Evaluation of Code-Based Long-Term Deflection of Prestressed Concrete Beam

Sholihah, Eva Ayu; Kristiawan, Stefanus Adi; Saifullah, Halwan Alfisa

doi:10.22059/ceij.2025.387635.2211

Evaluation of Code-Based Long-Term Deflection of Prestressed Concrete Beam

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Authors

Department of Civil Engineering, Faculty of Engineering, Sebelas Maret University, Surakarta, Indonesia

10.22059/ceij.2025.387635.2211

Abstract

Long-term deflection in prestressed concrete is influenced by several factors, including shrinkage, creep, and the relaxation of the prestressing steel. While these factors are crucial for the serviceability of prestressed beams, concrete design codes often quantify their effects using simplified methods. This simplification raises concerns about the accuracy of long-term predictions. This paper evaluates the code-based long-term deflection of prestressed concrete beams and compares the results with the displacement method, which is regarded as a more accurate alternative for estimating the effect of shrinkage, creep, and relaxation on long-term deflection. A sensitivity analysis was also conducted to determine the sensitivity of parameters to affect the long-term deflection. The results indicate that code-based methods (ACI 209R-92 and FIB 2010) give a lower estimation (within 4%) of deflection compared to the displacement method. This seemingly minor deviation may raise serious concerns in circumstances where tolerances are strict or structural integrity is critical. The sensitivity analysis identifies relative humidity as the most significant parameter affecting deflection. The outcome of this detailed study paved the way to properly select and utilize shrinkage and creep models, taking into consideration the key contributing factors affecting the long-term deflection..

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