Infrared thermography for condition monitoring – A review

Modelling ground penetrating radar by GprMax

This paper reviews the state of non-destructive testing (NDT) methods as applied to the civil engineering industry in the Millennium Year, 2000. The basic principles of NDT methods are described with particular reference to the five major factors that influence the success of a survey: depth of penetration, vertical and lateral resolution, contrast in physical properties, signal to noise ratio and existing information about the structure. The main NDT methods used in engineering investigations are discussed and illustrated with brief case histories from the literature. The integration of NDT surveys into the investigation of structures is described. The underlying reasons why NDT methods are perceived as ‘not working’ by the structural engineer are identified as: a lack of understanding of variability of both the construction materials used and NDT methods themselves.

Review of NDT methods in the assessment of concrete and masonry structures

Porous Materials Water in Porous Materials Flow in Porous Materials Unsaturated Flows Unsaturated Flow in Building Physics Composite Materials Evaporation and Drying Topics in Water Transport Appendices Symbols Used Properties of Water Minerals, Salts and Solutions Other Liquids Other Data

Water Transport in Brick, Stone and Concrete

Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances ...

Statistical models of fracture

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 ~AE! 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.

Assessing Damage of Reinforced Concrete Beam using b -value Analysis of Acoustic Emission Signals

Within recent years there has been an increase in the use of NDT methods to detect defects and anomalies in various civil engineering structures. Infrared thermography, which has been successfully used in the USA in civil engineering applications, is being increasingly applied in the UK as an NDT technique. For example, the technique is now included in the Building Regulations for the assessment of thermal insulation for all new non-domestic buildings from April 2002. One of the perceived limitations of infrared thermography is that in temperate climates it is too cold to use this technique since there is rarely the extreme solar exposure that has enabled the successful use of thermography to detect render debonding and concrete spalling utilising solar heating. However, with the advancements in modern technology it is now possible to detect smaller changes in temperature (down to 0.08 °C). This paper shows that even with the low ambient temperatures experienced in Europe it is possible to use infrared thermography to identify correctly known areas of delamination in a concrete bridge structure and also to investigate the internal structure of a masonry bridge.

Application of infrared thermography to the non-destructive testing of concrete and masonry bridges

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.

The conduction of electricity through concrete

https://pure.hw.ac.uk/ws/files/7458259/pre_production.pdf

Michael Forde

Papers

Review of NDT methods in the assessment of concrete and masonry structures

Assessing Damage of Reinforced Concrete Beam using b -value Analysis of Acoustic Emission Signals

Application of infrared thermography to the non-destructive testing of concrete and masonry bridges

The conduction of electricity through concrete

Numerical modelling of ground borne vibrations from high speed rail lines on embankments