Analysis Of Torsional Characteristics Of Double-Box And Single-Chamber Corrugated Web Steel Box-Concrete Composite Beam Bridge

With the large-scale construction of highways in China,the bridge construction is booming,and the bridge span and bridge deck width are gradually increasing.The proportion of corrugated steel webs composite box girder bridge in bridge construction is gradually increasing due to its advantages of large web spacing,wide deck width and large lateral cantilever.The test take a 30 m Double-box and single-chamber corrugated steel webs steel boxconcrete composite box girder bridge as the research object.Combining theoretical analysis with numerical simulation to test the torsional behavior of the composite beam.The main research contents and results are as follows:(1)The corrugated steel webs and steel bottoms with longitudinal stiffeners are equivalent to orthotropic plates by means of displacement and stiffness equivalence principles.Based on the second theory of Umansky constrained torsion theory and energy variational method,the constrained torsion control differential equation of the composite structure is established.The differential equation is solved by the initial parameter method.The formulas for calculating the torsion angle,warping deformation coefficient,restraint torsion double moment and total torsion of the simply supported box girder bridge with double-box and single-chamber corrugated steel webs and steel box-concrete composite under concentrated and full span uniform torsion are derived.Through the comparison and analysis of the theoretical calculation value and the finite element value of the section torsion angle,the two agree well and verify the correctness of the calculation formula.(2)The formulas for calculating the shear flow and torsional inertia moment of the section of a simple supported box girder bridge with double box and single cell corrugated steel webs are derived by using the membrane analogy method.Based on the second constrained torsion theory and the energy variational method,the constrained torsion control differential equations of the combined structure are established.The relationship between shear force and external torque of double-box and single-chamber corrugated steel webs steel box-concrete composite simple-supported box girder bridge is deduced through internal and external torque balance.The three-dimensional finite element analysis model of the composite simple-supported box girder bridge is established,and the correctness of the model is verified by the elementary beam theory.Based on the validated model,the distributions of cross-section torsion angle,warping deformation coefficient and restrained torsion moment along the longitudinal direction of double box and single-chamber corrugated steel box-concrete composite simple-supported box girder bridge and the distributions of top and bottom plate normal stress and corrugated steel web shear stress under the coupling of torsion and distortion are analyzed.(3)Based on Umanski’s torsion theory and structural dynamics theory,the restrained torsion frequency formula of double-box and single-chamber corrugated steel webs steel boxconcrete composite simple-supported box girder bridge under free vibration is derived.The correctness of the calculation formula is verified by finite element simulation.The influence of diaphragm,box lateral combination and cross-section parameters on restrained torsion frequency of double-box single-room corrugated steel webs steel box-concrete composite simple-supported box girder is analyzed by finite element simulation.(4)Symmetrical and eccentric loads are applied in the midspan of double box and singlechamber corrugated steel webs steel box-concrete composite simple-supported box girder bridge,the normal stress at the intersection point between the bottom plate and the web of the eccentrically loaded side of the 10-point section of the main girder is extracted and its magnification factor is calculated.The shear stress is extracted from the center node of corrugated steel webs with the above section and the magnification factor is calculated.The effects of height-span ratio,width-span ratio,thickness of corrugated steel webs,transverse connection between boxes and thickness of bottom plate on stress of double-box singlechamber corrugated steel webs steel box-concrete composite box girder bridge under symmetrical and eccentric loading are analyzed.