This issue brings a good spread of topics with something to interest most readers, from the scale of material tests to member and the whole structure scale (the content of which can be found at www.icevirtuallibrary.com/content/issue/stbu/166/10). The growing importance of performance-based engineering and design drives the need for deeper and broader understanding of fundamental concepts while simultaneously challenging established orthodoxies. This offers researchers rich pickings in terms of topics to work on and abundant opportunities for innovation and creativity to practising engineers who strive relentlessly for better, more sustainable and more economical solutions to their problems. Such solutions predictably are many and diverse. Our field faces distinct challenges, some of the most pertinent are the following.
• Uncertainties in the properties of construction materials, and specifically concrete, have refused to disappear despite the tremendous progress in concrete technology leading to a proliferation of materials being classified as concrete.
• The introduction of new polymeric materials in construction, such as fibre reinforcements, offer opportunities but also present new challenges.
• Aging infrastructure is an ever growing problem, particularly in industrialised economies, and drivers such as sustainability and climate change have created the need to consider the ‘life cycle' performance of infrastructure.
• Natural and anthropogenic hazards have always been a challenge to structural engineers because of their inherent unpredictability and the need for an improved characterisation has never been greater in order for structures designed to overcome such hazards to have predictable resilience and robustness.
These topics represent a large part of modern structural engineering research so it is serendipitous that the four papers in this issue, from four different countries and three continents, cover elements of them all.
The first paper, by Dillon and Rankin in the UK, presents an interesting study of concrete strength obtained from different test procedures and also proposes the relationships between them, some of which seem to provide a potential refinement of previously used correlations. The study also demonstrates the potential value of the pull-off test as a convenient indirect method, however, the authors propose further research into establishing improved correlations between pull-off strength, which measures tensile strength, and compressive strength. They also advocate conservatism in the practical use of pull-off tests because of the high variability of the results.
The second paper, from Yi and Cho in South Korea, proposes the use of hybrid fibre reinforcement for retrofitting degraded concrete beams. The authors show that the use of a mixture of fibres (such as carbon and glass) produces a more ductile behaviour under failure loads. They do, however, report the common problem associated with fibre reinforced polymer reinforcements, that of bond failure at the ends.
The third paper, by Pape and Melchers from Australia, also studies degraded beams, in their particular case, 45-year-old prestressed concrete bridge beams and the assessment of their remaining life. Given the large number of aging bridges around the world these sorts of studies are clearly of great value. The authors' tests on three bridge beams with different levels of observed degradation and corrosion (from low to high) showed that all the beams failed to reach their theoretical design capacity and that the ultimate loads achieved were consistent with the observed condition. They present, examining many factors, an interesting discussion on the possible reasons for the significant reduction in capacity found.
The fourth paper, by Hansen in Denmark, presents an improvement on the Scruton number, which the author calls a general non-dimensional mass-damping parameter. He shows that the improved parameter produces more reliable predictions of the susceptibility of structures to vortex induced vibrations and makes a strong case that this should be adopted in the Eurocodes instead of the Scruton number.
This issue also includes a book review by Rafeeqi of the fifth edition Adam Neville's influential book, Properties of Concrete. Based on the review it appears this new edition is well worth acquiring for universities and research centres interested in concrete.
I hope you will enjoy the diversity of topics in this issue, please remember that you can also access articles ahead of print at ICE Virtual Library (http://www.icevirtuallibrary.com/content/journals).
