A737 Dalry Bypass, Scotland

Sustainable Infrastructure

Location: Scotland

Client: Farrans Roadbridge Ltd.

Status: Complete

Overall Project Value: £32m

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Brief Description

The A737 Dalry Bypass involves the construction of a new off-line bypass to the east of the town of Dalry and associated junctions to connect to the existing A737 Trunk Road. The project includes the Design, construction and maintenance of the scheme including:

Approximately 3.8km of new carriageway comprising 2.45km of Wide Single 2 + 1 layout with overtaking lanes in opposing directions & 1.35km of single carriageway layout including the provision of a differential acceleration lane (DAL).
A five span steel viaduct bringing the mainline across the River Garnock floodplain and Glasgow to Ayr Railway line;
Blair Road overbridge a single span concrete overbridge bringing Blair road over the mainline;
One farm accommodation Underpass bringing a private access track beneath the mainline;
Mine consolidation works (grouting works);
6 No. culvert structures to accommodate watercourses;
2 No. Mammal underpasses adjacent to the culverts on the Coalheughglen Burn;

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FT Responsibilities

Fehily Timoney and Company Ltd (FT) responsibilities included the design of all structures on the scheme including the River Garnock Viaduct a 256m long viaduct over the River Garnock floodplain and adjacent Glasgow to Ayr Railway line.

The structure is a 5 span, weathering steel ladder deck bridge with precast concrete deck and piled in-situ concrete abutments and piers.

The steelwork for the bridge was assembled on the west embankment and push launched into place due to difficult access conditions between the river and railway. FT carried out the temporary works launch study to assess the impact on the bridge steelwork along with the load and deflection analysis for the temporary bearings, launch nose and tail design. Deflections during the launch over the railway span was particularly critical due to railway overhead electrical lines.

Precast concrete deck panels were designed to support a 40 Tonne crawler crane allowing the panels to be placed from deck level and then to support the crane for placement of adjacent panels. Precise detailing of the panels was essential to ensure that protruding reinforcement fitted precisely with adjacent panels and shear studs from the deck steelwork.

Scour protection measures for intermediate support columns within the floodplain were also required as part of the design.