近场区竖向地震动对钢筋混凝土框架结构抗震性能的影响

Effect of vertical ground motion on seismic behavior of RC frame in near-fault region

对竖向地震动进行统计分析,采用与水平地震动相比较的方法来间接反映竖向地震的特性。对断层距、震级、场地条件、震源机制进行分类,考察诸因素对加速度峰值比的影响。分析断层距对加速度反应谱比的影响,在近场区及短周期段,竖向地震动伪加速度反应谱值大于水平方向的谱值,远大于规范中所采用的0.65的系数。采用OpenSees程序对一地震模拟振动台的框架试验结果进行分析,验证了分析方法的可行性。8层钢筋混凝土框架结构的非线性动力分析表明,在竖向和水平地震动共同作用下,近场区钢筋混凝土框架柱的承载能力可能由拉-弯和拉-剪受力状态控制。

Statistical analysis is applied to the vertical earthquake,and a comparison with the horizontal earthquake ground motion is made to indirectly reflect the characteristics of vertical earthquake.Based on the classification of fault distance,earthquake magnitude,site condition and focal mechanism of earthquakes,their effects on the ratio of peak ground acceleration are investigated.By analyzing the influence of fault distance on the ratio of acceleration response spectrum,it is found that the pseudo acceleration response spectrum value of vertical ground motion is greater than that of the horizontal ground motion in the near-fault zone and short-period segment,and moreover the spectrum value is much greater than the coefficient of 0.65 specified in seismic design code.To verify the feasibility of the analyzing method,the OpenSees program is used for the earthquake response analysis of a RC frame on the earthquake shake table.Based on the analysis of nonlinear dynamic responses of an eight-story RC frame structure,it is observed that under the combined action of vertical and horizontal earthquake,the ultimate bearing capacity of columns for the frame in near-fault region may be controlled by the tension-bending and tension-shear forces.