The Energy from Waste facility (EfW) at Javelin Park near Gloucester is designed to treat 190,000 tonnes of combined industrial & municipal waste pa., generating enough clean electricity to power 25,000 homes. The 14.5MW facility aims to reduce the county’s dependence on landfillling by 70 per cent and to reduce carbon emissions by 40,000 tonnes a year.
Urbaser Balfour Beatty (UBB) is under contract with Gloucestershire County Council, the Waste Disposal Authority, to construct and operate the facility. The project has been operational since autumn 2019. Ramboll was employed by UBB to provide civil and structural engineering, building services and other specialism inputs.
The building’s distinctive shapes relate to the changes in function of each part of the building from the low-level bottom ash building, through to the tipping hall, the waste bunker, the boiler hall and the tall flue gas treatment area adjacent to the stack.
Ramboll's multi-disciplinary team worked effectively to deliver a fully coordinated design with the Tier 2 contractors (Babcock & Wilcox Volund and LAB) and Architect (Fletcher Rae). This process was facilitated using a detailed 3D federated model.
Ramboll developed innovative solutions to assist the client with increasing the structural efficiency and speed of construction, including elements of pre-cast offsite construction. This resulted in large programme saving and a dramatic reduction in temporary works.
Waste Bunker Stability and Fatigue Design
The sub-structure was designed for a large hydrostatic head equivalent to 14m of water. Ramboll engineers developed a structural design that catered for the permanent and temporary load conditions associated with deep basement design. A tension pile base slab and contiguous piled walls were implemented, restrained at the head by a ring capping beam. To the tipping hall side, the capping beam required additional lateral support to span the 45m length. Ramboll designed an efficient system of steel tie rods, tying the capping beam at regular centres back to a system of dedicated laterally loaded piles.
In addition, vertical and lateral loads from the steel framed weather envelope and waste bunker crane support structures had to be effectively transferred into the bunker ‘box’ structure. Any steel elements and steel to concrete connections subject to loading from the crane had to be designed for fatigue to account for the millions of predicted load cycles.
Turbine Hall – Pre-Cast Conversion
The Turbine Hall is a large box structure of approximate 23m x 23m x 16.5m height, housing the steam turbine and a service crane. The roof of the box supports several very heavy plant items with stringent settlement requirements. With no internal floor plates, tall slender columns and 2m deep long span downstand beams to the roof, the client had always highlighted the construction as a critical path item. Using their extensive expertise in offsite construction techniques and working collaboratively with the client and their sub-contractors, Ramboll converted the original cast in-situ design to pre-cast internal columns, beams and roof slabs. The perimeter walls and columns were also designed and detailed to allow for slip formed construction. The result was a large programme saving and dramatic reduction in temporary works requirements.
Flue Gas Treatment (FGT) – 48m tall sway frame
Due to the specific requirements of the FGT, limited floor plates were present to the lower levels only and no internal full height columns were possible due to the service crane tracking the length of the building. Therefore, Ramboll was challenged to produce a design which would meet the ‘open plan’ requirement but also achieve the necessary stiffness to maintain the stringent crane rail tolerances during operation. The solution comprised a sway frame formed from truss columns and roof trusses. The columns were rigidly connected to the pile caps and roof trusses to create stiff moment frames. Detailed analysis was undertaken to provide an efficient design which would allow significant lateral deflection of the structure under wind loading whilst ensuring that the crane rails would not separate by more than the specified limits under all load cases.
Winner of Industrial or Process Structures Award, Structural Engineering Awards 2019 (Midlands Counties Regional Group)