Development of NDE Technologies for Post Earthquake Damage Assessment of Jacketed Bridge Columns

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9812585 Feng The enhanced structural performance of bridge columns retrofitted by steel or fiber-reinforced polymer (FRP) composite jackets has been well demonstrated and a large number of highway bridge columns have indeed been retrofitted with such jackets in the United States and Japan. However, seismic damage of the columns covered by the jackets and thus made invisible can considerably weaken the columns. In order to solve this problem. this project will develop nondestructive evaluation (NDE) techniques, particularly electromagnetic (EM) and ultrasonic imaging technologies, and experimentally investigate their effectiveness for assessing post-earthquake damage of reinforced concrete columns wrapped with steel or FRP jackets. Under consideration are damages such as delamination cracks, debonding between concrete and reinforcing rebars, delamination between concrete columns and jackets. The primary tasks of this research include (1) development of prototype EM and ultrasonic imaging devices, (2) further development of the image reconstruction algorithms for both EM and ultrasonic devices, (3) verification of the EM and ultrasonic imaging technologies by testing the prototypes on steel-and FRP- jacketed bridge columns damaged to different levels in laboratory, and (4) verification of the EM and ultrasonic imaging technologies by field testing on steel- or FRP-jacketed bridge columns. The PI is currently directing an experimental testing program funded by the Federal Highway Administration (FHWA), the California Department of Transportation (Caltrans), and the Society for the Advancement of material and Process Engineering (SAMPE), where twenty-seven half-scale bridge columns wrapped with different FRP jackets are tested and damaged under cyclic loads in both single and double bending configurations. This program provides and excellent opportunity to verify the effectiveness of the proposed technologies in detecting damage in the columns and voi ds in the bonding interfaces, with no cost to the proposed project for building and damaging these columns. To facilitate closer collaboration and promote educational benefit, graduate students will be selected to spend two summers at PWRI to conduct joint experiments in Japan, while one junior research engineer from PWRI will spend one summer at UCI to participate in the field experiment involving Caltrans bridges. This project will also expose undergraduate students to interdisciplinary and collaborative research experience. This is an award under the first round (FY'98) competition of the CMS-INT initiative NSF 98-36 "US-Japan Cooperative Research in Urban Earthquake Disaster Mitigation". ***