CAMBRIA STEEL. 



based upon the Least Radius of Gyration, are given on pages 268 to 

 271 , and data relating to the proper sizes of lattice bars and stay-plates 

 to be used with these columns are given on pages 272 and 273. 



On pages 232 and 233 are given the Principal Dimensions of Plate 

 and Channel Columns with comparatively narrow plates called^ for 

 convenience of reference, Series A, and on pages 234 and 235 for 

 Series B, which differs from Series A, in having wider plates. Mo- 

 ments of Inertia and Section Moduli about two rectangular axes 

 are given for Series A and B on pages 236 to 242 inclusive, and the 

 Safe Loads for different lengths, based upon the Least Radius of 

 Gyration, are given on pages 274 to 301 inclusive. 



Safe Loads for I-Beams used as Columns or Struts are given on 

 pages 244 to 247 , and the dimensions of these sections can be obtained 

 from the tables on pages 186 to 189 inclusive. 



The Plate and Channel Columns given in Series A are particularly 

 useful in buildings or locations in which it is desired to keep the ex- 

 treme dimensions of the cross section as small as possible for this style 

 of column, although in this series the Radius of Gyration about the 

 central axis parallel to the channel webs is somewhat smaller than the 

 Radius of Gyration about the axis perpendicular to the channel webs. 

 This makes the narrower columns of Series A somewhat less economi- 

 cal of material than the wider columns of Series B , which, however, is 

 small in amount for columns of ordinary story length of 10 feet to 14 

 feet, such as are used in skeleton buildings. 



In Series B of Plate and Channel Columns with wider plates, the 

 Radii of Gyration about the two axes are practically equal for the 

 intermediate thicknesses and these columns are slightly more eco- 

 nomical of material than those of Series A, although they require 

 somewhat more space on account of their wider sections. 



The Safe Loads for columns of various kinds, as given on pages 244 

 to 301 inclusive, are expressed in thousands of pounds, and have been 

 figured by the use of Gordon's formula, as stated at the heads of the 

 various tables, using the safety factor 4, which relates to static or 

 quiescent loads such as occur in ordinary buildings. 



On page 229 is given a table showing the Distances Back to Back for 

 Spacing Two Channels of the same size in order to produce equal Mo- 

 ments of Inertia about the two rectangular axes. This table will be 

 found to be useful in designing compression members of trusses, etc. 



The Safe Loads of the tables are assumed to be centrally applied, 

 and for convenience in computing the proper sizes required to support 

 eccentric loads the tables of Moments of Inertia and Section Moduli 

 for the different sections of columns are given. 



The Safe Loads in the various tables are figured for extreme ratios 

 from 30 to 150 for , in which 1 is the length of the column and r the 



Least Radius of Gyration, both expressed in inches. 



The weights of columns stated in the tables are per lineal foot of 

 shaft, and do not include any allowances for bases, brackets or other 

 connections, as these depend upon the particular details and require- 

 ments of each case. 



Loads for other safety factors can be figured from the tables by 

 inverse proportion, thus: 



New safety factor : 4 :: load from tables : new loads. 



Drawings of typical details of steel columns are given on page 243. 



