274 



STRENGTH OF MATERIALS 



strength of 23,116 Ib./iii. 2 , a modulus of elasticity ranging from 

 31,500 lb./in. 2 to 1,800,000 lb./in. 2 , and a shearing strength ranging 

 from 1735 lb./in. 2 to 2518 lb./in. 2 . The average of thirty tests on 

 sandstone gave an ultimate strength of 4109 lb./in. 2 , and a modulus 

 of elasticity ranging from 32,000 Ib./iii. 2 to 400,000 lb./in. 2 . 



From a series of tests on building stone from outside the state of 

 Wisconsin, the same report gives the ultimate strength of limestone 

 as ranging from 3000 lb./in. 2 to 27,400 lb./iu. 2 , and the ultimate 

 strength of sandstone from 2400 lb./in. 2 to 20,000 lb./in. 2 . This 

 report also gives tables showing the effect of freezing and tli awing 

 on the strength of stone, the effect of sulphuric acid on limestone, 

 and the effect of high temperatures on building stum 1 . 



The following table shows the results of a series of compressive 

 tests made upon limestone at the Watertown Arsjnal.* 



From another series of tests made at tin- Wain-town Arsenal on 

 a different grade of limestone, the average value of the ultimate 

 strength was found to be 7647 lb./in. 2 , and the modulus of \ 

 to be 3,200,000 !b./in. 2 .t 



This wide range in the strength of building stone is explained by 

 the method of its formation, which makes the character of the 

 from one locality often differ entirely from that of a neighboring 

 locality. Average values of the strength of building stone are 

 fore of little value, and must be used with a largo factor of sal 



Problem 183. A granite block was tested in compression, the load at first crack 

 and at maximum being 203,000 Ib. and 417,400 Ib. respectively. The sectional aiva 

 was 10.4 in. 2 . Find the intensity of stress at first crack and at iu:ixi:mi:ii. 



< : Watertown Arsenal Report, 1900. 



t Watertown Arsenal Rppor 



