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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4. Ultimate Limit State assessment for end block splitting The equations in section 6.7 of Hendy and Smith (2007) can be applied to utilise the tensile strength of the concrete in the hinge to resist the end block splitting action where the existing reinforcement is found to be insufficient at SLS or if it is entirely absent. This leads to a maximum axial force before splitting occurs of: = 2.4 2 − (2) where: f ctd is determined to EN 1992- 2 Cl. 3.16(102)P assuming α ct = 0.80 to EN 1992-1-1 Cl. 12.3.1 for plain concrete in flexure; a is calculated assuming the ULS applied axial force acting on the hinge and is equal to x ’ in section 3 above The sudden failure of a hinge by splitting is unlikely to trigger a catastrophic global failure of the structure and is monitoring-appropriate; inspection of cracking to the end blocks is generally possible as part of the regular inspection regime for the exposed hinges without any requirements for special access. 5. Ultimate Limit State assessment for shear CS468 (2019) requires shear to be carried across the joint in friction, with a coefficient of friction not exceeding 0.33, ignoring the presence of any reinforcement across the interface. This is specified to avoid the need for consideration of: i. corrosion of any hinge reinforcement present across the interface; there is a greater risk of corrosion when the hinge is shown to be cracked at SLS; ii. the interaction between shear, vertical load and rotation on the compression field for the verification of bearing pressure; iii. the complex interaction between shear and bending moment in two directions on the reinforcement demand in an interface shear check. Due to the above, consideration of reinforcement across the hinge throat in the interface shear resistance is generally not advisable unless the actual condition of the hinge throat reinforcement can be determined through site inspection and it needs to be ensured that corrosion is not taking place; if there is any evidence of corrosion, the reinforcement should not be considered in the shear resistance. Sections 6 and 7 below refer to inspection needs generally for applicability of the methods in this paper. A general method of assessment is proposed for axial force, shear in two directions, moment about minor and major axis and also torque in Markic and W Kaufmann (2023). Its application may very often lead to much higher shear resistances and rotations than proposed in this paper, but it does not make allowance for any deterioration of the hinge reinforcement. 6. Acceptability of considering hinge performance at Ultimate Limit State only The durability risks to the structure that exist as a result of exceeding the serviceability limit state criteria in CS468 (2019) are believed to be low and can be mitigated by preventative measures such as hinge sealant and effective water management to the structure. However, if active corrosion of reinforcement crossing the interface is detected (e.g. from observations of rust staining) the ULS methodology in this paper would need careful review for validity as reinforcement corrosion will obviously reduce any additional shear strength available from reinforcement as set out in section 5 but, more importantly, it may also cause spalling of hinge concrete which will potentially invalidate the other ULS methods in sections 3 and 4.