Parametric Study of a Cable-Stayed Bridge Under Seismic Loads

The topic of this paper is a parametric study of a cable-stayed bridge under seismic loads. The bridge modeled in this study is the Bill Emerson Bridge crossing the Mississippi River at Gape Girardeau in Missouri. A description of the development of the 3-D finite element model for both a linear and nonlinear dynamic analysis is given by using the original bridge design. Then a collection of parameters was studied as to their effect on the dynamic response. Different deck elements (e.g. girder box, slab, etc.), pylons (e.g. A-shape, H-shape, etc), cable areas, and material properties are used. Linear and nonlinear multiple, single response spectrum analyses with an emphasis on the nonlinear cable behavior are performed in this parametric study. The study showed that a composite concrete steel girder and a concrete box performed the best. Further it showed that A-shape towers stabilized the structure horizontally and increased the torsional stiffness. The doubling of the cable area decreased the vertical displacements up to 30 %. Therefore, a doubling of the cable area might be reasonable depending on the applications. The multiple response-spectrum analysis lead to higher displacements than the single response-spectrum analysis. Consequently a multiple response spectrum analysis is preferable, if multiple excitation-input data are available. The comparison between the non-linear and linear analysis demonstrated that for this bridge the non-linear effects of the cables were small and could be ignored. Nevertheless, for long span cable stayed bridges, the nonlinear effects of the cables should be considered