Issue 12

The lnstitution of Structural Engineers sought to ascertain from employers, colleges, and qualified Associate-Members (structural technician engineers), the role that is played by its own professionally trained engineers with the title TEng, AMlStructE. Just what value do Associate-Members have in the eyes of the public, in their own eyes, and in those of the chartered engineers they so often support; indeed, how does the Institution view the scenario?

Dr. J. D. Ball (Simon Engineering Laboratories, University of Manchester): I congratulate the authors on unravelling data and providing design guidelines for wind forces on certain complex structures, and I would like to draw their attention to a similar problem in water flow.

Dr. W. S. Baraiiski (Technical University, Lodi, Poland): I would like to comment on the problem of internal instability illustrated in Fig 11. It seems that any purely elastic model of soil is not appropriate for the phenomenon because-as it can be easily derived-elastic internal instability requires great values of stresses to be applied.

The importance of connection stiffness in influencing the behaviour of steel frames is discussed. Experimental data on connection performance are cited which show that all practical forms of beam-to-column connection operate as semi-rigid joints. Against this background the assumptions of the ‘simple design’ method for non-sway frames are reviewed and a more rigorous behavioural study is presented. Potential benefits and disbenefits of allowing for semi-rigid action in design are discussed. For sway frames the philosophy of the ‘wind connection method’ is explained and conditions under which its use should result in reasonable frames are identified. Some attention is also given to the assessment of effective length factors that properly reflect the restraint available to columns in non-sway frames. D.A. Nethercot

Suddenly applied loads In September, we published a letter from Mr N. W. Sutton of New Zealand, posing a question about dynamic loading. He sought the help of readers in resolving his uncertainty in proving that the stress due to the sudden application of a load is twice the stress due to its gradual application. The response was rapid and comprehensive from many parts of the world, and we were faced with the most unusual situation of having more letters than we could publish and also of having to select one letter as being broadly representative of the whole response. The letter that we now reproduce was one of thecfirst to be received and came from Mr N. M. Hallett of The City University. Mr Hallett offers the following explanation: Verulam