Superspan Bridge - Jimboomba Creek, Queensland

Along the Mt Lindesay Highway, 50km south east of Brisbane, a superspan bridge was built to cross the Jimboomba Creek. Replacement of the old, narrow two lane timber truss bridge was required to alleviate dangerous traffic problems. The new structure is an upgrade to a four lane dual carriageway crossing.

Superspan Bridges

Queensland Department of Transport and Ingal Civil Products came up with the solution of twin Superspan ellipses, each spanning 7.87 metres, to accommodate the peak flows for the 1 in 100 year storm.

Compacted select backfill is then placed around the steel to form a low cost composite steel/soil structure that is able to withstand considerable dead & live loads. Further advantages of Superspan structures include low weight which minimise foundation loads and also their ability to tolerate substantial differential settlement while in service.

Jimboomba Creek

On completion of excavation for the first half of the new bridge, two of the 30 metre long ellipses were constructed alongside their final resting position. This was done to reduce time spent with materials in the creek bed, which is prone to frequent flooding. Once constructed, they were lifted into position using two 90t cranes. The ellipses were built by pre-bolting of sub-assemblies or incrementally, plate-by-plate, in their final position which minimised the crane size required. Steel tie rods inside the tubes ensure that correct geometry is maintained during installation.

Diversion of the existing roadway over the new bridge was achieved on completion of the first half of the twin superspans. Removal of the timber bridge then took place, allowing the second half of the bridge to be built.

Construction Aspects

The bridge achieves protection from the possibly abrasive effects of stream flow sediment, by placement of a concrete slab once embankment construction is finished.

Although the site crew from DOT - Beaudesert Works Office had no prior erection experience on a similar structure, assisted by Ingal Civil Products, they were able to complete the project under time and budget.