Structural behaviour of post-installed reinforcement bars in moment connections of wall-slabs

Post-installed reinforcement (PIR) bars helps to facilitate retrofitting works, mitigate misplaced reinforcement problems, as well as support newly casted additions. However, the use of PIR has not been addressed in the major reinforced concrete (RC) design codes worldwide. Recently, the European standards have introduced a beneficial coefficient of moments in EN 1992-4 2018 for concrete fastenings which allows compliant PIR systems to be designed by using the bonded anchor (BA) design method. However, when applying this method to wall-slab connection design, the moment resisting capacity is often limited by the lack of bar spacing and small concrete covers. This means that the method neglects long embedment depths and the connections designed based on this method are prone to brittle failure. In this paper, the strut and tie model (STM), which can better describe PIR with long embedment depths, together with the fundamental reinforced concrete (RC) theory is used to improve the ductility of moment connections with PIR bars. An experimental study is conducted to explore the structural behaviour of applying PIR bars that connect the wall and slab. Validations on the proposed STM and supplement to the BA design methods are made. From the experimental findings, measures are then proposed to enhance the ductility of the moment connections

Design and installation of post-installed reinforcements: A state-of-the-art review

Post-installed reinforcement (PIR) helps facilitate retrofitting works, mitigate misplaced reinforcement problems, as well as support newly cast concrete members such as modular integrated construction. However, it has not been holistically addressed in major international reinforced concrete (RC) design codes. Nonetheless, based on established design philosophy and associated failure modes, the cast-in reinforcement design method in RC can be extended to design qualified PIR systems. The qualification of PIR system can be referenced to AC 308 (2016), European Assessment Document (EAD) 330087 (2018) and EAD 330499 (2017) in the US and Europe, respectively. In Hong Kong, PIR is conservatively limited to shear connections. Its assumption of pinned connection is less justifiable for some deep sections of beams, which may induce hogging moments, causing tension at the top reinforcement of the supports. In some cases of cantilever slabs, moment connections are necessary to maintain equilibrium. Hence, this paper reviews an up-to-date design methodology and installation guide to complement the Hong Kong Code of Practice for Structural Use of Concrete (HKBD) by referring to the recently published international design codes and documents. The proposal is useful to promote economical, sustainable and technically sound use of PIR system