81 



diagrauimatic form in the Transactions of Tlie American Railway Engineer- 

 ing and Maintenance of Way Association, Vol. V, 1804, pages 620 and 027. 

 Empirical equations of simple form are presented in The Engineering Re- 

 view of I'nrdne I niversity. Vol. I. 1905. 



In calculating the strength of the reinforced concrete beam sufficiently 

 approximate results can be obtained by omitting consideration of the tensile 

 stresses in the concrete, and supposing a rectilinear relation between stress 

 and strain. The moment of flexure is then most simply expressed as the 

 total force in the steel multiplied by the distance to the centroid of the 

 compressive stresses. This latter distance is expressed with sufficient ac- 

 curacy as a fraction of the depth of the beam, this fraction having been 

 determined by experimental measurement on the tested beams. 



Care in all cases nnist be taken to compute the maximum compressive 

 stress arising in the concrete under the conditions of the problem, and also 

 the aiuount of diagonal terision at the ends of the beams must be computed 

 and provided for by stirrups, or by I tending up some of the rods at the ends. 



To conclude this brief consideration of reinforced concrete, a conserva- 

 tive estimate would include the following principles : 



1. Concrete is durable and fireproof when made of the proper aggre- 

 gate. 



2. The strength of combination of steel and concrete may be calcu- 

 lated with a sutliciently close degree of accuracy. 



3. Shapely and beautiful structures may be built of this material. 

 It is particularly adapted for mill buildings because of the absence of vibra- 

 tions which are induced in the ordinary type of mill buildings by the 

 rapidly revolving machinery. 



4. The cost of a properly designed I'einforced concrete building, where 

 wooden forms are used to advantage, need not exceed more than C) or 10 

 per cent, of the cost of mill Ituildings of the ordinary type with brick walls 

 and wooden beams of the so-called slow-burning construction, provided that 

 the concrete may be laid as at present by unskilled labor. 



6— A. OF Science. 



