Many reinforced concrete (RC) frame structures were severely damaged or even collapsed during the May 12, 2008 great Wenchuan earthquake. Based on survey data collected in Dujiangyan, it was found that plastic hinges appeared at column end, instead of beam end, in many frame structures. This did not coincide with "strong column-weak beam" seismic design criterion. It was believed that one of the main reasons was insufficiently understanding the cast-in-place floor slab effect on frame structures. Applying finite element software ABAQUS, 3D elastic-plastic time history simulation of a "strong beam -weak column" RC frame structure in Dujiangyan was analyzed to probe the influence of cast-in-slab on frame seismic performance from structural view. Results showed that RC frame designed according to current codes usually can not achieve "strong column-weak beam" yield mechanism. The numerical results suggested that the rebar in the width of six times of the plate thickness may take part in calculating the bearing capacity of negative moment at the beam end; the model of a frame structure with floor slab is suitable for analyzing the elastic-plastic deflection of frame structures under rare big earthquakes.%“5.12”汶川地震造成一些钢筋混凝土框架结构损坏甚至倒塌.灾后调查发现,框架结构震害特点也一是柱端而非梁端出现塑性铰的“强梁弱柱”破坏形式,这与结构抗震设计概念中的“强柱弱梁”不符.国内外研究表明现浇楼板增大了梁端抗负弯承载力,但其对整个框架结构屈服机制的影响研究依然不足.针对这种现象,应用有限元软件ABAQUS对汶川地震中都江堰市某典型“强梁弱柱”框架进行三维动力弹塑性时程数值模拟,着重从结构角度上分析了现浇楼板对框架结构抗震性能的影响、探讨了负弯矩作用下梁端有效翼缘的取值.经分析,发现按照目前我国规范设计的框架在遭遇大震时较难实观“强柱弱梁”屈服机制.框架设计时宜在柱端弯矩增大系数不变的情况下,负弯矩作用下梁端有效翼缘范国内的板筋参与梁受弯,建议该范围取6倍板宽；大震下框架弹塑性变形验算宜采用考虑现浇楼板的计算模型.
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