Research On Mechanical Behavior Of Cable And Beam Of Luoxi Bridge During Construction And Completion

With the vigorous development of modern urban traffic,the span of cable-stayed Bridges are getting longer and longer,concrete cable-stayed bridge has been difficult to meet the requirements of long span Bridges,so the composite beam cable-stayed bridges have been developed rapidly.Construction process,ambient temperature,and concrete shrinkage and creep affect the construction of the main bridge,therefore,the calculation and analysis of these influencing factors will be instructive to the construction of the bridge.Therefore,based on the widening project of Luoxi Bridge,this Thesis analyzes how much the construction process,the temperature effect during closing,and the shrinkage and creep of the concrete in the completed state affect the construction of the composite beam cable-stayed bridge,and provides guidance and suggestions.The mian work of this thesis is as follows:1.After consulting the literature,review the development of composite beam cable-stayed bridges at home and abroad and the current research status of temperature and concrete shrinkage and creep effects,and explain the research significance and main work of this article.2.Use Midas Civil to establish a cable-stayed bridge model with standard segment main girder under three different construction schemes and a cable-stayed bridge model with secondary dead load under two different cable adjustment time schemes.According to the results calculated by the software,the construction scheme of two sections lagging behind one section pouring wet joints of the bridge deck and the second stage cable adjustment before the second stage dead load is selected.3.The closure of the side and middle span of Luoxi Bridge are calculated and analyzed by using Midas Civil.The effects of closure temperature difference,cable-beam temperature difference and vertical temperature gradient of main girder on deflection,internal force,stress of main girder and cable force of stay cable during side and middle span closure are analyzed.The results show that the temperature difference between cable and girder and the vertical temperature gradient of main girder have obvious effect on the side and middle span closure.4.The influencing factors of concrete shrinkage and creep are expounded,the concrete shrinkage and creep of Luoxi Bridge after completion of the bridge are calculated by using Midas Civil.After the completion of the main bridge,the changes in the elevation and stress of the main girder due to the shrinkage and creep of the concrete are obtained: the maximum displacement and stress changes in the main girder are in the first year.Considering the influence of different loading ages of concrete bridge decks on the elevation and stress of main girders under completed bridge,four different loading ages of concrete bridge decks are defined and calculated,it is found that the effect of concrete shrinkage and creep becomes stable after180 days of concrete bridge decks.