Analysis in service of prestressed composite concrete members with unbonded internal tendons under short and long-term loads

Abstract

Based on the step-by-step method for the analysis over time of the strain in the concrete, in this work a formulation for the analysis of prestressed composed concrete beam with unbonded internal tendons without using the finite element method is developed. This formulation takes into account both the short and long-term analysis, the uncracked and cracked state of the member, the creep and the shrinkage of the concrete, the relaxation of the prestressing steel and the presence of non-prestressed steel reinforcement. In addition, the profile of the prestressing tendons can be generic. From the developed formulation, a computational algorithm for the analysis of this kind of beams is proposed. This computational implementation allows the analysis of both statically determinate beams and continuous beams. The effectiveness of the proposed computational algorithm is evaluated from the comparison with experimental studies, obtaining as main conclusions that the proposed computational model predict satisfactorily the loss of prestress and the deformations of the member over time.