Evaluation of the in-plane shear strength of a combined retrofit system for masonry walls

A combined system of retrofitting measures for out-of-plane and in-plane strengthening of clay brick masonry has been subject of in-plane shear tests. Previous research at the Eindhoven University of Technology has shown that retrofitting clay brick masonry using Deep Mounted (DM) Carbon Fibre Reinforced Polymer (CFRP) strips embedded in grooves filled with a ductile adhesive considerably increases the out-of-plane flexural capacity of unreinforced masonry walls. For in-plane strengthening of unreinforced masonry walls Fabric-Reinforced Cementitious Matrix (FRCM) overlay has proven to be a suitable retrofitting solution. Wallettes strengthened with the combination of both retrofit measures have been subject of a testing campaign. In-plane shear performance of strengthened wallettes were tested under the diagonal compression test method. Moreover specimens only strengthened with a DM CFRP strip were tested to investigate whether the out-of-plane strengthening, influences the shear strength negatively. A total of 13 half brick clay masonry wallettes, of 0,7 m ² in size, were structurally tested in induced shear. Of these specimens, four were unreinforced wallettes, three were only strengthened by a DM CFRP strip and six were strengthened by a DM CFRP strip and a FRCM overlay applied to one surface. Test results revealed that the observed shear strength increase for test wallettes having FRCM on one surface was at least 83%. It was further found that the matrix layer thickness did not have a significant influence on the shear strength. Moreover the testing program showed that the out-of-plane strengthening method by DM CFRP strips does not have a degrading effect on the in-plane shear strength of wallettes.