Research On Non-stationary Buffeting Response Of Long-span Cable-stayed Bridge In Mountainous Area During Construction

As more and more long-span cable-stayed bridges are built,people realize that their structural rigidity becomes smaler and smaler.Under the wind conditions of natural conditions,the sensitivity of the larger-span cable-stayed bridge will become more apparent.Due to the characteristics of mountainous terrain and landforms,the wind fields in mountain valeys often show strong wind gusts,and the non-stationary characteristics are particularly prominent.General y,the traditional buffeting analysis considers pulsating wind as a zero-mean stable random process.The stochastic process is obviously unreasonable.At present,scholars in the field of bridges are mainly studying the buffeting response of large-span bridges in the completion stage.Compared with the bridge construction stage,the structural flexibility during construction is greater.Under the action of natural wind,the large-span bridge structure is prone to a large buffeting response and the bridge structure is damaged.Under the action of non-stationary wind speed field,it is necessary to conduct in-depth study on the aerodynamic stability of long-span bridges under construction.In this paper,the non-stationary chattering response of the cable-stayed bridge structure during the construction process under the influence of wind in the mountain area is studied by means of numerical simulation methods and field measurement data of the bridge location.In the future,more refined bridge buffeting analysis will provide more constructive suggestions for the construction of super-span bridges.This article mainly carried out the following aspects of work:(1)According to the structural composition and construction process of the cable-stayed bridge relying on the project,the finite element model of the cable-stayed bridge was established using the finite element analysis software ANSYS,and the calculation and analysis of the key construction process and the dynamic characteristics of the bridge structure at the completion stage.(2)Using wavelet analysis theory,the time-varying average wind of the measured wind speed is extracted.The measured data shows that the mountain wind is composed of time-varying average wind and non-stationary pulsating wind.Based on the wind speed field at the bridge location of the project and the measured wind speed,the pulsating wind field was simulated using the harmonic synthesis method for the main beam and other structures of the cable-stayed bridge,and then the simulated pulsating wind field was carried out.Wind speed power spectrum test and correlation test.The test results show that the simplified wind speed field method and the pulsating wind simula tion algorithm written in this paper are feasible and can solve practical engineering problems.The method of time-domain static wind load,self-excited force and buffeting force is studied.Using the simulated non-stationary pulsating wind,load it into the ANSYS model after time-domainization,and analyze the non-stationary chattering response.(3)The analysis results of the non-stationary buffeting response of the cable-stayed bridge relying on the project show that the displacement response of the main beam of the cable-stayed bridge under non-stationary pulsating wind is compared with the mean square value of the displacement response of the cable-stayed bridge under the action of pulsating wind The mean square value is larger.The non-stationary wind field is more conservative and safer than the measured conditions.During the cantilever construction process,the main beam’s buffeting displacement at the cantilever end is the largest.To reduce the cantilever’s buffeting response,wind resistance cables and auxiliary supports can be set during the construction process.After mid-span closing,the mid-span 1/2-point buffeting torsional displacement is greatly reduced;after the transition of the tower beam temporary consolidation system is released,the mid-span response is reduced compared to before the system conversion;The mid-span response has been reduced compared to before the lanyard.