Academia. The Teaching of Civil and Structural Engineering at Kingston Polytechnic

Shear in concrete slabs having concentrated loads close to supports In February, we published two letters from readers responding to a request from Mr R. N. Morgan (19 December 1989) for opinions on how to deal with this problem, he having found that the requirements contained in BS 8110 and BS 5400 could lead to significant differences in the resulting required depths of slabs. While our correspondents were able to contribute some information, they both concluded that much remained unknown. This it appears is also the opinion of Angus Low of Ove Arup & Partners. Mr Low finds in this an illustration of the necessity for more openness in our attitude to 'areas of ignorance' in the drawing up and interpretation of Codes: Mr Morgan asks about the 'black hole', otherwise known as BS 5400's treatment of shears due to wheel loads in deck slabs. This omission in the Code has been unfortunately masked by an excessively detailed treatment of punching shear. When remote from a support, shear can be considered to disperse from a wheel in four directions. When near a support almost all the shear will go direct to the support so the shear intensity will be about four times greater. Even allowing for the common haunching of deck slabs it is difficult to imagine a situation where punching shear is critical. Verulam

BS 5950: Part I appears to give no guidance regarding the effective lengths about the xx axis to be used in the design of columns in portal frames. This paper attempts to throw some light on why the information that engineers seek may have been omitted and to offer some guidance regarding the correct way to design portal frames for inplane stability. Some deficiencies in clause 5.5.3.2 of BS 5950: Part I are revealed, and the paper concludes with a proposal for a revision of this clause. Professor J.M. Davies

The approach to the design of timber joints adopted in the draft Eurocode 5 differs radically from that used in the current British Code, BS 5268. This paper outlines the theoretical basis of the Eurocode approach and makes comparisons with BS 5268. It then suggests a modified approach for future Codes. L.R.J. Whale