Estudo da tensão última em cordoalhas engraxadas de uma viga protendida: avaliação teórica e orientações para instrumentação como subsídio para a realização de programa experimental

Abstract

It is well known the importance of unbonded prestressing technique face the current needs of it in the construction market. With the increased use of the technique, what also grew was the need for studies that help in the improvement of the process and the material. Thus, the present work comes as a subsidy for numerical studies about the ultimate stress in unbonded tendon, which is a subject little discussed because it is a problem of complex geometric formulation. Normally, to calculate, numerically, the increased tension at ultimate load, it is common use the standard values or equations developed by other authors, facing the difficulty of numerical analysis and the impossibility of conducting frequent experimental trials. Despite these difficulties, aiming at the realization of an experimental program to measure the increased tension in unbonded tendons, this work comes as a subsidy for the realization of it, presenting theoretical and experimental guidance for future implementation of such program. For this, it was developed a computational model of a prestressed beam, which served as the basis for the numerical study of increased tension, getting data from axial force in the unbonded tendons when applied with the loads increments until the load of ruin. This article also provides guidance for the instrumentation of these unbonded tendons with strain gages, for obtaining tension data in experimental programs. Based on the results obtained, it is possible to affirm that the computational model developed well represents the beam model chosen and it is able to evaluate the increase in tension, sustained by comparing its results with results from empirical equations provided by standards as well as by some other authors. And still, the good results obtained by the experimental procedure performed with the instrumented unbonded tendons indicated the success of the instrumentation methodology provided in this work. Thus, it is believed that the present work can contribute as a subsidy for complete experimental programs that aim at studying the ultimate stress in unbonded tendons of prestressed pieces