Static Analysis of Long-Span Suspension Bridges: Surrogate Model and Explicit Solutions

The static analysis of long-span suspension bridges under live loads has been a concern in serviceability design. However, the formulation of closed-form solutions is very challenging, owing to the highly static indeterminacy of suspension bridges. For all that, in this paper, a surrogate model is presented that consists of several equivalent springs to represent the horizontal stiffnesses of the cables and towers. Based on this model, explicit static solutions for typical live load cases are derived, which are also verified using the finite-element method and field measurements. The solutions can also be extended to suspension bridges with sliding saddles. Subsequently, parametric studies are conducted on the two general layout parameters, that is, the sag-to-span ratio and side-span to main-span ratio. The findings indicate that these two parameters have substantial effects on the cable horizontal stiffness and tower top displacement and are strongly related to the maximum vertical displacement for cases of either full-span or half-span live loads. Overall, the proposed surrogate model offers a practical and rapid method, with acceptable accuracy, for the static analysis of long-span suspension bridges in their conceptual design.