Strengthening of the existing structure was one of the major challenges. Due to the additional weight of the new roof, it was necessary to replace and/or strengthen the existing V-columns and significant strengthening works were carried out to the existing compression truss. For the compression truss strengthening work alone the amount of hierarchical complex calculations involved the steelwork contractor developing his own in-house software to process over 10,000 calculations - a task that would have been impossible using traditional methods. The ambitious new cantilevered roof now stands as the world’s largest with every seat in the stadium now covered by the new roof. The 14 new lighting paddles are positioned beneath the new roof. Each lighting paddle houses up to 41 lamps, many of which are the original lamps that shone over the stadium during the London 2012 games. Four 600 tonne capacity cranes operated in tandem to lift the lighting paddles and the other roof members into position. The tolerance in the fabrication and quality of finish was expected to be very high and the design was made with security in mind. Most of the geometry was complex and specialised jigs were manufactured to fabricate some of the complex tubular nodes. A total station was employed to set out all of the brackets for the lighting paddles which all lean towards the pitch and are all slanted in three opposing planes. Not least, the oval shape of the stadium and the movement and tolerance requirements only gave the opportunity for single pieces to be replicated twice, which meant that half of the stadium structure was fabricated with unique members. Following the V-column and compression truss strengthening work, to maintain equilibrium until the oval was fully formed the erectors worked in two teams at opposite ends of the stadium working in a clockwise rotation constructing the back roof first, then the front roof complete with the lighting paddles and walkways. To ensure the correct distribution of forces through the cable support structure to the compression truss, the front and back roof are completely independent of each other. However, for the installation of the lighting paddles, the front roof had to be temporarily tied to the back roof to ensure that the lighting paddles did not overturn until the full ring stiffness of a complete oval was achieved. 4D programming using BIM modelling was the key to delivering this successful project to a very high profile deadline, which was originally the 2015 Rugby World Cup taking place in September 2015. However, this was brought forward even more to fit in the Sainsbury’s Anniversary Games which took place in July 2015. This meant that all major construction had to be complete by May 2015. The new structure now has a lifespan of over 60 years and is set to become the new national competition centre for UK Athletics, and in 2017 will host the IAAF World Athletics Championships and IPC World Championships. The stadium has already hosted five games of the 2015 Rugby World Cup and motor racing’s 2015 Race of Champions. The stadium has also been upgraded to a 54,000 all-seater UEFA category 4 football stadium, which is the highest category of football stadium possible in the world. JUDGES’ COMMENT The need to modify the roof and seating of the 2012 Olympic athletics stadium to accommodate a multi-purpose sports venue posed formidable challenges. The geometry and behaviour of the original structure were very complex but, with extremely detailed study and fine engineering skill, most of the original elements have been re-incorporated. The challenges have been met superbly and the project is a triumph for the team and for structural steelwork.
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