Study On Mechanical Properties Of Prefabricated Assembled Composite Box Girder Bridge With Corrugated Steel Webs

In this paper,the researcher took a kind of new structure-prefabricated composite steel box girder bridge as the research object,which is suitable for small and medium span bridges.Its relative advantage to traditional prefabricated concrete composite beams were introduced. The factory production process of prefabricated composite steel box girder and its assembly process was briefly described.The deflection calculation considering the influences of shearing deformation and shear lag effect and the fatigue performance of local weld were studied.The distribution regularity of normal stress and web shear stress in prefabricated composite steel box girder was studied. Based on that, the deflection calculation formula under concentrated load, distributed load and symmetrical load considering shear deformation was deduced, and a finite element model of 30m simply supported prefabricated composite steel box girder bridge was set up. The deformation results of both using finite element method and theoretical calculating method were compared. According to the results, the difference value was no more than 5% and it illustrates the validity of the theoretical calculation formula. The study carried out an analysis on the the effect of shearing deformation on deflection as the height-span ratio and width-height ratio changes. The paper gives the limiting value of height-span ratio in 20 to decide whether to take shearing deformation into consideration in deflection calculation.The study chose the energy variation method and finite element method to look into the shear lag effect in prefabricated composite steel box girder. The additional deflection induced by shear lag effect was chosen to be the generalized displacement function, cubic parabola as the warping displacement function. The calculation formulas of shear lag coefficient and stress distribution on cross-section under concentrated load and distributed load were given. The calculation formula separates the influence of general beam theory and the shear lag effect. The calculation theory is clear and simple to solve. The researcher used theoretical method and finite element method to look into the shear lag effect on bottom plate and top plate, and its variation in longitudinal direction. The effect of height-span ratio and width-height ratio on shear lag effect. The results showed that under that situation, the massive shear lag coefficient is 1.2. The study took height-span as the the independent variable, for its significant impact on shear lag coefficient. Regression method was used to give the calculation formula of the massive shear lag coefficient in cross section. Based on the calculation results, the effective distribution width of prefabricated combined steel box girder was given. This paper compared the results using finite element method and theoretical method with the results calculating from Chinese code and Japanese code and Canada code, and found that results using codes tend to be more conservative than the results using theoretical method.A finite element model of a prefabricated composite steel box girder bridge was set up, as well as sub models of simple simulated weld. Base on the calculation of longitudinal and transverse impact line in the focus point, the researcher adopted Matlab as a tool to simulate the fatigue loading process, and got the most unfavorable loading position of the concerned weld.On the basis of determining the mesh size and extrapolation method, the hot spot stress histories in most unfavorable position using finite element method were obtained. The stress amplitude due to fatigue test was obtained using discharge method.The research combined all this with Miner linear damage accumulation criteria to calculate the damage caused by the vehicle fatigue.Finally,the fatigue life-span of prefabricated composite steel box girder was obtained.