Beam Finite Element Including Shear Lag Effect of Extra-Wide Concrete Box Girders

摘要

The paper presents a new formulation of a beam finite element for the time-dependent analysis of self-anchored suspension bridges, considering the shear lag in a multicell concrete box girder. The beam kinematics are deduced using a displacement-based approach. Warping of the girder section is captured with a warping intensity function representing the warping magnitude along the girder axis and a series of segmental shape functions describing the warping shape of the asymmetrical multicell box section, which is deduced based on shear flow transmission. A three-dimensional 14 degree-of-freedom (dof) beam finite element employing hermitian polynomials to ensure consistent displacement interpolation is proposed. The proposed beam element is implemented in ANSYS as a user-defined element. The convergence test results and comparisons with the refined analyses using a solid finite-element model demonstrate the accuracy of the proposed element. Time-dependent behavior of concrete is calculated using the B3 prediction model and the age-adjusted elastic modulus method. The moment estimation method is adopted to conduct the random analysis, which yields the 95% confidence limits of the structural responses obeying approximately the normal distribution. Application to a full-scale bridge structure shows the efficiency and accuracy of the proposed method and its ability to describe the elastic and time-dependent behavior of a self-anchored suspension bridge with extra-wide concrete girders.