Location: Hong Kong
Client: Maeda, Hitachi, Kumagai and Yokogawa
More than 300 tonnes of specially designed RMD Kwikform formwork was used throughout the construction of the Ma Wan Viaduct, Hong Kong, as part of the Lantau fixed crossing, linking the new airport at Chek Lap Kok to the central Kowloon and Hong Kong Island.
The viaduct, built by joint venture comprising Maeda, Hitachi, Kumagai and Yokogawa, carries 3 lanes of traffic in each direction on the deck surface, with a twin rail track and emergency access lanes located with the prestressed box sections of the flyover.
Sitting on the 35m high concrete piers constructed using climbing forms, the box section viaduct is approximately 8m deep to the soffit of the carriageway deck.
RMD Kwikform supplied wall forms to the Joint Venture, dealing mainly with engineers at Maeda, for the outside face of the box section, a Rapidshor travelling table form for the underside of the deck and wheeled travelling wallforms for the internal faces of the box section, as well as a special Megashor and Superslim Soldier tower set up and table form system for the viaduct soffit.
The underside of the concrete box section and the soffits of the deck were cast against an RMD Kwikform table form system supported on hundreds of Megashor and oversized Super Slim towers, bolted and braced together to heights of up to 35m.
Altogether, more than 350 containers were used to ship the formwork sections from Australia and Europe to a specially constructed terminal on Ma Wan Island.
The system was purpose designed for the viaduct by RMD Kwikform engineers in the UK. Towers comprise four Megashor legs in either 3.6 x 3.6m2 sections, or 3.6 x 2.7m2 rectangular sections, placed at 3.6m centres. Bracing of the structure is achieved through 65m x 8m flat bars bolted diagonally between the legs. Where no diagonal bracing was possible on the tower itself, it was fitted between and used to hold the individual towers together.
The four legs of each tower sit on pre cast pile beams an caps provided by the JV contractors. These beams have recesses set in, into which the legs of the towers sit. Once the steel levelling shims had been fitted, high strength cement grout was applied around the base.
The standard Megashor base sections were 5.4m high and when these were in place and levelled, three further 5.4 intermediate sections of the tower were lifted into position on top of the base section, using either a Potain tower crane or a Manitowoc 4100 W crawler unit.
The final sections fitted varied in height depending on the level of the soffit of the box section, in relation to ground level. This height varied from 33-35m, and the top sections of the towers incorporate a 610mm UB header beam to receive the table forms.
The towers were laid out in a grid form pattern, with either four or six towers supporting the deck section spaced in either three-space-three or two-space-two configurations. Cylindrical holding braces spanned the spaces between the towers to provide extra strength and support.
There were two sizes and two shapes of table form used, one with a flat surface and one with splayed top edges forming the outer parts of areas of the soffit.
The table forms were 6m x 6m on plan, with smaller units 6m x 2m being sited under the webs. All forms were sited on eight supports, and faced with garuda ply from Indonesia.
The cantilever forms for the top deck sat on Alform Beams, resting on the UB header beams, and were 2.5 - 2.75m wide. They stayed in position, complete with planking, handrails and kickboards for approximately 3 days. Once the deck had been stressed to the correct levels and the concrete cured, the forms were struck and moved on.
Inside the deck section, RMD Kwikform provided a travelling Rapidshor wall form system, 23m long and 6m high, which was used to form the inner walls and roof sections of the viaduct main section. The wall form completed a full section every seven days. The reinforced concrete wall section averaged 575mm thick, thickening out around 1000mm above piers and stress anchors.
Each box section of the viaduct required about 60m2 of formwork and 60m3 of 50mpa concrete for every linear metre of deck. The weight was approximately 150 tonnes/linear metre.
