Research Article Modeling of Magnetorheological Dampers under Various Impact Loads K. Sarp Arsava and Yeesock Kim Department of Civil and Environmental Engineering, Worcester Polytechnic Institute (WPI), Worcester, MA 01609-2280, USA Correspondence should be addressed to Yeesock Kim; yeesock@wpi.edu Received 16 October 2014; Revised 22 December 2014; Accepted 5 January 2015 Academic Editor: Nuno M. Maia Copyright © 2015 K. S. Arsava and Y. Kim. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Magnetorheological (MR) damper has received great attention from structural control engineering because it provides the best features of both passive and active control systems. However, many studies on the application of MR dampers to large civil structures have tended to center on the modeling of MR dampers under seismic excitations, while, to date, there has been minimal research regarding the MR damper model under impact loads. Hence, this paper investigates nonlinear models of MR dampers under a variety of impact loads and control signals. Two fuzzy models are proposed for modeling the nonlinear impact behavior of MR dampers. hey are compared with mechanical models, the Bingham and Bouc-Wen models. Experimental studies are performed to generate sets of input and output data for training, validating, and testing the models: the delection, acceleration, velocity, and current signals. It is demonstrated that the proposed fuzzy models are efective in predicting the complex nonlinear behavior of the MR damper subjected to a variety of impact loads and control signals. he proposed fuzzy model resulted in an accuracy of 99% to predict the impact forces of the MR damper. 1. Introduction 1.1. Collision Load. In recent years, the threat of impact or explosive loads has become an important topic to be taken into account in the design of structures [1–7]. he impact and impulsive loads due to accidents, collisions, and terrorist or military conditions can threaten the integrity of structures (Figure 1). For instance, the nonlinear material behaviors and high velocity responses, which are not considered in most of the existing structural design methods, can cause severe damage to the structural components. he partial or complete collapse of load bearing elements and shiting or unseating failures of upper parts in structures are the most common failure mechanisms due to such impact loadings. To address such issues, structural control systems have been proposed as smart impact energy absorbers [8]. However, it is quite challenging to develop an efective structural control algorithm due to the complicated nonlinear behavior of the integrated systems and the uncertainties of high impact forces. 1.2. Impact Response Mitigation: Structural Controls. A con- trol system can be implemented into a structure to adjust the stifness or damping of the structure [9–12]. Such control systems can be categorized into three main groups: passive, active, and semiactive systems [13–16]. Due to their low cost and relative easy design, passive dampers are the most widely used devices for structural control system design in the ield of civil structures [10]. Passive control systems do not require any external power source to operate the control device to damp the responses of excited structures. However, the efectiveness of the passive control systems is dependent on the design spectra of destructive environmental forces since they do not have the capability of a feedback-based parameter updating [17]. On the other hand, active control systems adjust the force levels of the mechanical devices within the structure based on the structural response feedback [9]. However, active controllers are highly dependent on a large external power suppliers to operate large actuators [18, 19]. If there is an electricity cut or some of the control feedback components such as wires and sensors are damaged, Hindawi Publishing Corporation Shock and Vibration Volume 2015, Article ID 905186, 20 pages http://dx.doi.org/10.1155/2015/905186