Analysis of Different Bascule Bridge Architectures

Bascule bridges are widely used nowadays to overcome the obstruction of ships passage as crossing waterways and in some roadways to overcome transport vehicle height limitation. A Bascule bridge is a movable bridge with a counterweight that continuously balances a span, or "leaf", throughout its upward swing to provide clearance for boat or ship traffic. It may be single or double leafed. Balance Beam Bascule Bridge is one of the famous bascule bridge architecture in which bridge span counter balance weight is attached to a balance beam in the movable bridge operating mechanism. Although hydraulic cylinders is a particularly common solution to power majority of modern bascule bridges, it is very important to understand the kinematics and motion of the bridge leave for optimum operation of the bridge with prober counter balance selection. In this study a review of two operating hydraulic actuators arrangements; push arrangement and pull arrangement is carried out based on both design aspects and safety consideration. 3D model of the study mechanisms are constructed and a kinematics of bridge leaf (span) opening mechanisms are developed for early stage design configuration of bridge mechanism. kinematic analyses of bridge mechanism operation in both push and pull arrangements based on rigid body consideration is performed and Numerical analysis using finite element method is carried out in which stress distribution over tie rods is obtained. Some failure scenarios are introduced. Results show that tension forces acting on tie rods in pull arrangement is lower than that in push arrangement, work done by hydraulic cylinders (Actuators) in both arrangement is nearly identical and pull arrangement is much better than push arrangement from safety point of view.