MITIGATIONS
It has been established that visual inspections play an important role in the current inspection regime, and that engineers are generally happy with the data they obtain using existing methods. The data is used to plan further inspections or investigations, and to plan maintenance work. However, the literature reports a number of issues and problems affecting visual inspections which suggests that the quality of data provided to bridge engineers is perhaps not as good as they believe, and could certainly be improved. A number of factors have been identified which influence the success of visual inspections, such as the inspector’s fear of the inspection environment or eyesight, the physical environment in which the inspection takes place and the way the inspection is carried out
The problems with visual inspections are not confined to the collection of bridge data. The literature describes many instances where problems with visual inspection data have been encountered in other industries and applications. There are a number of measures which have been proposed to alleviate the problems and improve visual inspection data quality.
Technological approaches and tools have been successfully used to help collect visual condition data in a variety of fields and industries. Some applications (manufacturing, aerospace, food) have full control and are relatively straightforward computer vision problems; others (archaeology, accidents, construction, pavement condition monitoring) must operate in environments where there is less control over the orientation of the object, the scene background or the lighting, and are more akin to the requirements of bridge inspections.
There have been calls ((Middleton, 2004), (Woodward, 2006)) to develop suitable systems and methodologies which would enable technological tools to be used to assist and improve visual inspections on bridges. A similar process was undertaken between 15 and 20 years ago in pavement condition monitoring. Machine based surveys are now routinely performed on the majority of roads in the UK, and data from such surveys is accepted and used by those responsible for the maintenance of the road network. It is recognised that the problems faced in collecting data on roads and bridges are different, and that the move from the current situation where manual inspections are the norm, to one where a more technological approach is used will be a long process.
In order to be accepted by engineers, an Image-Based Inspection (IBI) system would need to produce data at least comparable to that currently obtained by traditional visual inspection methods, and would require ways of collecting, processing, analysing, interpreting and reporting this data. A number of researchers are investigating the use of image-processing tools to automatically detect and report defects such as cracks in images of concrete structures ((Abdel-Qader, et al., 2003), (Abdel-Qader, et al., 2006), (Adhikari, et al., 2014), (Jahanshahi, et al., 2009) (Li, et al., 2013) (Matsumoto, et al., 2014) (Moon & Kim, 2011) (Yamamoto, et al., 2014)), but little or no work has been undertaken to develop a standardised, methodical method for the collection of the images on which these tools can work.
5.1
Research question
The work carried out in Part 1 of the research has helped to properly define the research question:
Can systematically collected, high-resolution image data be used to enable General Inspections to be performed which provide at least as much information to engineers as traditional on-site General Inspections? If so, how can the data be collected, presented and interpreted, and what are the benefits of such an approach?
PART 2 – IMAGE-BASED INSPECTION SYSTEMS:
REVIEW, DEVELOPMENT AND TESTING
Part 1 established that visual inspections play a vital role in the collection of bridge condition data and the management of the assets. It also showed that visual condition inspections are susceptible to a number of problems, resulting in subjective and variable outputs. A number of approaches for improving the quality of visual inspection data were discussed, as were examples of successful applications of these. Part 1 concluded that investigating the use of a technological solution to help the inspectors collect and interpret the necessary data would be beneficial.
Part 2 discusses the work performed leading to the development and testing of an Image-Based Inspection System (IBIS).
Chapter 6 discusses the requirements of any potential IBIS. This establishes through experimentation the way in which the size of feature which can be identified by inspectors varies with viewing distance and at different image resolutions, and considers the implications of this. Chapter 6 concludes by outlining a specification and list of requirements for an IBIS to be used for UK highways bridge GIs.
Chapter 7 reviews some existing systems and approaches which could be used to collect images or assist in a GI and discusses their strengths and weaknesses, and possible suitability for adoption and use as a routine tool for inspectors and engineers.
Chapter 8 covers the development of an image collection, display and interpretation system. This discusses the decisions made during the development, and explains why they were made, and why the alternatives were not.
Chapter 9 presents the results of the testing of the system, and the feedback received from practising engineers and inspectors who used it.
Chapter 10 presents an overview of the work done in Part 2 of the research, summarising the system requirements, the suitability and shortcomings of existing systems, the development of the prototype system and the results and feedback, highlighting the areas which require improvement.
The findings and conclusions of the work are presented in Chapter 11, followed by ideas for future research in Chapter 12.