Analysis of Bonded Post-tensioned Partially Prestressed Concrete Beams under Sustained Loads

Abstract

A simple and rational analytical model that allows the determination of the history of strain and stress distribution in uncracked bonded post-tensioned RC concrete sections is proposed. Expressions for the direct computation of the time-dependent strain are extended to consider a two-stage sustained loading and the state of shoring or unshoring during the period of initial hardening. The analysis is performed at arbitrary points in time satisfying the conditions of force and moment equilibrium as well as the strain compatibility between all layers of steel and the surrounding concrete. The effects of the change in modulus of elasticity of concrete and the change in geometric properties due to grouting of tendon ducts are taken into account. A numerical example of a precast post-tensioned beam is given to demonstrate the method. Keywords: Compatibility, concrete, creep, equilibrium, prestress relaxation, Time-dependent stresses