Analytical Algorithms For The Cable Configuration And Construction Parameters Of A Suspension Bridge

With the rapid development of economic and ever-growing traffic demand,suspension bridges present a development trend of increasing span-length and diversification of forms.In order to reduce the weight of the structure and the amount of materials,the safety factor of main cable continues to be reduced.Therefore,the suspension bridge needs more refined calculation of the main cable configuration and key construction parameters in the design and construction phases.In this paper,focusing on the cable configuration and based on the multi-segment catenary theory and the Jindong bridge,a series of studies were carried out on the configuration of the main cable in both the completed bridge state and construction stage:(1)Based on the multi-segment catenary theory,a systematic analytical method for the configuration of the main cable in the completion state and the free cable state and relevant construction parameters is proposed.A high-precision and efficient numerical algorithm is established incorporating the generalized reduced gradient method to avoid the complicated iterative process in the finite element method,improving the versatility and applicability of the analytical method.Finally,A steel truss suspension bridge with a main span of 730m—Jindong Bridge is taken as an engineering example to verify the feasibility and effectiveness of the method.(2)Based on the above analytical algorithm,the mechanical equilibrium condition,geometric compatibility condition and unstressed length conservation condition are summarized to establish the analytical method for the main cable configuration of suspension bridges under different temperatures.The influence of temperature on the cable shape and construction parameters under different construction stages and boundary conditions is further analyzed.(3)To further tap the potential of the above theory,an analytical algorithm for the reverse identification of the hanger tensile forces of a suspension bridge is proposed based on the measured configuration of the main cable,effectively avoiding the problem of "poor precision in the short hanger force measured by the vibration frequency method".In addition,the sensitivity of the parameters in the algorithms of "geometric conditions(complementary measurement of a nonhanging point’s coordinates)" and "mechanical conditions(complementary measurement of the internal force of a hanger)" is analyzed.(4)The multi-segment catenary theory is extended to the form-finding analysis of spatial cables,and the analytical method of the cable configuration and hanger tensile forces of the suspension bridge with spatial cables is established.The segmented catenary expression,parameter recurrence relation and control equation of the spatial cable are derived.The relationship between the vertical and horizontal sag to span ratio of the main cable is further discussed.Moreover,a self-anchored suspension bridge and an earth-anchored suspension bridge with spatial cables are taken as examples to verify the feasibility and effectiveness of the method.