The A1 is one of the arterial roads between Scotland and the South of England, which is being up-graded to Motorway status. With a number of other motorways it connects all important adjacent urban and economic areas. In particular, the junctions have reached their maximum capacity due to the constant increase of individual and goods traffic. This is why in the Leeds region, several bypass roads are under construction which are part of the new route planning for the A1M and its access roads. One of these bypasses is the “Holmfield Interchange” with exceptionally designed bridge piers. RMG, the joint venture company building the Interchange, chose the expert knowledge and the creativity of the MEVA engineers to fulfil this job.
At the beginning of 2003, the invitation was issued to tender for the expansion of the A1 between Darrington and Dishforth into a motorway, which would include a junction with various fly-overs on different levels, where the M62 was to join the A1M. This was to be a DBFO-project for which a joint building venture assumes the Design, Building, Financing and Operation of the project. The contract was awarded to the joint venture RMG (AMEC, McAlpine, Dragados, Kellog Brown and Root). They had to build the bridge piers with high architectural requirements made on form and surface.
A total of 22 piers with varying heights between 6 m and 17 m had to be formed while heavy traffic kept running on the M62. The piers have a series of vertical features, which was achieved by screwing shaped timbers onto the forming face, and their Y-shape tapers with a radius of 7 m. Also, the 1.25 m wide walls of the piers are wineglass-shaped, to blend in with local landmarks. The ideal solution would be achieved with a formwork system which is steplessly adjustable in height, is able to take up the corresponding concrete pressure, and also meets the high safety requirements. It also has to guarantee an outstanding concrete finish, especially showing the features and curved areas of the piers. The contractor chose a solution which the MEVA formwork engineers offered: Mammut standard large formwork panels were combined with a few custom-built steel parts with pre-bent alkus facing sheets.
The typical stems of the piers – which for some piers reached up to a height of 11.5 m – were poured in the first concreting cycle. The complete wineglass shaped pier heads were poured in a second cycle. Climbing scaffolds KLK 230 served as support for the formwork and, at the same time, as a safe working platform. Since the pier heads had different gradients the two curved head wall formwork units were set up independently at different heights for every bridge pier.
The formwork for the piers, which are located in the central reservation between the lanes, required a special kind of bracing. A conventional bracing system would have led to narrow lanes during the construction process. MEVA were able to tailor a perfect solution with standard rentable parts. The wind loads were transferred by two Space shoring towers, which were also positioned in the central reservation.
The contractor was extremely satisfied with the formwork systems and the concrete finish obtained. Also, the formwork and bracing, which consisted mainly of standard parts with to the purpose built additions, as well as all necessary safety accessories, gave a fast and easy to assemble system for use in this situation. Altogether, a well planned contract which, from spring 2006 on, will guarantee an undisturbed flow of traffic from the South of England to the North and Scotland.
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