The paper describes an investigation into the accuracy of determination of the torsional properties of a noncircular section by the membrane analogy and by relaxation methods. A circular section with a circular groove was investigated, the section being considered most suitable because an analytical solution is available and because it has a region of high stress comparable to the re-entrant comers of structural sections in which the authors are interested. W.B. Dobie and A.R. Gent
Beton Precontraint, by Y. Guyon. Preface by E. Freyssinet. (Paris : Eyrolles, 1951.) Pp. 728, 1O in. x 7 in., 503 Figs. 4,500 Fr. As the author points out in the preface, prestressing is a general principle which may be employed by different means in a great variety of cases. To write a complete treatise on the subject seems to be an impossible task. The purpose of the author is to develop general principles by analysing a few applications in detail and to describe the methods of execution which may be adopted for other applications. The present book, comprising 700 pages, is the first volume of a comprehensive work on the subject.
I. The evolution of steel construction, like any evolution, displays external and internal characteristics. The external characteristics are nearly always more evident, and can thus be more easily recognised than the internal ones. On the other hand, it is very often only the internal or intellectual characteristics that make evolution possible. In steel construction particularly, the external evolution and the great progress made during the last 1OO years would not have been possible without the evolution of the corresponding scientific bases. Professor Dr. F. Stussi
The CHAIKMXN. proposed a vote of thanks to the authors and declared the meeting open for discussion.