In recent earthquakes, unreinforced masonry (URM) structures built of masonry walls containing openings such as doors and windows have been shown to have poor seismic capacity. However, although different sizes and positions of openings are known to reduce the stiffness and strength of URM walls, the relationships between the size and position of openings and seismic capacity of the walls are not clear. Therefore, a series of numerical analyses has, for the first time, explored many possible opening sizes and opening positions under simulated seismic loading to identify their impact on the in-plane behaviour of URM walls. The numerical models were built using the code “3DEC” which is based on the discrete element method (DEM). The key feature of the DEM is that it allows the development of large displacements between elements with contacts being recognized automatically during the analysis. Thus, this numerical method can capture the whole degradation progress from the initial cracking of the masonry walls right through to collapse, with the bricks being modelled as rigid blocks and the mortar as Coulomb-slip joints with zero thickness. Both load-based and displacement-based quasi-static pushover analysis procedures have been studied and the modelling methodology and the calibration of numerical models is described. The results from the analyses, the crack patterns and collapse mechanisms of the masonry walls are identified and discussed, and a key output from this work is the characterization of the relationships between the sizes and positions of openings and the in-plane performance of URM walls.

中文翻译：

---

开口的大小和位置对无筋砌体墙面内承载力的影响

在最近的地震中，已证明，由带有开口（例如门和窗户）的砖石墙建造的非增强砖石（URM）结构的抗震能力很差。然而，尽管已知开口的不同尺寸和位置会降低URM壁的刚度和强度，但是开口的尺寸和位置与壁的抗震能力之间的关系尚不清楚。因此，一系列数值分析首次探索了在模拟地震荷载作用下的许多可能的开口尺寸和开口位置，以识别它们对URM墙面内行为的影响。使用基于离散元素方法（DEM）的代码“ 3DEC”建立了数值模型。DEM的关键特征是，它允许在分析过程中自动识别接触的元素之间产生大位移。因此，这种数值方法可以捕获从砌体墙的最初开裂一直到坍塌的整个降解过程，其中将砖建模为刚性块，将砂浆建模为零厚度的库仑-滑动缝。研究了基于载荷和基于位移的准静态推覆分析程序，并描述了建模方法和数值模型的校准。从分析结果中，确定并讨论了砌体墙的裂缝模式和倒塌机理，