三向地震作用下麦积山石窟栈道地震动力响应研究

The Dynamic Response of Plank Roads at the Maijishan Grottoes Site under Three-dimensional Seismic Loads

为探究麦积山石窟人行栈道在三向地震作用下的响应规律,评估地震发生时石窟栈道的安全性,结合现场勘察情况,利用ABAQUS有限元软件建立第191石窟处栈道实体模型,分析栈道在三向地震作用下的加速度、位移、应力响应特性,结果表明,栈道结构在竖向的加速度响应明显大于水平方向,栈道斜梯各向加速度响应均大于平台板响应,平台板随其嵌固位置高度的增大,加速度响应峰值增大,梯段加速度响应取决于斜梯跨度和梯段嵌固位置两个因素;栈道位移响应规律与加速度响应规律相似,斜梯跨度越大,嵌固位置越高,竖向位移响应峰值越大;栈道结构悬臂梁嵌固端部与变截面处混凝土应力较大,斜梯梁跨中钢筋应力较大,栈道悬臂梁和梯段斜梁均易发生受弯破坏,栈道结构中受力构件悬臂梁的嵌固端部、梯段斜梁中部均为易损部位,应被作为抗震加固的重点关注对象,栈道斜梯跨度大,竖向刚度小,竖向地震对其响应的影响不容忽略。

To investigate the response patterns of the pedestrian plank roads at the Maijishan Grottoes site under three-dimensional seismic loads,and to evaluate their safety in the event of an earthquake,a soild model of the plank road in cave 191 was created based on in-situ survey results that were collected using ABAQUS finite element software to analyse the acceleration,displacement,and stress response characteristics of the road under the three-dimensinal seismic loads.The results show that the vertical acceleration response of the plank road is significantly greater than that in the horizontal direction.In particular,the inclined stairs have a larger acceleration response than flat platform boards,and peak acceleration response was found to increase with the height of a given platform board.The acceleration response of the inclined stairs depends on the two factors of the span and fixed position of the planks.The displacement response pattern of the plank road was similar to the pattern for acceleration response,including the results related to inclined stairs and planks with a larger span and higher fixed position.At the fixed ends of cantilever beams and the variable cross-sections of the plank road,the concrete stress is significant,while stress on the steel reinforcements under girding the mid-span of the inclined stair beams is also relatively large.Under seismic action,it was found that bending is likely to occur on both the plank road's cantilever beams and inclined stair beams.The fixed ends of the cantilever beam and the mid-section of the inclined stair beam,both of which are force-bearing components of the plank road structure,are vulnerable sections that should be given priority attention when taking seismic reinforcement measures.The vertical impact of earthquakes on the inclined stair,with its large span and low vertical stiffness,cannot afford to be ignored when calculating the likely response.