Analytical Formulations For The Mechanical Behaviors Of Self-Anchored Suspension Bridge

Self-anchored suspension bridge is a special form of suspension bridge with main cable anchoring on stiffened beam that constitutes a self-equilibrium cable supported structural system. The mechanical properties of the structure and relevant theories differentiate it from traditional ground-anchored suspension bridge due to the anchorage form. Currently the methods for the characteristic analysis of self-anchored suspension bridge mainly depend on finite element method, which only lead to certain numerical results that fail to directly provide design references. Therefore it is necessary to further investigate simple calculation methods for self-anchored suspension bridge.Basic assumptions of computational theory of suspension bridge were introduced. Based on the principle of minimum total potential energy and the Ritz’s method, analytical solutions were obtained for the calculation of the equivalent film tension force of the suspender, the changes of the central sag of the main cable, the horizontal displacement at the top of the tower and the deflection of the girder for the self-anchored suspension bridges with two towers and single span under uniform live load. Besides, Midas/Civil software was used for the verification of formulation. The calculation error of the analytical method is less than 8%, which satisfies the accuracy requirement in preliminary design. Error analysis was performed for the assumption of the formulation and its rationality was verified.With the same assumption and method, analytical solutions were obtained for the calculation of the equivalent film tension force of the suspender, the changes of the central sag of the main cable and the deflection of the girder for the self-anchored suspension bridges with symmetric single tower and twin-span under uniform load. Verified by finite element analysis, analytical formulation has error percentage less than 11%, satisfying the preliminary design requirements. The factors that led to larger calculation errors were investigated.Design parameters were analyzed for two towers with single span and single tower with double-span through analytical formulation. With alteration of design parameters such as rise-span ratio, side-to-main-span ratio, main tower height, bending stiffness of stiffened beam as well as main tower and tensile rigidity of main cable, their effects were analyzed for the equivalent film tension force of the suspender, the changes of the central sag of the main cable, the mid-span deflection and the horizontal displacement at the top of the tower. The rule of changes between deformation and parameters was derived and reasonable value range of design parameters was proposed, which can provide reference for the design of this kind of bridge.The correctness and reliability of the formulation was verified by finite element software and error analysis for the assumptions. Parameter analysis by obtained formulation can clearly inform its influence on the deformation of self-anchored suspension bridge, help designers understand its mechanical properties and provide a simple and reliable method for its design.