Masonry behaviour and modelling

In this Chapter we present the basic experimental facts on masonry materials and introduce simple and refined models for masonry. The simple models are essentially macroscopic and based on the assumption that the material is incapable of sustaining tensile loads (No-Tension assumption). The refined models account for the microscopic structure of masonry, modeling the interaction between the blocks and the interfaces.(undefined

Homogenization and seismic assessment : review and recent trends

The mechanics of masonry structures has been for long underdeveloped in comparison with other fields of knowledge. Presently, non-linear analysis is a popular field in masonry research and advanced computer codes are available for researchers and practitioners. The chapter presents a discussion of masonry behaviour and clarifies how to obtain the non-linear data required by the computations. The chapter also addresses different homogenisation techniques available in the literature in the linear and rigid-plastic case, aiming at defining a catalogue and at discussing the advantages and disadvantages of the different approaches. Special attention is given to stress assumed models based either on a polynomial expansion of the micro-stress field or in the discretization of the unit cell by means of a few constant stress finite elements CST with joints reduced to interfaces. Finally, the aspects of seismic assessment are presented and case studies involving the use of macro-block analysis, static (pushover) analysis and time integration analysis are discussed.(undefined

A micro-mechanical homogenisation model for masonry: Application to shear walls

An improved micro-mechanical model for masonry homogenisation in the non-linear domain, is proposed and validated by comparison with experimental and numerical results available in the literature. Suitably chosen deformation mechanisms, coupled with damage and plasticity models, can simulate the behaviour of a basic periodic cell up to complete degradation and failure. The micro-mechanical model can be implemented in any standard finite element program as a user supplied subroutine defining the mechanical behaviour of an equivalent homogenised material. This work shows that, with the proposed model, it is possible to capture and reproduce the fundamental features of a masonry shear wall up to collapse with a coarse finite element mesh. The main advantage of such homogenisation approach is obviously the possibility to simulate real complex structures while taking into consideration the arrangement of units and mortar, which would otherwise require impractical amount of finite elements and computer resources.- (undefined

A students‘ challenge for the estimation of the maximum compressive load of masonry prisms:Studentenwettbewerb zur Ermittlung der maximalen Druckfestigkeit von Mauerwerksprismen

The paper presents the “IMC Students' Challenge” competition held in 2014, during the 9th International Masonry Conference, in Guimarães. The objective of the competition was to predict the maximum compressive load of two masonry prisms built of solid bricks, and of hollow blocks, with mortar joints. To increase the complexity of the problem, all prisms were tested under eccentric load. The students, who enthusiastically participated in the final laboratory tests, presented different approaches to estimate the maximum eccentric compressive force on masonry prisms. The challenge was a great experience, not only for students and conference participants, but also for sponsors and organizers

Simulation of moisture transport in fired-clay brick masonry structures accounting for interfacial phenomena

This paper presents a numerical study on moisture transport in brick masonry walls with a special focus on the simulation of their hygric performance as well as the hydraulic phenomena at the brick-mortar interface. A diffusivity model based on Fick's law is used to describe the moisture transport accounting for both liquid and water vapor movement. The necessary hygric parameters are obtained directly from experimental tests or determined by curve fitting. The proposed model is validated with respect to water absorption and drying tests. The good-fitness of the results is qualitatively assessed and an overall good agreement is found between the simulated and measured curves. It is demonstrated that the chosen liquid water diffusivity expression needs to be adjusted to represent drying processes; the necessary adjustment is made through a diffusivity factor implemented in the original analytical expression. The interface impact on water absorption is introduced as a hydraulic resistance. Moreover, it is hypothesized that the presence of successive interfaces entails an additive in-series effect. Conversely, the interfacial impact on drying is negligible. Finally, the proposed model is extended to different modeling approaches commonly used for mechanical studies of masonry. The necessary input data, modeling methodology, advantages and disadvantages associated with each modeling strategy are also discussed. The present study points out the need of studying water absorption in multi-layered structures made up of constituents with relatively similar hygric behavior. In such cases, the impact of imperfect contact at the interface between materials is not negligible.Article publishing charge (APC) funded by agreement between Portugal (FCT/FCCN) and Elsevie

Homogenised limit analysis of masonry walls : part II : structural examples

The homogenised failure surfaces obtained through the simple micro-mechanical model developed in the first part of the paper are here used for the analysis of in-plane loaded masonry walls. Both upper and lower bound homogenised limit analyses are employed for treating meaningful structural cases, namely a deep beam and a set of shear walls. Detailed comparisons between the experimental data and numerical results obtained using both a heterogeneous and a homogenised approach are also presented. The examples show the efficiency of the homogenised technique with respect to: 1) accuracy of the results; 2) reduced number of finite elements required; 3) independence of the mesh, at a structural level, from the actual texture of masonry. A final example on a large scale wall is presented with the aim to show an engineering application of the proposed approach.Project MIUR COFIN 2003 – "Interfacial damage failure in structural systems"

