Numerical analysis of unbonded prestressed concrete beams under long term service loads by Finite Element Method

Abstract

This work aims to develop a finite element formulation for a numerical analysis for long-term loads of unbonded prestressed concrete beams. The finite element formulation consists of unidimensional elements of plane frames with models of 7 degrees of freedom per element, based on the Euller-Bernoulli beam theory for the reinforced concrete section and a truss element for the simulation of the unbonded tendons. The formulation was developed for the examples of beam under long term loads with the purpose of evaluating the effects due to creep, shrinkage, and relaxation of the prestressing steel. The analysis used the Age-Adjusted Effective Modulus and normative relationships to obtain long-term effects. The numerical results were evaluated through a comparative study with long-term load-displacement curves from the literature, obtaining excellent approximations.