Paper Title
Development and Testing of a Computer Vision Based Method of Displacement Monitoring on Real World Bridge Structures

Abstract
Structural Health Monitoring (SHM) techniques can provide vital information on the performance and capacity of new and existing structures. Generally sensors are embedded or surface mounted to assess the integrity of the structure and provide a means of damage detection or failure prediction. However, existing systems are limited by the need for contact with the structure and demand onerous set up procedures. The lack of a permanent power supply on rural site adds an additional limitation to many existing systems. This paper details the development and testing of a fully portable vision based SHM system. Standard DSLR cameras along with adapted digital image correlation methods are utilized to measure deflections and associate the response to live loading. A series of laboratory investigations have been carried out at Queens University Belfast to develop and validate this system as a viable means of displacement measurement. The system was subsequently trialed at two bridge sites in Northern Ireland, a 20m span truss bridge and a 7m span masonry arch bridge. In each case the structures were identified as showing significant signs of deterioration and the outcome of visual inspections highlighted concerns for the asset owners. Existing SHM systems were not feasible due to access, power and cost limitations, the vision based system allowed for rapid site deployment and real time monitoring of the structures under live loading. The results obtained on site were then compared with theoretical analysis methods to determine the true structural condition. Index Terms - Computer Vision, Displacement Monitoring, Field Verification,Structural Health Monitoring.