Dynamic strength analysis and structural topology optimization of modular bridge expansion joints under vehicle impact loads

A Structural dynamics analysis and topology optimization are presented to solve the early damage of Modular Bridge Expansion Joints (MBEJ) in this paper. Firstly, a method for analyzing the dynamic strength of MBEJ under the moving vehicle is proposed, in which both the vertical and horizontal wheel loads are considered and applied at the most unfavorable position derived from the bending-moment influence lines of the center beam. The results of dynamic analysis show that the center beam has a combined bending and torsion deformation, and it leads to a highly uneven stress at the connection pad between the center beam and the transverse beams. Secondly, the pulsation strength theory is adopted to evaluate the safety of the MBEJ, and the maximum Mises stress at the connection pad exceeded the pulsation strength of steel Q345B, which is consistent with the damage of practical structure in engineering. Uncertainty analyses of the wheel load positions show that the maximum stresses are always at the connection pads and exceeded the pulsation strength, and the most unfavorable position from the influence line is proved to result in the maximum stresses. Finally, the topology optimization method is used to optimize the connection pad between the middle beam and the transverse beam. By maximizing the stiffness and limiting the volume and stress of the structure, a box-shaped support pad with strong bending and torsion resistance is obtained, and the optimized MBEJ structure meets the requirements of pulsation strength.