Jeroen van Ravenzwaaij
BREM foundation and monitoring, Reeuwijk, the Netherlands

Rodriaan Spruit, City of Rotterdam, the Netherlands
Ane de Boer, Ministry of Infrastructure and the Environment, Utrecht, the Netherlands

Presentation title:
New permanent optical monitoring techniques of constructions


Developments in sensor technology, in conjunction with the search for new maintenance strategies, have led to an explosive growth of monitoring systems that allow for monitoring the condition of a property, object or construction. Such systems can not only measure all kinds of building conditions, but, combined with smart data analyses, will also facilitate fully automatic analysis of the data. If prescribed alarm levels are met, mitigating actions may automatically be initiated. Through such monitoring, the security approach and the implementation of the (long-term) maintenance changed and can be planned in a better way. For example less periodic visual inspection on site is needed and maintenance strategy will shift from pre-programmed maintenance to maintenance on demand.

To allow for such long-term maintenance on demand strategies, the sensors that form the basis of the system, should have high long-term stability. Until recently, most sensors relied on the classic strain gauge principle. These sensors need frequent calibration or compensation, making them less suitable for long-term monitoring.

Since the late nineteen-nineties, optical fibre sensor technology started to take off, promising small sensor size, combined with extremely high long-term stability and equal or better strain resolution as compared to electrical strain gauges. Initially, the technology was held back by the steep prices for the measurement equipment, even though the sensors were relatively affordable from the start. From about 2005-2010 with gradually more affordable measurement devices being introduced, the number of monitoring applications increased rapidly. Currently the majority of new long-term monitoring project are based on optical sensor technology.

An overview of optical fibre sensor application experience by the authors will be given, starting from 1999. Sensor types will cover the FBG, OTDR, B-OTDR and interferometric principles. From this history of fibre optic measurements in a wide range of projects, an outlook onto future measurement opportunities will be extrapolated.

The RailTech Europe 2017 Conference will explore the following three themes: