Out-of-plane seismic retrofitting of masonry walls with Textile Reinforced Mortar composites

Masonry walls are particularly vulnerable against out-of-plane seismic actions. Steel tie-bars and crowing beams in reinforced masonry can prevent their overturning, but collapse may take place also by bending, leaf separation or disaggregation. Textile Reinforced Mortar (TRM) composites, comprising high strength fabrics and inorganic matrices, can be applied to effectively improve the seismic capacity of masonry load-bearing walls and infill panels. Nevertheless, a deeper knowledge on the dynamic response and ultimate capacity of retrofitted walls still needs to be gained before TRM systems can be confidently used in engineering practice. This work describes a shake table test carried out on two full-scale wall specimens, one made of regular tuff blocks and one of two leaves of rubble stones, subjected to seismic out-of-plane vertical bending. The walls were tested unreinforced, repaired and strengthened with TRMs and tested again. A unidirectional textile of ultra high tensile strength steel was used on the tuff wall, whereas a bidirectional basalt mesh was applied over the entire surface of the stone wall, with the addition of transversal steel connectors. The responses of the specimens before and after retrofitting are compared to show the improvement of acceleration and displacement capacity entailed by TRM retrofitting and the modification of deflection profiles, failure modes, damage development and dynamic properties. Test outcomes prove the effectiveness of TRM composites for the protection of existing masonry structures, including architectural heritage, in earthquake prone areas and provide information on the reliability of analytical predictions for seismic assessment.