Lajes planas protendidas pelo método de grelha equivalente

Abstract

This work aims to evaluate design and analysis of flat slab with prestressed concrete using unbonded tendons, a system utilized in post-tensioned slabs in Brazil, which is largely applied due to its ease of execution if compared to bonded tendons. The design is limited to the flexure, not being designed and analyzed the connection slab-column (punching shear). The design and verifications about ultimate limit state and serviceability limit state is based on Brazilian standard NBR 6118:2014. The model calculation of post-tensioned flat slab, utilized in the numeric example, is executed by the grillage analogy, using SAP200 as the software analysis. All the verifications are made by this method. The strain, reactions and deformations produced by the grillage analogy are compared to the finite element method, aided by SAFE software. It was concluded that based on the distribution of tendons and balancing adopted resulted in slab with partial post-tension. The reinforcement resulted in the minimum recommended by the standard. It was further noted that the difference between the bending moments varies up to 43,64% comparing both methods, which is the highest moment produced by the grillage analogy