STEEL OFFICE BUILDINGS. 



CHAP. II. 



buildings of four to six stories, but may be used for buildings of twelve to fifteen stories where the 

 supporting power of the soil is considerable as in Denver. With high buildings the footings 

 become so large as to be very expensive and also encroach upon the basement area. 



Timber grillage and timber piles must be kept permanently wet or the life of the foundation 

 will be very short. Many of the early tall buildings in Chicago were carried on timber grillages 

 and on timber piles, but the settlement of the structures was so great that the method was aban- 

 doned for the method of concrete wells. 



Steel grillage foundations have been much used for high buildings. With steel grillage the 

 foundations may be made very shallow so that the basement is not encroached upon. 



Bracket B 9 



Bracket 85 



Bracket B 20 



FIG. 21. DETAILS OF WIND BRACING IN UNITED FIRE COMPANY'S BUILDING. 

 (Eng. Record, Dec. 9, 1911.) 



In cities like Chicago and New York where real estate is so valuable that basements are 

 often made three or four stories in depth, and where nearby disturbances due to excavations and 

 tunneling would cause settlement it has been found necessary to carry the foundations to rock 

 by means of wells or pneumatic caissons. In Chicago the wells commonly vary from 5 ft. to 

 12 ft. in diameter and are sunk in the open and are lined with timber curbing. After bed rock is 

 reached the well is filled with concrete. 



For a description of the sinking of the foundations for buildings in New York City, see a paper 

 entitled "Foundations for the New Singer Building, New York City" by Mr. T. Kennard Thom- 

 son, Consulting Engineer, in Trans. Am. Soc. C. E., Vol. 63, June, 1909. 



SPACING OF COLUMNS. The spacing of columns in steel frame buildings varies from 

 about II ft. to 24 ft., depending upon the height of the building, the floor loads, the type of floor 



