74 



STEEL OFFICE BUILDINGS. 



CHAP. II. 



Minimum Roof Loads. Schneider's specifications contain the following: 



" In climates corresponding to that of New York, ordinary roofs, up to 80 ft. span, shall be 

 proportioned to carry the minimum loads in Table VI, per square foot of exposed surface, applied 

 vertically, to provide for dead, wind and snow loads combined: 



TABLE VI. 

 MINIMUM LOADS ON ROOFS. 



( On boards, flat slope, i to 6, or less 50 Ib. 



Gravel or Composition Roofing j On boards, steep slope, more than I to 6 45 



I On 3-in. flat tile or cinder concrete 60 



Corrugated sheeting, on boards or purlins 40 



ci t f On boards or purlins 50 



{ On 3-in. flat tile or cinder concrete .*. . 65 



Tile, on steel purlins 55 



Glass 45 



"For roofs in climates where no snow is likely to occur, reduce the foregoing loads by 10 Ib. 

 per sq. ft., but no roof or any part thereof shall be designed for less than 40 Ib. per sq. ft." 



LIVE LOADS ON COLUMNS. Schneider's specifications require that: 



"For columns, the specified uniform live loads per square foot, Table IV, shall be used, 

 with a minimum of 20,000 Ib. per column. 



"For columns carrying more than five floors, these live loads may be reduced as follows: 



"For columns supporting the roof and top floor, no reduction; 



"For columns supporting each succeeding floor, a reduction of 5 per cent of the total live 

 load may be made until 50 per cent is reached, which reduced load shall be used for the columns 

 supporting all remaining floors." 



The Chicago Building Ordinance (1911) requires that live loads on walls, columns and piers 

 be taken as follows: 



" (a) The full live load (see Table III) on roofs of all buildings shall be taken on walls, piers, 

 and columns. 



" (b) The walls, piers and columns of all buildings shall be designed to carry the full dead 

 loads and not less than the proportion of the live load given in Table VII. 



TABLE VII. 



PERCENTAGE OF LIVE LOAD FOR COLUMNS. 

 Chicago Building Ordinance (1911). 



Floor . . 



16. 

 IS- 

 H- 

 13- 



12. 

 II. 

 IO. 



9- 

 8. 



7- 

 6. 



5- 

 4- 

 3- 



2. 

 I. 



17 16 15 14 13 12 ii 



5 



85 per cent 



80 85 



75 80 85 



70 75 80 85 



65 70 75 80 85 



60 65 70 75 80 85 



55 60 65 70 75 80 85 



50 55 60 65 70 75 80 85 



50 50 55 60 65 70 75 80 85 



50 50 50 55 60 65 70 75 80 85 



50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 50 50 50 50 55 60 65 70 75 80 85 



50 50 50 50 50 50 50 50 50 50 55 60 65 70 75 80 85 



" (c) The proportion of the live load on walls, piers, and columns on buildings more than 

 seventeen stories in height shall be taken in same ratio as the above table. 



" (d) The entire dead load and the percentage of live load on basement columns, piers and 

 Walls shall be taken in determining the stress in foundations." 



