Pull-out tests on reinforcing bars using distributed fibre optical strain measurement
Author: Sebastian Wehrli
Language: English
Abstract
In the context of this master’s thesis, the bond behaviour of reinforcing bars and screw anchors is experimentally investigated. In 44 pull-out tests, fibre optic cables were installed on the specimens, allowing an almost continuous measurement of the strain over the entire bond length. Both embedded and glued-in reinforcing bars were tested and further parameters such as diameter, embedment length and the grade of the surrounding concrete were varied.
The proposed models of Eligehausen et al. [1] and the fib Model Code 2010 [2] are investigated in this thesis. The bond stress, steel stress and slip values along the specimens are calculated with a numerical algorithm. The fibre optical strain measurements are then used to make a direct comparison with the common bond stress-slip relationships. A comprehensive modular software was developed for the post-processing and evaluation of the data. The individual modules are independent of the problem statement and can therefore be used in future projects.
Some uncertainties regarding the preparation of the specimens and measuring instrumentation were identified in the course of the work and contained as far as possible with various measures. The use of adhesives for through holes is very demanding and asks for innovative ideas for the installation. It is found that there are no significant differences regarding the bond stress-slip behaviour between different compound types discernible. Furthermore, there seems to be a dependency of the bond stresses on the steel stresses.
Fibre optical strain measurements are challenging but provide an interesting insight into the specimens and can contribute to a better understanding of the bond behaviour and a further development of the current bond stress-slip models.
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[1] Eligehausen, R., Popov, E. P. & Bertero, V. V. Local bond stress-slip relationships of deformed bars under
generalized excitations. Earthquake Engineering Research Center, University of California, Berkeley, 1983.
[2] fib - federation internationale du beton. fib Model Code for Concrete Structures 2010. Ernst & Sohn
Verlag, Berlin, 2013.
