Investigation on the Effect of Mortar Quality on the Out-Of-Plane Seismic Performance of Unreinforced Masonry Walls

Abstract eng:
Unreinforced masonry (URM) walls are used in a broad range of building-stock worldwide. These walls are susceptible to a loss of functionality, structural damage, or complete collapse during earthquakes. Damage to URM walls due to the out-ofplane loading is usually characterized by weak modes of failure, due to cracking of the mortar joints and crushing failure of the masonry. In addition, historic buildings may present poor mortar quality, degraded and crumbled mortars, and variation of mortar quality through the wall thickness due to the weathering (and later outside repointing), workmanship and aesthetic preferences; this can make the walls more prone to complete collapse during a seismic event. This study aims to highlight the significance of mortar quality on the seismic performance of URM buildings and the potential need for retrofitting options for buildings with degraded mortar. A validated masonry material model is used to model a 1.4m wide by 2.8m high wall using the LS-DYNA finite element software. Several material parameters (e.g. compressive strength of masonry, tensile strength of bed joints) are varied through the thickness of walls to model the effect non-homogeneous mortar degradation on the out-of-plane performance of walls. These variations are repeated for two types of masonry: calcium silicate and clay walls. Furthermore, a full 3D model of a typical two-story URM building with the timber framing system is analyzed under earthquake conditions to determine the influence of these variations of mortar quality on its seismic performance.

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