Enhancing seismic resilience in weak masonry units: the impact of rebar reinforcement in concrete hollow block masonry structures

Abstract The use of low-compressive-strength concrete hollow blocks (CHB) as construction material in developing countries presents significant challenges to earthquake resilience. Weak CHBs are inherently vulnerable to earthquakes, not just at the structural level (in-plane, out-of-plane wall collapses, and roof failures), but also at individual masonry unit level. This vulnerability increases the risk of structural failures during earthquakes, posing a significant threat to the safety of building occupants. This study investigates the effectiveness of reinforcing bars (rebar) in strengthening weak masonry units. Two experiments were conducted, including static testing with diagonal tension and three-point bending tests, and dynamic testing using a shaking table. Due to limitations in the availability of full-scale CHBs and the capacity of the shaking table, the shaking table tests employed quarter-scale CHBs, while the static tests utilized full-scale CHBs. The performance of a rebar-reinforced house model was compared with an unreinforced house model, demonstrating that rebar can significantly increase the initial stiffness of masonry structures, enhance energy dissipation, and enable the structure to withstand higher input motions, enduring up to run 49 at Japan Meteorological Agency (JMA) intensity level 6 ~ . The interaction between the rebar, weak masonry units, and infill mortar is particularly noteworthy. Initial failures in the masonry unit or mortar led to decreased stiffness. However, complex interactions among the rebar, masonry unit, and infill mortar enable the house model to recover and bear the load, demonstrating how rebar reinforcement enhances the structural resilience and load-bearing capacity of masonry walls.