Geometrical exploration of a generalized nonlinear multi-span bridge system under multi-support excitation

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

This study uses a generalized and parametrized reduced-order model to evaluate the effects of asynchronous excitation on the transversal response of bridge structures. Bridge geometry parametric regions, corresponding conceptually to valley profile shapes, are explored. Both modal and bounding analyses, which are dependent on bridge geometry alone, are employed to highlight regions where the first mode is anti-symmetrical and the likely error between identical support excitation (ISE) and multi-support excitation (MSE) analyses is large.
Pier hysteresis is then incorporated into this generalized dynamic system to enable an inelastic time-history analysis of an MDOF bridge under multi-support seismic excitation. The hysteretic, nonlinear, relationship of piers is phenomenologically captured by a calibrated Bouc-Wen model.
A deterministic approach using real spatiotemporal ground motions recorded at the SMART-1 array, Taiwan, is employed as an alternative to a stochastic methodology used in current provision codes.
Benchmark experimental test data, using the multiple support excitation rig of a four-span bridge and SMART-1 array excitation, is used to validate/calibrate the proposed reduced-order model. An operational modal analysis is conducted to obtain least-square estimates of these key dynamic parameters using a Levenberg–Marquardt algorithm.
Numerical time history analyses, using a heuristic bridge case and spatiotemporal ground motion from the SMART-1 array, are employed. These analyses confirm that in parametric configurations where the first mode is anti-symmetrical the error between MSE and ISE is often larger. This confirms the utility of geometry only modal and bounding analyses in identifying critical regions.
Finally, Incremental Dynamic Analysis (IDA) is then performed to identify the performance levels at which this system transitions from elastic to inelastic behavior. A parametric study is then performed to explore the effect of the spatial variability of the ground motion while the pier hysteresis is taken into account.
Date of Award28 Sep 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorAnastasios Sextos (Supervisor) & Nicholas A Alexander (Supervisor)

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