Extreme Bridge Loads
342981 - Risk-Based Seismic Loss Assessment for RC Bridges, Accounting for Various Repair Strategies
Thursday, April 19
1:30 PM - 3:00 PM
Jakub Valigura, MS
Graduate Research Assistant
University of Colorado at Boulder, Department of Civil, Environmental and Architectural Engineering
This presentation discusses a risk-based seismic loss assessment framework for reinforced concrete bridges in seismic areas. The framework probabilistically quantifies the seismic hazard, damage states and repair costs, and considers various strategies for repairing damage. The goal of the framework is to facilitate comparison and selection of design details and post-earthquake repair strategies that minimize overall costs.
Current bridge design codes require that structural collapse is prevented during strong earthquakes (Caltrans 2013, AASHTO 2011). However, bridges may still sustain significant earthquake-induced damage, usually in the form of plastic hinging in the substructure (columns), and failure of shear keys. Following strong earthquakes, the usual practice in California and other earthquake vulnerable states includes visual assessment of bridge damage by field engineers using available inspection manuals (Veletzos et al., 2008). Visual damage assessment is followed by recommendations for potential repair strategies. However, there is no set of rules on what kind of repair should be used for certain level of damage. Although recent studies have investigated the post-repair performance in reference to different repair strategies, explicit assessment of economic costs of damage and the various repair strategies have not been fully investigated yet.
This study develops a framework that assesses bridge lifetime seismic performance, accounting for various repair methods that can be used to repair different damage levels of all the primary bridge components, and probabilistically evaluates costs associated with these methods. These goals are accomplished using a performance-based framework, in which a nonlinear model of a typical high overpass bridge structure is developed, and subjected to repeated dynamic analysis. The results of these analyses provide the basis for probabilistic loss estimation as a function of ground motion intensity. Here, a 3D spine model of a RC bridge, that is representative of bridges in California, is developed in OpenSees. Based on the computed dynamic response, damage states are probabilistically determined for the selected hazard intensities and repairs using several different methods, such as concrete patching; concrete, steel or FRP jacketing, and column replacement, are performed. The cost of each repair method are estimated considering both direct costs, i.e. location-specific estimates for labor, materials and equipment, and indirect costs, i.e. repair time before bridge is again operable. The repaired bridges will be re-analyzed under the same hazard to quantify their post-repair seismic performance within the same framework.
• Considering the need for performance-based design strategies that holistically account for costs and benefits over the lifetime of structures subjected to natural hazards, this presentation will be of regional, national and international interest.
• The target audience includes structural, bridge, earthquake and construction engineers from academia, practice and state agencies, as well as engineers interested in risk-based life-cycle assessment of structures.
• The audience will be introduced to a performance-based design framework that assesses the post-event performance of bridges repaired with various methods. The proposed framework quantifies both direct and indirect costs. This study can serve as a guide to field engineers to better choose repair methods based both on repair costs and post-repair performance.