Gairnshiel Bridge, Gairnshiel

The new Gairnshiel Bridge is a single span twin trapezoidal box girder structure made from steel plate grade S355J2W+N for steel less than 50mm thick or S355K2W+N for steel with a thickness greater than or equal to 50mm.

Testing & inspection was to quantified service fatigue category F56 in accordance with PD6705-2 2010+A1:2013

Execution Class 3 BSEN1090-2 2018

The weathering properties patina to form the unique natural look that will fit in with the surrounding Glen Gairn rustic landscape.

The new bridge is required to bypass the old existing humpback bridge 150m upstream build between 1748 – 1752 as part of the Hanoverian Military Road network, now a protected structure.

The shallow construction depth resulting from the box girder selection, allows the structure to have less of a restricted view of the old bridge and to blend in with the surrounding countryside.

The new bridge was fabricated at our J&D Pierce East Kilbride facility. The complexity of have a sloping outer web at 35 degrees to the horizontal with a 306mm camber at mid-span made the development of the sloping web critical to the vertical curve alignment of the finished structure.

The bridge was delivered in 4no. sections to site 2 @ 9.125m long weighing 26Te. and 2 @ 27.375m long, weighing 67Te. welded together on site using full penetration butt welds to form twin boxes each 35.5m long and weighing 93Te.

The box girders were installed using the Liebherr LG1550 strut jib mobile truck crane.  Both box girders and tie bracings installed and complete in a single 10-hour working window.