In the past decades, there has been an increasing effort to describe the local bond behaviour with a bond stress-slip model. Such bond models are often used in studies of long bond lengths, numerical calculations and crack width determination. An example of this is the approach of fibModel Code 2010. However, this approach is based on results of pull-out tests with a bond length of 5 times the bar diameter ds, which does not adequately reflect the bond conditions in real components.
Current investigations at the Technische Universität Dresden (TUD) deal with the bond behaviour and the bond stress distribution of ribbed steel bars in normal and high-strength concrete. The test program includes systematic investigations of the influence of the bond length on the ultimate bond stress using pull-out, and beam-end specimens with bond lengths from 1 ds up to 4 ds. The samples differ with regard to the concrete cover, the transverse reinforcement as well as the orientation of the ribs within the bond zone. Using different levels of confinement, it is shown how the development of splitting cracks and internal stress conditions influence the bond behavior.
This article deals with the experimental and instrumental setup, test results and the procedure of evaluation. Furthermore, it is discussed how different test setups represent the bond conditions of real components best.