British Airways i360
The world’s tallest moving observation tower, the spectacular, recently completed British Airways i360 features a gleaming 162-metre-tall vertical tower which pierces the skyline on Brighton seafront.
The tower, which opened in August 2016, includes a fully enclosed glass observation pod, which gently lifts groups of up to 200 passengers to a height of 138 metres, offering 360-degree views of up to 26-miles over Brighton and Hove, the South Downs, the South Coast and the English Channel.
The attraction also incorporates a restaurant, tea rooms, hospitality rooms and shop at its base.
The design and engineering of British Airways i360 is as impressive as it is innovative. The tower is acknowledged by Guinness World Records as the world’s most slender tower, with a height-to-width ratio of more than 40:1. State-of-the-art cable car technology is used to drive the pod up and down and energy is generated on its descent.
Eleven years in the making from design to reality, British Airways i360 is the brainchild of architect-entrepreneurs David Marks and Julia Barfield of Marks Barfield Architects, best known as the practice that conceived and designed the world famous London Eye.
Main contractors for the project were steel manufacturer Hollandia, who manufactured the steel tower.
The aim of the project was to give people a new experience of Brighton and Hove, promote regeneration of the seafront, and to provide an attraction which reflects the public appeal and spirit of the original West Pier in the twenty-first century.
British Airways i360 was designed to operate even in windy conditions and has a series of state-of-the-art measures installed which ensure that the ride is always smooth and safe.
Firstly, the perforated aluminium cladding around the tower diffuses and disrupts the flow of wind by allowing some wind to pass through it, thereby reducing wind-induced vibrations.
Secondly, dampers are installed inside the tower to prevent vibrations and, thirdly, dampers are also inside the pod, which is itself aerodynamically shaped for least resistance to the wind.
Construction commenced with driving over 2,000 interlocking concrete piles between 10 and 20m deep into the underlying chalk bedrock to provide a temporary support for the edges of the deep excavation for the foundation.
The foundations and substructure of the building and tower comprised the bored concrete piles forming a contiguous piled wall plugged with a mass concrete raft. Having established the final layout in early 2015, the next milestone was to excavate the foundations.
Long reach excavator specialists, WM Plant Hire, visited the project to identify a suitable machine and ensure the production output could be achieved. The 60 tonne long reach excavator played a crucial part on the excavation, reaching almost 10 metres deep into the chalk, below the tidal water level.
Huge amounts of shingle had to be shifted from the base of the new tower and their CAT 349 long reach excavator with 20m reach was able to move over 300 tonnes per hour – this high production rate coupled with their experienced operator proved a real asset to the project.
WM Plant Hire Director, Damian McGettrick, said:
“The tower construction was truly a world beating and remarkable achievement. The foundation excavation using the large long reach excavator was a key milestone in the project and the successful completion was a credit to the team.”
The tower consists of 17 steel cans each of 3.9 metres in diameter that are stacked and bolted together.
An innovative construction method meant the tower was essentially built from the top down.
Starting with the 17th, or top can, a jacking tower was used to lift the completed section of the tower upwards, enabling new cans to be inserted below with the assistance of a specially designed skidding track. The final lift weighed 900 tonnes.
The construction of the tower on the 4,150 tonne reinforced mass concrete base started on
15th June 2015.
Using a 200 tonne crawler crane, with a lifting capacity of 600 tonnes and featuring a 96-metre-high latticed boom, the 60-metre-high temporary jacking tower and seven cans (comprising cans 1, 2, 3, 14, 15, 16, and 17), were stacked and bolted one on top of each other up to a height just exceeding that of the jacking tower.
A 16 tonne steel collar within the jacking frame was used to lift the upper section of the tower. The steel collar was lowered within the jacking tower to ‘grip’ the top four cans of the tower.
Four strand jacks attached to the collar, each with a capacity of 450 tonnes, gradually jacked up the top four cans within the jacking tower high enough so that the next can could slide underneath on a skidding track, before the tower was lowered and bolted down to the new can. This procedure was carried out 10 times, until the tower reached its planned height of 162 metres.
The viewing pod is 18 metres in diameter and weighs 94 tonnes, including its chassis (which itself weighs 20 tonnes).
The double-glazing of the pod ensures that the views are magnificent and, because the pod ascends on the outside of the tower, the views are totally unobstructed. The underside of the pod is clad in double-curved mirrored glass.
The design of the pod is based on an oblate ellipsoid with a cylindrical core removed to allow the tower to pass through. The floor sectors of the pod are supported on 48 trusses which are bolted together and cantilevered off the chassis to support the floor.
The pod’s 24 glazed superstructure sectors consist of double-curved, double-glazed laminated glass assemblies mounted onto a light-weight painted mild steel frame.
The final task was to connect the pod to the counterweight inside the tower using eight high-strength flexible steel ropes, and to connect the counterweight to the drive system winch situated in the basement.
Such was the success of the British Airways i360 project, the structure has been nominated for two awards at this year’s RICS Awards, in the categories: ‘Tourism and Leisure’ and ‘Design through Innovation’.
Metal Roof Ltd
Metal Roof Ltd specialises in traditional hard metal roofing and cladding and has been trading since 2007. The company works on a range of projects in the South East, from town centre housing developments and office buildings to private houses in the countryside.
To date, Metal Roof Ltd has been involved on two projects featured on Channel 4’s Grand Designs – a house in Hurstpierpoint and a house in Brighton. Most recently, Metal Roof Ltd worked on the i360 project where they worked on the two tollbooths which stand either side of the tower.
The tollbooths replicate the original Victorian kiosks which stood on the site as part of Brighton’s West Pier. Working from contemporary photographs, Metal Roof Ltd has reproduced the curved, batten roll zinc roofs, which were first constructed 150 years ago!
Andy Grant, Metal Roof Ltd, said:
“We were pleased to get the opportunity to work on such a high-profile project which has allowed us to show off to huge numbers of people the care and attention to detail which we always pride ourselves on.”