Pounds per 

 square inch. 



Bottom flanges of plate girders ( 46), For For 



chords and webs of lattice and pin- livelo ^s. dead loads. 



connected trusses IO ' OO 2 > oo 



Verticals carrying floor beams ( 10). . . . 8,000 16,000 



For swing bridges and other movable structures, the dead 

 load unit strains, during motion, must not exceed three- 

 fourths of the above allowed unit strains for dead load on 

 stationary structures. 



The areas obtained by dividing the live load strains by 

 the live load unit strains will be added algebraically to the 

 areas obtained by dividing the dead load strains by the 

 dead load unit strains to determine the required sectional 

 area of any member. ( 50.) 



LOW Steel. 32. Low Steel ( 144) may be used in tension with unit 

 strains ten per cent, less than those allowed for Medium 

 Steel ( 138), except for eye-bars ( 125). 



33. When but one leg of a single angle is riveted to its 

 connection the section of that leg only will be considered 

 as effective in tension. 



N section. 34. In members subject to tensile strains full allowance 

 shall be made for reduction of section by rivet-holes, screw- 

 threads, etc. ( 63, 64). 



compressive 35. Compression members shall be proportioned by the 

 following allowed unit strains : 



For Medium Steel. 

 Chord segments P= 10,000 45 for live load. 



Medium steei. / ? =2O,ooo 90 for dead load. 



All posts of i 



through P== 8,500 45 for live load, 

 bridges. 



P=i 7,000 QOyfor dead load. 



