Structural Engineering

Aerospace Biological Civil Geotechnical Mechanical

Comprehensive Treatment of Uncertainties in the Performance-Based Seismic Design of Ordinary Bridges

Seminar Speaker
Professor Joel Conte
Seminar Date
Wednesday, May 26, 2021 - 12:00 pm
Sponsored By
Robert Asaro
Speaker Bio

Joel Conte is Distinguished Professor of Structural Engineering at the University of California, San Diego, where he currently holds the Eric and Johanna Reissner Chair in Applied Mechanics and Structural Engineering at the Jacobs School of Engineering. His primary research interests and professional consulting activities are in structural analysis, structural dynamics and earthquake engineering, random vibrations, structural reliability and risk analysis, probabilistic performance-based analysis and design of structures, shake table dynamics and control, experimental-analytical correlation studies, structural identification and health monitoring. He was a member of the design team for the Large High-Performance Outdoor Shake Table (LHPOST) facility at UC San Diego, which was developed as part of the NSF George E. Brown Network for Earthquake Engineering Simulation (NEES), is currently Director of the Englekirk Structural Engineering Center Laboratory at UC San Diego and is Principal Investigator of the NSF funded in progress project to upgrade the LHPOST to six degrees of freedom.

This study focuses on the development of a rigorous framework for risk-targeted performance-based seismic assessment and design of Ordinary Standard Bridges (OSBs) in California. Rooted in the formulation of this framework is the performance-based earthquake engineering (PBEE) assessment methodology, developed under the auspices of the Pacific Earthquake Engineering Research (PEER) Center, integrating site-specific seismic hazard analysis, structural demand analysis, and damage analysis in a comprehensive and consistent probabilistic framework. Metrics of structural performance are formulated in terms of the mean return periods of exceedances for several strain-based limit-states (concrete cover crushing, onset of bar buckling, and precursor stage to bar fracture). This framework explicitly considers the following basic sources of uncertainty: (1) the seismic hazard associated with the seismic intensity measure defined as the average spectral acceleration over a period range and the record- to-record variability by using ensembles of ground motions consistent with the conditional mean spectrum and the natural conditional variability of earthquake ground motions; and (2) the uncertainty in the capacity of the various strain-based limit-states as represented by the corresponding fragility curves. At the heart of the PBEE methodology is the explicit quantification of pertinent uncertainties and their propagation through the various steps of the assessment methodology. The current study enhances the previous work by the inclusion, quantification, and propagation of the following additional sources of uncertainty: (i) the aleatory uncertainty associated with finite element (FE) model parameters (e.g., constitutive material model parameters, damping model parameters); and (ii) the epistemic parameter estimation uncertainty associated with using finite datasets to estimate the parameters of the aleatory probability distributions characterizing the FE model parameters. The targeted additional sources of uncertainty considered are commonly omitted or neglected in PBEE by invoking that the earthquake ground motion uncertainty is the predominant source of uncertainty. However, this study shows that the effects of these additional sources of uncertainty can be significant and must be included for a comprehensive seismic performance assessment of structures. The analytical and computational framework previously assembled is extended via modular incorporation of these additional sources of uncertainty. Four OSB testbeds and their risk-targeted redesigned versions are analyzed with and without these additional sources of uncertainty to evaluate their significance.

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