The reinforced concrete beam

Abstract

Although the geometry of the influence of the load on a beam is identical irrespective of material there is a fundamental difference in the way that a reinforced concrete beam produces the resistance moment. Within very small limits, a plain concrete beam would behave like any other elastic material. Long before the maximum compressive stress in the concrete were reached (which could be very high), it would fail in tension. So the tension zone is replaced by steel and the tensile contribution of the concrete is discounted. This is made possible because the coefficient of thermal expansion of concrete and steel is almost identical and also because a very good natural grip strength (or “bond”) between concrete and steel develops during the setting process.