Prediction of Rubble-Stone Masonry Walls Response under Axial Compression Using 2D Particle Modelling

Abstract

To predict the structural behaviour of ancient stone masonry walls is still a challenging task due to their strong heterogeneity. A rubble-stone masonry modeling methodology using a 2D particle model (2D-PM), based on the discrete element method is proposed given its ability to predict crack propagation by taking directly into account the material structure at the grain scale. Rubble-stone (ancient) masonry walls tested experimentally under uniaxial compression loading conditions are numerically evaluated. The stone masonry numerical models are generated from a close mapping process of the stone units and of the mortar surfaces. A calibration procedure for the stone-stone and mortar-mortar contacts based on experimental data is presented. The numerical studies show that the 2D-PM wall models can predict the formation and propagation of cracks, the initial stiffness and the maximum load obtained experimentally in traditional stone masonry walls. To reduce the simulation times, it is shown that the wall lateral numerical model adopting a coarser mortar discretization is a viable option for these walls. The mortar behaviour under compression with lateral confinement is identified as an important micro-parameter, that influences the peak strength and the ductility of rubble-masonry walls under uniaxial loading.

Numerical Evaluation of Transverse Steel Connector Strengthening Effect on the Behavior of Rubble Stone Masonry Walls under Compression Using a Particle Model

“…Previous studies conducted by the authors on URM specimens [24,27] have demonstrated that particle models can be effectively utilized as a predictive tool for rubble-stone masonry walls constructed with hydrated air lime mortar [2,10] under uniaxial compressive loading conditions. As demonstrated in [24,27], good agreement can be achieved with stone masonry wall behavior, including elastic response, peak strength, and ductility, provided that the calibration of the contact parameters is based on experimental data of the components obtained from laboratory tests.…”

“…In the study presented in [24], three important findings are reported: (i) the lateral numerical model can reproduce the URM peak strength and overall mechanical behavior; (ii) a coarser mortar discretization can be employed without affecting the quality of the numerical predictions; and (iii) a maximum contact compressive yielding stress is necessary to adopt under compression due to the heterogeneity of URM. These findings are encouraging for the use of the 2D-PM model in evaluating the efficacy of transverse reinforcement strengthening systems.…”

“…where at time t, F i (t) is the force vector and M 3 (t) corresponds to the applied moment; F d i (t) and M d 3 (t) are the force vector and moment associated with the local non-viscous damping [24]; ẍi is the acceleration, ω3 is the angular acceleration of the particle; i = 1, 2 indicates the global x and y directions; and m and I correspond to the particle's mass and inertia of the spherical particle.…”

“…In this paper, a detailed micro-modeling strategy based on a particle model (2D-PM) [21][22][23] is adopted, which is known to successfully model the complex macroscopic failure with simple constitutive models by taking into account the material structure at the grain scale. This approach has been adopted by the authors in the modeling of traditional rubble stone masonry walls under uniaxial compression loading [24]. After calibrating the contact parameters using known mortar and stone experimental data, the 2D-MP model is capable of predicting and representing the elastic response, the process of crack formation, propagation in rubble masonry walls, and the peak load value in uniaxial compression based on simple interaction models [24].…”

“…This approach has been adopted by the authors in the modeling of traditional rubble stone masonry walls under uniaxial compression loading [24]. After calibrating the contact parameters using known mortar and stone experimental data, the 2D-MP model is capable of predicting and representing the elastic response, the process of crack formation, propagation in rubble masonry walls, and the peak load value in uniaxial compression based on simple interaction models [24]. The 2D-PM model is also an excellent framework to generate the heterogeneity that is present in rubble masonry walls.…”