Study On Temperature Gradient Model And Temperature Effect Of Composite Box-Girder Bridge With Corrugated Steel Webs

The composite box girder bridge with corrugated steel webs makes full use of the advantages of the two construction materials-steel and concrete,and has the characteristics of light weight,good seismic performance,and reasonable structural mechanism.Due to the long-term exposure to the external environment such as solar radiation and the atmosphere,an uneven temperature field will be generated on the box girder;in addition,the difference in the thermal conductivity of such two materials will cause secondary stress in the cross section,which will adversely affect the structural behavior of the bridge.Nowadays,most domestic and foreign scholars have focused on the study of the temperature field and its effects on concrete box girder,and the design codes do not specify the temperature gradient model of the composite box girder bridge with corrugated steel webs,so it is imperative to conduct relevant research.Based on a composite box girder bridge with corrugated steel web—Yinzhou Lake auxiliary channel bridge in Jiangmen City,Guangdong Province,this paper studies the temperature gradient model and its effect on both composite box girder with corrugated steel webs and concrete encased webs by using the methods of field measurement,finite element simulation and probability statistics.The main research contents and results are as follows:1.Through the temperature measurement of two types of composite box girder with corrugated steel webs(concrete encased or not),the temperature variation laws at the top and bottom slab,corrugated steel webs and concrete encased webs were obtained,and the positive and negative temperature gradient models of such two-type box girder sections were established.2.The transient temperature field analytical model of composite box girder with corrugated steel webs was established by finite element software ANSYS.Referring to the relevant literature and the field measurement data,the corresponding material and environmental parameters were determined.The spatial temperature distribution of both two sections during monitoring process was simulated and compared with the measured results,and the efficiency of the analytical model was verified.Then,taking wind speed and radiation absorbing rate of steel and so on as variables,the parametric sensitivity analysis of temperature field for composite box girder with corrugated steel webs was carried out,it was found that radiation absorbing rate of steel and wind speed have great influence on temperature distribution,which needs to be paid attention to in engineering design.3.The temperature distributions of two types of cross-section in summer and winter were obtained through numerical simulation,and the positive and negative temperature gradient models along the height of the cross-section were fitted.In addition,the daily average temperature difference and the maximum temperature difference at the top,bottom slab and the web of the box girder were obtained.Using the generalized extreme value distribution function and taking the 50-year return period as the criterion,the most unfavorable positive and negative temperature distribution of the box girder with corrugated steel webs and concrete encased webs were extrapolated,the corresponding temperature gradient model was proposed and compared with that specified by the Chinese highway bridge and culvert code and British BS5400 design code.4.The finite element models of composite box-girder bridge with corrugated steel webs under maximum cantilever state during construction stage and the complete stage were established using software MIDAS/Civil.The stress state and displacement of the box girder subjected to the proposed and code-based temperature gradient were calculated and compared.The results show that there is little difference on temperature effect under three positive temperature gradient models,but obvious difference under negative temperature gradient,in the construction stage and the completed state.It is suggested to apply proposed temperature gradient model for preliminary design.