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The President: Before l propose a vote of thanks to our authors, I would like to make a few remarks about the profession. We, in fact, hear many remarks about our profession
when collapses or other troubles occur. This is a paper about an extremely difficult job-one which posed ever-changing problems. The outcome was successful-after all, Ove Arup Et Partners are the leading structural consultants-and yet, what does the Press say? Ove Arup were getting advice; they were using outside experts. I think they ddeserve considerable praise.
Structural frames are usually designed to satisfy deflexion requirements by trial and error. Recent optimization methods are restricted to small or very specialized structures. In the general method proposed herein an efficient analysis program is used to determine linear approximations to the rates of change of deflexions with the section properties of the frame members. A simple linear programming procedure then determines the most economical changes of section required to satisfy the deflexion constraints. Cycles of analysis and optimization continue until a satisfactory design is obtained. Comparisons with other methods show that this design is likely to be close to the optimum. Haunched frames can be designed and the reduction in frame stiffness due to compressive axial loads can also be allowed for. Examples of the application of the method to plane steel frames are given.
D. Anderson and J. Salter
Situations are described in which it is advantageous to use composite steel-concrete beams with fewer shear connectors than the number required for full interaction. From a study of the results of tests and computations, simple rules are derived for estimating the ultimate flexural strength of such beams, and for checking deflexions in service, both by calculation and by the use of limiting span-depth ratios.
R.P. Johnson and I.M. May