214 



Journal of Agricultural Research 



Vol. VI, No. 6 



FiGUREC 6. — Two curves, A and B, are shown here to indicate the def- 

 ormations which resulted from the removal of the forms. The flow, or 

 increase in the deformations, is about 8o per cent in three days. The 

 curves C-D, K-F, G-H, I-J, and K-L show the large difference in the 

 deformation and effective width values between those obtained by the 

 use of a zero strain-gauge reading taken several weeks before, with sev- 

 eral intervening loadings, and those obtained from a zero reading taken 

 just before the loading. The data and results of curves C, E, G, I, and K 

 are the only ones of value. 



Fig. 5. — Concrete deformation curves for concentrated center load on slab 835. 



Figure; 7. — The difference between these curves shows the magnitude 

 of the set, or permanent deformation, which may occur between two 

 applications of the load, each loading having been applied immediately 

 after a zero reading of the strain-gauge points, with 24 hours intervening 

 between the loadings. The second application shows a smaller deforma- 

 tion than the first. This is true for both the concrete and the steel 

 deformations. The effective widths are based upon the first application 

 of the load. 



Figure 8. — These curves are shown to emphasize the importance of 

 considering the time factor and its effect upon the deformations in con- 

 crete structures. Curve i shows the immediate effect of the load. After 

 about 5 hours the load was removed, then again applied 20 hours later 



