FOUNDATIONS AND EETAINING WALLS 



203 



mil 



CONCRETE 



162. Column footings. In the modern construction of tall build- 

 ings the design frequently provides that the entire weight of the 

 building and its contents shall be carried by a steel framework of 

 columns and 

 girders. This 

 "skeleton type" 

 of tall-building 

 construction, as 

 it is called, ne- 

 cessitates a new 

 type of founda- 

 tion, since each 

 column load 

 must be calcu- 

 lated separately 

 a n<l transmitted 

 t the soil by a 

 footing of suffi- 

 cient size to 

 give the neces- 

 sary amount of 

 ing area. 



If the col- 

 u in us reach 

 solid rock, the 

 footing may 

 1st simply 

 ise plate of 

 such form as to 

 give the column 

 a solid bear- 

 ing and afford 

 sufficient anchorage to prevent the footing from lateral movement. 



For compressible soils the column is usually supported by a cast- 

 iron base plate resting on a footing consisting of two or more layers 

 of steel rails or I-beams, the whole resting on a concrete base, as 

 shown in Fig. 141. 



o 



FIG. 141 



