Temperature Field Analysis Of Super Wide Steel Box Girder Of Large Span Suspension Bridge Based On SHMS

Bridges,as the preferred structure for crossing mountain streams,are increasing by tens of thousands every year in China.However,in the long-term operation process,the bridge structure will be affected by various environmental adverse factors including temperature load,which will seriously threaten the health state and personal safety of the bridge structure.Temperature field analysis of bridge structures based on Structural Health Monitoring System(SHMS)has been widely concerned by researchers at home and abroad,and relevant studies have been carried out based on theoretical analysis,numerical simulation,field measurement and other methods.However,it still faces some problems such as more complex structure form,diverse regional climate and insufficient data mining.Based on this,based on the long-term monitoring data of bridge SHMS,the temperature field characteristics of an ultra-wide steel box girder(49.7 m wide)of a longspan(main span 1200 m)suspension bridge in South China were measured and analyzed in this thesis.Combined with the measured results and the finite element method,multistage deflection and strain threshold lines were set for the bridge.Finally,based on the characteristic analysis results and mathematical theory,a sample sequence simulation method for the whole life cycle of temperature field is established,which provides a data basis for the whole life cycle state assessment of ultra-wide steel box girder of long-span suspension bridge.The main work and achievements of this thesis are as follows:(1)The statistical characteristics of the measured temperature and temperature difference were analyzed by using the least square method and the hypothesis test method,and then the standard values of temperature and temperature difference in different return periods were calculated by using the extreme value analysis method.The temperature difference distribution model of the ultra-wide steel box girder under the action of extreme temperature was obtained by combining the correlation analysis method and the most unfavorable composition method.The results show that the measured transverse temperature difference of ultra-wide steel box girder is as high as 15.28℃,and the vertical temperature difference exceeds the value of "General Code for Design of Highway Bridges and culverts".The probability density model of temperature and temperature difference using mixed multimodal Gaussian distribution fitting is better.The transverse temperature difference distribution model of super wide steel box girder roof with two shape characteristics of ’M’ and ’W’ is analyzed.(2)A refined segment model of ultra-wide steel box girder was established by using ABAQUS software,and the sunshine temperature field characteristics in each quarter of a year under extreme temperature weather were analyzed.Based on the temperature sensitivity characteristics of ultra-wide steel box girder,the deflection and strain response under the combined conditions of the most unfavorable temperature load and live load in multiple time scale were analyzed by Midas/Civil software.The results show that the overall simulation effect of the finite element model is good,and the transverse and vertical temperature differences of ultra-wide steel box girder are not uniform.The deflection and strain thresholds of suspension Bridges under the most unfavorable temperature load and live load combination in different seasons are different.Based on the calculation results,a three-level early warning mechanism of deflection and strain response is established for the bridge.(3)Based on the statistical characteristics of the probability density of the measured data,combined with the theory of inverse transformation and Latin hypercube sampling,a method was proposed to simulate the sample series of the temperature field in the whole life cycle of the ultra-wide steel box girder under the complex probability density statistical model.The results show that the whole life cycle temperature field of ultrawide steel box girder can be simulated well with the maximum error of 5% based on the Latin inverse transformation sampling method and the temperature characteristic retuning method.