Experimental and Numerical Investigation of the Expansion Mechanism of Beam-End Expansion Devices in Large-Span Bridge

The beam-end expansion device of a large-span bridge is critical equipment for relieving temperature stress and also a weak point. In this paper, a detailed analysis of the expansion mechanism and jamming phenomenon of the beam-end expansion device is conducted for the first time. A dynamic model of the beam-end expansion device is established using complex flexible body coupled kinematics theory. The model overcomes two major challenges in simulation: (1) the expansion function of the scissor device provides the beam-end expansion capability while transmitting force to drive the movable sleepers, and (2) the coupling effects in the longitudinal, vertical, and horizontal directions between the movable sleepers and the upper structure need to be simulated to provide not only vertical support stiffness but also force on contact surfaces during expansion motion. The phenomenon of jamming caused by the asymmetry of the scissor device is found and the reason is analyzed. By comparing the paths of load transmission caused by different types of scissor devices, the influence on scissor devices and movable steel sleepers is summarized. The conclusions derived from theoretical deductions are consistent with the simulation results and validated through four monitoring data sets. The research findings of this paper can provide insights for addressing the design, operation, and maintenance issues of beam-end expansion devices in large-span bridge projects, ensuring that they meet the requirements of engineering practice.