Structural Health Monitoring:
Structural Health Monitoring
Many bridges have deteriorated over the years and have reached the point where they no longer meet the standard specified in codes of practice whilst others have simply outlived their design lives. Nevertheless, these bridges are often safe, especially if they are monitored and/or inspected on a regular basis. This can provide engineers with reassurance on their level of safety, provided the monitoring/inspection system is reliable and accurate. Traditionally, the task of detecting/monitoring damage in bridges has consisted of visual inspections. With the increase in computational power and signal processing capacity, there has been a move towards automatic sensor-based analysis of bridge condition – so called Structural Health Monitoring (SHM). By continuous monitoring, many uncertainties can be removed such as, uncertainties in the analysis model (e.g., load sharing between beams), uncertainty in understanding the response of the structure to imposed loads, uncertainty surrounding the appropriateness of traffic load models for assessment, uncertainty about actual traffic on the bridge (frequency and weights) and uncertainty concerning the extent of illegal overloading Similarly, as the cost of sensors and data acquisition systems falls, road/rail owners and managers are increasingly instrumenting bridges with sensors to find out more information about the true behaviour of the structures under load. As well as saving money, SHM reduces the carbon footprint of transport infrastructure by extending the safe working lives of these structures.
ROD-IS has particular expertise in SHM, most notably in closing the gap between what data is available and what the bridge owner/operator needs to know. In the specification of SHM systems we ensure that the valuable and usable results are extracted. ROD-IS can also provide road/rail owners and administrations with the necessary advanced technical back-up to plan sensor schemes and to analyse the output for SHM in the context of structural safety assessment and life cycle maintenance optimisation.
SHM can also be combined with Weigh-in-Motion (WIM) systems as there is a considerable overlap in the technologies used for Structural Health Monitoring and Bridge WIM so the cost does not necessarily have to be significantly increased. Knowing the source of response variables adds a great deal to any monitoring system as it allows variables other than those measured directly to be calculated, such as the characteristic load effects throughout the bridge. With Bridge WIM, the complete bridge safety can be monitored on an ongoing basis.
Equally SMH can be used to provide a better indication of the safety of an existing structure and the outputs can be employed in analysis ranging in complexity from simple determination of actual induced load effects (as opposed to those theoretically estimated by computer models) for comparison with the corresponding member capacities or alternatively, in sophisticated Reliability Analysis