Study On Stress Amplification Factor Of Composite Box Girder Bridge With Corrugated Steel Webs Considering Torsion And Distortion Effects

The composite box girder bridge with corrugated steel webs is developed from the development demand of high strength and light weight of traditional concrete box girder.It is a new type of steel-concrete composite structure in modern bridge construction.It has the characteristics of light weight,fast construction and reasonable structure,so it should be widely used in Bridge Engineering at home and abroad.However,compared with the traditional concrete box girder,the web and the top and bottom plates of the composite box girder with corrugated steel webs are connected by shear pieces,so the performance of resisting torsion and distortion is lower,so it is necessary to study the torsion effect and distortion effect of the composite box girder with corrugated steel webs under eccentric load.In this paper,simply supported straight-line corrugated steel webs composite box girder bridge is taken as the research object,and the torsion and distortion effects of corrugated steel webs composite box girder bridge under eccentric Lane load are studied in detail.(1)Firstly,the mechanical characteristics of the composite box girder with corrugated steel webs are analyzed,the effective shear modulus of the section is calculated and the section is transformed.Then,the torsional geometric characteristics of the composite box girder with corrugated steel webs are calculated according to the traditional torsional analysis theory of concrete box girder.According to the second theory of Ubbelohde,the calculation formulas of torsional double moment and torsional warping stress are deduced to establish the torsional differential equation The correctness of the formula in this paper is verified by an example,and the variation law of the torsional double moment and the bending torsional moment under the eccentric load is analyzed.Through the analysis,it is found that the torsional double moment has the maximum value in the midspan section,so the maximum value of the torsional warping stress also occurs in the midspan section.(2)The more general distortion angle and distortion center are defined,and the transverse bending rigidity,distortion warping strain energy,transverse frame strain energy and distortion load potential energy of corrugated steel webs are calculated.The calculation formulas of distortion double moment and distortion stress are derived.The distortion differential equation is established according to the principle of potential energy standing value,and the differential equation is solved by the initial parameter method Through the analysis,it is found that the distortion double moment has the maximum value in the middle of the span,so the maximum distortion warping stress is also in the middle of the span.(3)Combined with an engineering example,the paper calculates the stress amplification coefficient of torsion warping stress and distortion warping stress under the eccentric Lane load and considering the torsion and distortion effects at the same time.Through analysis,it is found that the warping normal stress is mainly caused by the distortion effect,and the warping shear stress is mainly caused by the torsion effect and the distortion effect has little influence on the shear stress,so the distortion can be ignored in the calculation of warping shear stress Through the analysis of the value of stress magnification factor,it is found that the normal stress at the intersection of the web and the bottom plate of the midspan section under the eccentric Lane load is 1.6 times of the bending normal stress when the lane load is symmetrically arranged.Finally,the parameter analysis of the height width ratio,the width span ratio,the width of the cantilever plate and the thickness of the web plate that affect the stress magnification factor is carried out The influence of web shape and thickness on the shear stress value is greater.