Seismic Performance and Design of Hybrid Concrete-Masonry Structures

Seismic Performance and Design of Hybrid                 Concrete-Masonry Structures

Students:  Laura Redmond

The 2010 Haiti earthquake (M7.0) was a strong reminder of the earthquake risks that exists in the Caribbean. The earthquake caused 28% of the buildings in Port-of-Prince to collapse, most of which were either unreinforced masonry (URM) or reinforced concrete frames with URM infill (DesRoches et. al. 2011). CMU is an excellent building material for the hurricane prone region since it is effective in resisting heavy wind and minimizing damage from debris.   However, in seismic events, the lack of continuity between the URM infill and the RC frame can cause the infill to fall out of plane and sometimes trigger soft-story collapses. Reinforced concrete buildings with masonry infill are vulnerable in earthquakes because the masonry walls often fail due to out-of-plane forces and can trigger soft-story collapses. In order to prevent these failures, many engineers in the Caribbean have partially reinforced the infill walls and connected them to the reinforced concrete frame. This forms a hybrid concrete-masonry structure. Hybrid concrete-masonry structures have the potential to improve the seismic performance of many structures across the globe, as they are an easy adaptation from traditional unreinforced masonry infill. However, there is little codified guidance for this type of structure, and the influence of the masonry infill on the in-plane behavior of the frame is often neglected. This paper summarizes the current design practices and construction practices, recommends changes to the construction and detailing of the infills, and suggests a method to account for the infill when designing hybrid concrete-masonry structures in earthquake zones.

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