Long-term Monitoring Of Temperature Gradients In Steel Truss Bridges And Engineering Design Methods

At present,the construction of high-speed railway bridges in China is booming,among which steel truss bridges are widely used because of their high strength and uniform materials.The existing research shows that the temperature field of steel truss bridge will have some adverse effects,such as concrete slab cracking and bridge bearing diseases.However,China’s Code for Design of Highway Cable-Stayed Bridges,European EN1991-1-5 Code and American AASHTO Code have not clearly defined the temperature gradient of steel truss bridge.Based on the actual monitoring data and finite element simulation,this thesis explores the temperature gradient law of steel truss bridge,and puts forward the recommended mode of engineering application by combining probability and statistical characteristics with correlation analysis.The main research contents and achievements of this thesis are as follows:(1)Long-term monitoring and law analysis of temperature field of steel truss bridge.Based on the measured data of steel truss bridge,a preprocessing method for inaccurate data is proposed,and then the monitoring law of time-varying and spatial distribution of steel truss bridge is explored.The time-varying monitoring law of steel truss bridge is mainly reflected in the seasonal variation characteristics of each node,which is "summer in summer and winter in cold",and the annual temperature timehistory variation conforms to a sinusoidal curve,and the variation amplitude in summer is greater than that in winter.Then,the temperature variation trend monitored by concrete sensor and steel structure temperature sensor is compared,and it is found that the data monitored by concrete sensor is gentle.The spatial distribution monitoring law of steel truss bridge is mainly explored from the cross section of a single bar member,the transverse temperature gradient distribution characteristics of bridge deck members and the overall vertical temperature gradient distribution characteristics of bridge deck construction.It is found that there are temperature gradients,and the temperature gradient of side truss is greater than that of middle truss.(2)Analysis of influencing factors on temperature gradient of steel truss bridge under sunlight radiation.Based on Ansys software,the finite element simulation of steel truss bridge is carried out,and the accuracy of the model is verified by comparing with the measured data.The variation law of steel truss bridge model under the action of roof thickness,flange plate length,seasonal parameters and thermal parameters is discussed,and the correlation between each parameter and node temperature,transverse and vertical temperature gradient of steel truss bridge is summarized.(3)Engineering design method of steel truss bridge under temperature action.Based on the probability and statistical characteristics,the extreme value samples of temperature gradient are fitted,and the best cumulative distribution function of sample data is selected by fitting error formula,and the influence of time interval on fitting effect is considered.Through mathematical statistics,the standard value of temperature action is calculated when the extreme value of temperature gradient is in service for100 years,and the inherent law between the measured extreme value of steel truss bridge and the standard value of temperature action is revealed through fitting expression.Based on the correlation between the standard value of temperature action and the sample data of temperature gradient,a method to solve the most unfavorable temperature gradient model is proposed.There are 68 pictures,28 tables and 73 references in this thesis.