A mixed micromechanical homogenisation scheme for the prediction of the 3D orthotropic elastic properties of different masonry bond typologies

Masonry structures composed of two distinct material phases (units and mortar) with potentially vastly different elastic properties are characterised by strong orthotropy. The variety of commonly employed bond typologies for masonry walls, featuring unit groups and mortar joints with different orientation with respect to the plane of the wall, result in complex stress and strain interactions between the material phases.Postprint (published version

Micro-modeling of stack bond masonry in compression using a plasticity law

A set of experimental tests to determine the compressive strength of masonry stack prisms has been numerically simulated using a combined plasticity-smeared crack constitutive law employed in three-dimensional analysis

In-plane behaviour of rammed earth under cyclic loading: Experimental testing and finite element modelling

The intent of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective load-displacement relationships as well as the failure modes. The calibration of the numerical model (finite elements method) was carried out using the experimental results. A micro modelling approach was considered. The behaviour of rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between layers. Although the results of the numerical model well fit the experimental results a sensitivity analysis was performed to define also the influence of different input parameters. As expected the sensitivity analysis shows that the occurrence of sliding failure is mainly influenced by two parameters of the interface elements: the tensile strength and the friction angle. Moreover the cohesion and the layers thickness show a limited influence on the shear behaviour.Peer ReviewedPostprint (author's final draft

Seismic behaviour of the walls of the Parthenon: A numerical study

A numerical study of the behaviour of the walls of the Cella of Parthenon subjected to seismic loading is presented. Commonly used numerical codes for masonry structures based on continuum mechanics are unable to handle the behaviour of discontinuous walls of ancient monuments, in the same way as continuum models cannot capture the behaviour of drum-columns. In this analysis, the discrete element method was used, which has been proven, in previous research, capable to accurately predict the response of discontinuous structural systems. The marble structural stones of the walls were modeled as rigid blocks with fric- tional joints between them. Two types of models were used in the analyses: (i) a sub-assembly consisting of only a section of the wall of limited length, either as it is in-situ (partially col- lapsed) or with its full height (restored) and (ii) considering the whole structure partially re- stored. In one of the models of type (i), the existing damage of the stones was also implemented. Analyses were performed with and without considering the metallic elements (clamps and dowels) that connect adjacent stonesPart of the research presented in this paper was funded by the Committee for the Preserva- tion of the Acropolis Monuments (YSMA), which also provided the restoration scenario that was used for the full-structure model of Figure 3. Special thanks are due to A. Vrouva, civil engineer with YSMA and N. Toganidis, architect with YSMA, for their help with the con- struction details of the monumenPostprint (published version

Analytical models to determine in-plane damage initiation and force capacity of masonry walls with openings

Masonry panels consisting of piers and spandrels in buildings are vulnerable to in-plane actions caused by seismicity and soil subsidence. Tectonic seismicity is a safety hazard for masonry structures, whereas low-magnitude induced seismicity can be detrimental to their durability due to the accumulation of light damage. This is particularly true in the case of unreinforced masonry. Therefore, the development of models for the accurate prediction of both damage initiation and force capacity for masonry elements and structures is necessary. In this study, a method was developed based on analytical modeling for the prediction of the damage initiation mode and capacity of stand-alone masonry piers; the model was then expanded through a modular approach to masonry walls with asymmetric openings. The models account for all potential damage and failure modes for in-plane loaded walls. The stand-alone piers model is applicable to all types of masonry construction. The model for walls with openings can be applied as is to simple buildings but can also be extended to more complex structures with simple modifications. Model results were compared with numerous experimental cases and exhibited very good accuracy.Peer ReviewedPostprint (author's final draft

