Seismic Vulnerability Evaluation of a Historical Masonry Tower: Comparison between Different Approaches

Abstract

Throughout the last few decades, the scientific community has paid great attention to the structural safety of historical masonry constructions, which have high vulnerability with respect to seismic activities. Masonry towers are very widespread in Italy and represent an important part of the built heritage to be preserved. Different numerical methods with different levels of refinement were developed in the literature to evaluate their seismic performance. The present study shows a practical application of the seismic vulnerability evaluation of a masonry tower using different approaches. The aim is to provide practical suggestions to engineers for the successful evaluation of the performance of masonry towers under seismic loads. An in situ survey was performed to characterize the geometry of the structure and its constitutive material. All the collected information was introduced in a building information model, later used to generate different finite element models for the structural analyses. The global capacity of the structure was evaluated using three different models with different levels of complexity: the first simplified model is made of beam elements with cross-sections discretized in fibers; the second model is made of shell elements and uses a concrete damage plasticity model to describe the nonlinear masonry behavior; the third model adopts solid elements with a concrete smeared crack constitutive law. A preliminary eigen-frequency analysis is performed on the shell model to obtain some basic information about the structural behavior. Nonlinear static analyses were carried out for each model to understand the response of the tower under seismic loads, highlighting the main differences between the approaches. The behavior factor was evaluated on the basis of the analyses results and compared with the ones suggested by the Italian building code. The results showed that the towers do not satisfy the seismic demand required by the standards for all the considered models. Furthermore, the behavior factor calculated according to the Italian design code is overestimated, while the one evaluated by the simplified model is underestimated due to the neglection of the shear behavior. From all the analyzed configurations, the shell model resulted as a good compromise between reliable results and computation efficiency.

Seismic Assessment and Retrofitting of an Historical Masonry Building Damaged during the 2016 Centro Italia Seismic Event

“…This modeling hypothesis is derived from the damages observed in this type of construction subjected to seismic event which show that, usually, cracks and failure modes are localized in piers and spandrels, while little damage is observed at their intersection, thus justifying the adoption of rigid offsets in the modelling process. Bending moments between orthogonal walls have been released to represent the unperfect toothing and avoid out-of-plane response of piers [28]. According to [26], the following collapse mechanisms have been considered for the structural elements: (i) diagonal shear cracking, (ii) sliding failure and (iii) rocking failure due to bending moment.…”

About the Use of Concrete Damage Plasticity for Modeling Masonry Post-Elastic Behavior

“…This model was first developed for modeling concrete [39,40] and through the years has also found application in modeling high-strain events such as blast and impact loads [41,42]. Later, it has been also applied to the study of masonry structures, both for micro models [43][44][45][46][47] and for homogeneous models [48][49][50][51][52][53][54][55][56]. There are a number of constitutive models available in the libraries of commercial FE software for masonry, which, drawing on decades of studies and advances in the field of masonry mechanics, all have in common the ability to effectively describe the highly nonlinear behavior, plasticity and damage development, and hysteretic dissipation that characterizes such a material.…”

Path of Knowledge for the Assessment of Structural Safety of the Pisan Tower of the Royal Palace of Palermo in Italy

“…However, masonry structures have a highly nonlinear behavior due to their nature, i.e., being composed of assemblages of resisting blocks and dry or mortar joints, with diverse dimensions, thicknesses, and material properties. Different approaches are currently available in the literature for the vulnerability assessment of masonry structures, such as numerical continuum and discrete methods (e.g., [6][7][8][9]), or novel approaches based on the sensitivity-informed parameter reduction of detailed mechanics-based models [10,11]. Among the numerical methods, one of the most efficient is the discrete element method (DEM) used for the simplified micro-modelling of masonry (e.g., [12,13]).…”