Performance-Based Design and Real-Time Large-Scale Testing to Enable Implementation of Advanced Damping Systems
Vibration can cause structural damage, leading to downtime of the structure, and possible life loss of the occupants. Numerous research has been devoted to vibration control techniques. Semi-active Magneto Rheological (MR) has been shown to be particularly promising in achieving better seismic performance over passive control while addressing a number of challenges facing active control. The adaptability of structures using these semi-active devices to extreme loading is expected to effectively minimize the seismic hazard. However, such innovative systems have been slow to be applied in practice due to a lack of appropriate design procedures and adequate testing methods to validate these systems.
This project will involve developing a simplified performance-based design procedure for steel frame structures with MR dampers. Multiple performance objectives, each of which is associated with a specific damage level for a selected seismic hazard level will be considered. Through the performance-based design procedure, the MR damping devices will be integrated into the design of seismic load resisting frames. The design procedure developed will be evaluated and validated using the existing real-time hybrid simulation test bed at the Lehigh NEES equipment site.
Magneto Rheological (MR) damper are particularly suitable for civil engineering applications due to their high force capacity and reliable design. The inherently stable nature of these devices makes it possible to implement high authority control strategies for better performance against severe seismic hazard. Various models and control algorithms have been developed to simulate and control the behavior of a structural system with MR dampers. Due to the nonlinear nature of MR dampers, researchers typically simplify the system to consider the MR damper as a linear device to develop a nominal design. This nominal design is then iteratviely adjusted to account for the nonlinear properties of the MR damper and the control laws. Optimization or iterative nonlinear time history analyses are usually recommended to size and place the dampers to minimize the response quantities of strutural systems subjected to earthquakes. This approach greatly inhibits the application of MR dampers into practical design, since engineering design offices are not suited for this type of analysis and design.
This project will develop a performance-based design procedure where a prototype steel frame with MR dampers is designed as an integrated system to satisfy different performance objectives associated with selected hazard levels. Multiple performance levels (operational (OP), immediate occupancy (IO), life-safety (LS) and collapse prevention (CP)) and multiple seismic hazard levels (frequently occurring earthquake (FOE), design basis earthquake (DBE), or maximum considered earthquake (MCE)) will be considered. The objective of this design procedure is to facillitate the practical design of building structures with MR dampers. Real-time hybrid simulation will be used to validate the developed design procedure, where the MR dampers are isolated as the experimental substructures and the rest of the building structure is modeled analytically. Thus different design structures can be considered and evaluated in a cost-effective manner. Existing control laws for the damper will be evaluated, and consideration given towards developing new ones. However, developing methods for real-time hybrid (RTH) testing of these systems is essential to enable the validation of these approaches. In this NEESR project, large-scale structural models, controlled with MR devices are being tested at the Lehigh RTMD NEES Equipment Site using RTH techniques.
Further validation studies are the real-time hybrid simulations (RTHS) performed at Lehigh University NEES facility. The RTHS tests a 9-story benchmark structure equipped with one or two MR dampers (installed in the 1st and 2nd stories, respectively), using the two large-scale MR dampers and the large-scale steel frame constructed in the lab at Lehigh. The purpose of this testing is four-fold: (1) validate the performance of a new semi-active control algorithms developed during the project, (2) identification of the designed-braced frame built in the Lehigh lab, (3) design of the adaptive actuator compensation scheme, and (4) design of the model-based feedforward-feedback actuator compensation scheme.
Photos of Test Setup
Shirley J. Dyke – Purdue University
James M. Ricles – Lehigh University
Richard Sause – Lehigh University
Bill F. Spencer – University of Illinois, Urbana Champaign
Richard Christenson – University of Connecticut
Anil K. Agrawal – City College of New York