A New Design Methodology Of Reinforced Concrete Squat Shear Walls For Ductile Seismic Behavior And Predictable Shear Strength

A New Design Methodology of Reinforced Concrete Squat Shear Walls for Ductile Seismic Behavior and Predictable Shear Strength

Reinforced concrete (RC) squat walls (with a height-to-length ratio of 2.0 or less) have high strength and stiffness which makes them a popular seismic force-resistant system for buildings and nuclear power plants. However, extensive studies on squat shear walls showed that squat walls have limited drift ductility because a flexural yielding mechanism is difficult to achieve, thereby undermining the role of squat walls as structural fuse members in earthquake-resisting structures. This research proposes a new design methodology of squat walls for ductile seismic behavior. While ACI 318-19 requires a mesh of steel bars to reinforce squat walls, the proposed design methodology fortifies the squat walls by several steel cages which contain vertical bars enclosed by transverse hoops. These steel cages can be easily prefabricated to significantly reduce the onsite assembling work. Seven ACI compliant and proposed walls with an aspect ratio of 0.5 or 1.0 were tested under symmetric cyclic loading protocols. Similar to prior research results, ACI compliant walls exhibited a fast deterioration in shear strength at low drift ratios and failed in a sliding shear failure mode after severe damage at the wall base due to intersected compression struts under cyclic loading. On the other hand, the proposed squat walls showed excellent behavior by confining the concrete at the most critical zone of the wall base, thereby enhancing the ductility of the compression struts and eliminating the sliding shear failure. As a result, the proposed walls reached a drift ratio as twice as that attained by the ACI compliant walls, indicating a high ductile behavior of the proposed squat walls. The proposed design methodology allows squat walls to develop a ductile seismic behavior which is essential to promote levels of safety during seismic events. An accurate strut and tie model-based proposed equation was discussed and used to evaluate shear strength of 54 previously tested walls.

Journal of the American Concrete Institute

Seismic Design of Concrete and Masonry Structures