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Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.

Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, such as earthquake, wave and wind excitation, thus reducing structural damage and preventing failure. The magneto-rheological (MR) fluid damper is a promising device for use in civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate dependent. Thus a challenging aspect of applying this technology is the development of accurate models to describe the behavior of such dampers for control design and evaluation purposes. In particular, a new type of experimental testing called real-time hybrid simulation (RTHS) combines numerical simulation with laboratory testing of physical components. As with any laboratory testing, safety is of critical importance. For RTHS in particular the feedback and dynamic interaction of physical and numerical components can result in potentially unstable behavior. For safety purposes, it is desired to conduct pretest simulations where the physical specimen is replaced with an appropriate numerical model yet the numerical RTHS component is left unchanged. These pretest simulations require a MR damper model that can exhibit stability and convergence at larger fixed integration time steps, and provide computational efficiency, speed of calculation, and accuracy during pretest verification of the experimental setup. Several models for MR dampers have been proposed, including the hyperbolic tangent, Bouc-Wen, viscous plus Dahl and algebraic models. This paper examines the relative performance of four MR damper models of large-scale 200 kN MR dampers as needed for pretest simulations of RTHS. Experimental tests are conducted on two large-scale MR dampers located at two RTHS test facilities at the Smart Structures Technology Laboratory at the University of Illinois at Urbana Champaign and the Lehigh University Network for Earthquake Engineering Simulation facility. It is shown that each of the MR damper models examined has relative merits and the ultimate selection of the particular model is dependent on the specific RTHS being tested.

Magneto-rheological (MR) fluid dampers can be used to reduce the traffic induced vibration in highway bridges and protect critical structural components from fatigue. Experimental verification is needed to verify the applicability of the MR dampers for this purpose. Real-time hybrid simulation (RTHS), where the MR dampers are physically tested and dynamically linked to a numerical model of the highway bridge and truck traffic, provides an efficient and effective means to experimentally examine the efficacy of MR dampers for fatigue protection of highway bridges. In this paper a complex highway bridge model with 263 178 degrees-of-freedom under truck loading is tested using the proposed convolution integral (CI) method of RTHS for a semiactive structural control strategy employing two large-scale 200 kN MR dampers. The formation of RTHS using the CI method is first presented, followed by details of the various components in the RTHS and a description of the implementation of the CI method for this particular test. The experimental results confirm the practicability of the CI method for conducting RTHS of complex systems.

Learning style changes from generation to generation. With the advancement of technologies, the current and incoming tech-savvy learners grow up with the digital world. Such technology advancement makes learning more accessible. As one of the examples, mobile learning has become a commonly accepted and embraced concept among the younger generations. Effective learning occurs when the teaching styles align well with the learning styles. To better serve the need of the next-generation learners in a more accessible way, a standalone mobile learning module was developed for an undergraduate upper division class, Mechanical and Structural Vibration, at San Francisco State University (SFSU). The developed mobile learning module consisted of three interconnected components, namely Analysis, Simulation and Experiment, representing the three important elements in a good engineering learning environment-theory, practical example and physical experimentation. Besides delivering the theoretical knowledge and important concepts, the learning module also allows students further examine the gained knowledge through animated simulations in the interactive Apps. In addition, the module includes a mobile remote shake table laboratory (RSTLab) which provides students the opportunity to remotely participate and conduct physical shake table experiments in real-time through smart mobile devices (e.g. smartphones and tablets). Through these physical experiments, students may easily use scaled physical models to test theories and implement their own innovations to observe how structures behave under different ground excitations. A telepresence robot is innovatively adopted and integrated with the mobile RSTLab to actively engage students and provide them a real sense of in-person participation without the need of being physically present in the laboratory. The learning module was implemented in Fall 2016 at SFSU as a "flipped laboratory". Pre-and post-surveys were conducted to evaluate the effectiveness of the mobile learning module to fulfil course learning outcomes. Survey results demonstrated the readiness of the mobile learning and improvement in participants' knowledge competence after using the module. The obtained information will be utilized to guide the future refinement of the learning module and understand what strategies could be used to better fit the need of the new generation learners.