Summary of Presentation from the 2015 ESI SimulationX User Forum
Conference Presentation by Uwe Grätz - ITI GmbH (now ESI Group), Dresden, Germany
The designers of the Poole Twin Sails Bascule Bridge applied SimulationX to expedite and validate their design of the bridge's hydraulic lifting system. By dynamically simulating the bridge's emergency stop scenario with SimulationX and adjusting the flow deceleration in the hydraulic system, they ensured that the maximum pressure in the lifting cylinders remained below the required 340 bar.
MBS model of the bridge platform and cylinders in SimulationX
The bridge model's mechanics were developed by importing a CAD file of the bridge platform, applying geometric constraints from technical drawings, and incorporating wind force data curves to calculate the load on the hydraulic cylinders. The hydraulic system consists of the cylinder, valve manifold, and power unit subsystems. The cylinders are represented using a 1D hydraulic cylinder, mass, and gravitational force, connected to the 3D mechanics through a force element. The valve manifold controls the cylinders using a combination of counterbalance, check, and pressure relief valves. Pressure limitation and directional valves channel flow from two variable displacement pumps to the cylinders, all managed by an integrated control system.
Diagram view of bridge model in SimulationX with hydraulic subsystems boxed
In an emergency stop, power is cut from the system, causing the pumps to shut down, pressure relief valves to open, and directional valves to close. The bridge must stop at 6 degrees above the lowered position—the point of highest static pressure load—without exceeding a maximum acceleration of 0.01 rad/s² or a maximum pressure of 340 bar in its cylinder chamber. By increasing the closing time of the directional valve, more flow can enter the cylinder during deceleration, reducing system stiffness and keeping the maximum pressure below 340 bar.
Cylinder force plotted against stroke length during emergency stop
Using SimulationX, the bridge design was refined to meet deceleration and maximum pressure requirements by effectively modeling the dynamic behavior of the mechanical-hydraulic integrated system.
References
[1] Grätz, U., Dynamic Analysis of a Hydraulic Drive for a Lifting Bridge, ITI GmbH Dresden (2015).
If interested in additional information, please contact us for the full proceedings of the 2015 SimulationX User Forum.
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