Interview. Taking the Lead

Dr S. B. Desai (F) (Department of the Environment, Transport & the Regions) You state, under eqn (8) of the paper, that the core will remain uncracked if the principal shear stress voldV does not exceed fct/3, where fct is the concrete tensile strength given by fct= 0.3(f'c)2/3. This implies that the shear strength is related to (fc)2/3. Although this relationship may agree with that given in EC 2, it tends to give unsafe results for higher values off,. BS 8110 relates concrete shear strength to the cube root of compressive strength, which is more realistic.

Mr A. N. Beal (M) (Thomason Partnership) This paper adds valuable experimental results to the database of concrete column tests, particularly for very high strength concrete. However, there is an unfortunate, misleading statement in the synopsis: 'These tests ... have indicated that the Codes are safe design documents for concrete strengths as high as 96N/mm²'. In fact, the tests reported in the paper covered only short-term loading and the 'conclusions' state that 'BS 8110 might not be conservative enough for long-term loading...'. Outside of the laboratory, very few concrete columns are subjected to only short-term loading: indeed, most real concrete columns are subjected to high proportions of long-term load, so this is a point of fundamental importance.

Settlement cracks and cavity wall insulation Andrew Shaw, from Wakefield, W Yorks., writes: My practice investigates inter alia building movement, frequently subsidence-related. I wonder whether the pages of Verulam can be used to air a matter that somewhat perplexes me?