Location: Hong Kong
Client: Dragages – China Harbour JV
Rising up to 60 metres high, the new $1.012 billion construction of the East Tsing Yi Viaduct in Hong Kong is the latest landmark to appear on the city’s horizon. Forming part of the new Route 8 project, linking Sha Tin in the Eastern New Territories to Tsing Ma Bridge and on to Lantau, the viaduct links the adjacent Stonecutters Bridge to Nam Wan Tunnel and West Tsing Yi Viaduct.
Constructed for the Hong Kong Highways Department the joint venture between Dragages Hong Kong and China Harbour Engineering Corporation uses formwork supplied by RMD Kwikform Hong Kong. Scheduled for completion in early 2008 site work on the 1.25km dual three lane main Viaduct and 5km single lane of associated ramps, began in December 2004.
With approximately 100 columns varying in size from 4.8m x 3.0m to 5.6m x 5.0m with heights reaching up to 60m, (total almost 4,000m heights), the structures complex design and method of construction required high levels of planning and technical expertise in order to meet the tight programme times and guarantee worker safety.
Commenting on the viaduct construction, Noel Kennedy, Sales Manager for RMD Kwikform said: “ The substantial scale of this project required a unique solution in order to construct the individual columns, particularly when they reached up to 60 metres in height. When constructing any structure at height, the impact of external factors like environmental elements pay an increasing part in the overall design of formwork and falsework, particularly when assessing the health and safety issues surrounding the construction. It is for these reasons that we designed and manufactured specialist steel formwork especially for the project.”
The East Tsing Yi Viaduct column formwork was designed to pour up to 6m in height using the skip and crane method of construction to lift and pour concrete into the formwork. Each column was formed using cranes to raise the formwork after each section, up to 9 in total, was poured and striked. In order to inspect the column construction and carry out remedial work, trailing platforms were designed to attach to the base of the formwork. To allow workers to safely reach the trailing platforms, Rapidshor stair towers were constructed in-situ as the formwork advanced. A total of nine sets of specialist formwork were fabricated to construct the columns, some of which were adjustable to suit various column sizes, allowing simultaneous construction to take place.
In addition to column formwork, specialist formwork was designed to construct 51 in-situ pier segments, varying in width, depth and length. In total four sets were supplied, three of which were adjustable to suit varying Type B segments and one to suit Type C segments.
As part of the construction of the viaduct, special heavy-duty brackets along with formwork were designed for casting the hammerheads and part of the portal beams. In order for the portal beams to be constructed the first pour above columns was cast, using the heavy-duty brackets, prior to casting the portion between the columns, followed by the casting of the cantilevers. To ensure the formwork is held in place on the column correctly, anchor brackets were used to fix the main truss members, with strand jacks used to hoist and lower the soffit formwork.
With equipment used to withstand loads of up to 2,000kN understanding, designing and manufacturing the formwork required a significant investment in technical expertise. With support from RMD Kwikform engineers at the regional office in Australia, RMD Kwikform Hong Kong spent more than 12 months designing formwork solutions for the project. By being able to incorporate and take advantage of a wide variety of existing equipment like Rapidshor, Megashor, Superslim Soldiers and R700 trusses in the final design, the team were able to reduce the overall cost of the formwork. This in turn led to a reduction in construction time and overall programme management.
Noel: “The overall technical input was particularly important when looking into the construction of the portal beams, as we were able to design and manufacture the specialist formwork to combine with existing R700 truss components, by means of overhead trusses sitting on the cast first pour with hanging soffit formwork for casting the portion between columns plus the cantilever sections. Using R700 tried and tested components also added to the availability, reliability and safety of the overall design.
“When designing the formwork solution we had to take into account the availability and cost of support equipment. With columns, in-situ pier segments, hammerheads and portal beams reaching heights of up to 60 metres, we had to deal with the issue of crane safety, capacity and weight restriction for individual elements. By taking this into consideration at the design stage we were able to design a solution that reduced the weight of individual elements, allowing segments to be lifted into place for simple installation and removal, without the need for added investment into hiring additional larger cranes.”
With Hammerheads up to 9m deep x 17m long x 4.7m wide and portal beams up to 9m deep x 50m long x 4.7m wide, combining flexibility, strength, weight restrictions and construction time within the overall formwork design was paramount. With programme time so important, the availability of other equipment like Rapidshor enabled the technical team to design Rapidshor falsework for the construction of the lower level portal beams.
Noel: “ With specially designed formwork, differing sections and very specific requirements, all constructed at height, as part of our commitment to ensuring construction is kept on schedule we have also provided two dedicated members of staff to support the construction team. Tasked soley with the management of the formwork and falsework the project engineer and site supervisor have already made a valuable contribution to the success of the project.”