Study On The Wind-resistance Performance Of A Long-span Suspension Bridge During Cable Erection

With the continuous development of the economy,science and technology,more and more long-span suspension bridges are being built around the world.However,as the span of the suspension bridge increases,the stiffness and damping of the bridges are relatively reduced,resulting in an increasing sensitivity to wind.Because long-span suspension bridges generally have a long construction period and harsh construction wind environment,coupled with low stiffness and poor wind resistance performance of temporary structure,some wind effects that do not occur when the bridge is completed may occur during construction.As the important construction platform for suspension bridges,catwalks are large-span flexible structures and typical wind-sensitive structures.Under the action of wind loads,the displacement and vibration generated by the catwalks will affect the accuracy and stability of the main cable construction and erection,as well as the comfort and safety of construction workers.During the construction period,the shape of the main cable is constantly changing,it is not a circular cross-section,so the wind-resistance performance is also constantly changing,and thus may experience galloping instabilities.Therefore,it is necessary to study the wind-resistance performance of the catwalk and the temporary main cable of the suspension bridge during the construction period.In this thesis,the Lingdingyang Suspension Bridge of the Shen-Zhong link is taken as an engineering example.The wind resistance performance of the catwalk and the main cable of the long-span suspension bridge during construction are investigated as following:(1)Using ANSYS finite element software,the full and local finite element models of the catwalk of the long-span suspension bridge were established,and the vibration frequency and mode shape of the catwalk were calculated.(2)The rigid segment model of the construction catwalk with a scale of 1:10 was designed and made,and the wind tunnel test was carried out in the XNJD-1 wind tunnel laboratory,and the three-component force coefficient of the catwalk with and without the influence of the construction temporary main cable were obtained,the difference between the two situations was compared and analyzed.(3)Using the two-dimensional linear static wind analysis theory,the torsional failure wind velocity of the catwalk was calculated;using the three-dimensional nonlinear static wind analysis theory and the related program,the displacement response of the catwalk under different wind velocity was calculated,the static wind stability of catwalk with and without the influence of temporary main cable is analyzed.(4)Using ANSYS finite element software,the finite element model of the main cable during the construction of the long-span suspension bridge is established,and the dynamic characteristics of the main cable are analyzed.(5)5 kinds of temporary main cable rigid segment models with a scale of 1:10 were designed and made,and the wind tunnel test was carried out in the XNJD-1 wind tunnel laboratory.The three-component force coefficients of five different cross-section main cables with and without the influence of catwalks are obtained.The influence of the catwalk on the three-component force coefficients of five different main cables under different initial wind attack angles was compared and analyzed,and the galloping force coefficients of the five main cables under were calculated.Using the time domain analysis method,the buffeting response of the catwalk was calculated(6)Two main cable sections were selected,and the model wind tunnel test was carried out,and the analysis theory of the single-degree-of-freedom galloping vibration model was verified.The critical wind velocity for galloping vibration of the temporary main cable of a long-span suspension bridge is calculated.