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Forth Road Bridge Crawler Gantries

We have built upon the previous cable crawler gantry work that we have done to design two new gantries for use on the Forth Road Bridge cable band bolt replacement project. The Forth Road Bridge which lies on the east coast of Scotland measures over 2000 metres and features a main vehicle way as well as a pedestrian and cycle path. It was originally built to connect Edinburgh to Fife and the rest of Northern Scotland.

Key facts

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Location

Forth Road Bridge, Scotland

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Client

Forth Estuary Transport Authority

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In Partnership with

The Spencer Group

Following their successful collaboration on the Humber Bridge Dehumidification Project, The Spencer Group asked Eadon Consulting to design two new cable crawler gantries for the Forth Road Bridge cable band bolt replacement contract. In total four gantries are being used. These consist of two brand new gantries, a gantry previously used on the Humber Bridge, and a gantry which was originally used on the Forth Road Bridge Dehumidification Project in 2008.

The Humber Bridge Gantry was modified to suit the smaller cable diameter and different hanger cable arrangement of the Forth Road Bridge, whilst the original Forth Road Bridge gantry was improved to include the developments in gantry design since the original was first made. The two new gantries were based on the more up to date Humber Bridge Gantry design but were dimensionally smaller to suit the Forth Road Bridge cable. All four gantries were fitted with lifting davits and fabric covers to assist in the cable band bolt replacement works.

As with previous cable crawler gantry projects the structures were designed with the aid of STAAD.Pro structural analysis package to BS5950-1, Structural Use of Steelwork in Building, using safety factors from BS EN 1808, Safety Requirements on Suspended Access Equipment. The travelling gantry mechanisms were designed using BS 2573, Rules for the Design of Cranes. After successful load testing the two refurbished gantries were installed on the cables in January 2013 and the two new gantries followed in May 2013. The replacement of all cable band and bolt assemblies was complete by the end of 2013.