Cable loss and progressive collapse in cable-stayed bridges

The failure of one structural element can lead to the failure of further structural elements and thus to the collapse of large sections or the entire structure. Such disproportionate collapses have been discussed and investigated for some years, but mainly for buildings. In the field of bridge engineering, this phenomenon attracts only sporadic attention. Although international guidelines for cable-stayed bridges require that the loss of one cable must not lead to the collapse of the entire structure, comprehensive analyses that include non-linear dynamic effects are rare. To simply account for dynamic effects, a quasi-static analysis with a dynamic amplification factor of 2.0 is recommended. This value is possibly too large, leading to uneconomic solutions. Therefore, this work examines the structural response of a cable-stayed bridge to the loss of one cable by means of dynamic analyses including large displacements. The effects of cable sag, transverse cable vibrations and structural damping are determined and dynamic amplification factors are computed.