From: Methodology for Testing Rebar-Concrete Bond in Specimens from Decommissioned Structures
Test setup | Advantages | Disadvantages |
---|---|---|
Direct pull-out
| Simple test setup Force in the bar is known Well-defined embedment length, unless a cone failure occurs | Compressed concrete while the bar is in tension Friction at the bearing end Cone failure near the loaded end needs to be considered when evaluating results Challenge of grabbing bars |
Indirect pull-out
| Force in the bars can be calculated with reasonable accuracy | Risk of asymmetry can cause bending and rotation Clamping can be difficult to manage Specimens need a lot of modifications |
Beam-end
| Forces in bars are known Well-defined embedment length, unless inclined cracking occurs | Challenge of grabbing bars Bond capacity or embedment length needs to be small enough to avoid bars yielding Effect of support pressure |
Beam tests, general (all advantages and disadvantages hold for all sub-groups of beam tests) | Relevant as they closely approximate real application Gripping of bars is avoided | Requires thorough design to obtain anchorage failure instead of other failure modes. E.g. choice of three or four-point bending, spans etc. For symmetrical test setups, the side that will fail is not known in advance, which increases need for instrumentation Forces in bars need to be calculated |
Beam test, suspended supports
| Experience exists, (Lundgren et al. 2015a; Tahershamsi et al. 2014) Specimens with spalled concrete cover can be tested | Likely requires strengthening to withstand hanging support reactions Relatively complicated setup Inclined shear cracks will interact with spalling cracks. Thus, the available anchorage length might not be well-defined |
Beam test, direct support
| Simple and straightforward Available anchorage length rather well-defined. Inclined shear cracks expected towards direct supports | Effect of support pressure Support area may need repair |
Beam test, narrow direct support
| Simple and straightforward Limits the effect of support pressure | Risk of tilting Balancing the anchored force may entail having a stirrup just outside the support area Support area may need repair |
Beams with spliced reinforcement
| Simple and straightforward Relevant, as they closely approximate real application | Can be difficult to locate splices, or splices may not be suitably positioned |