SPECIFICATIONS. 103 



Birders and floorbeams. A typical floor plan of the tower is shown in Fig. 22. The columns are 

 in. uli- of two channels, reinforced with plates where necessary. Details of a typical column are 

 shown in Fig. 27. The wind bracing of the steel frame is shown in Fie. 24. A plan of the wind 

 bracii;;; in the tower is shown in Fig. 25. The panels that have heavy full lines were wind braced 

 to the 33d story on the exterior and to the 36th story on the interior. Heavy dotted lines indi- 

 cate wind bracing to the I4th story. Fine lines indicate no diagonal bracing. Circles on diagonal 

 intersections represent anchor bolts. In designing the bracing the loads were distributed as 

 follows: It will be noticed that in a north and south direction there are 1 1 lines of wind bracing 

 in the tower, nearly symmetrically placed. It was therefore assumed that on each story eacn 

 line of X-bracing took -fa of the total wind pressure of 30 Ib. per sq. ft. The loads on the bracing 

 in an cast and west direction were distributed in a similar manner. The details of the X-bracing 

 -re shown in Fig. 26. Each of the 12 ft. square towers was assumed to act independently and 

 me uplift of the columns was provided for. 



SPECIFICATIONS FOR STEEL OFFICE BUILDINGS. 



BY 



MILO S. KETCHUM, 

 M. Am. Soc. C. E. 



1914. 



I. Design. In all steel frame or skeleton buildings the stresses due to external and internal 

 s and wind stresses shall be transmitted to the foundation by the steel framework, no reliance 

 ing placed on the strength of the walls and partitions. Beams and girders shall have riveted 

 connections to the steel columns. All columns shall be of structural steel with their different 



rs riveted together and shall be riveted to the beams and girders connecting to them. 

 2. LOADS. The structure shall be designed to carry the following loads. 

 3. Dead Loads. The dead load shall consist of the weight of all permanent construction 

 and fixtures, such as walls, roofs, interior partitions, and fixed or permanent appliances. The 

 weights of different materials shall be assumed as given in Table I. The minimum weight of 

 fireproof floors to be assumed in designing the floor system shall be 75 Ib. per sq. ft. The actual 

 weight of floors shall be used in designing columns. The minimum weight of movable partitions 

 11 be taken as 10 Ib. per sq. ft. 



4. Live Loads. The live load shall consist of movable loads and loads due to machinery 

 other appliances. 



The live loads required by Schneider's specifications and given in Table IV shall be used 

 for the different classes of buildings. The maximum stresses due to any one of the three systems 

 of loads shall be used in the design. Floor slabs for office buildings may be designed for a uniform 

 load equal to twice the distributed load given in the second column of Table IV, and the effect 

 of the concentrated load may be neglected. The concentrated load and load per linear foot of 

 girder shall be considered in the design of all beams and girders. Flat roofs of office buildings, 

 hotels, etc. that can be loaded by crowds of people shall be designed as the floors. 



5. Impact. For structures carrying traveling machinery such as cranes or conveyors, or 

 machinery such as printing presses, 25 per cent shall be added to the stresses resulting from live 

 load to provide for impact and vibrations. 



6. Snow Loads. The snow loads on roofs shall be taken the same as for steel frame mill 

 buildings, Fig. I, Chapter I. 



7. Wind Loads. All structures shall be designed to resist the horizontal wind pressure on 

 the surface exposed above surrounding buildings as follows. 



a. The wind pressure on roofs shall be taken as the normal component, calculated by Duchem- 

 in's formula, Fig. 3, Chapter I, of 30 Ib. per square foot on the vertical projection of the roof. 



b. The wind pressure on the sides and ends of buildings except as otherwise provided in the 

 following paragraph shall be assumed as 20 Ib. per square foot acting in any direction horizontally. 



c. In designing the steel or reinforced concrete framework of fireproof buildings the frame- 

 work shall be designed to resist a wind pressure of 30 Ib. per square foot acting on the total exposed 

 surface of all parts composing the framework or a horizontal wind pressure of 20 Ib. per square 

 foot acting in any direction horizontally on the sides and ends of the completed building. The 

 strerfgth of reinforced concrete floors may be considered in calculating the strength of the frame- 

 work in the completed structure. The framework before the structure has been completed shall 



