Comparison of Simplified Methods for Immediate Deflection Calculation in Prestressed Beams

Resumo

Verifying structural deformations is essential to ensure the performance and safety of the designed system. For prestressed concrete beams, deflection calculations involve additional particularities compared to reinforced concrete beams. These include, for instance, the need to account for the effect of prestressing force on the concrete and the presence of prestress-induced hyperstatic effects in continuous beams. In cases of partial prestressing, the calculation of the immediate deflection component requires consideration of the stiffness reduction due to concrete cracking, just as with reinforced concrete beams. Although prestressed beams typically exhibit lower levels of cracking compared to reinforced concrete beams, it is still necessary to account for this effect in deflection calculations. Therefore, it is essential to comprehend how various design standards address these elements. This study aims to compare simplified methods for calculating short-term deflections in simply supported and continuous prestressed concrete beams with partial prestressing levels, following the provisions of the Brazilian standard NBR 6118 [1] and the fib Model Code [2]. Deflection values are computed using both normative models for a set of simply supported and continuous prestressed concrete beams designed with partial prestressing. A comparative analysis is presented, discussing the differences observed between the methods.