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Yeongdodaegyo Bascule Bridge

Eadon Consulting’s extensive experience of moving bridges was called upon to carry out a Category 3 check of the mechanism for the Yeongdodaegyo Bascule Bridge in South Korea. The bridge has a nose span of 31m and is 24m wide carrying 6 lanes of traffic. The bridge is raised and lowered through an angle 75° using a rack and pinion drive system mounted about the horizontal pivot of the bridge. The total mass of the bridge is approximately 1600 tonnes, 1100 tonnes of which is a mixture of steel and concrete counterweight.

Key facts

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Location

Busan, Korea

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Client

Cowi A/S, Denmark

Eadon’s involvement was to check the design of the electric drive system and emergency braking systems. The drive consisted of two 160kW motors working synchronously to power a primary gearbox. Two output shafts from the primary gearboxes provide the inputs for the secondary gearboxes which in turn drive the pinion gears. Curved racks fixed about the pivot point of the bridge allow the bridge to articulate when torque is applied through the pinion gears. Braking systems are fitted to both the primary and secondary gearboxes and allow the bridge to be held safely in an emergency. The drive motors are powered by variable speed controllers to enable smooth bridge operation and braking.

Many different load cases were analysed for the bridge and, unusually for a bascule bridge of this type, it was found that the load case with full wind on the bridge can result in a requirement to power the bridge down from fully raised.