Effectiveness of composite grids embedded in mortar layers for strengthening of masonry walls

Angelo Garofano
2014
Conference paper

The strengthening method characterized by the application of composite grid reinforced mortar layers onto the surface of masonry walls is a quite new technique and, thus, still requires deep experimental and numerical investigation. This strengthening technique can be very effective to increase both the load-carrying and deformation capacity of unreinforced masonry walls subjected to cyclic loads. Moreover, it combines the advantages of both traditional and innovative types of intervention, since the composite grid is a high performance material and the mortar is a compatible material with respect to the masonry substrate. In the present paper the experimental results of in-plane shear tests on masonry walls subject to cyclic loads and externally strengthened with composite grid are synthetized. Then, the experimental results are compared with the numerical ones given by a Finite Element model. The FE model has been also used for carrying out several parametric analyses aimed at evidencing the effect of the reinforcement on both strength and displacement capacity of the wall. Two types of masonry, three values of shape factor (1.0, 1.3, and 2.0), different values of the compressive strength of the mortar layer and of the axial stiffness of the composite grid were investigated in the analysis. Finally, the effectiveness of the strengthening with mortar layers reinforced with a traditional steel grid has been investigated.

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Angelo Garofano
2014
Conference paper

Abstract

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https://infoscience.epfl.ch/record/202652?ln=en

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Modelling of the in-plane behaviour of masonry walls strengthened with polymeric grids embedded in cementitious mortar layers

Angelo Garofano

The seismic reinforcement of masonry walls needs to be carried out through appropriate and effective techniques aiming at providing both adequate strength and displacement capacity. The present research concerns experimental results about the in-plane behaviour of masonry walls strengthened through an innovative technique employing polymeric grids embedded in cementitious mortar layers applied on the wall surface. The behaviour of strengthened masonry walls subjected to cyclic shear-compression tests is examined in order to quantify the strength and displacement capacity increment provided by the reinforcement. A Finite Element Model of the unreinforced and reinforced panels has been developed and parameters defining masonry and strengthening materials have been calibrated by means of comparisons with the experimental results. The effectiveness of the strengthening system has been then numerically investigated through a wide parametric analysis varying the masonry strength, the wall shape, the axial stiffness of the strengthening grid and the strength of the mortar. Finally, a comparison of the effectiveness of the polymeric grid with a traditional steel one embedded in the same mortar layer is also reported. (C) 2015 Elsevier Ltd. All rights reserved.

Elsevier2016

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In this paper we use the novel Disturbed Stress Field Model (DSFM) from Facconi et al. (2013) to model the lateral in-plane behaviour of different unreinforced masonry (URM) walls which we tested at the laboratory of the EPF Lausanne, Switzerland. The model uses the failure criterion developed by Ganz (1985) for URM and is implemented in the software VecTor 2. In the first part of this article, we show that the DSFM gives good estimates for the initial stiffness of the walls but underestimates the displacement and force capacity of our URM walls. This is due to the confinement of the mortar base joint which is confined by the wall foundation. However, we show that this phenomenon can be accounted for by replacing the compression strength of the masonry of the first brick layer by the strength of the brick itself. Using this improved model, we compare the numerical results to the experimental results with regard to displacements and strains. We show that the simplification of the masonry to a continuous material is correct when comparing the global engineering demand parameters (EDPs), e.g., force-displacement behaviour of the walls or crack pattern. However, when comparing local EDPs, e.g., strains and crack widths, significant differences can be obtained. These differences are mainly caused by the torque of the bricks inside the walls (Mann and Müller, 1982). We show that this distortion gets less important with increasing shear span and that for a wall with higher shear span the assumption of a continuous material gives reasonable results even at the local level.

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Static behaviour of earth block masonry: experimental testing and Finite Element Modelling

Angelo Garofano, Urs Müller

In this paper an extensive research campaign aimed to define the mechanical performance of earth block masonry panels is presented. Uniaxial compression and diagonal compression tests were performed. The test results confirmed the brittle behaviour of earth block masonry under uniaxial compressive load and showed that the failure of earth block masonry under shear load occurs by sliding of the earth blocks along the mortar joints after initial cracking in mortar joints and earth blocks. For diagonal compression test results showed that building technique practice is one of the key factors affecting the structural performances. Experimental behaviour was modelled with a non-linear model capable of describing cracking behaviour. Both micro-modelling and macro-modelling implementing isotropic or orthotropic material laws were used to assess the reliability of different modelling strategies. The model calibration was carried out by sensibility analysis of the input parameters to understand the influence of unit strength on the shear behaviour of masonry.

2014