川西藏羌石砌民居建筑的抗地震倒塌性能

Seismic Collapse-Resistant Performance of Stone Houses in Tibetan and Qiang Autonomous Prefectures of Western Sichuan

我国川西地区的传统藏羌石砌民居具有较高的文化遗产保护价值,但在近年来的历次地震中出现了大量破坏.结合该类房屋的砌筑材料和建筑布置特征,对其抗地震倒塌性能进行研究.首先,开展了3组黏土试件的无侧限抗压强度试验和一个1/2缩尺黏土-石砌墙体试件的水平抗剪承载力试验,并通过显式动力数值计算手段对试验过程进行模拟;其次,针对黏土和毛石材料均采用Holmquist-Johnson-Cook(HJC)本构模型,基于随机分布离散型有限元方法,根据实际墙体中两种材料的分布比例建立相应数值模型,并通过与模型试验结果的对比验证,明确了数值计算中的关键参数;在此基础上,对一典型二层平面L型缩进式民居结构进行动力时程分析计算,通过与实际震害情况的对比分析了其地震破坏机制,再现了地震倒塌全过程,并开展了结构的抗地震倒塌易损性分析,研究了不同晒台缩进面积的影响.研究结果表明,在罕遇烈度下,平面L型缩进式结构中晒台面积比例由30%增加至45%时,结构倒塌概率增大16.7%,抗倒塌储备系数下降9%,对易损性曲线影响并不显著;但当晒台面积比例减小至15%时,二层墙体开洞率增大18%,导致结构的地震倒塌概率增加143%.

Traditional stone houses in the Tibetan and Qiang autonomous prefectures of Western Sichuan,deserve preservation as indicators of cultural heritage;however many of them have been damaged during earthquakes in recent years.Based on the characteristics of masonry materials and architectural layout,seismic collapse-resistant performance of stone houses was investigated.Unconfined compression tests on three clay specimens and lateral shear tests on a half-scaled clay-brick rubble masonry wall specimen were conducted and also modeled via an explicit dynamic numerical approach.The Holmquist–Johnson–Cook(HJC)constitutive model was applied to the clay and rubble,and a randomly-distributed discrete finite element model was built to show the proportion between clay and brick rubble.Through the comparison of experimental and numerical results,the numerical model was verified and key parameters were calibrated.According to above work,a structural model of a typical two-storey residential stone house with an L-shaped indented platform was built,and its dynamic time-history analysis was conducted.By comparing the calculated seismic damage modes with its real seismic damage,the collapse mechanism was analyzed and the collapse process was simulated.Moreover,the structural fragility of seismic collapse was studied based on the influence of the indented area of the platform.The results indicate that,under rare seismic intensity,when the indented area is increased from 30%to 45%,the probability of structural collapse increases by 16.7%,and the collapse margin ratio decreases by 9%,which has little effect on the fragility curve.However,when the indented area is reduced to 15%,the failure rate of walls on the second floor increases by 18%,leading to the increase of 143%in the probability of structural collapse.