The A9 is a busy traffic route in Scotland, running between Perth and Inverness. To ease congestion and improve traffic flow, Transport Scotland is in the process of expanding almost 80 miles of single carriageway into a dual carriageway. Eight new structures are being constructed across the route from Luncarty to Pass of Birnam, all of which are being formed using PERI formwork and shoring.
A feature finish was specified for the columns and abutments, keeping it consistent with projects that had previously been developed by Transport Scotland. Whilst taking the finish into consideration, the design also had to combine new panels with the customer’s existing PERI equipment where possible.
Balfour Beatty also wanted to improve the rate of rise to speed up the construction process. The only way to do this was by increasing the temperature of the concrete, which in turn would increase the concrete pressure and the demand for additional support. This became a challenge, as it was not possible to tie the reinforcement solution into the panels due to the type of finish that was required.
The reinforcement solution
We designed an RCS wraparound along the perimeter of the TRIO shutters. This involved using clamps to hold all external corners of the shuttering together. The connection was strengthened using long dwidags that were installed in both directions between the RCS rails.
Abutments and VKP parapet
We designed ply-lined TRIO for the abutments to deliver a seamless finish. With the abutments, columns and beams in place, the next step was to tie the structures together by pouring the diaphragm. This was formed using a MULTIPROP and PERI UP shoring scaffold comprising GT 24 girder primary and ALU MPB secondary beams faced with plywood.
For the parapet, our technical designers looked at various load cases and combinations to ensure the formwork was being used in conjunction with safe working loads. We used the cantilevering VKP parapet system, as it was ideal for the specified F4 finish. This type of system offered lighter loading and quick installation on to the precast beams.
For a more information about this project, download our case study.