Repair of piers and spandrel masonry assemblies with grouting and FRCM systems: An experimental and analytical study

The current work investigates the repair of damaged unreinforced masonry (URM) piers and spandrel assemblies using grouting and Fiber Reinforced Cementitious Matrix (FRCM) systems. Two real-scale brick and lime mortar URM piers and spandrel assemblies were initially subjected to extensive flexural and shear damage from a differential vertical uplift test. Post-damage, one assembly was repaired with a high-performance lime-based grout, while the other received both grout and FRCM. Subsequent retesting demonstrated that both techniques effectively restored in-plane stiffness and shear capacity. The grouted assembly regained the shear capacity of the undamaged specimen, with notable post-cracking stiffness and ductility. The assembly repaired with grout and FRCM showed a significant increase in shear capacity and displacement ductility, exceeding initial values by at least 50 % and 56 %, respectively. The dynamic properties were analyzed using Ambient Vibration Testing (AVT), confirming the improved in-plane stiffness following changes in dynamic properties. The study's results were analyzed with analytical models, accounting for the effect of timber lintels, masonry arches and the FRCM, validating the repairs' effectiveness with high correlation. The results highlight the potential of these techniques for restoring structural integrity in damaged URM structures, with recommendations for further validation on the proposed analytical formulations through additional experimental studies. • Uniform strengthening is verified experimentally in damaged URM piers and spandrel. • Lime-based grouting in URM piers and spandrel restored shear capacity and stiffness. • FRCM in cracked URM piers and spandrel increased shear capacity by at least 50 %. • AVT confirmed the in-plane stiffness increase in repaired URM piers and spandrel. • Analytical models matched experimental results in repaired URM piers and spandrel.