Parametric study on the dynamic response of cable stayed bridges to the sudden failure of a stay, Part I: Bending moment acting on the deck

The existing recommendations on cable stayed bridges propose the use of a static analysis with a dynamic amplification factor of 2.0 for evaluating the response of cable stayed bridges to the sudden loss of a cable. The application of this simplified procedure has been found to be critical and to control the design of some recently erected bridges. The present paper deals with the dynamic response of cable stayed bridges to the sudden loss of a stay. Its objectives are to quantify the relative importance of the accidental ultimate limit state of failure of a stay in the design of the bridge, and to determine the safety level provided by the simplified procedure of using a static analysis with a D.A.F. of 2.0. For this purpose, a parametric study has been carried out. In this study, ten cable stayed bridges have been analyzed and the effect of characteristics such as the layout of the stays, either fan or harp pattern, the number of planes of stays and the stiffness of the deck have been studied. First, this paper describes the geometry and materials of the cable stayed bridges studied, the numerical models and the basis of the static and dynamic analysis developed. Next, the results related to the deck cross sections are presented and discussed. Finally, some conclusions related to the design and analysis of the cable stayed bridges are provided. A second companion paper (i.e. Part II) is focused on the response of the pylons and the stays.