LONG TERM DEFLECTIONS OF REINFORCED CONCRETE BEAMS

Abstract

A study of long term deflections in reinforced concrete beams is presented in this thesis. Two simply supported beams and four contin uous beams were tested under sustained loads for periods of about 1 i/2 years. When the deflections were compiled it was observed that all beams had long term to short term deflection ratios that exceeded ACT and CAN3-A23.3 Code limits. A finite element program was developed to model concrete behaviour for short term and long term loading. When compared with experimental data, the model predictions were almost always within the normal variability limits for deflections. A parametric study using the Factorial Design Method was under taken to develop an accurate long term deflection prediction method using deflections generated by the finite element model. The ACT and CAN3-A23.3 Code approach of using a long term to short term deflection ratio was adopted in this study. The resulting relationship had mixed results which raises questions about the advisability of using the deflection ratio approach for predicting long term deflections.