39 6 



SPECIFICATIONS 



Compressivt 

 Stress. 



Plate Girders. 



Alternate Stress. 

 Joinb<ne4 Stress. 



Shapes liable to sudden loading as when used 



for crane girders ...................... 10,000 



Expansion rollers per lineal inch ............ 600 X D 



where D = diameter of roller in inches. 



Laterals shall be designed for the maximum stresses due 



to 5,000 pounds initial tension and the maximum stress due 



to wind. 



29. Allowable Unit Compressive Stress for Medium Steel. 

 For direct dead, snow and wind loads 



= 16,000 70 - 



where 



5 = allowable unit stress in pounds per square inch; 

 / i= length of member in inches c. to c. of end con- 

 nections ; 

 r = least radius of gyration of the member in inches. 



30. Top flanges of plate girders shall have the same 

 gross area as the tension flanges. 



31. Shear in webs of plate girders shall not exceed 10,000 

 pounds per square inch. 



32. Members and connections subject to alternate stresses 

 shall be designed to take each kind of stress. 



33. Members subject to combined direct and bending 

 stresses shall be proportioned according to the following 

 formula : 



o .. P _ My, 



P/ 2 



where 



S = stress per square inch in extreme fibre; 

 P direct load; 

 A = area of member; 

 M = bending moment in inch-pounds; 

 y^ = distance from neutral axis to extreme fibre ; 



/ = moment of inertia of member ; . 



/ = length member, or distance from point of zero 



moment to end of member in inches ; 

 E = modulus of elasticity = 28,000,000. 



