Title: Effect of Misalignment on Pulloff Test Results: Numerical and Experimental Assessments

Author(s): Luc Courard, Benoît Bissonnette, Andrzej Garbacz, Alexander Vaysburd, Kurt von Fay, Grzegorj Moczulski, and Maxim Morency

Publication: Materials Journal

Volume: 111

Issue: 2

Appears on pages(s): 153-162

Keywords: bond; coring; inclination; misalignment; numerical simulations; pulloff test; repair; stress concentration

DOI: 10.14359/51686451

Date: 3/1/2014

Abstract:
The successful application of a concrete repair system is often evaluated through pulloff testing. For such in-place quality control (QC) testing, the inherent risk of misalignment might affect the recorded value and eventually make a difference in the acceptance of the work. The issue of eccentricity in pulloff testing has been ignored in field practice because it is seen as an academic issue. This paper presents the results of a project intended to quantify the effect of misalignment on pulloff tensile strength evaluation and provide a basis for improving QC specifications if necessary. The test program consisted first of an analytical evaluation of the problem through two-dimensional finite element modeling simulations and, in a second phase, in laboratory experiments in which the test variables were the misalignment angle (0, 2, and 4 degrees) and the coring depth (15 and 30 mm [0.6 and 1.2 in.]). It was found that calculations provide a conservative, but realistic, lower bound limit for evaluating the influence of misalignment upon pulloff test results: a 2-degree misalignment can be expect to yield a pulloff strength reduction of 7 to 9%, respectively, for 15 and 30 mm (0.6 and 1.2 in.) coring depths, and the corresponding decrease resulting from a 4-degree misalignment reaches between 13 and 16%. From a practical standpoint, the results generated in this study indicate that when specifying a pulloff strength limit in the field, the value should be increased (probable order of magnitude: 15%) to take into account the potential reduction due to testing misalignment.