Case Study

Park Live - presented by British Airways

INTRODUCTION Amongst many ‘firsts’ claimed at London 2012 was the first ever provision of a “Live Site” (the Olympic equivalent of a football Fan Park) within an Olympic Park. Also a first that this was a joint venture between an Organising Committee (LOCOG) and a commercial partner (British Airways) with input from the BBC. The complex contractual relationships coupled with widely differing aspirations, critical responses from planners to initial designs and a severe budget over-run almost led to the project being abandoned (at Stage H). LOCOG then agreed to let BA’s brand activation contractor (M-is plc) take over management of the project. At a ‘crisis’ meeting on 13th February 2012 Star Events Group Ltd (SEGL) was asked by M-is plc whether a solution could be found. The outline requirement was to create a temporary structure in the River Lea that would support two giant TV screens, plus a stage for the interviewing of medal winners and crowd entertainment, with integral TV studio and associated support facilities Given that the date of the Opening Ceremony was absolutely set in stone, SEGL was faced with taking the project from Stage A (Appraisal) to Stage J (Mobilisation) in just 13 weeks, followed by only 6 weeks for Stage K (Construction to Practical Completion).

PROJECT RESTRICTIONS • No access for vehicles or plant within 175m of the

structure.

• No piles, other ground penetrating foundations or anchor systems permitted due to anticipated presence of UXO (Unexploded Ordnance) within the river bed.

• Onerous Environment Agency restrictions on column sizes and bracing members within the water body.

• Structure to be raised above the 1 in 100 year flood level, approximately 3m above normal water level.

• Absolute structure width limitation of 12.5m, due to the requirement to keep navigation open for security boats and pyrotechnic firing barges.

• Newly planted bio-diverse wetland bowl surrounding the structure that could not be touched, at all.

• Every part of the installation had to be removed from site within 4 weeks of the Paralympic closing ceremony.

Case Study

CREATIVITY AND INNOVATION SEGL determined that the only viable scenario in the short time scale was to take 100% responsibility for all aspects of the engineering design and build. Given the specialised nature of Temporary Demountable Structure engineering, SEGL has an internal six person engineering team that also offers consultancy and structural design to the entertainment industry. The design & build process is summarised below to explain how the project was ‘salvaged’ through the application of creative engineering techniques, being delivered exactly on schedule and within the original allocated budget. The short time scales meant that the engineering and logistics were inextricably linked. This case study focusses on the engineering but explains some of the logistical issues where those impacted significantly on engineering decisions or solutions. Due to the inability to access the location by land we looked at what could be done with floating plant. Our first thought was a large crane on a pontoon. However it quickly became apparent that due to the very low headroom of bridges on the river and the existence of the in-water security systems this was not feasible. The only viable alternative was that the structure would have to be built on a pontoon adjacent to the downstream bridge and floated into place. It would also have to be capable of being jacked up above the 1 in 100 year floor level (replicating to some extent the earlier abandoned designs based on marine jack-leg barges).

Outside of marine engineering, large scale concert stage roofs are also based on self-climbing systems, where a load-bearing horizontal frame climbs a series of vertical masts or legs. We therefore started with stage roof technology, to create a self-climbing floor, the legs of which would be supported from the river bed. Another similar system was then imposed on top, with its masts supported on the floor frame. The obvious result was that all the loads from the upper frame would have to be resolved through the lower frame and in turn, the legs going to the river bed. Faced with the constraints of the structural width limitations, water depth variation, crane capacity limitations, foundation type and lack of access for powered construction equipment, it became necessary to construct a three dimensional model of the structure and the terrain in Autodesk Inventor. This model enabled us to simulate the construction process and design out any foreseeable problems. The structure was then analysed and designed using Autodesk’s Robot structural analysis program. Once the design was verified, the final construction drawings were generated using the 3D model in Inventor. Due to the inability to create any form of anchorages or conventional foundations we had to strike a very fine balance between adding self-weight to resist over-turning whilst reducing self-weight to prevent settlement. In this we were completely successful, with a stable structure that did not suffer settlement, despite high winds and serious flood conditions before the Games.

M-is plc produced this CGI after a rapid joint design exercise between M-is, Richard Partington Architects and

Star Events Group.

It subsequently received Planning Consent on 27th March 2012.

Construction commenced

17th May 2012.

