Simulation And Measurement On Temperature Effect Of A Long-span Cable-stayed Bridge

With the enhancement of economic strength,the transportation industry in China has entered a flourish development.Since the demand for crossing natural barriers such as rivers,lakes and seas has brought out higher requirements for bridge spans,cable-stayed bridge has become one of the main types for long-span bridges due to its excellent spanning capability.Generally lighter steel main beams are adopted in long-span cable-stayed bridges,however,due to the low specific heat capacity of steel,the temperature fluctuation of the structure under the action of ambient temperature is relatively large,and the resulting temperature effect cannot be ignored.Therefore,the temperature load effect on long-span cable-stayed bridges is one of the research hotspots in bridge engineering.Taking the Sutong Cable-stayed Bridge(SCB)as engineering background,this thesis focuses on the temperature effect simulation of long-span cable-stayed bridges.Combined with the measured temperature data and vibration data of the structural health monitoring system(SHMS)on the SCB,simulation and measurement research on temperature effect of the cable-stayed bridge are conducted based on ANSYS.The research results can provide reference for the temperature effect analysis of long-span cable-stayed bridges.The main research contents include:(1)Measurement and analysis of temperature field distribution characteristics of the main girder of the long-span cable-stayed bridge.Based on the long-term temperature data of the flat steel box girder collected by the SHMS on SCB,the statistical law of temperature and temperature difference at each measuring point is analyzed on the mid-span section,and the heat transfer law of steel box girder is also studied.The probability density of temperature and temperature difference is quantified by least squares estimation,hypothesis testing and other methods,and the probability distribution model of temperature and temperature difference of each measuring point is thus obtained.Also,the power spectral density and spatial coherence function of temperature at each measuring point are calculated from the perspective of stochastic process.Finally,an effective model of temperature spectral density and coherence function is established,which lays a solid foundation for the subsequent temperature field simulation of the main girder.(2)Numerical simulation of temperature field at the main girder of the long-span cable-stayed bridge.Based on the statistical law of the temperature at the measuring points,the non-Gaussian property of the measured temperature field is analyzed.With the introduction of forward Hermite transformation,the measured temperature field is Gaussianized.Also,the fitted power spectral density model and spatial coherence function model are utilized to build the cross-spectral density matrix.Based on the harmonic synthesis method,the numerical simulation of the temperature field at the steel box girder is conducted.On this basis,the Hermite inverse transformation is used to obtain the simulated temperature field in accordance with the measured characteristics.In order to verify the rationality of the simulation results,the probability density function,power spectral density and spatial coherence function of the simulated temperature field are compared with the measured values.(3)Modal parameter identification and temperature correlation study of the long-span cable-stayed bridge.Based on the long-term vibration data of the main girder collected by the SHMS on SCB,the vibration responses of the mid-span section of the main girder are analyzed,and the study on the relationship of the structural vibration response RMS and the temperature in all directions is accomplished.Also,the long-term modal parameters of the bridge are identified by random decrement method,moreover,the correlation between the typical modal frequencies and temperature of each order is obtained.The results could provide verification basis for the subsequent finite element modeling and temperature effect simulation.(4)Simulation and measurement verification of temperature effect of the long-span cable-stayed bridge.The finite element model of SCB is established in ANSYS according to its structural design parameters.According to the results of the dynamic and static load test report of SCB,the vertical deformations of the finite element model under no-load and standard static load conditions are calculated.Comparisons are carried out between the calculated and experimental results to verify the static validity of the finite element model.The effect of temperature load on the static characteristics of the long-span cable-stayed bridge is further analyzed on this basis.Besides,modal frequencies of SCB are calculated under different temperature conditions,and the accuracy of the established model is verified by the comparison with the previous modal identification results and third-party calculation results.By increasing and decreasing the temperature of the main girder and stayed cables,the variation law of the structure modal frequencies under temperature load is obtained and compared with the measured results.