Connector development for hybrid masonry seismic structural systems

Abstract

Hybrid masonry construction has relatively recently been developed as a means to provide a more efficient use of masonry infill walls by designing these walls to function as a part of a structure's lateral force resisting system, with current applications in low seismic regions (Seismic Design Categories A, B, and C). In regions of higher seismicity (Seismic Design Categories D and greater), there exists a much greater need for a clearer understanding of the mechanics of the interaction between the steel frame of a building and the masonry shear wall as well as the development of specific detailing requirements to provide for a ductile and somewhat predictable response in a seismic event of significant magnitude. The scope of this thesis is the investigation of the connection between the steel beam and the top of the masonry wall for a Type I hybrid masonry system, using a proposed steel connector plate through-bolted to the masonry wall bond beam, in order to provide preliminary guidelines and recommendations for the development of energy dissipating hybrid masonry connector plates. The first portion of this study focused on the development of connector plate designs to determine which provided the most stable, ductile cyclic response. The second portion of this study investigated the strength and limit states of the through-bolted connection to the masonry wall bond beam under shear loading. Based on these experiments, recommendations are provided for the most suitable connector plate designs as well as a general evaluation of the connection to the masonry wall and potential limit states to consider in future design applications. For a "rigid" connection between the steel frame and CMU wall, link connectors with a thickness greater than 0.5 inches is recommended, whereas fuse Type T was proven to be superior for a ductile, energy dissipating connector plate. ACI 530-08 design values for bolt shear yielding and masonry shear failure were determined to be the most appropriate limit states for determining an approximate design values for the thru-bolted CMU wall connections.