6 th International Conference on Advances in Experimental Structural Engineering 11 th International Workshop on Advanced Smart Materials and Smart Structures Technology August 1-2, 2015, University of Illinois, Urbana-Champaign, United States Fragility Analysis of Structures Incorporating Control Systems A.K. Wilbee 1 , F. Pena 2 , J. Condori 2 , Z. Sun 3 , S.J. Dyke 4 1 Undergraduate Research Asst., Lyles School of Civil Engineering, Purdue University, West Lafayette, United States. E-mail: akwilbee@hotmail.com 2 Graduate Research Asst., Lyles School of Civil Engineering, Purdue University, West Lafayette, United States. E-mail: fpena@purdue.edu, jcondori@purdue.edu 3 Graduate Research Asst., School of Mechanical Engineering, Purdue University, West Lafayette, United States. E-mail: zxsun152@gmail.com 4 Professor, Schools of Mechanical and Civil Engineering, Purdue University, West Lafayette, United States. E-mail: sdyke@purdue.edu ABSTRACT Dynamic hazards present a challenge to the structural designer. Structural control devices offer one effective approach to protect structures during these dynamic hazards. Various classes of control systems have been explored in recent years and have been demonstrated to be effective for reducing structural responses to extreme events. However, the design of advanced damping systems has not been addressed from the broad perspective of performance. Recent interest in Consequence Based Engineering (CBE) has opened an avenue to change that. CBE works to incorporate the predicted performance of a structure as a factor in its design. This research seeks to demonstrate the potential use of the fragility analysis of controlled structures in CBE. Specifically, this study investigates the sensitivity in the fragility of seismically excited buildings to various passive control configurations. A benchmark model of a 20-story structure is employed. Magneto-rheological (MR) dampers, subject to a constant voltage, act as the source of passive damping for these models. Through these studies, we demonstrate the utility of fragility analysis as a design and modeling tool for eventual use as a facet of CBE. KEYWORDS: fragility analysis, passive structural control, dynamic hazard mitigation 1. INTRODUCTION Over the last thirty years, the use of structural control has gained attention in the Civil Engineering community. Indeed, the design and implementation of such systems has garnered recognition in the community because of their capability to protect structures against natural hazards and aid in rehabilitation due to aging or deficiency in the design or construction processes (Soong and Spencer, 2002). Control systems are classified as passive, active, or semi-active, according to the energy needed for their operation. Passive systems operate without adding energy to the structure, and are thus inherently stable. Instead, they enhance the energy dissipation capacity of structures by introducing friction, yielding, phase transformation, or deformation of viscoelastic fluids (Soong and Spencer, 2002). This dissipation takes place as a response to the intrinsic movement of the structure. Alternatively, active systems use feedback and have the ability to control specific responses of structures with real-time exchanges between the sensors, controllers, and actuators. This class of devices demands significant additional energy for operation. Without proper attention to the design process, this injection of energy has the potential to lead to instability in the structure. Semi-active systems offer a compromise between passive and active operation. They require a modest amount of supplemental energy, and essentially act as controllable passive devices. Typically, validation of these control systems is realized by comparing the performance of the uncontrolled and controlled structures for a small suite of representative ground motions. However, these chosen earthquakes only represent a reduced number of data points. This inhibits decision-makers from fully understanding the potential performance that the controlled structure can achieve. For this reason, fragility analysis is an attractive option for informing designers and owners. Fragility analysis assesses a particular aspect of performance, for example, the drift between stories of a building, and expresses the likelihood for which a limit state of that aspect will be exceeded at a certain hazard condition. More formally, it is defined as the conditional probability of a system or component meeting or exceeding a prescribed performance limit state given the occurrence of a particular demand or hazard (Taylor, 2007). This analysis method is less complex and costly than a fully coupled risk analysis, easy to understand, uses a wide range of regionally representative hazards, and can be simply summarized in a single figure, a fragility curve (Taylor, 2007).