Influence of measurement uncertainty inherent in sustained load testing data on the displacement forecast of bonded anchors

The product qualification of bonded fasteners is regulated in a European Assessment Document, where a comprehensive test program to evaluate the sensitivity of bonded fasteners to different installation and environmental conditions is included. Sustained load testing as part of this program is used for the long-term displacement forecast to assess the creep behaviour of the anchors over time. The prescribed standard procedure for the assessment of sustained load tests is the Findley power-law methodology. The measured displacements are extrapolated to a working life of 50 years and compared with the displacement at loss of adhesion as limiting value. As a result of this power-law methodology, also the inherent measurement uncertainty of the displacements is extrapolated over time. The first step to quantify this influence is the determination of the measurement uncertainty for the considered sustained load testing task and the used equipment for a specific sustained load data set. Based on Monte-Carlo simulations with the measured displacement and the combined standard uncertainty of the testing task as input parameters, a high number of displacement curves is generated. By analysing the scatter of the calculated displacement extrapolations for 50 years, the influence of the measurement uncertainty is quantified for the considered data set.