394 



SPECIFICATIONS 



Snow Loads. 



19. SNOW LOADS. Snow loads shall be taken from 

 the diagram in Fig. I. 



Wind Loads. 



Mine Buildings, 



Concentrated 

 Loads. 



Purlins. 



Roof Covering. 



Minimum Loads. 



fbrf&e/f/c 



Aria/ Reg/ons use one- 



/ce and s/eet for a// slopes 



F 



a. 



40 



50 5f 



I 



30 35 40 45 50 



Latitude in Degrees 



FlG. I. SNOW LOAD ON ROOFS FOR DIFFERENT LATITUDES, IN 

 LBS. PER SQUARE FOOT. 



20. WIND LOADS. The normal wind pressure on 

 trusses shall be computed by Duchemin's formula, Fig. 2, with 

 P 30 pounds per square foot, except for buildings in ex- 

 posed locations, where P = 40 pounds per square foot shall be 

 used. 



21. The sides and ends of buildings shall be computed 

 for a normal wind load of 20 pounds per square foot of ex- 

 posed surface for buildings 30 feet and less to the eaves; 30 

 pounds per square foot of exposed surface for buildings 60 feel 

 to the eaves, and in proportion for intermediate heights. 



22. Mine, smelter and other buildings exposed to the 

 action of corrosive gases shall have their dead loads increased 

 25 per cent. 



23. Concentrated loads and crane girders shall be con- 

 sidered in determining dead loads. 



24. Purlins shall be designed for a normal load of not less 

 than 30 Ibs. per square foot. 



25. Roof covering shall be designed for a normal load 

 of not less than 30 Ibs. per square foot. 



26. No roof shall, however, be designed for an equiva- 

 lent load of less than 30 pounds per square foot of horizontal 

 projection. 



