A multi-million pound conversion of the Olympic Stadium was kick-started this week with football club West Ham United finally confirmed as anchor tenant.
Client London Legacy Development Corporation (LLDC) director of infrastructure Colin Naish told NCE the stadium would now undergo a “complex” refit to transform it into a multi-use stadium.
“We are working up our transformation design for the stadium to suit a multi-use arena,” said Naish. This will include football as well as other events such as concerts. “But it will keep athletics at its heart,” he added.
“We are working up our transformation design for the stadium to suit a multi-use arena ”
Colin Naish, LLDC
Work on the retrofit includes extending the roof inwards to cover all the seats, installing retractable seats and redesigning the iconic floodlights.
Installing West Ham as main tenant comes after three years of legal wrangling with the cost of transformation estimated to be as much as £190M.
Funding for the conversion will come from a combination of sources including £40M from Newham Council, £15M from West Ham and £25M from government.
Construction of the original Olympic Games stadium cost £486M.
The original stadium design team - consultant Buro Happold and architect Populous, as part of Team Stadium - will be responsible for the retrofit design along with Mace as programme manager.
Two of the biggest components of the retrofit will be designing the new roof and installing new retractable seating.
The existing roof consists of a PVC coated fabric membrane supported on a cable net with an inner tension cable ring and an outer steel compression truss. The outer ring truss is around 900m long and 12m deep and is supported at 32 positions by inclined raking tubular columns down to ground level.
The inner cable tension ring consists of 10, 60mm diameter cables connected by steel brackets at 6m centres and is supported by 80mm diameter suspension cables connected to the top boom of the compression truss. The system is tensioned by 70mm tie down cables connected to the bottom boom of the compression truss.
“We will take down the existing roof, fabric and cable net and dismantle [the roof],” said Naish.
He said the original roof fabric will be recycled and the cable net structure can be reused elsewhere.
The new roof will involve a similar tension ring design but it will cover a larger area of the stadium plan. It will comprise steel trusses supporting a “hardened roof “, although the actual material has yet to be decided, according to Naish.
The iconic floodlight structure will not be reused. Engineers have instead opted to develop a similar design that will be inverted beneath the roof structure using the same lighting.
Under the new design the upper seating tier will remain largely the same but the lower tier will be remodelled.
Retractable seats will be nstalled to sit over the running track during football games.
The seats will slide out of the longer sides of the stadium and will be pushed into position at the ends.
Naish said the distance between the spectators and the pitch had not yet been confirmed.
Work to convert the stadium is split into three contracts. Five contractors are bidding for the main contract - original Team Stadium contractor Sir Robert McAlpine will bid against Balfour Beatty, ISG, Buckingham Group and Shepherd Construction.
The contract is estimated to be worth £135M, according to construction industry analyst Glenigan.
Naish said he hopes to have the main contractor in place by the end of the year.
The contract to convert the roof was released last week - Glenigan estimates this to be worth £40M. An M&E contract will be advertised shortly.
These two contracts will then be novated to the main contract when a winner is appointed.
Original plans involved converting the 80,000-seat stadium to a 25,000-seat athletics track after the Olympic Games, but this was changed in 2010 to attract a new owner that would keep the larger capacity.
The stadium will now be reduced to 54,000 capacity. LLDC and Newham Council will operate the venue and will financially benefit from events held there. West Ham has signed a 99 year lease with matches starting after summer 2016.