Evaluating the cable tension results by lift-off and vibration method in Viet Nam

The tension force value in cable of cable stayed bridge is the importance problem and necessary to control in design and service stage. The tension force value in cable is adjusted to ensure the internal force distribution of the structure is most reasonable and to ensure the camber, deflection or general deformation of the entire bridge. This tension adjustment has been performed and verified on many normal cable-stayed bridges. The cable-stayed bridge with more than 2 towers and 3 spans which is the trend of choice in the world as well as in Vietnam with beautiful architectural styles and suitable for use in difficult or limited conditions by topography, this verification is very limited. Recently, Bach Dang cable stayed bridge with 3 towers and 4 spans has opened for service in Viet Nam in Septemper, 2018, the authors have had the opportunity to approach the project and conduct tension measurements in cables by using the vibration analysis method at the time before project has opened for service. In order to evaluate the accuracy of the measurement results, the paper compares the results of tension force in cables that analyzed from measured by vibration method with the values of tension in cables that are directly measured by the lift-off method. These results are also compared with the results in design stage when analysing of bridge structure on software.