Uncertainties related to strain measurements in piles

Abstract

In recent years, distributed fiber optic sensing (DFOS) technology has been widely used in monitoring the strains developed in the structures.
The main focus of this report is to identify strains distribution while hammering/
jacking pile and analyzing the uncertainties between the theoretical, measured strain through datalogger in concrete and steel piles. This assessment is done to gain confidence over the feasibility of using DFOS technology. Fiber optic cables are embedded all along the length of the concrete and steel piles with ends connected to the datalogger. To confirm the accuracy of the datalogger, other strain measuring devices like load cell and strain gauges are also glued to the piles. For both the piles load with in the yield limit is applied and strains are measured. fTb 2505 datalogger posses high accuracy with lower spatial resolution where as Luna Odisi datalogger has high spatial resolution and less accuracy which can be directly reflected through the strains obtained from both datalogger. Results obtained from steel pile reflects that strains obtained from Luna Odisi datalogger and load cell matches with in the accuracy and with no slippage . But for concrete piles fTb 2505 datalogger shows more fluctuating strains as compared to the strain gauges with uncertainties included in both the devices.