A Proposal of Simple Design Equationsfor Evaluating Flexural Serviceability Performance of Reinforced High and Low Shrinkage HSC Beams

摘要

This paper shows the importance of autogenous shrinkage on serviceability performance of reinforced high-strength concrete (HSC) flexural beams, and also the effectiveness of low-shrinkage HSCs (LS-HSC) that is made by using an expansive additive and/or shrinkage-reducing chemical agent and/or Belite-rich low heat Portland cement with regards to the improvement of flexural serviceability performances of the beams. In addition, this paper, from a simple design equation point of view, proposes a new concept for evaluating flexural crack widths and deformation of RC beams, considering the early age deformation of concrete before loading. The experimental results show that autogenous shrinkage of HSC increase crack width and deformation of the RC beams significantly, while LS-HSCs markedly improve its serviceability performances. The present concept, taking into account strain change in tension reinforcement and curvature change at cracked section before and after loading, is effective in explaining the effects of shrinkage and expansion of concrete before loading on maximum crack width and flexural deformation. JSCE (Japan Society of Civil Engineers) code equations for predicting maximum crack width and flexural deformation into which the present concept is incorporated improve the prediction accuracy compared with conventional ones and show fairly good agreement with experimental results.