Influences of shrinkage and construction loading on loss of tension stiffening in slabs

Abstract

Tension stiffening is shown to be lost more rapidly after loading than predicted by models attributing loss of tension stiffening to shrinkage. Furthermore, contrary to predictions of shrinkage models, tension stiffening is lost quicker in slabs that crack significantly on loading than in slabs that crack mainly after loading due to shrinkage. It is concluded that shrinkage does not contribute significantly to loss of tension stiffening after loading in cracked members. An improved method is proposed to account for loss of tension stiffening in deflection calculations. A simplified method for taking account of construction loading in deflection calculations is shown to give reasonable estimates of deflections in the slabs in the in situ concrete building at Cardington.