PSI - Issue 64

Chris Hendy et al. / Procedia Structural Integrity 64 (2024) 206–213 Hendy C / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1: Hypothetically reduced throat width (indicated in blue) – modified figure from CS 468 (2019)

3. Alternative resistance to cracking validation model at ULS: ULS stress block Where Serviceability Limit State (SLS) checks outlined in CS468 (2019) cannot be satisfied, an alternative Ultimate Limit State (ULS) approach can be proposed to confirm that the hinges themselves are safe against collapse or rupture. A visual inspection of the hinge joints then provides an SLS assessment by checking that there has been minimal deterioration over the previous service life in conjunction with measures to ensure water ingress to the hinges themselves is prevented. The ULS resistance proposed here however does not require the hinge throat reinforcement itself to be intact, just the throat concrete. Rotation of the hinge can cause a crack to develop in the hinge throat. The remaining uncracked throat section is generally able to resist the stresses until the crack reaches the middle of the throat as found by Leonhardt and Reimann (1965) who developed a simple mechanical model to describe the behaviour of the hinges under rotation assuming a linear strain distribution in the throat, with no tension transmitted due to the crack formation. A range of tested hinges (Marx and Schacht (2010)) demonstrated that high rotations can still be achieved when small n ormal force is applied to the hinge. They concluded: “For plane systems and loading conditions at the ultimate limit state, hinges are subjected to axial loads N d and rotation around the axis of rotation α d . An overstraining of the concrete in the throat of the hinge, due to axial loads or rotation, is theoretically possible but has never been detectable in any experimental investigation. Failure occurred in all tests in members adjacent to the hinges due to the yielding of reinforcement”.