CAMBRIA STEEL. 105 



From the Table of Safe Loads, page 111, it is found that this will 

 require two 15-inch standard I-Beams, each weighing 60 pounds 

 per foot. 



On account of the advisability of spacing the floor beams equally, 

 the arrangement outlined above would reduce their distances to 



22 



-7- = 5.5 feet center to center, so that 10-inch I-Beams, weighing 



40 pounds per foot, might be used for the body of the floor, as may 

 be determined by referring to the Table of Spacings of Cambria 

 I-Beams, page 127, and calculating as before, with the result that 

 the allowable spacing for these conditions is found to be 5.7 feet. 

 The 10-inch 40-pound beam under these conditions, will, how- 

 ever, deflect almost to the allowable limit for plastered ceilings, 

 besides, they are heavier than the 12-inch 31.5-pound beams 

 first considered, so that the latter will be the stiffer and more 

 economical. 



Although the load on the girder is not uniformly distributed, 

 but concentrated at three points between the supports, the bend- 

 ing moment in this case will be the same as if the load were figured 

 to be distributed uniformly, and for similar cases with different 

 spacings the moments would be very nearly identical. 



TABLES OF MAXIMUM BENDING MOMENTS. 



The Tables of Maximum Bending Moments for beams and 

 channels given on pages 136 and 137 are useful in determining the 

 proper section required to support one or more irregularly located 

 concentrated loads or various arrangements of loads to which the 

 tables of safe loads uniformly distributed will not apply. 



The method used consists in computing the maximum bending 

 moment in foot pounds resulting from the specified loading, the 

 proper section corresponding to a fibre stress of 16 000 or 12 500 

 Ibs. per square inch, being taken directly from the tables without 

 further computation. 



