The impact of a PEER funded research project “Resolution of Non-Convergence Issues in Seismic Response Analysis of Bridges” is highlighted below. The project Principal Investigator is Filip Filippou, Professor of Structural Engineering, UC Berkeley. The research team includes Thanh N. Do, Postdoctoral Researcher, UC Berkeley; Jade Cohen, Graduate Student Researcher, UC Berkeley; and Jiawei Chen, Graduate Student Researcher, UC Berkeley.
The Performance-Based Earthquake Engineering (PBEE) concepts show great promise for improving design practice. The safety performance objective is defined in terms of an “acceptable” probability of collapse. Collapse shall be quantified as realistically as possible, using non-linear dynamic analysis (NDA) which incorporates several suites of ground motions. A challenge with the proposed analysis procedure is that under high levels of loading, a significant percentage of nonlinear time history analyses fail to converge. Ignoring these runs completely may result in a substantial underestimation of the true collapse probability. Conversely, assuming all instances of non-convergence as representing physical collapse would result in an overestimation of the collapse probability.
A comprehensive set of guidelines will form the starting point for addressing the complexity inherent in nonlinear softening response under large displacements and deformations and will contribute to the acceptance of nonlinear response studies in professional practice. The deployment of a new class of bridge pier models that account for localized phenomena such as shear and reinforcement pull-out in a consistent iterative element formulation will help minimize the non-convergence issues that arise with the large collection of zero length nonlinear spring and plastic hinge elements currently in use in nonlinear bridge response simulations. The development of intelligent nonlinear solution strategies that coordinate the structure, element and material state determination will improve the state of the art and practice of nonlinear dynamic analysis of structures for sophisticated structural elements accounting for multi-axial interaction and several local phenomena. The standardized templates for element testing and NDAs of bridge structures will form the starting point for the collaborative growth of improved methods for nonlinear dynamic analysis of bridge models. It stands to reason that these tools will be useful for other types of structures.