frame under bi-directional horizontal seismic action is obviously worse than that of the corresponding plane frame.Regular reinforced concrete 3D spatial frame of the second seismic grade at 8-earthquake intensity 0.2g-region was designed strictly according to the Chinese code,and seven spatial frame examples were obtained by the combination of varying strong column-weak beam measure in the upper stories with moment amplification factor at bottom sections of ground floor column.Based on the OpenSees framework,the flexibility method based fiber model was adopted to simulate the nonlinear responses of columns under biaxial bending and varying axial force effectively.The nonlinear response analyses of the seven frames under rare earthquake excitation were carried out.The results showed that under bi-directional horizontal seismic action,the strong column-weak beam measure of the second seismic grade at 8-earthquake intensity of Chinese code is evidently weak;the spatial frame develops column hinges mechanism with story side-sway mechanism occurs at some floors.When strong column-weak beam measure in the upper stories is based on the actual reinforcement area of beam ends,namely ∑Mbua,the controlling effects on plastic hinge mechanism are acceptable,but excessive nonlinear damage focuses on the bottom sections of ground floor columns.When the moment amplification factor at bottom sections of ground floor columns increase to 1.8,and strong column-weak beam measure in the upper stories remains to be ∑Mc=1.25∑Mb,a relatively optimal controlling effect on plastic hinge mechanism could be obtained.更多还原