Title: Deflections of Reinforced Concrete Members: A Simple Approach
Author(s): Pieter C. Pretorius
Publication: Journal Proceedings
Appears on pages(s): 805-812
Keywords: beams (supports); concrete slabs; cracking (fracturing); creep properties; deflection; modulus of elasticity; moments of inertia; reinforced concrete;
stiffness; structural analysis.
A new simplified method for long-term deflection calculations of reinforced concrete members is presented. The method defines a modular ratio for creep conditions based on laboratory verified strain distributions in beams for both immediate and long-term conditions. A simple formula is derived for the ratio of long-term to immediate deflections. A value for the creep factor is assumed but a series of curves is recommended that relates the creep factor to ambient relative humidity, age of loading, and surface area to the volume ratio of the member. Calculated deflections using the method are compared with laboratory measured values reported in the literature.