Seismic design and analysis of hybrid masonry with fuse connectors

Hybrid masonry is a new structural system that is composed of reinforced masonry panels within a steel frame; currently, the application of this system has been limited to low seismic regions where wind loads tend to control the design of the lateral force resisting elements. To establish a fundamental understanding of seismic behavior for hybrid masonry structural systems, simple analytical models are developed to predict the ultimate strength of hybrid masonry systems and to illuminate fundamental aspects of system behavior. The inelastic behavior of hybrid masonry is of great interest when considering the structural response of buildings located in areas dominated by high seismic activity, and it is dictated by the relative capacities of its system components. Thus, two design approaches may be used depending on whether the engineer decides to concentrate yielding in the masonry panels or in the steel connector elements that attach the masonry panels to the steel frame. Typical capacity design principles may be applied to the design of a hybrid masonry system in which the critical yielding elements are detailed to provide adequate ductility while the remaining structural elements are proportioned to remain elastic throughout the duration of a seismic event. The analytical models that are developed are also used as a basis for designing a suite of representative prototype buildings to help evaluate the feasibility of application of the hybrid masonry structural system for a range of seismic hazard. Numerical models are used to conduct a more detailed study of the inelastic behavior of the Type I system where focus is placed on modeling the inelastic response of the fuse type connectors. The results from the analytical and numerical models are used to understand the sequence of inelastic behavior and discuss implications for seismic performance and system feasibility. A great deal of effort is then put into further developing the design procedure for this new system. As interest in hybrid masonry grows, the need for an accurate design procedure will increase, especially because no such procedure currently exists. A capacity-based design procedure will be described using simple design examples to explain the major concepts and design methodology. The completion of a full design procedure should serve as a beneficial tool which will further the development of the hybrid masonry system and the range of its application. It is the hope of the author that the findings summarized in this report help to inspire future research as well as encourage the use of the hybrid masonry system by industry practitioners. Certainly future research efforts are required to further explore the limits of hybrid masonry application and to determine the necessary system response coefficients before this new system can be fully integrated into existing building codes and design specifications