NUMERICAL MODELING OF LOSS OF PRESTRESS IN CONCRETE BEAMS

Resumo

The correct estimation of prestressing losses has fundamental importance for preventing damage and
improving the design of prestressed structures. In prestressed concrete beams the level of prestressing force
initially applied is reduced instantly and over time. The progressive prestressing losses constitute an important part
of the total loss and are related to shrinkage, creep of the concrete and the relaxation of the prestressed steel.
Thereby, this work aims to develop a computational tool using the positional approach of the finite element method
to evaluate the mechanical behavior of bonded prestressed concrete structures. The concrete matrix is represented
by plate finite elements with cubic approximation, whereas, for reinforcement, one-dimensional finite elements
are considered. The coupling between matrix and reinforcement is performed by means of the embedded
technique, without adding degrees of freedom to the problem. The prestressing loss due to shrinkage and creep of
the concrete are determined by the model B4 (WENDNER; HUBLER; BAŽANT [1]). The loss by relaxation of
prestressed steel is calculated using the model proposed by Model Code 10 (CEB-FIB [2]). The numerical
applications performed demonstrated the accuracy of the developed model, evidencing its capacity in the analysis
of prestressing loss in bonded prestressed concrete elements.