Hagia Sophia: Justinian’s Church of Divine Wisdom, later the Mosque of Ayasofya, in Istanbul

Shear in concrete slabs having concentrated loads close to supports In our column for 19 December, Mr R. N. Morgan asked whether other of our readers were aware of published works giving elastic influence coefficients for shear forces in plates due to loads close to supports. We have received a response to Mr Morgan's request from Von Dipl.- Ing. Bjorn Vik of Sandvika in Norway: I believe there are some answers to Mr Morgan’s question about shear in concrete slabs. He mentions Pucher’s book, in which unfortunately the influence fields for shear forces were seriously in error. However, in the book Platten und Behalter, by E. Bittner (Springer-Verlag 1965) several correct influence fields are presented. Also a paper by the writer, in Bauingenieur, 1964/12, deals with shear forces from loads in the vicinity of the support. Verulam

Mr A. C. G. Hayward (F) (Cass Hayward & Partners) The authors argue the pros and cons of permissible stress or limit state Codes and note that designs compare closely. This, of course, was a deliberate policy when the limit state Codes were written, the values of partial factor being fixed so that the overall safety of common structures under the then prevalent loading remained the same. Thus, the changed philosophy of the new Codes would at least start from a common base of experience. When the loading is changed (e.g. resulting from the recent increase in highway bridge loading discussed by the authors), differences in designs under the Codes may become evident.

The ultimate strength of plate girders with perforated webs under shearing and bending is investigated. The girders considered are transversely stiffened panels with aspect ratios (b/d) between 0.7 and 1.5. The holes in the webs are centrally located and they are of circular, rectangular and elongated shapes. The ultimate strength is determined using a theoretical model developed on the basis of stress fields and loading-carrying mechanism observed experimentally from test results and numerically from finite element calculations simplified to allow for the variation in panel and hole size. The predictions obtained from the theory are compared with experimental and numerical results available, and it is found that the theory provides reasonably accurate estimates. M.M.K. Lee