The implementation of nonlinear structural analysis under large deformation demands has enabled more realistic response prediction in comparison with the classical linear approaches. However, the sensitivity to modeling assumptions, element and material formulations, implementations, and parameter selection may lead to unreliable results. While previous works have led to a better understanding of how to best model nonlinear static responses of bridge components and systems, the introduction of dynamic loads and the corresponding material hysteresis presents an additional source of variability in the nonlinear responses. The current research involves the analysis of two ordinary standard bridges in California under seismic load in SAP2000 and OpenSees after a calibration phase to standardize the material, section, and element-level nonlinear static responses. The bridges were defined using simplified steel and concrete constitutive models in concentrated plasticity elements, with common unloading-reloading rules, damping, and mass. Analyses showed that minor differences in the material constitutive models did not impact agreement of drift, base shear, and curvature time histories. The column hinge and abutment nonlinear characterization clearly dominated the dynamic response variability of the bridge models. The bias analysis of the nonlinear model concluded that both software agreed after improving the hinge length and the inclusion of gaps in the abutments. The same SAP2000 models were used to analyze the sensitivity of the most representative nonlinear parameters in the columns, superstructure, and abutments, as well as sensitivity to the hysteresis behavior of the concrete and the reinforcement steel. The prediction of the sensitivity was obtained applying the finite difference method, perturbing each parameter forward and backward by a coefficient of variation. The results obtained indicate that the selected bridges have a strong sensitivity in the longitudinal direction to the hysteretic assumptions and to small variations in parameters such as steel yield strength, superstructure Young's modulus, and abutment strength, while the displacement response in the transversal direction seems to be insensitive.
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Master of Science in Civil Engineering (M.S.C.E.)
College of Engineering and Computer Science
Civil, Environmental and Construction Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Rodriguez Caballero, Andres, "Bias and Sensitivity of Nonlinear Models for Seismic Response of Ordinary Standard Bridges" (2020). Electronic Theses and Dissertations, 2020-. 405.