SPECIFICATIONS 



When combined direct and flexural stress due to wind 

 is considered add 25 per cent to the above allowable ten- 

 sile and compressive stresses. 



34. Soft steel may be used in mill buildings with unit 

 stresses ten per cent less than those allowed for medium steel. 



35. Where the stress due to the weight of the member or 

 due to an eccentric load exceeds the allowable stress for direct 

 loads by more than ten per cent, the section shall be increased 

 until the total stress does not exceed the above allowable stress 

 for direct loads by more than ten per cent. 



The eccentric stress caused by connecting angles by one 

 leg when used as ties or struts shall be calculated, or only one 

 leg will be considered effective. 



36. Rivets shall be so spaced that the shearing stress shall 

 not exceed 11,000 pounds per square inch; nor the pressure on 

 the bearing surface (diameter x thickness of piece) of the 

 rivet hole exceed 22,000 pounds per square inch. 



Rivets in lateral connections may have stresses 25 per 

 cent in excess of the above. 



Field rivets shall be spaced for stresses two-thirds those 

 allowed for shop rivets. 



Field bolts, when allowed, shall be spaced for stresses 

 two-thirds those allowed for field rivets. 



Rivets and bolts must not be used in direct tension. 



37. Pins shall be proportioned so that the shearing stress 

 shall not exceed 11,000 pounds per square inch; nor the pres- 

 sure on the bearing surface (diameter x thickness of piece) of 

 the pin hole exceed 22,000 pounds per square inch; nor the ex- 

 treme fibre stress due to cross bending exceed 24,000 pounds 

 per square inch when the applied forces are assumed as act- 

 ing at the center of the members. 



38. Rolled beams shall be proportioned by their moments 

 of inertia. 



39. Plate girders shall be proportioned on the assump- 

 tion that the flanges take all the bending moment, and that the 

 shear is resisted by the web. 



The distance between centers of gravity of the flange areas 

 shall be considered as the effective depth of all girders. 



40. The webs of plate girders shall be stiffened at bear- 

 ings and at all points of concentrated loading, and at inter- 



397 



Soft Steel. 



Stress due to 

 Weight of- Member. 



Rivets. 



Pins. 



Rolled Beams. 



Plate Girders. 



Stiffenera. 



