Improved Structural Health Monitoring of London’s Docklands Light Railway Bridges Using Digital Image Correlation

Abstract

As our transportation infrastructure ages and the challenge of keeping it serviceable grows, the need for improved condition information on which to make good cost-effective maintenance decisions becomes ever more vital. Gathering this condition information requires structural health monitoring and inspection on a grand scale and, for it to be useful, it must be accurate, inexpensive, easy to interpret and avoid interfering with traffic flows—whether rail or highways. Digital image correlation (DIC) is a noncontact photogrammetry technique that can be used for monitoring by imaging a bridge periodically and computing strain and displacement from images recorded at different times or operating conditions. This paper discusses the use of DIC for determining the in situ stress state for steelwork details on the London’s Docklands Light Railway bridge structures, including a fatigue-sensitive existing detail with a stress concentration and an impact damaged area, with a view to avoiding the need for strengthening. Application of DIC technique in asset management proved to be cost effective. Throughout the monitoring, the structures were left untouched and were in full service operation.