Often, once monitoring requirements for a structure have been determined, the most difficult part of obtaining usable data is access to the structure (whether because of traffic loading, or difficulty accessing underneath the bridge). It is also not always possible to set strain gauges, accelerometers and prismatic targets in the ideal location, and the amount of cabling required can prove expensive and logistically challenging.
As a video based technology, Imetrum’s system can be set up safely out of the way, meaning no disruption to traffic and a safer working environment for those gathering the data. Compromises no longer need to be made in terms of determining where to measure, and accuracy can often be increased – whether by measuring displacement directly (rather than inferring it from strain gauges or accelerometers), or by the inherent accuracy of Imetrum’s system, which does not suffer from mechanical drift and typically has a resolution in excess of 1 part in 100,000 (i.e. if the camera can see a 40m wide structure of roadway, a resolution of greater than 0.4mm can be achieved).
The Imetrum Technology was originally developed for monitoring movement on the Humber Bridge and 2nd Severn Crossing, and can cope well with a single camera measuring the overall movement of the deck at specified locations. Areas of interest can also be highlighted for a more detailed investigation, as in the case of the pier bending in the image above right. The Video Gauge™ pattern recognition technology works on rivets, bolts, beams, masonry, concrete staining – almost all typical bridge material, without the need to fit targets.
Even in the early days, before a rugged system was developed, good data was being produced from a portable setup. The images here show a load test on a concrete motorway bridge, where the video system was used in conjunction with LVDTs, producing similar results with just a 30 minute set-up time. Elsewhere on this site you will find case studies using our current hardware, which can run on 12V battery power only.
CS116 - Measuring road bridges