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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 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