Shear Strength Parameters of Masonry Elements with Damp-Proof Course Membrane

A research project on the shear behaviour of masonry elements (triplets) with damp-proof course (DPC) membrane placed in the bed joints is underway at the Institute of Structural Engineering of ETH Zurich. The main goal of the research project is to investigate the influence of DPC on masonry behaviour under shear and to assess the shear strength parameters: cohesion and friction coefficient.

Within the framework of the first phase of this project load tests on four series of masonry triplets have been performed. Each series consisted of 12 specimens with dimensions of either 290x250 mm (series A, B, C) or 230x250 mm (series D). The elements’ thickness was 120 mm. A standard cement mortar was used to produce 10 mm thick bed joints. A DPC elastomer-based membrane has been placed in each bed joint of the specimens of series B, C and D, whilst 12 specimens of series A were built without DPC and served as control specimens. The DPC was placed either in the middle of the bed joint (series B) or between the masonry unit and bed joint mortar (series C and D). The elements of all series were built using clay blocks, except for series D specimens where the outer units were concrete bricks, which were used in order to simulate the concrete slab. Twenty eight days after preparation the elements were firstly subjected to certain pre-compression and subsequently subjected to shear load that was applied in a deformation-controlled manner up to failure of the specimen. Four different levels of pre-compression were considered (0.2 MPa, 0.6 MPa, 1.0 MPa and 1.5 MPa) and for each level three replicates were tested for each series.