Numerical Analysis And Simplified Calculation On Shearing Performance Of Box-girder Bridges

Nowadays, box-girder bridges are widely used for their large stiffness of torsion,good performance on bearing stress, suitable for all kinds of construction methods.Aiming at the formula of shear resistance capacity in《Code for Design of HighwayReinforced Concrete and Prestressed Concrete Bridges and Culverts》(JTGD62-2004) is mainly suitable for the small open cross-section beams with T-typesection,Ⅰ-type section and rectangular section, and no definite formula is given forbox-girder bridges with large cross-section. The shear strength of box-girder bridgesis studied by using nonlinear finite element software.On the background of the six-span-continuous beam transferred fromsimple-supported beam with each span of 70 meters, one of the span is taken as aresearch object when the continuous beam is under a simple-supported condition.According to the achievement at home and abroad, the main factors effect on theshear strength of box-girder bridges include shear-span ratio, intensity of concrete,stirrup ratio, level of longitudinal reinforcement, web thickness and level of verticalprestressing. Twenty-five pieces of box-girder beams with different parameters aremodeled and analyzed. The shear behaviors as well as the failure modes of thesebeams are investigated. The shear mechanisms and their variations vs parameters arerevealed. The process analysis provides data basis for studying the shear strengthinfluential factors analysis and the simplified calculating method of box-girderbridges.According to the calculated results, the influence of the main factors to the shearstrength of box-girder bridges including the shear strength, principal compressivestress of concrete and deformation is analyzed. The simplified calculating formula ofshear strength is established by using regression analysis and theoretical analysis.Then a formula for shear strength design is concluded after modifying the obviousone according to principle for reliability design of highway concrete bridges. Finally,by comparing the formula with codes of JTG D62-2004, ACI and AASHTO, theapplicability of the formula is analyzed.