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Concrete bridges in the United Kingdom represent a major legacy that is starting to show signs of distress. Therefore, the need for monitoring them is an urgent task. The acoustic emission ͑AE͒ technique was proposed as a valid method for monitoring these bridges but more study is needed to develop methods of analyzing the data recorded during the monitoring. The writers would like to propose a b-value analysis as a possible way to process AE data obtained during a local monitoring. The b-value is defined as the log-linear slope of the frequency-magnitude distribution of acoustic emissions. This paper presents the results of a b-value analysis carried out on data recorded during a laboratory test on a reinforced concrete beam designed as representative of a bridge beam. During the experiment, the specimen was loaded cyclically and it was continuously monitored with an AE system. The data obtained were processed and a b-value analysis was carried out. The b-value was compared with the applied load, with a damage parameter, and with the cracks appearing on the beam. The damage parameter represents the cumulative damage in terms of total sum of acoustic emissions. The results showed a good agreement with the development of the fracture process of the concrete. From a study of the b-value calculated for a whole loading cycle and for each channel, some quantitative conclusions were also drawn. Further development work is needed to make the b-value technique suitable for practical use on a real bridge.

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Synopsis This paper examines the relationship between mix proportions, electrical properties of the constituents of concrete and the over-all electrical resistivity for concrete. The mechanisms for the conduction of electricity through the heterogeneous medium of concrete are discussed and an electrical model is proposed. Analysis from a purely theoretical standpoint is also described and the values of electrical resistivity obtained experimentally are shown to compare favourably with the theoretical model.

This paper reviews, synthesises and benchmarks new understandings relating to railway vibrations. Firstly, the effect of vibrations on passenger comfort is evaluated, followed by its effect on track performance. Then ground-borne vibration is discussed along with its effect on the structural response of buildings near railway lines. There is discussion of the most suitable mathematical and numerical modelling strategies for railway vibration simulation, along with mitigation strategies. Regarding ground borne vibration, structural amplification is discussed and how vibration mitigation strategies can be implemented. There is also a focus on determining how 'critical velocity' and 'track critical velocity' are evaluated-with the aim of providing clear design guidelines related to Rayleigh wave velocity. To aid this, conventional site investigation data is reviewed and related to critical velocity calculations. The aim is to provide new thinking on how to predict critical velocity from readily available conventional site investigation data.