Comparative Field Study of Cable Tension Measurement for a Cable-Stayed Bridge

Abstract

Cable tension is one of the important indexes of cable integrity as well as bridge stability and can be measured by various tension measurement methods. In this study, three widely used methods (i.e., the lift-off test, electromagnetic sensor method, and vibration method) have been implemented for two multistrand cables of a cable-stayed bridge under construction. The test bridge is Hwamyung Bridge in Korea, which has a prestressed concrete box girder. The field tests are executed during the second tensioning stage just after the installation of the key segment. The tensions are estimated before and after tensioning the cable and 5 days later (i.e., after finishing the tensioning of all the cables). The tensions measured by the three methods are compared with the design tension of the tensioning stage, and all three methods show very good performance in accuracy with minimal difference. Their cost and difficulty are compared based on test experiences. Additionally, an improved vibration method is proposed by ignoring apparent negative bending stiffness identified from measurement errors and validated in this test by improving the accuracy.