FO UN DA TIONS. 237 



2502 X 12 



- .9 tons per sq. ft., 

 32572 



while 



W 



A'-~-^ 

 or a total of 4.8 tons per sq. ft. of bearing. 



If, after suitable tests, the soil was considered capable of 

 sustaining this load, the foundations could be carried verti- 

 cally, and directly under the structure without any "spread," 

 and in such a case only a sufficiency of masonry need be pro- 

 vided to secure a proper anchorage, and intended simply to 

 resist the overturning moment, without increasing the bear- 

 ing-area. In such a case, the stability of the structure having 

 been determined by the principle of moments, as has been 

 explained, and a sufficient number of rods provided to pre- 

 vent the overturning of the structure, the holding-down 

 power of these rods must be secured by designing for each 

 rod a "washer" or bearing-surface, upon which a sufficient 

 load could be imposed in the shape of masonry as to resist 

 the effects of the horizontal action of the wind tending to 

 overturn the structure at its toe. 



Now this overturning moment has been found to be 

 approximately 2592 ft. -tons, while the resisting moment, 

 being 80 tons of material, multiplied by its leverage, 12 ft., 

 is 960 ft. -tors, leaving an excess overturning moment of 

 1632 ft. -tons which must be resisted by designing some form 

 of anchorage. 



The load which the anchorage is required to resist is 

 found by dividing the excess, 1632 ft. -tons, by the leverage 

 of the anchorage, in this case say 12 ft. ; hence the com- 

 bined strength of the anchorage to prevent overturning is 

 136 tons, and the strength required of each rod is found by 

 dividing this product by the number of rods. 



