地震作用下无筋砌体墙的抗剪可靠度分析

Structural reliability analysis of unreinforced masonry walls under lateral loads

无筋砌体墙主要用来承受重力荷载,同时当受到风荷载和地震作用时又需要承受横向荷载。横向荷载和竖向荷载同时作用使砌体墙处于受拉、受压和受剪状态,砌体受拉和受剪破坏会导致砌体垮塌、人员伤亡以及经济损失。目前关于无筋砌体墙受压或受弯性能已有大量的研究,但对于无筋砌体墙在受竖向荷载和横向荷载同时作用时抗剪能力研究甚少。本文采用概率模型来分析无筋砌体墙在地震作用下的抗剪承载力可靠度。无筋砌体墙受剪极限状态是基于已有的试验结果和有关文献评论来定义的,抗剪切能力考虑了砌体墙在受压和受剪下的不确定因素以及活荷载/雪荷载与恒荷载的比率和砌体墙高宽比。利用蒙特卡罗方法来进行砌体墙可靠度的分析,其中还考虑到计算模型的影响。最后,影响无筋砌体墙在地震作用下抗剪能力各因素的敏感度分析,分析结果为确定其是影响抗剪性能的主要因素还是次要因素提供了理论依据。

Unreinforced masonry shear walls are mainly used to support gravity loads.In the meantime,the walls may need to carry the lateral loads when subjected to winds and earthquakes.The lateral and gravity loads result in tension and shear combined with compression in the masonry wall.The shear or tension failure of the shear wall may lead to the collapse of the building and result in casualties and economic losses.Although the reliability of unreinforced masonry shear walls under compression and/or bending moment has been studied,very little work has been done to investigate the reliability of unreinforced masonry wall under combined gravity and lateral loads.This paper presents a probabilistic model to determine the structural reliability of typical unreinforced masonry walls under combined gravity and lateral loads.A performance limit state is defined for the walls under the combined loads,based on experimental test results and literature review.Shear capacity is established incorporating the uncertainty in compression and shear strength of masonry,ratio of snow/live load to dead load,and ratio of wall height to thickness.Monte Carlo Simulation is used to perform the reliability analysis.Model error is considered in the analysis.Lastly,a sensitivity analysis is performed to identify the key contributors to the reliability of the unreinforced masonry wall under the lateral loads.The results provide a base to evaluate whether consistent safety is achieved for unreinforced masonry walls that are subjected to different load combinations.