Assessment of the properties to characterise the interface between clay brick substrate and strengthening mortar

João A.P.P Almeida,Davide Bordigoni,Eduardo B Pereira,Joaquim A.O Barros,Alessandra Aprile

doi:10.1016/j.conbuildmat.2015.11.036

João A.P.P Almeida, Davide Bordigoni + Show 3 more

Open Access

https://doi.org/10.1016/j.conbuildmat.2015.11.036

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Abstract

The behaviour of masonry elements under in-plane and out-of-plane loads can be improved through the application of strengthening systems based on reinforcing overlays. After strengthening, the transition region between the original substrate and the strengthening layer is especially stressed, and premature failure of the strengthened masonry is reached if insufficient interfacial capacity is assured. Therefore, the assessment of the mechanical behaviour of the interface is critical to the development of the masonry strengthening system based on the application of strengthening overlays.In this research a method for the characterisation of the interface behaviour between two different materials, a polypropylene fibre reinforced mortar (PFRM) and a ceramic brick used for masonry construction is presented. Direct shear tests were carried out in couplet specimens. Due to the orthotropic nature of the bricks surface, the shear load was applied along three different directions in order to perform an overall estimation of the interface behaviour. The peak and residual shear stresses, as well as the failure modes, were obtained at different levels of the normal stress. Based on these experimental results constitutive laws were assessed for the simulation of the interface mechanical behaviour based on the Mohr and Mohr–Coulomb failure criteria.

Highlights

Masonry was one of the main techniques used in the construction of old structures and still is widely used in new buildings
Considering that the strengthening overlay in service conditions is typically subjected to low normal stresses, the characterization of the shear response of the interface was carried out initially considering normal stresses below 0.5 MPa
The test setup developed in this research aimed to assure a direct characterization of the interface behaviour between a ceramic brick substrate and the polypropylene fibre reinforced mortar (PFRM) strengthening overlay

Summary

Introduction

Masonry was one of the main techniques used in the construction of old structures and still is widely used in new buildings. The evolution of the design codes has tended to impose more demanding requirements, especially in the case of the action in seismic regions. Due to this and other durability driven performance insufficiencies, techniques to retrofit existing masonry constructions have recently been developed, and their performance evaluated. A considerable number of strengthening techniques are nowadays based on the application of reinforcing overlays. These systems often show vulnerability at the level of the interface due to the sharp gradient of mechanical properties between the substrate and the reinforcing material [1]. The results obtained were used to derive the orthotropic constitutive laws of the interface based on both the hyperbolic Mohr and the Mohr-Coloumb failure criteria

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