Case Study

The bridge immediately down-stream of the site was both temporary and uprated to deal with earthmoving vehicles of a particular specification. For reasons we still don’t know we were not able to get any engineering information from the bridge manufacturer or installer. Therefore we analysed the loads that the earth-movers had been imposing and designed steel spreaders that would enable us to position a 70t crane in the middle of the bridge without exceeding those loads. This was to be our only equipment access to the water. The spreader design was a particular challenge as they had to support 2 of the crane outriggers (point load around 300kN each) whilst sharing loads to 2 main bridge spans, which were at 4.5m centres. However, the clearance under the crane outriggers during deployment was only 300mm. Eventually we were able to find a combination of positions and beams that enabled us to deal with point loads of 250kN per outrigger. This limited the size of crane that we could lift onto a pontoon to a 10t machine, which meant that the whole design was driven by the capacity of that crane when floating, typically only 1.4t at 10m radius.

Every one of over 300 lifts from the bridge was individually calculated and adjusted for radius when necessary to keep the outrigger loads under 250kN, which were electronically monitored by the lift supervisor. A spreadsheet calculator was created to assess the trim and buoyancy of the crane pontoon under the many different load combinations.

70t crane on spreaders lowering 10t crane onto pontoon

BASE-PLATES

Installing late arriving base-plates using site made counter-balanced C-frame, following FEA design

We were able to source existing river bed survey data from Hyder Consulting. Their engineers advised that we should limit the foundation bearing pressure to 70kN/m2 subject to a potential allowable settlement of 50mm. The very late arrival of this information meant we had less than 24 hours to go to manufacture so we used Finite Element Analysis to verify the design even as the manufacturing drawings were being created. Even so we had to fit some of the base plates out of sequence due to delivery delays. This required some ingenuity, with a counterbalanced C frame rapidly designed by our site engineer which allowed the 750kg plates to be slid under the bottom of the raised legs prior to being bolted into place. The bearing capacity limitations contributed to the final number and spacing of the legs that were fitted to support the structure off the river bed.

CREATIVITY AND INNOVATION - EQUIPMENT HANDLING

Case Study The need to install rubber rollers between the horizontal frames and the vertical legs and masts limited the efficiency of the moment connections. The effect of this limitation on the rigidity of the frame was modelled by applying the correct releases to the connections in the analysis software (Robot). The reduction in the rigidity of the moment connection meant additional sway stability had to be provided using steel tension bracing. The stability of the structure during the construction phase also had to be considered and designed for. Due to the bespoke nature of the structure and the unconventional terrain and environmental loads it was subject to, the verticality of the structure had to be monitored regularly using a structural monitoring scheme which was designed in-house to ensure that verticality was maintained at all times. Two key design requirements were to support the scenic cladding and the huge TV screens. At 132m2 each they were amongst the largest temporary screens ever seen in the UK. Whilst rated for vertical (suspended) loading, the Japanese manufacturers were not able to provide any data for resistance to horizontal wind action, other than advising that any deflection across the face of the screens must be limited to 20mm (1 in 775). We therefore had to retrospectively add a total of 14 vertical truss members behind the screens (7 each) to take the horizontal design loads.

The scenic items derived all their strength and wind resistance from structural truss frames designed by SEGL and free issued to the scenic contractor.

Side elevation, showing screen modules and supports

End elevation, showing tension bracing

Overall structural analysis model and with loadings applied

Double legs were required either side of each roof mast to keep the combined loads from the roof and deck within the river-bed bearing pressure limits.

CREATIVITY AND INNOVATION - DESIGN

Case Study The installation of the final base plates signalled the move to the final position. Our concerns were focussed heavily on the water flow that varied between 1 and 30 m3/s (equating to a velocity varying between 0.2 and 4 m/s) that was acting to push our 154 tons of floating structure back into the bridge. We used a spreadsheet to quickly calculate the water forces on the pontoon which took into account the varying draught as the structure was assembled and the variable water velocity which was measured locally. The same spreadsheet was used to assess buoyancy and stability. By fitting the crane pontoon with both ‘spud’ legs and large wire rope winches we were able to winch the floating structure into position in a series of short pulls. Some of the structure legs were lowered to act as anchors between winch pulls. We positioned one end in the required position and dropped a leg at that corner. We were then able to pivot the whole structure about that point until the other end was at the precise distance from the bank to enable the planned access bridge to fit. Due to the protected status of the new reed beds, the nearest point of the structure was 25.2m from the land and that set the length of the required access footbridge. The roof frame was then raised slightly off the main deck legs (using chain climbing hoists) and then the remainder of the 26 legs were lowered to the river bed. Legs were then fitted with chain climbing hoists and electronic load-cells that were linked back to a single computer. All 26 chain hoists (each with a lift capacity of 6.4 tons) were individually controlled from a single equipment rack connected to the computer. After taking a little load to each hoist they were all operated together to lift the entire structure clear of the pontoon. The structure was left slightly above the pontoon for 48 hours to check for any settlement. The use of the load-cells allowed us to monitor in real-time the actual loads being applied to the river bed at each base plate and were left operational throughout the lifetime of the project. It was gratifying to see the close correlation between our calculated figures and the measured reality. The whole platform was then lifted to its final height, just above the 1 in 100 year floor level, some 3.0m above the normal river level.

