Structures Congress 2020 144 © ASCE Seismic Evaluation of Repaired Bridge Bent Using Dynamic Analysis Ruo-Yang Wu, Ph.D., P.E., M.ASCE 1 ; and Chris P. Pantelides, Ph.D., S.E., M.ASCE 2 1 Wilson and Company, South Jordan, UT; Dept. of Civil and Environmental Engineering, Univ. of Utah, Salt Lake City, UT. E-mail: ruoyang.wu@utah.edu 2 Dept. of Civil and Environmental Engineering, Univ. of Utah, Salt Lake City, UT. E-mail: c.pantelides@utah.edu ABSTRACT Seismic performance evaluation of a structurally deficient as-built reinforced concrete bridge bent and a comparison to a retrofitted bridge bent was conducted. The as-built bridge bent had deficient seismic details and was retrofitted with a carbon fiber-reinforced polymer (CFRP) donut, which included a CFRP shell, eight headed steel bars, nonshrink concrete, and a steel collar around the column; CFRP composite jackets were also employed to increase column shear capacity. Detailed design guidelines of the rehabilitation method by using a simplified strut-and- tie model (STM) were presented which could be applied to rehabilitate similar reinforced concrete bridges. A fiber-based model was developed in OpenSees; in addition, soil-structure interaction (SSI) was considered using simplified springs; the bridge bent model was validated using experimental results from previous research of an existing bridge. A comparison of the as- built and retrofitted bridge bents under nonlinear static pushover analysis, incremental dynamic analysis (IDA), and fragility analysis using 22 far-field ground motions, showed that the rehabilitation method improved the seismic performance in terms of load capacity and structural stiffness. Keywords: Seismic evaluation; Retrofit; Repair; Rehabilitation; Earthquake; Concrete; Bridge; Fragility analysis; Incremental dynamic analysis; Soil-structure interaction. INTRODUCTION According to the infrastructure report card conducted by the American Society of Civil Engineers (ASCE) in 2017, about 40% of the bridges in the national inventory are 50 years or older and 9.1% of the bridges were considered to be structurally deficient. Bridges are considered structurally deficient when significant load-carrying components are in poor condition due to material deterioration, damage, or both. Existing bridges in high seismic zones that were built during the period from 1950 to 1970 may not have adequate seismic resistance as required by current codes, standards, and guidelines (MCEER/ATC-49 2003). Repairing damaged bridges after an earthquake is preferable to replacing them, since it is less costly and requires less interruption of regular service. To improve the seismic performance of existing structurally deficient reinforced concrete (RC) structures, extensive research has been conducted on developing seismic rehabilitation techniques (He et al. 2015). Carbon fiber reinforced polymer (CFRP) composites have been used since the early 1990s because of their high strength, light weight, and noncorrosive properties. A seismic repair method, referred to as the CFRP “donut”, had been developed using a CFRP cylindrical shell, and headed steel bars anchored into the footing/cap beam for precast columns connected with splice sleeves (Parks et al. 2016). An improved method using nonshrink repair concrete cast inside the CFRP shell made of hoop and longitudinal (vertical) CFRP layers, and a steel collar was implemented for the repair of two cast-in-place bridge columns with concrete crushing and Structures Congress 2020 Downloaded from ascelibrary.org by 54.161.69.107 on 07/24/20. Copyright ASCE. For personal use only; all rights reserved.