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

Publisher Copyright: © 2022 by the authors. This research received no external fundingTo 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.publishersversionpublishe

Discrete element modeling of masonry structures: Validation and application

The failure mechanism and maximum collapse load of masonry structures may change significantly under static and dynamic excitations depending on their internal arrangement and material properties. Hence, it is important to understand correctly the nonlinear behavior of masonry structures in order to adequately assess their safety and propose efficient strengthening measures, especially for historical constructions. The discrete element method (DEM) can play an important role in these studies. This paper discusses possible collapse mechanisms and provides a set of parametric analyses by considering the influence of material properties and cross section morphologies on the out of plane strength of masonry walls. Detailed modeling of masonry structures may affect their mechanical strength and displacement capacity. In particular, the structural behavior of stacked and rubble masonry walls, portal frames, simple combinations of masonry piers and arches, and a real structure is discussed using DEM. It is further demonstrated that this structural analysis tool allows obtaining excellent results in the description of the nonlinear behavior of masonry structures

Historic Masonry

Masonry is a composite material characterised by its good behaviour under dead loads and in a nonaggressive environment. However, this noble material does not satisfactorily resist seismic loads. The different types of historical masonry that have remained over time are characterised by an adequate mixture of materials with low chemical reactions that are degrading due to environmental conditions. There are numerous historical masonry construction techniques in the world, reflecting local conditions of materials and workmanship. The key to its permanence and maintenance over time despite the effects of earthquakes is the construction technology and quality of materials used. As a result of earthquake damage observation and experimental research, various technical solutions for rehabilitation and retrofit of masonry are now available. Finite element modelling has become a very useful tool to identify the damage problem in historical masonry but requires a significant contribution of parameters obtained from destructive and nondestructive tests

A Methodological Framework for Seismic Vulnerability Assessment of Masonry School Buildings: Application to Nepal

Due to the high seismic risk posed by the school infrastructure in developing countries and the lack of technical quantitative tools for risk assessment and strengthening prioritization, this study aims to develop a seismic vulnerability assessment methodology recognizing the high variability in the seismic performance of different masonry typologies. The expectation is that such framework should be applicable to countries in the Himalayan belt and possibly further afield. To this end, the Nepalese school portfolio is used to develop as well as validate the framework. A first step in this study is to classify a number of masonry typologies of school buildings, differentiated by construction materials, building height and seismic design level. Although these parameters are sufficient to qualitatively rank the vulnerability of a typology, other construction features such as diaphragm type or wall panel length are critical to quantitatively determine its expected seismic response and fragility, as proven by the vulnerability results in this study. The identification of these relevant parameters underpins a globally applicable taxonomy. The applied element method is employed for the analysis so as to accurately represent the seismic capacity and failure mechanism of different masonry typologies. For the typologies lacking box-like behaviour, a tailored pushover analysis approach is developed, allowing computation of in-plane and out-of-plane capacity and fragility separately, then combined to derive a mean global vulnerability function. The vulnerability results for distinct typologies better inform effective risk reduction policies, by allowing prioritised and incremental strengthening strategies. In the Nepalese context, the results show that most of the masonry school typologies are in need of immediate strengthening while traditional seismic safety measures such as horizontal bands prove to be effective in order to comply with the life safety performance level under seismic hazard and also to ensure adequate functionality requirements

THE EARLY PHRYGIAN GATE AT GORDION, TURKEY: AN INVESTIGATION OF DRY STONE MASONRY IN SEISMIC REGIONS AND RECOMMENDATIONS FOR STABILIZATION

The archaeological site at Gordion, Turkey is located in a region of high seismic activity, which threatens the standing masonry structures—particularly the dry laid limestone walls—of the ancient Phrygian capital. First excavated in the 1950s, the citadel gate is composed of an ashlar limestone veneer encasing a rubble core. Although the gate has been the focus of several conservation efforts, the unreinforced masonry structure requires study and possible stabilization to mitigate and prevent further bulging or even collapse. The gate’s current conditions include extensive cracking, spalls, split faces, missing chinking stones, open joints and bulges, which partially result from the complex history of the site. Constructed around 900 BC, the Early Phrygian Gate only briefly served as the main entryway to the citadel; it was then affected by fire and burial and used as a foundational support for later structures. Partial excavation has largely exposed the North and South Courts of the gate complex. However, several courses of the later building stone remain in localized areas of the gate walls, and the interior of South Court still contains the almost 3,000 year old clay construction fill. These factors have contributed to displacement of the multiple leaf system by exerting lateral force and causing compression and shear cracks. This thesis synthesizes existing knowledge of the behavior of masonry during seismic events, properties of dry stone structures and site-specific characteristics as a basis for constructing recommendations for future monitoring and stabilization efforts

Effect of the vertical component of ground motion on a rubble masonry wall model

In this paper the influence of the vertical component of ground motion on the performance of an unreinforced masonry wall is analysed using sets of one-component and two-component ground motions. The set of motions represents the actual seismicity of L'Aquila, while the investigated wall mimics an experimental specimen with two unconnected external leaves and a rubble core. The model falls within the mixed finite element method – discrete element method and accounts for crack formation, complete separation and new contact formation. The modelling strategy is capable to simulate the out-of-plane seismic response and the progressive loss of compactness of the wall up to collapse with the separation between the two external leaves. The vertical component increases the fragility of the wall and confirms the relevance of vertical ground motion for very vulnerable constructions. Nonetheless, to worsen the response, the vertical component needs to overcome specific, non-negligible intensity measure thresholds

Seismic performance of historical buildings based on discrete element method: an adobe church

This article presents the main concepts and the application of the discrete element method (DEM) for evaluating the seismic performance of historical buildings. Furthermore, the out-of-plane behavior of an adobe church with thick walls, in which the morphology of the cross-section can have an influence on the response, was evaluated by the DEM. The performance of rigid and deformable blocks models was compared, and the sensitivity of the numerical model to the variation of critical parameters was investigated. The results allowed the identification of the most vulnerable elements and a proposal of recommendations for reducing the seismic vulnerability

2015 Nepal earthquake: seismic performance and post-earthquake reconstruction of stone in mud mortar masonry buildings

This report is an outcome of the analysis of data and information related to the damage and post-earthquake reconstruction of residential buildings, collected during the field survey by the authors, in light of 2015 Nepal earthquake sequence