PROBLEMS IN DESIGN OF BEAMS 87 



the bending moment in foot pounds must be multiplied by 8 and 

 the tables on pages 164 to 167 consulted. The size of beam is 

 given in Col. 12 on page 167 and we find that a 12-in. I-beam, 

 weighing 31.5 Ibs. per lin. ft., will be required. On the pages 

 mentioned is a column containing distances center to center of 

 beams required to make the radii of gyration equal; a very useful 

 table to use when designing columns. 



In this book the student should read carefully pages 144 to 

 163 inclusive. 



Jones & Laughlin, "Standard Steel Construction" (1916 

 edition : This book does not contain a table of bending moments 

 for I-beams, neither does it contain a table of factors, C. or F. 

 Our problem is solved as follows; Since the moment divided by 

 the fiber stress equals the Section Modulus, divide the bending 

 moment in foot pounds by the fiber stress, 16,000 Ibs., and this 

 gives the section modulus in feet. Multiply by 12 to obtain 

 the section modulus in inches. Look up this value on pages 

 105-106. Proceeding in this fashion we get (46,680 -h 16,000) 

 X 12 = 35 in. - S. On page 106 the nearest value is 36, cor- 

 responding to a 12-in. I-beam weighing 31.5 Ibs. per lineal foot. 



The student should now become familiar with pages 95 to 175 

 inclusive, and with page 243 in this book. 



Bethlehem (1911 edition): On page 38 a 9-in. girder-beam 

 weighing 38 Ibs. per lin. ft. has a resisting moment of 50,630 Ibs. 

 On page 39 a 12-in. Bethlehem I-beam weighing 28.5 Ibs. per lin. ft. 

 has a resisting moment of 48,050 ft. Ibs. 



To understand why the Bethlehem beams are stronger than 

 standard I-beams of equal depth, read pages 3 to 9 inclusive. Then 

 study pages 30, 31, 56, 66, 68, 99 to 103 inclusive. 



In studying the pages mentioned the student should work 

 examples in order to become familiar with the use of the tables. 

 The tables of deflection factors should be thoroughly understood, 

 which is not a difficult matter if the remarks on deflection in this 

 chapter have been given proper attention. 



After thoroughly mastering the subject matter on the pages 

 enumerated the student should study pages 283 to 292 inclusive 

 in Carnegie ; 56 to 71 inclusive in Cambria ; 104 to 107 in Beth- 

 lehem. The pages mentioned in each book cover the same sub- 

 jects, so it is not necessary to use the throe books, one giving all 

 that is necessary. Should the student, however, possess the three 



