Block-Based Simulation of the Out-of-Plane Seismic Response of Non-Framed Unreinforced Masonry Walls with Pre-Existing Settlement-Induced Damage

Abstract

This paper presents a numerical investigation on the effects of settlement-induced pre-damage on the seismic out-of-plane (OOP) response of two-way spanning non-framed unreinforced masonry (URM) walls, investigating also the suitability of static analysis procedures for simulating the dynamic OOP response of pre-damaged walls. For this purpose, the finite-element block-based modeling approach developed and validated by the authors in previous works is employed. URM walls with various geometries and boundary conditions are simulated to investigate the effects of openings and wall-to-diaphragm connections on pre-damage effects. Each specimen is subjected to various settlement profiles, and different levels of obtained settlement-induced damage states are used as initial conditions for OOP analyses. Static and dynamic OOP simulations, the latter considering both induced and tectonic seismicity, and modal analyses are performed. The outputs show that settlement effects on the OOP response emerged as early as the light pre-damage state. Sagging, previously considered in literature less damaging than hogging, caused the greatest OOP stiffness and strength reduction, up to 92% and 80%, respectively. Hogging led to a 60% stiffness and 30% strength drop, particularly in walls with openings. Induced seismicity did not lead to collapse. Static analyses accurately estimated OOP strength and failure mechanisms.