256 PRACTICAL STRUCTURAL DESIGN 



uncertainty often exists in the minds of draftsmen as to the 

 amount of eccentricity. The author assumes that the load from 

 the beam is delivered to the column in a uniformly varying amount 

 from the face of the column to the vertical axis. The vertical 

 load acting through the center of gravity makes the moment 

 arm for each beam equal to one^third the width, measured from 

 the center of the column, that is, two-thirds of half the width. 

 Multiply each load by this arm, add the products, and divide by 

 the sum of the loads, which will give the eccentricity measured 

 from the center of the column. 



When columns are connected by girders then the deflection in 

 the frame will vary with the relative rigidities of the connected 

 members and this will fix the stresses at the connections. 



Wind Bracing for Columns and Frames 



In the handbook of the Passaic Rolling Mill Co., a number of 

 years ago the whole subject of wind bracing in buildings was dis- 

 posed of with the presentation of 



H f j*"M j*- b -H Fig. 166 and Fig. 167. In the 



| "Bethlehem Handbook" (1908) of 



r 



_i which only the one edition, now 

 out of print, was issued the same 

 figures and formulas were given. 

 In the following formulas col- 

 umns are considered as fixed at 

 both ends. If columns are not 

 fixed at the ends substitute 2h for 

 h, everywhere in the formulas. All 

 Fig. 166 Case I of Portal Framing members are constructed to resist 



tension (-) and compression (+). 

 H = total horizontal force at top of frame. 



Stress in the knee braces = H I -= + j- W- 



Stress in the columns = H f a + 

 Stress in the girder = = H (l + )- 



Mb on the columns = H + -r 



fl b\ f h\ 

 M b on the girder = # ( - - -^ ) ( a + ^ ) 



