1864.] 



of Impact, S^c. on WroughUlron Girders, 



123 



The girder subjected to vibration in these experiments was a wrought-iron 

 plate beam of 20 feet clear span, and of the following dimensions : — 



Area of top 4*30 square inches. 



Area of bottom 2*40 „ 



Area of vertical web 1'90 „ 



Total sectional area 8*60 „ 



Depth 16 inches. 



"Weight 7 cwt. 3 qrs. 



Breaking-weight (calculated). . , 12 tons. 



The beam having been loaded with 6643 lbs., equivalent to one-fourth of 

 the ultimate breaking-weight, the experiments commenced as follows : — 



Experiment I. 



Experiment on a wrought-iron beam with a changing load equivalent to 

 one-fourth of the breaking-weight. 



Date. 



Number of 

 changes of 

 Load. 



Deflection 

 produced by 

 Load. 



Eemarks, 



i860. 







202,890 

 449,280 

 596,790 



0-I7 

 o'i7 

 o-i6 

 o*i6 



Strap loose on the 24th March. 

 Strap broken on the 20th April. 



The beam having undergone about half a million changes of load by 

 working continuously for two months night and day, at the rate of about 

 eight changes per minute, without producing any visible alteration, the load 

 was increased from one-fourth to two-sevenths of the statical breaking- 

 weight, and the experiments were proceeded with till the number of changes 

 of load reached a milhon. 



Experiment II. 



Experimeut on the same beam with a load equivalent to two-sevenths of the 

 breaking weight, or nearly 3g tons. 



Date. 



Number of 

 changes of 

 Load. 



Deflection, 

 in inches. 



Eemarks. 



i860. 







85,820 

 236,460 



403,210 



0'22 

 0-22 

 0"2I 



0*23 



In this experiment the number of 

 changes of load is counted from 0, 

 altliough the beam had already un- 

 dergone 596,790 changes, as sIioato 

 in the preceding Table. 



The beam had now suffered one mil- 

 lion changes of load. 



L 2 