The compressive behaviour of mortar under varying stress confinement

The confinement of mortar in masonry under compression is one of the key processes influencing the compressive strength of the composite material. It is triggered by the mismatch of elastic properties between units and mortar, coupled with deformation conformity between the two material phases. In cases where the mortar is particularly deformable compared to the units, this confinement results in a peak stress many times the uniaxial compressive strength of the mortar. Therefore, a careful examination of this effect is critical in understanding the failure mechanisms of masonry in compression.Mortar under compression can be modelled in a damage mechanics context, following the establishment of a) a constitutive stress-strain relation, b) a model for the increase of the compressive failure stress under lateral confinement and c) a model for the development (increase) of the Poisson’s ratio of mortar under different stress levels. The first aspect is approached using established hardening-softening curves used for quasi-brittle materials, such as concrete. The second aspect is dealt with through the adoption of a suitable and sufficiently flexible failure criterion. The third aspect is addressed through fitting against experimental data.The above aspects are expressed in a damage mechanics context, resulting in fast calculations of the compressive stress-strain curves for confined mortar. This approach allows the quantification of the development of damage in compression, the development of the apparent compressive strength and the relation between orthogonal strains in the mortar, leading to a full characterization of the stress, deformation and damage of the material. The analysis results are compared to experimental findings on different mortar types and are used for their interpretation and evaluation. The complexity of the behaviour of confined mortar is demonstrated, motivating the use of advanced numerical models for its accurate simulation and assessment.Peer ReviewedPostprint (author's final draft

Laser scanning, monitoring and analysis of a reconstructed masonry vault

Reconstruction of historic building elements is often necessary in adaptive re-use projects. Optimally this is performed with as much original material as can be sal- vaged. However, the use of hydraulic lime mortars in reconstructed masonry can lead to long curing time and excessive deformation under mechanical loadsThe authors would like to thank V. Wirix from Denys NV and F. Noë from VK Engineering for their support of the on-site work, and WTA-NL-VL for the financial supportPostprint (published version

Experimental analysis and detailed micro-modeling of masonry walls subjected to in-plane shear

A detailed experimental campaign is presented dealing with masonry walls subjected to shear. The masonry walls are modeled using detailed micro-modeling techniques. Good agreement is found between the experimental and the numerical results. The importance of the compressive strength of masonry is highlighted.Peer ReviewedPostprint (author's final draft

The confinement of mortar in masonry under compression: experimental data and micro-mechanical analysis

The present paper deals with the behavior of several types of mortar in masonry under compression. The quantification of the response of mortar to triaxial confinement afforded by the masonry units in the composite subjected to compressive stresses is paramount in the determination of the peak stress of wallettes and pillars under compression. This behavior is greatly affected by the behavior of the mortar micro-structure and is manifested by the constrained lateral expansion of the mortar in the joint. A series of experimental results is presented, carried out on different assemblages of masonry composites (couplets and wallettes) with different types of masonry units and mortar, ranging in type from pure lime to cement based mortars. These experiments are subsequently simulated numerically using micro-mechanical techniques accounting for the shifting behavior of the Poisson's ratio of the mortar for varying levels of applied compression. Masonry is treated in a micro-mechanical framework as a composite material composed of two macroscopically distinct material phases: units and mortar. The experiments and their simulation provide insight into the complexities of masonry under compression that need to be accounted for in numerical analysis, including a discussion on the progression of damage in each material phase. The results and their analysis are further enriched through a comparative parametric study. A clear difference emerges between the assigned and the apparent Poisson's ratio for the material components.Funding for this work was procured through the GEPATAR project (“GEotechnical and Patrimonial Archives Toolbox for ARchitectural conservation in Belgium” BR/132/A6/GEPATAR), which is financially supported by BRAIN-be, BELSPO (Belgian Research Action through Interdisciplinary Networks, Federal Public Planning Service Science Policy Belgium).Peer ReviewedPostprint (author's final draft

Numerical Analysis of a Masonry Infill (Divided Into Smaller Wallettes) Under in-Plane Cyclic Tests

asonry infill in reinforced concrete frames has been recognised as being a strong factor influ- encing the seismic behaviour of buildings. Therefore, the development of innovative infill systems, coupled with the rigorous study of their behaviour, is of significant importance. Within the framework of the IN- SYSME project (http://www.insysme.eu/), a new infill system was designed and tested. The defining feature of the system, composed of clay units, is the division of the masonry wall into smaller, and thus more flexible, wallettes separated by vertical joints. The frames are subjected to in-plane cyclic shear loading to the point of irreversible damage of the masonry. Subsequently, the experiments are simulated using nonlinear finite ele- ment analysis in an effort to highlight the features of the response of the actual structure, to predict the maxi- mum force and to reproduce the failure modPostprint (published version