Nathan M. and Anne M. Newmark Endowed Chair in Civil Engineering
Director, Newmark Structural Engineering Laboratory
Director, Multi-Axial Full-Scale Sub-Structured Testing and Simulation Facility
Director, Smart Structures Technology Laboratory
Structural optimization has been shown to be an efficient and effective method to obtain the optimal design balancing competing objectives. A performance-based optimization approach for nonlinear structures subject to stochastic dynamic excitation is presented. The optimization procedure is formulated as a multi-objective problem considering various performance objectives. The excitation is modeled as a zero-mean filtered white noise and combined with the nonlinear equations of motion of the structure to create an augmented state space representation of the system. The optimization objectives are defined in terms of the variance of stationary structural responses, which are obtained via equivalent linearization. Thus, the stochastic optimization problem is converted into its deterministic counterpart. Numerical examples are provided to demonstrate the efficacy of the proposed approach. Three levels of seismic magnitudes, i.e., low-level, frequent earthquake, medium-intensity earthquake and high-intensity earthquake, are investigated. For each seismic magnitude, two performance objectives are considered. The first performance objective considers serviceability, seeking to minimize floor acceleration response; and the second performance objective considers structural safety and seeks to minimize inter-story drift response. The Pareto optimal fronts are calculated to illustrate the intrinsic tradeoffs between serviceability and safety of designs subject to all seismic magnitudes.
B.F. Spencer, Jr. received his Ph.D. in theoretical and applied mechanics from the University of Illinois at Urbana-Champaign in 1985. He worked on the faculty at the University of Notre Dame for 17 years before returning to the University of Illinois at Urbana-Champaign, where he currently holds the Nathan M. and Anne M. Newmark Endowed Chair in Civil Engineering and is the Director of the Newmark Structural Engineering Laboratory. His research has been primarily in the areas of smart structures, stochastic fatigue, stochastic computational mechanics, and natural hazard mitigation. He is a Fellow of ASCE, a Foreign Member of the Polish Academy of Sciences, the North American Editor in Chief of Smart Structures and Systems, and the past president of the Asia-Pacific Network of Centers for Research in Smart Structures Technology.