Mechanical effects of bed joint steel reinforcement in historic brick masonry structures

Several masonry structures of historic centers show; diffuse crack patterns and hazardous safety conditions, especially due to their dead load and the consequent time dependent phenomena, together with environmental cyclic actions. In the paper, the structural problem is briefly examined considering some case histories, and some relevant analyses results are reported. A bed joint reinforcement consolidation technique, performed by insertion of bars or plates of several possible materials (steel, FRP laminates) and successive repointing of the joints is then proposed. Some considerations on the technical feasibility are first illustrated (joint preparation, selection of materials, both for strengthening and repointing) and the results of a numerical model taking into account the essential non-linearities of the material properties are shown. Steel reinforcement has been for the moment considered and synthetic resin and lime mortars have been tested to fill the reinforced joints. Results of some laboratory tests performed on sample brick wallets reinforced by steel bars and subjected to uniaxial compression up to failure are also presented.