|Location Map ( geo)|
|Perth and Kinross|
|Crossings related to the A827|
There are two bridges across the Tay at Grandtully, the old bridge which is barely serviceable to vehicles and the new Pitnacree Bridge A little downstream.
Until it was replaced, the old Steel Truss bridge at Grandtully used to carry the A827 across the River Tay. Fortunately, today it just carries a minor village road, and the new route of the A827 allows larger vehicles to bypass it.
The old bridge suffers from a number of constraints. Firstly, it is at right angles to the river, while the road at either end runs parallel to the river. This means that traffic has to make two right-angled turns to use the bridge, one at either end. The second, and possibly more difficult problem is that the bridge is only really wide enough for single-file traffic, but this issue pales into insignificance compared to the final problem - the bridge is subject to a 3 Tonne weight limit, with signs requesting that no more than one vehicle is on the bridge at any one time! It has now also been subjected to an advisory 10mph speed limit.
The bridge consists of 3 spans of double triangular trusses, the central span being double the length of the flanking two. The roadway is carried between, rather than above or within the trusses, the deck resting on the lower members of the trusses. Despite being the same length, the two trusses are not identical, albeit both are original. The bridge engineer also worked on the Forth Rail Bridge, but it is unclear which came first, so while there are a number of comparisons between the steelwork of the two, it is not clear if Grandtully was used as a trial, or if the changes were made during construction, using ideas taken from the larger bridge.