Savvas Saloustros

An Enhanced Finite Element Macro-Model for the Realistic Simulation of Localized Cracks in Masonry Structures: A Large-Scale Application

ABSTRACT Finite element macro-modeling approaches are widely used for the analysis of large-scale masonry structures. Despite their efficiency, they still face two important challenges: the realistic representation of damage and a reasonable independency of the numerical results to the used discretization. In this work, the classical smeared crack approach is enhanced with a crack-tracking algorithm, originating from the analysis of localized cracking in quasi-brittle materials. The proposed algorithm is for the first time applied to a large-scale wall exhibiting multiple shear and flexural cracking. Discussion covers structural aspects, as the response of the structure under different assumptions regarding the floor rigidity, but also numerical issues, commonly overlooked in the simulation of large structures, such the mesh-dependency of the numerical results.

Tracking of Localized Cracks in the Finite Element Analysis of Masonry Walls

Macro-models are a common choice for the numerical analysis of large-scale masonry structures. Despite their efficiency in terms of pre-processing and computational cost, these strategies often result in a poor representation of cracking, not properly localized and biased by the finite element mesh orientation. This work presents a remedy to the previous shortcomings through the enhancement of the standard smeared crack approach with a crack-tracking algorithm. The smeared crack approach reduces the computational cost and ensures a computationally efficient analysis of small- and large-scale structures. The crack-tracking algorithm aids the localized representation of cracking and improves the mesh-objectivity of the numerical results. A novel crack-tracking algorithm is introduced allowing the modelling of intersecting and multi-directional cracks, which commonly occur in masonry structures under cyclic loading. At constitutive level, a simple and explicit algorithmic formulation is presented, which includes the description of irreversible deformations into an orthotropic continuum damage model. The proposed numerical model is used to simulate the response of an experimentally tested masonry wall under shear cyclic loading.

Vulnerability Assessment of Monumental Masonry Structures Including Uncertainty

Existing heritage structures are frequently composed of diverse masonry typologies, corresponding either to various structural members (e.g. arches, walls, piers) or to additions constructed in different eras. The identification of the material properties of the different masonry typologies is usually demanding due to the high cost of the necessary specialized in-situ experimental testing procedures and to the restrictions posed by the cultural value of historical buildings. This lack of information underlines the importance of probabilistic studies considering the uncertainties connected with the evaluation of the material properties. Such activities become essential in studies dealing with the conservation of built cultural heritage against hazardous events, such as earthquakes. This work investigates the seismic vulnerability assessment of large monumental structures with complex geometry. The church of Santa Maria del Mar in Barcelona is considered as a case study, and a representative macro-element of the bay structure is studied against in-plane horizontal loading through pushover analysis. A Monte Carlo simulation is used to estimate the effect of the uncertainties on the material properties, which are considered as random variables. The developed fragility curves express the safety level and the damage expected on the structure for different seismic hazard scenarios.