CHAPTER III 

 CONCRETE AND STEEL IN COMBINATION 



23. Advantages of the Combination. The highest success in 

 the use of concrete and steel in combination is attained only 

 when maximum strength is secured at minimum cost. This is 

 accomplished when the steel and concrete are placed in such a 

 manner as to derive their greatest strength, and when economical 

 proportions of these materials are employed. 



Steel can be put into a form to resist a given tensile stress much 

 more cheaply than it can be put into a form to resist a cor- 

 responding compressive stress. This should be clear, when it is 

 considered that the solid bar is well adapted to take tensile 

 stresses, while for compressive stresses the steel must be made 

 into forms of more extended cross-section, in order to provide 

 the necessary lateral rigidity. There is a serious objection to 

 the use of steel in many locations due to its lack of durability 

 and its failure to stand up under a high heat. Steel is also a 

 relatively expensive building material. 



Concrete, on the other hand, cannot be used in tension except 

 to a very limited extent, but its compressive strength is fairly 

 high. It is also a good fireproof material and has great durabil- 

 ity. In addition, concrete is a comparatively cheap material; 

 is readily available in almost any locality, and tests and the 

 results of observations show that it thoroughly protects em- 

 bedded steel from corrosion. 



From the above considerations, it follows that reinforced 

 concrete construction is advantageous to varying degrees in 

 different types of structures. In structural forms subjected to 

 both tension and compression, such as beams, the proper com- 

 bination of the two materials meets with the best success. 

 Steel rods embedded in the lower side of the beam carry the 

 tensile stresses while the compressive stresses are carried by the 

 concrete. Here, then, the steel is used in its cheapest form and 

 the whole structure may be made strong, economical, and very 

 durable. For columns, also, a combination of the two materials 

 is quite advantageous although to a varying degree and, in any 

 case, not to such a large extent as in beams. In this type of 



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