50 



W. H. WARREN. 



resistance was determined by pulling out specially prepared 

 bars of Bessemer steel | inch diameter, from prisms 12 

 inches long by 4 x 4 inches in cross-section, consisting of 

 one part of cement to three of builders' sand, and also of 

 one part of cement to two parts of sand and two of stone 

 broken to f inch gauge. 



The steel bars were prepared with parallel portions 6 

 inches long, abutting at the centre of the prism, and were 

 pulled out by means of a gradually applied load in the testing 

 machine. The results obtained are recorded in Table I., 

 A, B, and O. 



Table I.— ADHESIVE STEENGTH OF CONCEETE TO STEEL. 

 A. Bars with natural skin on. Hardened in air. 













Surface 











Composition— 





Age 



area of 



Total 



Adhesion 



Number 









in 



bars im- 



Load 



Pounds 





Cement 



. Builders' , -| Nepean 

 Sand • Shivers 



Water 

 per cent. 



Days 



bedded 

 sq. in. 



pounds 



per sq. in. 



I. 



1 



: 3 : - 



12 



45 



11-78 



2550 



216-5 



II. 



1 



. 3 : - 



12 



45 



11-78 



2600 



221-0 



III. 



1 



: 2 : 2 



10 



45 



11-78 



2175 



184-5 



IV. 



1 



: 2 : 2 



10 



45 



11-78 



2000 



170-0 



B. Bars cleaned with emery paper before embedding. Hardened in air. 



I. 



1 



3 



_ 



125 



45 



11-78 



1400 



118-0 



II. 



1 



3 



- 



12-5 



45 



11-78 



850 



720 



III. 



1 



2 



2 



10 



44 



11-78 



1820 



154-0 



IV. 



1 



2 



2 



10 



44 



11-78 



1825 



155-0 



C. Bars cleaned with emery paper before embedding. Hardened in water. 



I. 



1 



3 



- 



12 



45 



11-78 



1820 



154-0 



II. 



1 



3 



- 



12 



45 



11-78 



2255 



191-0 



III. 



1 



2 



2 



10 



45 



11' 78 



2410 



204-0 



IV. 



1 



2 



2 



10 



45 



11-78 



2250 



191-0 



b. The experimental determination of the neutral axis 

 in a plain and in a reinforced concrete beam, crtso 

 the curves of strain for loads increasing from zero 

 to the load producing fracture. 



In deriving the equations for determining the position of 

 the neutral axis and the moment of resistance of a trans- 

 verse section in a reinforced concrete beam, it has been 

 assumed by all authorities up to the present, that a trans- 



