Projeto executivo de uma viga biapoiada em concreto protendido com monocordoalhas engraxadas: estudo de caso

Abstract

Buildings with slender structures and increasingly bold architecture require spans that may not be overcome by the reinforced concrete structural system. To solve this problem, the use of prestressed concrete has been increasing in Brazil in recent decades, encouraging in-depth study of the subject by civil engineering students and professionals.Therefore, this work aims to develop the executive project of a post-tensioned prestressed beam without adherence, with demonstration of manual calculations. The methodological procedure consists of a case study that simulates the removal of the central pillar of a previously continuous beam, making it simply supported and with a span of approximately 16 meters. With the aim of demonstrate that reinforced concrete is not a viable structural solution for this case study, the beam was computationally designed in reinforced concrete using the Eberick® program, resulting in high deformations and reinforcement rates. As a solution, the beam was designed in unbonded prestressed concrete using manual calculations, resulting in a cross section of 60 x 90 cm and 28 prestressing cables. To prove that the results of the manual calculation were coherent, they were compared and analyzed against the results of the computational sizing of the V-PRO® program, a prestressed beam calculator developed by the company TQS®. The comparative analysis demonstrated irrelevant variations regarding the design of active and passive reinforcement, resulting in very similar steel areas between the two calculation methods. Regarding the calculation of prestressing losses, manual sizing resulted in 20% total losses compared to 25% in computational sizing. Such differences, despite being relatively considerable, are justified by the different equations between the calculation methods when calculating progressive prestressing losses.As the main result of this work, the executive design of the prestressed beam was prepared manually, containing all the technical information necessary for the execution of the beam, such as: details of the active and passive reinforcement, quantity of materials, design notes and legends.