Modelling time-dependent behaviour of axially-restrained reinforced concrete slabs

• Main Author: Kabosh, Mohammed Ahmed
• Published: Imperial College London 2007
• Subjects: 624.1834
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486309

This thesis is primarily concerned with modelling the influence of in-plane restraint of shrinkage on the deflection of reinforced concrete one-way slabs. In practice, slabs are often restrained in-plane to some degree and a time- varying axial forces is induced by restrained shrinkage, which increases long-term deflections. Previous research on restrained shrinkage has focused on the calculation of the restraining force in members not subjected to gravity loading. A rigorous numerical procedure, using the so-called layered approach, has been developed to model deflections in reinforced concrete one-way slabs subjected to bending and axial restraint. Nonlinear effects due to cracking; and time-dependent effects due to creep, shrinkage and loss oftension stiffening as well as geometrical nonlinearity due to second order effects have been incorporated into the model. Tension stiffening has been modelled using various methods including that given in Ee2. A computer program has been developed to implement the method. An iterative approach to calculate the axial force and bending moment distribution in axially restrained one-way slabs has been developed. The performances of tension stiffening models for deflection and axial displacement prediction have been investigated. The effects of in-plane restraint of shrinkage on deflections have been quantified by analysing various reinforced concrete one-way slabs with and without axial restraint. An extensive parametric study has been carried out to quantify the influence of relevant parameters on the long-term axial restraint force and deflection.