The Jamestown-Verrazzano Bridge over Narragansett Bay, Rhode Island is a 4,950-foot-long prestressed segmental box girder main bridge with 23 spans varying in length from 109 to 636 feet. NDT Corporation acquired over 93,000 linear feet of nondestructive sonic/ultrasonic impact-echo (sonic/ultrasonic) measurements on the main bridge’s concrete top slab, webs and bottom slab containing the tendons to evaluate the grouted tendon ducts for voids. Of the approximately 1,520 tendon ducts tested, 114 tendon ducts were determined to have voids. Void lengths ranged from over 314 feet to 1 foot. In most cases the tendons were grout covered but some of the tendons were exposed and corroded.
The nondestructive testing for void detection in the grout consists of two elements: Ground Penetrating Radar (GPR) to locate the duct and sonic/ultrasonic testing to detect voided tendon grout. Confirmation of nondestructive test results for the tendon ducts was accomplished by drilling a 1-inch diameter hole to the duct and using a 7/8- inch diameter hole saw or a modified screwdriver to open the duct. Video observations inside the duct and photo documentation are made using a bore-scope with a flexible shaft and articulating head.
Massachusetts Office Florida Office 153 Clinton Road 8413 Laurel Fair Circle, Ste 200-B
Sterling, MA 01564 Tampa, FL 33610