The deployment of fibres made of high performance materials such as aramid polymers is spreading in many different engineering applications. Thanks to their excellent mechanical properties, they are being applied also in the structural field. The question that prompted this study is whether nonlinearity can be used for assessing structural damage in aramid fibres. The idea was to detect weak nonlinearities in the dynamic response measured on fibres and ropes, and to look for correlations with damaged samples of the material. Positive results would usher the possibility of using such quantity as an indicator for evaluating the residual life span of aramid elements, cables and ropes. In order to investigate the sensitivity of this approach, nonlinear characterisation tests were carried out on aramid fibres by applying sweep-sine excitations at different loading levels. In order to have a comparison term and to test the setup machine, a similar characterisation procedure was also applied to fibres made with a different high performance material: silicon carbide.

The main objective of this paper is to evaluate the capabilities of the non-destructive impact-response method in detecting the existence of defects in piles with high slenderness ratio. The impact-echo technique was developed many years ago for non-destructive detection of defects in piles and structures. However, it is recognised that this method could be applied confidently for piles with length/diameter relationship up to 20. In the last years, with the development of hardware in computers and sensors, it is now possible to use this method for piles with high slenderness ratio. In this paper, piles of length/diameter relationship of about 40 are studied. A numerical-experimental study was carried out. It was shown that the results of the experiment were in agreement with those of the numerical studies and the accuracy of the impact-echo method was influenced by the type, size and location of the defects. Taking into account the uncertainties related to the studied problem, the obtained results preliminarily allow consider this NDT methodology as a promissory alternative to detect defects in piles with high slenderness ratio.

The work focuses on investigation of possibilities of single-fibre multimode interferometers application to development of sensors and multichannel measurement systems for monitoring of technical conditions of engineering structures. Features of use of correlation method for processing single-fibre multimode interferometers signals were studied. Peculiarities of development of separate sensors as well as multichannel measurement systems based upon single-fibre multimode interferometers were considered. Besides, some results obtained with use of abovementioned measurement systems during experimental studies of deformational processes within reinforce concrete constructions are discussed.