麦积山石窟栈道地震动力响应分析及损伤评估研究

Seismic dynamic response and damage assessment of the plank road in the Maijishan Grottoes

摘要:

为研究麦积山石窟人行栈道在地震作用下的动力响应,选取154石窟处栈道作为典型结构,利用ABAQUS建立三维实体模型,充分考虑麦积山石窟地震环境条件,基于麦积山石窟窟区地震危险性评价结果,分析石窟栈道在50年超越概率63.5%、10%、2%水准所对应地震作用下的加速度响应、应力和损伤分布情况,进而对栈道结构抗震性能水准进行划分。结果表明,在地震作用下,栈道结构斜梯加速度响应明显大于平台板处加速度响应,平台板随其所处位置高度的增加,加速度响应峰值增大;栈道结构悬臂梁与岩体嵌固的端部混凝土应力数值较大,斜梯梁与悬臂梁相交处钢筋应力较大;随地震作用的增大,栈道结构混凝土拉压损伤出现范围和数值均呈增大趋势,且主要集中在悬臂梁与岩体嵌固端部,呈现出上部受拉、下部受压的典型破坏特征;基于栈道结构材料应力应变和构件损伤程度对其抗震性能水准进行划分,栈道在多遇(PGA=70 gal)、设防(PGA=240 gal)地震作用下,地震损伤评估结果均为轻度损坏,在罕遇(PGA=450 gal)地震作用下,地震损伤评估结果为严重损坏。该研究结果可为麦积山石窟栈道震损评估和加固设计提供科学依据。

Abstract:

A typical plank road in Cave No. 154 was selected to investigate the dynamic response of pedestrian plank roads in the Maijishan Grottoes. A three-dimensional solid model was created using ABAQUS. Given the seismic environmental characteristics of the Maijishan Grottoes and based on the results of seismic risk assessment in the Maijishan Grottoes area, the acceleration response, stress, and damage distribution of the plank road under earthquake action corresponding to 50-year exceedance probabilities of 63.5%, 10%, and 2% were analyzed, and the seismic performance levels of the plank road structure were classified. The results show that the inclined ladder of the plank road structure had a considerably greater acceleration response than the platform plate under earthquake action. The peak acceleration response increases with the height of the platform plates. The concrete at the end of the cantilever beam, which is embedded in a rock mass, has a relatively high stress. The stress in the steel bars at the intersection of the inclined ladder beam and cantilever beam is relatively large. With the increase in earthquake action, the range and numerical value of tensile and compressive damage to the concrete of plank road structure increases and is mainly concentrated at the end of the cantilever beam embedded in the rock mass, showing typical failure characteristics of upper tension and lower compression. Based on the stress and strain of the material and the damage degree of components, the seismic performance level of the plank road is classified. The seismic damage assessment results of the plank road under frequent (PGA=70 gal) and design (PGA=240 gal) earthquakes reveal mild damage, and under rare (PGA=450 gal) earthquakes, the seismic damage assessment results indicate severe damage. The research results can provide a scientific basis for seismic damage assessment and reinforcement design of plank roads in the Maijishan Grottoes.