Steel orthotropic decks provide the most economical form of construction for long span bridges and other weight-critical structures. However, conventional stiffened plate decks are costly to produce and many have suffered premature deterioration or lacked wholly satisfactory longterm performance. This is largely because of fatigue susceptibility of fillet welds and also lack of endurance of roadway surfacing systems due to inherent flexibility of the lightly stiffened deck plate. Sandwich construction, with both lower and upper plates, would potentially be more efficient. In recent years laser welding technology has developed such that it is now feasible to fabricate sandwich panels from plates thick enough to be suitable for bridge decks. Fatigue endurance is critical in the design of steel bridge decks. At the present time there is little data on the fatigue performance of laserwelded joints apart from butt welds. In this paper the fatigue performance of laser stake welds in two different configurations is examined with a view to assessing the overall fatigue endurance of sandwich panel decks. It is shown that the performance of laser-welded joints is very promising. Hence, the overall sandwich panel configuration is also likely to have good endurance and affords a radical evaluation of steel bridge deck design. S. R. Bright, BEng, CEng, MICE Cass Hayward and Partners, York House, Welsh Street, Chepstow, NP16 5YL J. W. Smith, BSc (Hons), PhD, CEng, FIStructE, FICE Department of Civil Engineering, University of Bristol, Bristol BS8 1TR
Nature of a professional service We human beings have a role to play in relating our activities to the well-being of society, and to the care of the world in which we find ourselves. The Oxford Dictionary defines this duty as ethics: ‘The rules of conduct recognised in certain limited departments of human life. The science of human duty in its widest extent, including the science of law etc.’ Ethical decisions are concerned specifically with quality – with justice, with equity, with the consequences for all affected by the decision, with the personal and collective responsibilities which lie beyond the contractual obligations into which we enter. In complex developed societies certain functions, requiring special knowledge and responsibilities, affecting the quality of life of others, are described as professional, and the duties of practitioners are defined and monitored. Such professionals are required to relate their particular skills and knowledge, of both the humanities and the sciences, to the needs of society. James Armstrong, OBE BSc, FREng, FIStructE, FICE, CEng, Hon Deng
Current stainless steel structural design guidance is based largely on assumed analogies with carbon steel; the result is that the particular material properties that stainless steel exhibits are not being fully utilised. This paper describes a new approach to stainless steel structural design that adopts a more accurate material model and a continuous system of section classification and member design. The new method requires no iteration, involves a similar volume of calculations to current methods, and offers improvements in design efficiency of over 20%. The method has been validated against all available test results and has been subjected to a statistical analysis in line with the Eurocode requirements. Worked examples have been included to illustrate the method. L. Gardner, BEng, MSc, PhD, DIC, CEng, MICE Imperial College London D. A. Nethercot, PhD, DSc, FCGI, FREng, FICE, FIStructE Imperial College London