| The main cables is the main load-bearing structure of a large-span suspension bridge,and its performance determines the bearing capacity of the bridge.The influence of temperature change on the main cable is long-term,which is one of the reasons for the linear change the of suspension bridge and will have a great impact on the deformation and internal stress of the main cable.Taking a large-span suspension bridge as the engineering background,this paper studies the temperature effect of its main cables,sets the threshold value according to the temperature situation,constructs the prediction model,and sets the early warning,which provides the scientific basis for the maintenance of the main cables.The main contents and conclusions of this paper are as follows:(1)Based on the heat transfer theory and considering the influence of wind speed,this paper studies the temperature field of the main cable of a suspension bridge,and simulates the temperature field of the main cables in different seasons through the secondary development of ABAQUS.The calculation results show that the reliability of the model is verified by comparing the measured temperature value with the calculated temperature value at the measuring point of the midspan section.When considering the influence of wind speed,the temperature difference of each measuring point of the main cables is larger;Compared with other seasons,the high-temperature area of the main cable surface is concentrated in the upper left in winter,and it is more inclined to the upper right in summer,so it is necessary to monitor the temperature of these parts in different seasons.(2)Based on the temperature field of the main cables,aiming at the study of the temperature effect of the main cables,a three-dimensional solid model of the suspension bridge is established by ABAQUS,and the temperature field of the main cables is coupled with the dead load to study the deformation and internal force distribution of the main cables under the action of sunlight.The calculation results show that the changing trend of the deflection value of the main cables is basically consistent with the measured data,and the error is small,which verifies the accuracy of the model.Under the action of sunshine,the deflection of the main cables changes obviously,and the displacement of the main cable reaches the maximum at around 16 pm and the minimum at around 6 am.In terms of stress,the longitudinal compressive stress of the main cable decreases and turns into tensile stress,while the transverse tensile stress decreases and turns into compressive stress.In addition,under the action of sunshine,the temperature stress in the midspan section of the main cables changes obviously,with the time-varying difference of longitudinal stress reaching 20 MPa and transverse stress reaching 35 MPa.(3)Aiming at the early warning threshold of the main cables,a full-bridge model of the suspension bridge is established based on Midas civil,and the response of the main cable anchor span force and deflection is calculated according to the calculated worst seasonal temperature difference,the worst annual temperature difference and the worst lane load,and a reasonable early warning threshold is set for the main cable,and the multi-index and multi-level bridge early warning function is determined.(4)Aiming at the time series analysis model(ARIMA),based on the historical monitoring data of anchor span force,an improved wavelet time series combination model(wavelet-ARIMA)is proposed,and the main cables anchor span force and deflection are predicted by using the wavelet-ARIMA model.According to the comparison between the prediction results and the above threshold,different alarm states are established,and dynamic alarm before bridge structural damage occurs is realized,which is an effective supplement to the traditional bridge health monitoring system. |
