Wancheng Yuan

Seismic performance of cable-sliding friction bearing system for isolated bridges

During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.

Numerical simulation in dynamic analysis of deepwater group pile foundation of bridges

The influence of fluid-structure interaction on the dynamic characteristics of deepwater group pile foundation is investigated. For this purpose, a three-dimensional solid finite element model simulating the structure and a three-dimensional potential fluid model representing the water were developed using the software ADINA. Four parameters including the water depth, the width of pile cap, the height of pile cap and the superstructure mass were considered to investigate their effects on the fluid-structure interaction. Then possible improvement to the interaction influence by the change to the pile layout and number was examined. It is found that while the fluid-structure interaction due to water depth has significant influence on the dynamic characteristics of group pile foundation, effects due to the structural dimensions should also be included. In addition, the provision of raking piles can reduce the impact that water has on the foundation, but a larger pile cap with additional vertical piles can also produce this effect.

Seismic Analysis and Design Optimization of a Self-Anchored Suspension Bridge

The seismic performance analysis and design optimization of a self-anchored suspension bridge is studied in this paper. Based on the preliminary design of the bridge, a finite element model has been built for performing structural dynamic analysis. For time history analysis of the bridge subjected to seismic excitation, generated artificial site-specific earthquake waves were adopted as the ground motion input. The seismic performance objectives have been set for the bridge when earthquake events of expected intensities occur. The structural dynamic characteristics of the bridge have been obtained by performing modal analysis. In order to improve the seismic performance of the bridge, the tower design has been optimized and nonlinear fluid viscous dampers have been applied at the points of intersection between the two towers and the deck of the bridge. The parametric sensitivity analysis has been conducted on the design parameters of the dampers to determine a proper combination. Nonlinear time history analysis has been performed for the bridge. The analysis results show that the expected performance objectives of the bridge can be reached after the optimization of the towers design and the installation of dampers.

Numerical analysis of floating protection system for bridge structure subjected to vessel impact

A floating protection system is presented to protect bridge structures from vessel impacts. Based on general contact-impact nonlinear finite element technique, the high resolution models of the 5,000-DWT ship and the protection system are developed to evaluate the performance of the floating protection system under vessel collisions. The results show that the protection system can effectively absorb the moderate impact energy from the ship and avoid the damage of both the ship and structures. Finally, a general design procedure is discussed briefly for practical design.