Aspects to Consider in the Assessment of Effective Stiffness for Reinforced Concrete Beams

Abstract

The stiffness of any structural element depends on its geometrical form (prismatic or nonprismatic), its length, its supporting conditions, and its mechanical properties as a function of the constitutive laws, which are assumed to be satisfied by the used materials. For this reason, in the most general case, the stiffness of any element is obtained using a volume integral. This is a fundamental principle of structural analysis. In this paper, the author discusses and reflects, in an integral manner, the subject of effective stiffness for reinforced concrete beams in the seismic design practice based on analytical results and experimental evidence. Rational equations were derived to assess effective stiffnesses in reinforced concrete members if the designer wants to assume an incipient cracking (not easy to detect at first sight) before the design earthquake scenario strikes the subject structure.