The Paraslim system, supplied pre-assembled for the first time, has been adopted as вЂBest Practice’ by the contractor, which is delivering the job for the Highways Agency.
The A34 dual carriageway is a major access route for freight travelling up into the midlands from the port of Southampton and the south coast. The viaduct gives traffic passage over the Thames flood plain, a major rail line that runs into Birmingham, the Oxford Canal and the heavily used A40.
Whether the 47-year-old viaduct should be replaced or continually maintained has been the subject of much local debate. After carrying out remedial works on the viaduct it quickly became clear to the Highways Agency that it would be more cost effective to replace the structure rather than continually maintain it. The contract went out to tender and Costain won the contract to replace the viaduct whilst adhering to the guidelines put in place by both the Highways Agency and the local Council. The fact that the viaduct crosses a railway line, major road and canal made the project just that more challenging.
ADVERTISEMENTTayo Oyetan, Costain’s Structures Section Manager and Temporary Works Manager for this project talks about the viaduct and the construction programme ahead. “The challenge on this site is to replace the existing viaduct without disrupting traffic flows. The solution that Costain has proposed entails replacing the viaduct within its existing boundary. To achieve that we are building an offline viaduct, which will then give us the room to demolish the existing structures, build a new deck offline weighing 5000 tonnes and slide it into place during an overnight possession of the railway, road and the canal.”
For a project such as this, which is under constant public scrutiny, completion within programme time is of utmost importance. This is where RMD Kwikform’s pre-assembly facility helped provide significant gains in both time and budget.
Justin Bennet, RMD Kwikform Sales Representative for the Home Counties area commented, “After lengthy discussions with Costain we found that pre-assembly of the Paraslim members could offer a huge cost and time saving on this project. Additionally, safety was enhanced because the off-site assembly inherently reduces the risk of on-site accidents for the customer.”
Once the decision was made to pre-assemble, the panels were assembled at RMD Kwikform’s Aldridge yard. Superslim Soldier primary beams were tied to aluminium secondary beams in order to carry the contractor’s plywood deck, and the Paraslim undercarriage was assembled ready for final pinning into place on site.
The 49 Paraslim units were then delivered to site and lifted on to the bridge beams and the plywood deck added.
For Costain there has been clear benefits to using RMD Kwikform’s pre-assembled service, Tayo continues, “This facility provided a lot of benefits to us, particularly in terms of programme time. With the pre-assembled system we were able to have it delivered ready for the beams so we could achieve better productivity onsite.”
With the viaduct running over a major road, railway link and canal, along with works taking place next to moving traffic, health and safety considerations were, as always, top of the agenda.
Once the Paraslim sections were in place much of the work area was protected by Ultraguard edge protection and fully hoarded sections across both the A40 and the railway line.
Also, by using the pre-assembled Paraslim, access to the equipment beneath the soffit was kept to a minimum, with only minor levelling adjustments had to be made via a mobile elevated work platform rather than full in situ assembly. Ultraguard barriers can also be attached directly to the Paraslim sections.
The success of pre-assembled Paraslim on this project, will, according to Justin Bennet surely lead to further applications; “As a flagship scheme for RMD Kwikform we believe this is a real industry leap forward and we’ll be rolling this scheme out on several other projects, certainly within the UK and hopefully worldwide in the future.”
For Tayo Oyetan and Costain, pre-assembled Paraslim modules have been a success on all levels, resulting in Costain adopting the pre-assembled Paraslim approach as вЂBest Practice’ on projects of this nature. Tayo commented “For Costain it is a system we would certainly look to use again, as the benefits certainly enhance what the previous system provided for us. It is a clear improvement and the way forward, it’s an innovation that we will certainly look to take across to other projects as well.”
Work on the A34 Wolvercote viaduct is due to finish in Summer 2010.
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