Collaborative Research: An Integrated Model for Performance-Based Assessment and Design of Secondary Systems Mounted on Building Structures

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This research will develop, formulate, and validate an innovative and practical approach for assessing seismic demands and capacities of secondary systems. Secondary systems (i.e., nonstructural components) are those systems and elements housed or attached to floors, roofs, and walls of a building or industrial facility that are not part of the main load bearing structural system. The survival of secondary systems during and after an earthquake is important for the reduction of casualties, continuing functionality, and the reduction of direct damage costs, which can reach up to 85 percent of the total cost of the building. Shortcomings in the current state of knowledge and practice in the seismic demand assessment of such systems and the estimation of damage-induced losses are at least fourfold. First, in several cases, current code provisions provide inadequate estimates of seismic demands that will lead to damage and significant economic losses. Second, simplified design methodologies for such components do not explicitly account for the most important sources of uncertainties in the process. Third, current loss estimation methodologies are based on the summation of losses from individual components by which the concept of collateral damage (i.e., the effect of damage in one component on other components' damages) is not explicitly considered, which will result in an inaccurate estimate of losses. Fourth, very limited efforts have been placed to assess damages and associated losses for secondary systems using dynamic motions, which are more representative than commonly used quasi-static loading protocols. The goal of the study is to formulate and validate a methodology for applied assessment of demand and capacity of secondary systems mounted on elastic and inelastic primary structures. This methodology will account for uncertainties present in the process and ultimately help in the estimation of economic/casualty/down-time losses due to damages in secondary systems during earthquakes.Intellectual Merit: The results of the research are essential for (a) providing an understanding of the mechanisms and parameters that control the seismic response of secondary systems mounted on elastic and inelastic buildings, (b) formulating theoretical foundations of structural and nonstructural systems into a comprehensive computer model to quantify the seismic demands for such systems, (c) developing an integrated probabilistic model useful to provide a robust and reliable assessment of the peak acceleration (strength) and deformation demands of secondary systems, and (d) developing an applied and effective methodology for obtaining capacities of secondary elements using a dynamic loading protocol. The accurate and reliable prediction of seismic demands for secondary systems will incorporate the most important sources of uncertainty in the process. This is of paramount importance for accurate estimation of economic losses and injuries caused by damage to secondary systems during earthquake events. Broader Impacts: Results from this study will be of value to researchers, design engineers, and building code writers who have to make decisions and/or establish criteria for the seismic design and evaluation of secondary systems. The lessons learned from this project will be incorporated into recommendations for the design of experiments to understand and quantify the seismic capacity of secondary systems, as well as to reduce the uncertainty in this prediction. The probabilistic methodology will promote the concurrent incorporation of structural engineering, structural dynamics, earthquake engineering, and statistical and reliability theory concepts in the protection of secondary systems in buildings. This study will provide for the education of both graduate and undergraduate research assistants (one at the University of Maryland and one at the University of California, Irvine) and an undergraduate research assistant. The students will learn the research process and benefit by learning about structures, dynamics, earthquakes, probability, and novel earthquake engineering concepts. A pre-college student will also assist with the research activities for the duration of the project. The activity will promote the participation underrepresented pre-college and undergraduate engineering undergraduate students in research related tasks. One of the PIs is a member of an underrepresented group, so he will serve as a professional role model for underrepresented students.