Experimental and numerical assessment of the shear behaviour of lime mortar clay brick masonry triplets

Abstract

This study investigates the fundamental shear response of masonry triplets incorporating fired-clay bricks and hydraulic lime mortars. It examines the behaviour under ambient-dry and wet conditions, corresponding to 48h submersion in water, as well as the effectiveness of strengthening with fibre reinforced polymer (FRP) laminates and glass fibre meshes (GFM). After describing the materials, mix designs and specimen details, the main results from 50 triplet tests subjected to shear and normal pre-compression are presented. Digital image correlation measurement techniques, which are employed in order to obtain a detailed insight into the shear behaviour, enable clear identification and quantification of the main failure modes and response characteristics of the brick-mortar interfaces. The results show that the shear strength of wet triplets was about 20% lower on average than of those in dry conditions. Specimens provided with FRP sheets offered a higher strength enhancement than those with GFM. The strength increase using FRP was in the range of 16.6%-185.8% compared with the non-strengthened dry counterpart, depending on the laminate layout and normal stress level. In contrast, the strength increase using GFM, in conjunction with a mortar overlay, was typically less than 10% compared with the non-strengthened dry counterpart. A significantly higher strength contribution from both FRP and GFM was obtained for elements without pre-compression. Although the strength enhancement using GFM was generally modest, such strengthening is activated gradually leading to a relatively ductile interfacial behaviour in comparison with FRP. In order to provide further insights into the behaviour, complementary nonlinear numerical simulations are undertaken, using the key parameters obtained from the tests. The numerical models employ detailed surface-based cohesive-contact approaches, with due account for inelastic damage at the masonry interfaces, and damage-plasticity modelling for the constitutive response of brick materials. It is shown that the numerical approaches adopted are able to capture reliably the main behavioural characteristics and failure modes, and can therefore be employed for further numerical assessments.

In-plane lateral cyclic behaviour of lime-mortar and clay-brick masonry walls in dry and wet conditions

“…A recent complementary study carried out by the authors on triplets subjected to shear loading and varying levels of precompression, indicated that the initial shear strength was f v0 = 0.165 MPa for dry specimens and f v0 = 0.100 MPa for wet specimens (Bompa and Elghazouli 2020a). The triplets consisted of bricks which had identical properties to those from this paper, and the lime mortar had a strength similar to that in the WA-D and DA-D specimens.…”

“…The brick tensile strength f bt can be obtained from tests or typically assumed as 10% of the compressive strength f b (CEN 2018). In the assessments undertaken in this paper, the shear sliding parameters were determined based on previous test data (Bompa and Elghazouli 2020a), and by using the ranges illustrated in Fig. 13 and described before.…”

“…It has been shown that the mortar-brick interface shear response is dependent on the moisture content, porosity, mortar strength, and conditioning type (Gentilini et al 2012;Franzoni et al 2014a). A recent comparative study on wet and dry triplets also indicated that the shear strength of wet triplets is, on average, about 20% lower than those in dry conditions for practical ranges of precompression (Bompa and Elghazouli 2020a).…”

Experimental Investigation of Traditional Clay Brick and Lime Mortar Intended for Restoration of Cultural Heritage Sites

“…Generally, all of the mortar triplets exhibited minor values of shear stress, below 0.11 MPa. In other experimental results, when lime mortar was used, it had a low triplet shear strength value [30,[48][49][50]. Two types of failure mode were observed: (1) detachment of the mortar bed joint and bricks, and (2) detachment of the mortar layer.…”

Structural Behaviour of Clay Brick Lime Mortar Masonry Walls Under Lateral Cyclic Loading in Dry and Wet Conditions

“…The diagonal shear and sliding strength of URM is greatly dependent on the mortar-brick interaction. In general, the interface mortar-brick shear response greatly depends on the moisture content, porosity, mortar strength, and conditioning type (Mazzotti et al 2014;Bompa and Elghazouli 2020a), with saturation causing a deterioration in strength and stiffness (Franzoni et al 2015;Bompa and Elghazouli 2020b).…”