Methodology for the development of analytical fragility curves for retrofitted bridges

TLDR

Fragility curves for retrofitted bridges show how different retrofit measures affect the probability of reaching specified damage levels. The study develops an analytical methodology to generate fragility curves for retrofitted bridge systems, enabling comparison of system fragility before and after various retrofit measures. It employs analytical modeling, uncertainty treatment, and demand and capacity estimates to capture retrofit impacts on component vulnerability and produce system fragility curves. The findings demonstrate that retrofit effects on overall bridge fragility vary by component and damage state, and that assessing only component fragility can over‑ or under‑estimate bridge fragility. © 2008 John Wiley & Sons, Ltd.

Abstract

Abstract Fragility curves for retrofitted bridges indicate the influence of various retrofit measures on the probability of achieving specified levels of damage. This paper presents an analytical methodology for developing fragility curves for classes of retrofitted bridge systems. The approach captures the impact of retrofit on the vulnerability of multiple components, which to date has not been adequately addressed, and results in a comparison of the system fragility before and after the application of different retrofit measures. Details presented include analytical modeling, uncertainty treatment, impact of retrofit on demand models, capacity estimates, and component and system fragility curves. The findings indicate the importance of evaluating the impact of retrofit not only on the targeted response quantity and component vulnerability but also on the overall bridge fragility. As illustrated by the case study of a retrofitted multi‐span continuous (MSC) concrete girder bridge class, a given retrofit measure may have a positive impact on some components, yet no impact or a negative impact on other critical components. Consideration of the fragility based only on individual retrofitted components, without regard for the system, may lead to over‐estimation or under‐estimation of the impact on the bridge fragility. The proposed methodology provides an opportunity to effectively compare the fragility of the MSC concrete bridge retrofit with a range of different retrofit measures. The most effective retrofit in reducing probable damage for a given intensity is a function of the damage state of interest. Copyright © 2008 John Wiley & Sons, Ltd.