A study of the economic design of short span girder type concrete-steel highway bridges

The general principles underlying the design of concrete-steel structures are quite well known. Concrete itself is a structural material which is sightly, permanent, very strong in compression, thoroughly reliable when made honestly, almost fool-proof when once allowed to set properly, adaptable to an almost unlimited number of uses, practically fire-proof as well as water-proof, and in addition its cost is always very reasonable. The great objection to concrete is its lack of tensile strength, and likewise its lack of elasticity and toughness. Thus it is a fortunate circumstance that which is one of the least expensive of metals, and which possesses to a marked degree those qualities which plain concrete lacks, also has a coefficient of expansion which is almost identical with that of concrete. Thus steel may be imbedded sic in concrete in the proper place, manner, and amount, and the resulting combination call concrete-steel possesses the good qualities of both of the above mentioned materials, the steel supplying the tensile strength, while the concrete supplied the compressive strength --page 1 -2