Comparative Study On Key Design Parameters Of Highway Suspension Bridge In Chinese And Foreign Specifications

As the bridge type with the largest spanning capacity,the suspension bridge is widely used in modern traffic engineering.In the design process of suspension bridge,when the bridge span layout is determined,the design parameters of stiffening girder and main cable need to be determined first,and the design of other components need to be based on these parameters.In the past,the research on the design parameters of suspension bridges is sometimes limited to a single engineering background,so it's difficult to compare the parameters of suspension bridges with different spans and stiffening girder types.In addition,in the past,there are more research results on Bridge Specifications in China,Europe and the United States than in Japan.This paper mainly carries out relevant research and discussion on these problems.Firstly,based on the equivalent principle of shear stiffness,a convenient and feasible simplified modeling method for plate-truss stiffening girder is proposed in this paper,and the accuracy of the simplified method is verified by ANSYS finite element model calculation.Secondly,the design parameters of stiffening girder of suspension bridges are discussed.And this paper presents a method for determining the height of steel truss girder by using statistical data and torsional stiffness.Based on the above research results,six suspension bridge models with different spans and stiffening girder types are established to study the contribution ratio of girder vertical bending stiffness to overall vertical stiffness and the influence of gravity stiffness and geometric stiffness.Finally,this paper systematically introduces the specific provisions on vehicle live load and load combination in highway bridge specification of China,Europe,the United States and Japan,and compares these values of different specifications.Through the above research,it is found that the height of girder has the greatest influence on the torsional stiffness of stiffening girder,followed by the width of girder and the area of bottom connection members.For small span suspension bridges,the contribution of girder vertical bending stiffness can not be neglected.When drawing up the stiffening girder height for small span suspension bridges,a larger girder height should be selected appropriately.For small span suspension bridges,smaller rise-span ratio should be chosen to improve the overall stiffness of the bridge,and larger rise-span ratio should be adopted for large span suspension bridges to save material consumption.The geometric stiffness of the main cable decreases with the rise-span ratio,and the gravity stiffness increases with the decrease of the rise-span ratio.Generally,the influence of the gravity stiffness is greater than that of the geometric stiffness.Therefore,the overall vertical stiffness of the main cable increases with the decrease of the rise-span ratio.Based on the deflection effect of live load of suspension bridges as the criterion,the ranking of live load values in different specification is European Specification > American Specification > Chinese Specification > Japanese Specification;with the safety margin of main cables as the criterion,the ranking of load combination values in different specification is American Specification > European Specification > Japanese Specification > Chinese Specification.