ARTIFICIAL STONE, OR CONCRETE 



These practical demonstrations of the resistance of 

 concrete to shock only served to confirm the experi- 

 ments of engineers made on a small scale but along 

 similar lines. One of these experiments, undertaken 

 by some French railway engineers, was made by drop- 

 ping weights from a given height upon reinforced- 

 concrete floors, and comparing the vibrations produced 

 with the effects upon floors made of iron and brick. 

 The floors in each instance were built with the same 

 bearing, and calculated to sustain the same load. 

 When a weight of one hundred and twelve pounds 

 was dropped from a height of six and one-half feet 

 upon the brick floor, vibrations of five-sixteenths of 

 an inch amplitude, lasting two seconds, were produced. 

 But a weight twice as heavy, falling twice the distance 

 upon the concrete floor, caused vibrations of only 

 one-sixteenth of an inch amplitude, lasting only five- 

 sevenths of a second. This shows conclusively that 

 for resisting the shocks of locomotives passing over 

 bridges, or the pounding of projectiles in warfare, 

 reinforced concrete is superior to masonry. In prac- 

 tice it is rapidly replacing it. 



In view of the fact that concrete is so relatively 

 brittle a material it was thought for a time that rein- 

 forced-concrete buildings, and structures subjected 

 to severe strains, might collapse suddenly when over- 

 loaded, without giving any warning such as is given 

 by steel-frame buildings. Exhaustive experiments 

 have proved, however, that such is not the case; that 

 there is bending and sagging in reinforced-concrete 

 bars before the final breaking. A beam calculated to 



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