DISCUSSION OF RESULTS. 



The arches were built in order to study their behavior under a total load of 54000 Ibs. or a unit 

 load of 1500 Ibs. per sq. ft. and all of the arches were in excellent condition under this test load. 

 At this load the deflection of the center of the slab below the center of the I-beams varied from 

 Jf in. for slab N to | in. for slabs Q and P. When this maximum load was allowed to remain for' 

 five days on slab O, which had the lightest reinforcement, the increase in deflection was only ? V^ n - 

 When the slabs were fully loaded tension cracks were seen in the concrete near their center lines 

 and above the I-beams at the haunches, these latter cracks being much smaller, but in none of the 

 arches were any of the cracks serious. 



After the full load of 1500 Ibs. per sq. ft. had been placed on slab P it was decided to continue 

 the loading to failure. Under a load of 2230 Ibs. per sq. ft. the slab failed but this was apparently 

 caused by the falling and consequent impact effect of the piles of pig iron which were about 

 12ft. high and quite unstable. The rate of increase in the deflection readings did not indicate 

 approaching failure nor did the fracture show an initial failure of the slab 



The maximum load carried by the slab indicated that considerable arch action was developed 

 and that the slabs should not be considered as fixed beams, for, assuming the slab to be a fixed 

 beam, the maximum computed stress in the steel for a load of 1500 Ibs. per sq. ft. was about three 

 times as great as the ultimate strength of the steel as determined in a tension test. It was also 

 observed that the ^ in. rods connecting the 12 in. I-beams which had little initial tension, were 

 under a heavy tensile stress when the slab carried its full load. <j 



The tension cracks in the concrete at the haunches were very fine and did not increase in 

 wiith as did the cracks at the center of the arch, thus indicating little tension in the arch above 

 the haunches. 



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