Optimal bridge retrofit strategy to enhance disaster resilience of highway transportation systems.

PDFTech ReportPSU-2012-01LTI 2014-11DTRT12-G-UTC03Highway bridgesRetrofittingEarthquake resistant designScourResilienceSeismicityBenefit cost analysisJacketing (Strengthening)Statistical analysisOptimizationReinforced concrete bridgesBefore and after studiesUnited StatesMid-Atlantic Universities Transportation CenterBanerjee, SwagataChandrasekaran, SandhyaVenkittaraman, AshokThomas D. Larson Pennsylvania Transportation InstituteUnited States. Dept. of Transportation. Research and Innovative Technology AdministrationUS Transportation CollectionThis study evaluated the resilience of highway bridges under the multihazard scenario of earthquake in the presence offlood-induced scour. To mitigate losses incurred from bridge damage during extreme events, bridge retrofit strategies areselected such that the retrofit not only enhances bridge performance, but also improves resilience of the system consistingof these bridges. The first part of the report focuses on the enhancement of seismic resilience of bridges through retrofit. Toobtain results specific to a bridge, a reinforced concrete bridge in the Los Angeles region was analyzed. This bridge wasseverely damaged during the Northridge earthquake due to shear failure of one bridge pier. A seismic vulnerability model ofthe bridge was developed through finite element analysis under a suite of time histories that represent regional seismichazard. The obtained bridge vulnerability model was combined with appropriate loss and recovery models to calculate theseismic resilience of the bridge. The impact of retrofit on seismic resilience was observed by applying a suitable retrofitstrategy to the bridge, assuming its undamaged condition prior to the Northridge event. A difference in resilience observedbefore and after bridge retrofit signified the effectiveness of seismic retrofit. The applied retrofit technique was also found tobe cost effective through a cost-benefit analysis. A first-order, second-moment reliability analysis was performed and atornado diagram developed to identify major uncertain input parameters to which seismic resilience is most sensitive.Statistical analysis of resilience obtained through random sampling of major uncertain input parameters revealed that theuncertain nature of seismic resilience can be characterized with a normal distribution, the standard deviation of whichrepresents the uncertainty in seismic resilience. An optimal (with respect to cost and resilience) bridge retrofit strategy undermultihazard was obtained in the second phase of this study. A multi-objective evolutionary algorithm, namely Non-dominatedSorting Genetic Algorithm II, was used. Application of this algorithm was demonstrated by retrofitting a bridge with columnjackets and evaluating bridge resilience under the multihazard effect of earthquake and flood-induced scour. Three differentretrofit materials\ue2\u20ac\u201dsteel, carbon fiber, and glass fiber composites\ue2\u20ac\u201dwere used. Required jacket thickness and cost ofjacketing for each material differed to achieve the same level of resilience. Results from the optimization, called Pareto-optimal set, include solutions that are distinct from each other in terms of associated cost, contribution to resilienceenhancement, and values of design parameters. This optimal set offers the best search results based on selected materialsand design configurations for jackets