NON-DESTRUCTIVE TESTING CHALLENGES FOR THE CALIFORNIA TOLL-BRIDGE SEISMIC RETROFIT PROGRAM

This paper discusses the numerous nondestructive testing (NDT) challenges encountered during the seismic retrofit of California's toll bridges. The California Department of Transportation (Caltrans) has implemented a $4 billion statewide seismic retrofit program. The main focus of this program is seven large toll bridges. The San Diego-Coronado Bay Bridge and the San Mateo-Hayward Bridge, two specific examples of the seven major toll bridges, are discussed in this paper. Multiple NDT methods were utilized in order to assure that the welding on these projects met the design specifications. The major components of the retrofit of the San Diego-Coronado Bay Bridge were the "Pin-Assemblies" which required developing special ultrasonic testing procedures in order to verify the soundness of these critical complete penetration welds. The unique design of these assemblies required a high level of NDT evaluation. On the other hand the San Mateo-Hayward Bridge retrofit required welding of several 160-ft (48.8-m) long steel pipe pilings which ranged in diameter from 5 to 12 ft (1.52 to 3.66 m). This paper discusses the procedures employed to select the most useful NDT method to evaluate the complete penetration welds as well as the interesting challenges posed by the ultrasonic testing of the longitudinal welds on the smaller diameter steel pipe pilings. In both of the aforementioned examples, numerous NDT problems were encountered. This paper discusses these issues in detail.