CHAPTER VII 

 Columns and Structures 



A PIER is made of brick, stone, or concrete. That is, it is a 

 masonry post and because it is not safe to permit any bending 

 stress it must be limited in height. A concrete pier rein- 

 forced with steel may develop into a slender column. 



The Chicago Building Ordinance provides that no masonry 

 pier can have a height exceeding 12 times the least thickness. 

 When the height is less than 6 times the least thickness the allow- 

 able unit compressive stress is that fixed in the ordinance. When 

 the height exceeds 6 times the least thickness the fiber stress must 

 be reduced by the following formula: 



( L25 - 



in which / = reduced unit compressive stress; 



c = unit compressive stress mentioned in the ordinance; 

 H = height in feet; 

 D = least width, or thickness, in feet. 



The distinction between posts and columns is seldom definitely 

 drawn. It may be said that a post is solid and short. A column 

 is long and may be hollow or of some shape other than round or 

 rectangular. 



Specifications vary with the ideas of the men who write them 

 and great differences exist between specifications and building 

 onli nances the country over. The statements made in this sec- 

 tion are therefore not to be taken as meeting the requirements 

 of the leading designers but are presented merely as examples 

 of how such things are regulated in some places. 



In Chicago the maximum length of timber posts cannot exceed 

 30 diameters, or 30 times the least thickness. Hereafter when 

 diameter is mentioned in connection with columns and posts 

 it is understood to mean also the least thickness, if the column 

 is rectangular and not round. Timl>er posts, or columns, can- 

 not be used in buildings over one hundred feet in height, nor in 



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