Raising the roof
One of the major challenges was the construction of the 2,400 tonne compression truss which runs 860m around the perimeter of the venue.
The 28 sections that make up the compression truss were precision fabricated by Watson Steel Structures to achieve the close tolerances required. Made from recycled steel pipe, the tubes that form the truss sections are up to 1m in diameter. Delivered to site in component form, the 100 tonne truss sections were assembled on jigs on the field of play. These were designed so that the 30m long sections could be constructed in exactly the right geometry before being lifted into place and bolted together.
When the final piece of the compression truss was lifted into position in July 2009, the structure fitted together perfectly without the need for a single pack. Its installation marked the completion of the external structure of the stadium just 14 months after the start of construction.
Once the stadium’s ‘ring of steel’ was complete, the inner tension ring was laid out on a temporary scaffold built around the terracing, before being jacked into position 40m above the field of play.
Gantries were then installed from the compression truss to an inner walkway lifted with the tension ring, and the ceremonies tripods fixed in place around the outer rim of the truss.
Finally, the stadium’s 14 sports lighting towers weighing 35 tonnes each were lifted onto the inner tension ring and secured in position before abseilers set to work installing the fabric roof covering.
Mark Leeming, Project Director, Sir Robert McAlpine, was part of the original project team. He spoke to BBC Radio London last week to share his highlights when he was Construction Manager on the Olympic Stadium:
Working within this project team was a once in a lifetime opportunity, with chances to confront not just engineering but logistical challenges on a scale that I had never encountered before.
You can listen to his interview in full via BBC Sounds here >> (From 2h39mn until 2h51mn)
To read more about the stadium’s construction and the challenges overcome by the team, take a look at our Olympic Stadium case study here >>
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