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Verulam

Slender Columns It is not often that we get letters from foreign parts, but we have this plea for help from Mr Peter Hoole with the United Nations in Vienna: Having come fairly recently to use CP 110, and being in a somewhat isolated position here in Vienna, there is one aspect of the Code relating to column design that bothers me and on which I can find no advice. Perhaps some expert reader could enlighten me. The question relates to section 3.5.7 Part I: 1972. For various reasons, many of the columns in the structures I am concerned with are only 200mm wide and consequently, while for upper floors the columns are usually SHORT by definition, the ground floor legs are often around the margin between SHORT/SLENDER. This would not previously have caused too much concern. However, the effect on the design moments of a move from a SR of 11.9 to 12.1 with CP 110 is very significant, commonly 100-200% increase for unbraced column moments and requiring a similar percentage increase in the reinforcement. This effect is brought about by consideration of clause 3.5.7.2 which requires that a secondary moment proportional to the square of the larger effective length (commonly the unbraced x-x) divided by the column width be considered. Verulam