Roof frame assembled onto deck legs

Start of main move along river

Floor jacked off pontoon, roof up and first section of

footbridge being installed

CREATIVITY AND INNOVATION - INSTALLATION

Case Study Once the main frame was complete we were able to undertake a number of operations simultaneously: Footbridge Prior to our involvement, Buro Happold had designed a very elegant footbridge. Unfortunately no one could think of a method to position it due to its weight. Analysis of the best position we could achieve with the small floating crane showed that the maximum weight that could be lifted was 1.1t. Consequently we designed a bridge that was constructed of assemblies that each weighed less than 1.05t. The end result was engineered to a design load of 3.5kN/m2 as it was only for staff use. Legs Each leg was made up of several short lengths bolted together. There was sufficient redundancy in the design that we could remove the load from one leg at a time, remove relevant lengths to get the top below floor level and re-apply loads. This meant the use of leg sections in increments of 375mm, with section lengths of 375mm, 750mm, 1500mm and 4500mm being deployed, based on our surveys of the river bed profile.

Roof support In almost all cases with temporary event structures, the masts that support roof systems are taken directly to ground. However, we were not able to vary the height of the masts once in situ to compensate for variations in river bed profile due to lack of all-round crane access. Architecturally we needed the tops under the roof line and so designed a fixed height foundation system within the main floor deck to support the roof masts. Scenic cladding panels The design and installation of the (third party built) cladding panels was very challenging. Due to time, budget and access constraints, the panels were made in the largest sections that could be transported by road. Consequently they were too large and heavy to be handled solely by our floating crane. We conceived a system of suspending them between temporary winches in the roof of the structure and the crane. The eccentric CoG required horizontal movement at the bottom to be controlled, which we achieved by deploying the crane pontoon winches. In a week of bad weather with high winds this was a very fraught exercise.

Half-way through the lift of the first of 5 main rear panels

The application of all the other cladding was equally challenging without the possibility to use any MEWPs or similar access devices. Consequently every cladding element with the exception of the five rear panels had to be designed and engineered to be installed manually by SEGL crews deploying rope access techniques.

Case Study

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EXCELLENCE All of our design and engineering was signed off by the Olympic Engineering Design Services provider (Atkins) without any changes required. Park Live was the second most visited venue on the Olympic Park (after the main stadium). Extract of email received on day of Closing Ceremony, Paralympic Games from Bill Morris Director of Ceremonies, Education and Live sites LOCOG Please excuse my hasty and short note...we’re in the middle of the final rehearsal for tonight’s Closing Ceremony, but I had to say… We all know that the best things in life are not easy, and this project was tough to get off the ground (or, on to the water...) but was it worth it! You created the ultimate Park destination – THE place to spend time, to soak up the atmosphere and to show your support for the athletic achievements and the spirit of the games. My huge congratulations and thanks to you all. All the best, Bill

SUSTAINABILITY Most of the structure was built from stock items, all designed in-house.

• Over 90% came from and was returned to rental stock.

• A further 6% of ‘specials’ were redeployed to events in 2013.

• The remainder was stripped for recycling. • Zero to landfill. • No flora or fauna were damaged. • The site was cleared by end September 2012,

having floated the structure back to the bridge for disassembly.

VALUE The structure was designed, delivered and removed on schedule for a total sum under £1.75m. That was less than 50% of any other proposed solution, viable or otherwise. Over three-quarters of a million people were entertained at Park Live and LOCOG research showed that 74% of all Park Ticket holders rated Park Live as “Extremely Good”.