Estimativas de tensões residuais: aplicação a caso clássico de estacas instrumentadas em areia

Abstract

Residual stresses arise along the pile shaft and toe after the end of driving or after unloading in a static test. Although these stresses do not interfere in the load capacity of the piles, they can greatly modify the load transfer and, therefore, the behavior of the pile when submitted to the service load. The prediction of the residual loads has been the subject of research by several authors, having already been proven that the driving simulation, carried out in a sufficient time for the stabilization of the displacements in the pile, is a suitable tool for this purpose. The Unipile commercial program, among other applications, is usually used in practice also for the analysis of residual stresses. The objective of the present research was to perform a critical discussion to the Unipile and its capacity of prediction of the residual stresses. Initially, an attempt has been made to understand the program's ability by comparing the results of its application with a parametric analysis previously elaborated by Costa (1994), using the driving simulation to estimate the residual stresses. After pointing about some of the constraints of the Unipile program, a classical case contemplating instrumented piles including the measurement of residual stresses was analyzed by both programs: the driving simulation program and the Unipile program. The author compares and discusses the two calculation tools, their results, highlighting their potentialities and limitations. Although not being part of the initial main objective, the author also discusses the results of the instrumented loading tests, which had not been, at the time of publication, widely explored. The lack in interpretation was due, probably, to its execution been taken place long ago, when more recent knowledge was not available. The author then revisited and discussed some results in the light of newer publications.