Modelling the degradation of vibration characteristics of reinforced concrete beams due to flexural damage

This paper presents an improved crack model incorporating non-linearity of flexural damage in concrete to reproduce changes in vibration properties of cracked reinforced concrete beams. A reinforced concrete beam model with multiple-distributed flexural cracks is developed, in which the cracked regions are modelled using the fictitious crack approach and the undamaged parts are treated in a linear-elastic manner. The model is subject to incremental static four-point bending, and its dynamic behaviour is examined using different sinusoidal excitations including swept sine and harmonic signals. From the swept sine excitations, the model simulates changes in resonant frequency with increasing damage. The harmonic excitations are utilised to investigate changes in modal stiffness extracted from the restoring force surfaces, and changes in the level of non-linearity are deduced from the appearance of super-harmonics in the frequency domain. The simulation results are compared with experimental data of reinforced concrete beams subject to incremental static four-point bending. The comparisons revealed that the proposed crack model is able to quantitatively predict changes in vibration characteristics of cracked reinforced concrete beams. Changes are sensitive to support stiffness, where the sensitivity increases with stiffer support conditions. Changes in the level of non-linearity with damage are not suitable for damage detection in reinforced concrete structures because they do not follow a monotonic trend

Generation of higher harmonics in longitudinal vibration of beams with breathing cracks

This paper was accepted for publication in the journal Journal of Sound and Vibration and the definitive published version is available at http://dx.doi.org/10.1016/j.jsv.2016.06.025.Classical nonlinear vibration methods used for structural damage detection are often based on higher- and sub-harmonic generation. However, nonlinearities arising from sources other than damage – e.g. boundary conditions or a measurement chain – are a primary concern in these methods. This paper focuses on localisation of damage-related nonlinearities based on higher harmonic generation. Numerical and experimental investigations in longitudinal vibration of beams with breathing cracks are presented. Numerical modelling is performed using a two-dimensional finite element approach. Different crack depths, locations and boundary conditions are investigated. The results demonstrate that nonlinearities in cracked beams are particularly strong in the vicinity of damage, allowing not only for damage localisation but also for separation of crack induced nonlinearity from other sources of nonlinearities

Prediction of crack depth and position in vibrating beams using artificial neural networks

The aim of this paper is to develop a finite element procedure for crack prediction in vibrating beams. Based on this procedure, full frictional contact conditions are introduced between the crack surfaces in order to consider the breathing of crack. The region surrounding the crack is simulated by two-dimensional finite elements. An incremental-iterative procedure is employed to solve the nonlinear dynamic equations governing this problem. The obtained time response is processed with Fast Fourier Transform to extract its frequency components. The first three natural frequencies are input to a trained Artificial Neural Network for depth and position prediction of the crack. This study is validated for a dynamic loading cantilever beam. It is found that the proposed procedure is capable of predicting the crack depth and position with high accuracy

An ethical approach to marketing and valorisation

It is widely recognised that innovation is required for economic growth on a number of levels, such as in Small and Medium sized Enterprises (SMEs), large organisations, regions and nations. Innovation is an important driver for organisational survival, sustainability, improvement, long-term productivity and economic growth. However, innovation in isolation is not only wasteful but also not useful. All projects, and in particular innovation projects, need to disseminate and exploit their results for maximising achievements and increasing sustainability after their completion. This includes launching of the innovation to market, transfer of results and best practices to different and broader contexts; potential tailoring to the needs of others; continuation after the funding period has finished; influences on policy and practice; as well as serving the public good. The emphasis should be on optimising the value of the project and on boosting its impact. In this paper we customise a theoretical framework developed by the US Content Subcommittee of the Impact CS Steering Committee that specifies traditional moral and ethical concepts, which can be used to identify the moral issues concerning Valorisation. An application of these conventional and generic ethical concepts is made to the ideas of Dissemination, Exploitation, Mainstreaming and Sustainability. In Valorisation, players such as Incorporators, Producers/ Project Partnerships, Mediators and Mainstreamers must be aware of these ethical duties, which have been identified by the application of the moral and ethical concepts, as presented in this paper, in order to become more responsible professionals in general. We propose a set of heuristics for ethical engagement with the Valorisation process proposing that an effective Valorisation strategy must be underpinned with ethical consideration