地裂缝场地地震及不均匀沉降双重作用下的框架结构动力响应

以西安地铁二号线沿线近f₆地裂缝处框架结构为原型,基于地裂缝场地50年沉降预测情况,采用ABAQUS有限元软件建立地裂缝场地和上部结构共同作用模型,在不同年限场地沉降基础上施加El Centro波、Tangshan波及上海人工波3种地震波,研究地裂缝场地地表峰值加速度变化规律,对比分析地震及不均匀沉降双重作用下框架结构的层间剪力、层间位移角变化情况。结果表明:下盘场地地表加速度峰值在土体沉降前后随避让距离未出现明显变化,上盘场地地表加速度峰值出现较为明显的减小; 3种地震波作用下沉降前后框架结构的剪力时程曲线基本一致,正负向剪力峰值出现的时刻也近似吻合; 上下盘结构层间位移角变化规律相似,均随避让距离的增大而减小,距地裂缝越近,结构破坏越严重; 下盘结构最大层间位移角受不均匀沉降影响较小,最大变化幅度不足14%,上盘结构受影响较大,最大变化幅度超过50%,其中上海人工波作用下变化幅度最大,为73%,Tangshan波次之,为70%,El Centro波最小,为63%; 对于考虑不均匀沉降的地裂缝场地,框架结构抗震设计时应对水平地震影响系数最大值α_max进行调整,以确保结构的抗震安全性。

Dynamic Response of Frame Structure Under Earthquake and Uneven Settlement in Ground Fissure Site

Based on the frame structure that near the ground fissure f₆ along Xi’an Metro Line 2 and the settlement of ground fissure site in recent 50 years, the finite element software ABAQUS was used to establish the interaction model of ground fissure site and superstructure. El Centro wave, Tangshan wave and Shanghai artificial wave were applied on the basis of settlement in different years. The variation law of ground surface peak acceleration was studied, and the changes of shear force and displacement angle of frame structure under the action of earthquake and uneven settlement were compared and analyzed. The results show that the peak ground acceleration of the foot wall has no obvious change with the setback distance under uneven settlement, and the peak ground acceleration of the hanging wall is reduced obviously. The shear time-history curves of the frame structure before and after settlement under three kinds of seismic waves are basically consistent, and the time when the positive and negative peak appears is also approximately consistent. The change law of inter-storey displacement angles of the hanging wall and the foot wall is similar, which decreases with the increase of setback distance. The closer the frame structure is to ground fissure, the more serious the damage of the frame structure is. The maximum inter-storey displacement angle of the foot wall is less affected by uneven settlement, and the variation range is less than 14%. The maximum inter-storey displacement angle of the hanging wall is greatly affected by uneven settlement, and the variation range is more than 50%. The variation range is the largest one under Shanghai artificial wave, which is 73%. The variation range of Tangshan wave comes second with 70%. The variation range is the smallest one under El Centro wave, which is 63%. Considering the uneven settlement of the ground crack site, the maximum value of horizontal seismic influence coefficient α_max of the frame structure should be adjusted to ensure the seismic safety of the structure.