Disasters, and their Role in Education

Safe design using computers This theme continues to arouse wide interest. Though almost every engineer now uses computers in some form, and all those writing to Verulam agree that there are undoubted benefits, there is still a very great diversity of comprehension. The speed of change is bound to create a certain degree of puzzlement. David Brohn believes that some of the problems are inbred into the system but suggests that the Institution should define some guidelines. He writes: The responses from Alan Peet and Kenneth Northgreaves (The Structural Engineer, 18 July 1995), suggest that there is still a fair amount of confusion over this issue of the use of computers. It will not really be laid to rest until the Institution produces a definitive publication which addresses these issues and gives clear direction as to the way in which members of the Institution should handle the computer. Verulam

Brian Simpson will succeed Patrick Dowling as President of the Institution 1995-96 at an Ordinary Meeting at Institution headquarters on 5 October 1995. The handover will be at 6 pm when the new President will give his Presidential Address ‘Professional development’, the full text of which will be published in The Structural Engineer on 19 October.

Based on the concept of lumped masses and the established equivalent continuous approach for the analysis of coupled shear walls, a continuous-discrete approach for evaluating their natural frequencies is proposed in this paper. The coupled shear wall system is treated as a continuous system (i.e. where the discrete beams are replaced by an equivalent continuous medium) and a discrete system (or lumped mass system) at different stages of dynamic analysis. The advantages of the two types of analytical system are jointly utilised. The accuracy and eficiency of the methodology adopted in the continuous-discrete approach are verified by making comparisons with the precise classical approach and a couple of approximate approaches for evaluating the natural frequencies of typical coupled wall structures. The minimum number of lumped masses needed in the present approach to obtain an acceptably accurate value of natural frequency for any modal vibration of coupled shear walls is also discussed. In addition, a simple chart, based on the continuous and the continuous-discrete approaches, for estimating the fundamental frequencies of coupled shear walls is presented. A numerical example is given to show the application of the chart and the accuracy of the procedure in estimating the fundamental frequencies of coupled shear walls. Guo-Qiang Li and B.S. Choo