Flexural Resistance of Masonry Wall Retrofitted with Timber Panel under Out-Of-Plane Loading

Retrofit of unreinforced masonry (URM) structures is incessantly attracting interests of masonry professionals. Because there are enormous URM structure stocks in different parts of the world that have shown vulnerability to damage against out-of-plane actions due to having limited flexural strength and deformation capacity [1]. As such, there is a global trend of promoting the development of sustainable retrofit techniques for URM structures. The authors' previous study [2] has introduced the application of oriented strand board type 3 (OSB/3) as a prospective sustainable retrofit material for URM wall with evidence of improving the flexural performances. This paper presents, for the first time,experimental works on 1115 x 1115 x 215 mm double wythe single leaf URM walls. Specifically, quasi-static out-of-plane loading tests were carried out on two plain specimens, two single-sided retrofitted walls and two double-sided retrofitted walls. The flexural and displacement capacities were evaluated in both plain and retrofitted specimens, and the results substantiated that OSB/3 application improves the flexural capacity of masonry wall. Therefore, the application of OSB/3 for retrofitting URM buildings can be considered as an inexpensive, efficient and sustainable retrofit technique

Assessment of the Seismic Retrofitting of a Historical Masonry Mosque by means of Nonlinear Dynamic Analysis

Seismic actions have been a great challenge for structures in the structural engineering community, and the need for further developments has been approved by catastrophic seismic events at each time. Reproducing the dynamic behavior of structures with an acceptable level of accuracy is a complex task due to uncertainties related to the geometrical, material and physical structural system, more particularly, in the case of existing historical masonry structures. The use of dynamic analysis is a better choice than the use of static or quasi-static approaches since it is a better representation of the dynamic response of a structure by taking account of its energy dissipation capacity. The scope of the present paper is focused on a seismic assessment of a historical masonry structure, Kütahya Kurşunlu Mosque located in Turkey, before and after it has been retrofitted. The historical mosque is located in a seismic prone zone where it is crucial to ensure seismic safety of structures and the local community. Based on the condition of the structure reported from the site inspections, a seismi retrofitting by using steel girder elements was implemented on the structural load-bearing walls. The effectiveness of the seismic retrofitting to the seismic response of the mosque was investigated by means of the finite element method. Three bi-directional nonlinear dynamic analyses were performed by using real ground motion records aiming at the validation of the nonlinear dynamic response of the numerical model in terms of damage patterns, and demonstration of the contribution of the seismic retrofitting by comparing the representative model with its retrofitted counterpart. The comparison has been carried out in terms of peak displacement and damage patterns. It is found that the contribution of the seismic retrofitting is considerable for the out-of-plane displacements of the load-bearing walls. Furthermore, a good correlation between existing damage and the numerical damage is achieved, and, therefore, the validation of the nonlinear response of the representative model is attained

Continuous Structural Monitoring of Adobe Buildings: Summary of a Three Years Experience in Peru

The paper describes in detail the application of a vibration-based structural health monitoring system installed in the “San Pedro Apostol” church of Andahuaylillas located in Cusco (Peru), a 16th century adobe church considered a representative example of South America baroque architecture. The results of three years of long-term vibration and temperature and humidity monitoring program are reported in detail in the paper, with a focus on the long-term and short-term correlations between natural frequencies and environmental parameters. The results demonstrate that an accurate estimation of the first eight frequencies in the range 2-6 Hz is possible in the case of complex adobe structure and the existence of an annual cyclical behavior of the natural frequencies with a clear correspondence with the changes in environmental conditions due to seasonal influences. The performed correlations of ambient conditions and structural parameters confirmed the presence of different timescales and their not negligible influence in the case of a vibration-based structural health monitoring assessment of adobe systems with large thermal inertia large thermal inertia

Numerical Study of Out-of-Plane Behaviour of Timber Retrofitted Masonry Prisms

The present study addresses the retrofitting of running-bond masonry walls through the application of oriented strand board (OSB) timber panels aiming to increase the masonry flexural strength and deformation capacity under out-of-plane actions. This paper presents the numerical analysis of masonry prisms to complement the information provided by the experimental campaign developed on flexural performances of timber retrofitted masonries. The numerical model represents the masonry components (brick and mortar) as a three-dimensional volume via volumetric finite elements, i.e. hexahedral 8-node linear brick elements with reduced integration and hourglass control. The nonlinear properties of the mortar joints and the brick units have been calibrated through information that resorts from experimental characterization tests. The numerical damage pattern and load-displacement capacity curve are compared with the experimental observations. A good agreement has been found and, therefore, the calibrated model can be employed in parametric studies, to further analyse the efficiency of the proposed timber masonry retrofit technique, and to more complex structural study cases