2Ii 



Journal of Agricultural Research 



Vol. VI, No. 6 



The effective width is not materially affected for the 40,000-pound load; 

 but for the 80,000-pound load, which produces the working fiber stress, 

 the effective width is very largely increased. . 



Figures 10 and ii. — The curv^es on these figures show a more pro- 

 nounced local effect in the concrete at the load points than the same 

 character of loading on the thicker slab. It should be noted that for the 

 working load of 20,000 pounds the effective width for this 2-point loading 

 is the same as for the single-point center loading. 



Figures 12 and 13. — The results for 4-point loading under different 

 loads are shown in these cur^^es for slabs 835 and 934. The effective 



Fig. II. — Steel deformation curves for slab 934 with 2-point loading. 



width is materially affected by the width between the load points; it 

 seems to be increased by not less than 56 per cent of the span length for 

 slab 835, and 93 per cent for slab 934. 



Figures 14, 15, and 16. — The deflection data are shown on these 

 figures. The curves are plotted to show the deflection values along 

 a center strip parallel to the supports. In figure 14 cur%"es have been 

 plotted showing the flow^ and set in the slab under a sustained load and 

 as effected by two applications. Two values for effective widths are 

 shown, which have been obtained from the deflection curves in the 

 same manner as from the concrete deformation curves described above; 

 but these values should not be used in the design of slabs. 



