CAMBBIA STEEL. 



EXAMPLE III, 



What is the safe load uniformly distributed that can be placed 

 on an 8-inch, standard channel weighing 11.25 pounds per foot, 

 with a clear span of 15 feet for a maximum fibre stress of 12 500 

 pounds per square inch, the web to be placed vertically? 



From the table of Properties of Standard Channels, page 187, 

 column 16, the coefficient of strength F' for the given channel 

 under the conditions named, is found to be 67 300. Hence, the 

 total load may be 67 300 -r- 15 = 4487 pounds, and, as the channel 

 itself weighs 169 pounds, the net superimposed load which is can 

 safely carry under the given conditions is 4318 pounds. 



EXAMPLE IV. 



What is the fibre stress in a 5" x 3" angle weighing 8.2 pounds 

 per foot if loaded at the center with a weight of 1500 pounds, used 

 as a beam with a span of 6 feet, the 5-inch leg to be placed verti- 

 cally? 



The bending moment at the center will be 

 Wa + WJ _ 1500^X72 + 8.2X6X72 _ ^ ^ .^ ^^ 



Referring to the Table of Properties of Standard Angles, 

 Unequal Legs, on page 207, the Section Modulus for this angle, 

 corresponding to the axis 2 2, is found to be 1.89. 



The maximum fibre stress is obtained by dividing the bending 



moment by the section modulus, thus: = 14 520, which is 



the maximum fibre stress in pounds per square inch at the point 

 most remote from the neutral axis, which in this case is the 

 extremity of the longer leg of the angle. 



The second term in the above expression for the bending 

 moment is that due to the weight of the angle itself and is incon- 

 siderable, so that in practice it might be neglected for short spans, 

 but should be taken into consideration for the longer ones. 



