Issue 23/24

The author has researched a little known branch of mathematics and found that it is ideally suited to the presentation of structural theory both in the lecture theatre and in practice at every level from elementary beam theory to the numerical solution of the most intractable problems that may be encountered. At worst it is useful for verifying the output from computer analysis; at best it can replace the computer with more accurate solutions with no more labour than that involved in preparing input data and perusing output data, with the advantage that the results are in readily visualisable form, give clear messages about the magnitude of residual errors and restore that ‘hands-on’ feeling which has been lost with the advent of computer-aided design. This is achieved with low-level arithmetic. A brief introduction and a simple example are given in the hope of encouraging others to pursue the subject. J. M. Rolfe, BSc (Eng), PrEng, CEng, FIStructE

High-strength concrete is relatively brittle and its use in a reinforced concrete member might result in unacceptably low flexural ductility. One way of improving ductility is to provide confinement. However, in the case of beam design the effects of confinement are generally not considered due mainly to the lack of a suitable design method. In order to develop a design method for improving the flexural ductility of highstrength concrete members through the provision of confinement, the effects of confinement on the flexural behaviour of reinforced concrete beams have been evaluated in this study by complete moment-curvature analysis of beam sections with and without confinement provided. It was found that the provision of confinement significantly increases the ultimate concrete strain, balanced steel ratio and flexural ductility. Furthermore, design formulae for the flexural strength and ductility design of high-strength concrete beams with the effects of confinement taken into account have been developed. A. K. H. Kwan F. T. K. Au S. L. Chau Department of Civil Engineering, The University of Hong Kong, Hong Kong

This paper presents two new methodologies (one formal (NLFEM), the other approximate (CFPM)) which show clear differences – often quite considerable – with regard to code predictions needed to assess and rate existing concrete bridges. The work has obvious implications in terms of both economy and safety, and can assist the engineer in reaching more rational and accurate decisions on the true structural capacity and mode of failure of a structure. A. A. Mahdi, BSc, MSc, PhD, CEng, MICE Hyder Consulting, The Surrey Research Park, Guildford Prof M. D. Kotsovos, Dipl Ing, PhD, DSc, CEng Department of Civil Engineering, National Technical University of Athens, Prof M. N. Pavlovic, ,BEng, MEngSc, PhD, ScD, CEng, FIStructE, FICE, FConsE Department of Civil & Environmental Engineering, Imperial College, London