Western Australian Software Helps Launch Narrows Bridge

Innovative construction method uses Formation analysis software

Fremantle, WA, Australia - March 17, 2000; While the traditional cranes, concrete and barges dominate the construction site for the new Perth Narrows bridge, behind the scenes some innovative software technology from local company Formation Design Systems is helping make the process possible.

The new bridge is a replica in appearance to the original bridge however the design and construction techniques are radically different. Built using an innovative technique known as "incremental launching", the bridge is being built in 28 metre sections on the south bank of the river with each section being jacked or "launched" out into position over the river. This provides greater efficiencies in construction as well as keeping the waterway clear from large temporary support structures. Once launching is complete, the sections are connected together, temporary supports are removed, and the completed roadway remains on top of the permanent piers.

Launching the complete bridge out over the river results in some very high loads on the support structures, and this is where the Multiframe analysis software from Perth company, Formation Design Systems, plays its part. The main contractor, Leighton Contractors Pty Ltd, engaged temporary works consultants, Hawkins Engineering & Construction Pty Ltd (HEC), to design the falsework/formwork systems for the bridge construction and the trolley launch system. Peter Hawkins of HEC uses Formation's Multiframe software to design these temporary works.

The trolley launch system involves the design of varying height, heavily loaded trolleys, supporting loads up to 400 tonnes. The Multiframe software was used to simulate the bridge structure loading on the launch trolleys at the various stages of the launch. The software allowed the assessment of load conditions arising from settlement of the casting bed and lifting of the bridge during the launch.

Peter Hawkins is a consultant specialising in construction methods using the principles of "Value Engineering". Over the past 4 years, HEC have used Multiframe on a wide range of construction projects including investigations into launching techniques for incrementally launched bridges and complex temporary works for large scale offshore structures. HEC projects have taken him throughout the South East Asian region including Laos, Vietnam, Malaysia and Thailand as well as projects around Australia. His laptop and Multiframe travel with him at all times and form a core part of his mobile office. Email transfer of Multiframe and other files to the various design and construction offices in the project, ensures he can quickly react to the short deadlines typical of the construction industry.

The Multiframe suite of design and analysis tools allow him to sketch the shape on the structure on-screen, apply projected loadings, and then run a series of analyses to predict how the structure is going to respond. The system then visually displays how the structure is going to deflect under load and overlays colour shading to show regions of high stress or deformation. The software can even create an animated movie on-screen of how the structure is going to respond as loading is applied. Hawkins comments, "Multiframe is an ideal tool to do quick investigations into different alternatives for bracing and support on the structure. Its graphical display options really make is easy for me to visualize what's happening with the structure and which areas are most important".

Other projects in which HEC, in association with Taylor & Herbert Consultants, has used Multiframe, has been on the Wandoo Concrete Gravity Structure in Western Australia. The temporary works designs for this offshore structure included the design of 50m tall structural steel access towers around the main legs of the platform. In this project, Multiframe was used for the analysis of the slipform formwork (referred to as the "spiders") which circle the towers during construction.

Formation Design Systems develops computer aided design software systems for engineers, naval architects, shipbuilders, and designers. It has over 2000 customers in over 20 countries and supplies software to designers, consultants, builders, educational institutions and defense organizations. Formation customers include the largest construction companies and shipbuilders in Japan, universities such as Stanford, Harvard and MIT, the US and Australian Navies.