788 EXPERIMENT STATION RECORD. [Vol.36 



capacity and that a name be adopted for each of the sizes. It is further rec- 

 ommended that the gross carrying capacity of the wagon be shown by stencil 

 or plate on the back of the rear axle." 



Tests of large reinforced concrete slabs, A. T. Goldkeck and B. B. SiiiTH 

 (Proc. Amer. Concrete Inst., 12 {1916), pp. S2Jt-334, figs. 7).— Tests of three 

 reinforced concrete slabs to determine the distribution of stresses and the 

 effective widths are reported. Each of the three slabs was made of 1:2:4 

 gravel concrete, machine mixed, and was reinforced witli 0.75 per cent of plain 

 square steel bars with no transverse reinforcing. The slabs were 32 ft. wide, 

 of 16 ft. clear span, with a 10 in. bearing width on each support. Test* were 

 begun at the age of abeut 28 days and were continued periodically until the 

 time of breaking. One slab was broken at the age of about six months ; a 

 second at about five months ; and a third at three months. The deformation 

 values for each slab and for the different load values are shown graphically. 

 Each curve is plotted from the deformation values measured perpendicular to 

 the supports and spaced along the center line parallel to the supports. 



The general shape of the curves for all loads is the same for the concrete 

 and the steel. One of the important facts brought out is that the time element 

 is a very large and important factor in determining stress values and their 

 distribution from the fiber deformations. " Concrete exhibits a marked fl»w 

 or molecular adjustment under working stresses extending over time periods 

 of several weeks." 



From a series of experiments on the flow of concrete it is pointed out that 

 " when concrete is subjected to a compressive fiber stress of 700 lbs. the immediate 

 fiber deformation is only about 50 per cent of what it will be if the stress is 

 maintained for three weeks. Within 24 hours after the application of the 

 load the deformation has increased an additional 20 per cent ; during the first 

 hour the deformation may show a change of 5 per cent or more. Furthermore 

 the recovery of the deformations, after the removal of the load, is slow and 

 not complete. 



"All tests for stress and deformation values in concrete must be conducted 

 only with a full realization of the importance of the time factor. The immedi- 

 ate fiber deformation is the value which should be used, and not the value 

 obtained after a long-time suspension of the load, nor that wliich contains the 

 effect of several applications and removals of loads." 



From the data on effective width obtained when considering thickness and 

 load and its distribution it is noted that " there is a general tendency for the 

 effective width to increase slightly with the increase of load. Also the effective 

 width seems to vary inversely as the thickness of the slab. In the light of the 

 information available at the present time we should be safe in using a value 

 for the effective width equal to 0.7 of the span. This will probably result in the 

 design of a somewhat thinner slab than is usual ; but the fiber stress values 

 and the large ultimate breaking loads of these slabs are an indication of the 

 safety of such designs." 



A milk house for Texas, L. Rhodes {Texas Sta. Circ. 15 [1916), pp. 5-7, figs. 

 4). — This circular describes and illustrates with plans a milk house to be built 

 near the dairy barn and sufficient in size to provide room for handling the milk 

 from 20 or more cows. 



Principles of poultry house consti-uction, M. C. Kilpatkick {Agr. Col. Ext. 

 Bui. [Ohio State Univ.], 12 {1916-11), No. 2, pp. 32, figs. 37).— It is the pur- 

 pose of this bulletin to discuss briefly the fundamental principles which should 

 be considered in the housing of poultry, and to present a number of plans of 

 poultry houses for various purposes which are well adapted to Ohio condi- 

 tions. 



