Simplified Seismic Performance Assesment Over the Lifetime of a Highway Bridge Subject to Pier Reinforcement Corrosion

Abstract eng:
The lifetime seismic performance of a typical segmental three-span (75+120+75) Egnatia Odos Highway bridge is assessed, considering the corrosive action of chloride ions that leads to pier strength degradation over time. The aim is to show the influence of corrosion on the seismic demand and capacity over the entire design life of the bridge, as well as the usefulness of simplified single-degree-of-freedom (SDOF) models to minimize the computational cost to non-prohibitive levels for contemporary capabilities. Five different time instants are chosen within the 120 year design life of the bridge. For each instant, the piers’ reinforcement steel loss is calculated via a probabilistic model using Monte Carlo simulation to account for the uncertainty in the factors that affect the corrosion. While incremental dynamic analysis (IDA) of the complex model would be the method of choice for a comprehensive evaluation, we employ instead approximate IDA of equivalent SDOF systems with capacity curves derived by static pushover analysis. Such analyses are efficiently executed for different time moments of the design life of the bridge, taking into account the active pier rebar diameter due to corrosion effects. Thus, the usefulness of the equivalent SDOF system concept combined with nonlinear dynamic analysis or a powerful R-μ-Τ relationship such as SPO2IDA is shown. This usefulness turns to a necessity when more factors of epistemic uncertainty beyond the corrosion process are added in this already complex problem, disproportionately magnifying the required computational load.

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