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Effects of anchorage deterioration on the shear behaviour of reinforced concrete half-joint beams

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Mak, MWT 
Sheasby, MP 
Lees, JM 


Reinforced concrete half-joint structures, also called dapped-end beams, are a common type of support configuration in bridges and precast structures. They are characterised by a sudden reduction in depth at the end of a suspended structural element. This detail has advantages for design and construction that justified their widespread use in the past. However, there are numerous problems associated with this type of joint that can translate into significant maintenance costs. A recurrent issue is leakage of water and contaminants that cause corrosion of the internal steel reinforcement. The expansive nature of corrosion products can lead to cracking, delamination or complete spalling of the concrete cover. This is detrimental to the anchorage of the reinforcement. The subsequent reduction in load-transfer capacity is difficult to quantify when assessing damaged structures. It can lead to failure modes that are not taken into account by code provisions for new design. Due to the limited understanding of the behaviour of deteriorated half-joints, experimental evidence is necessary to develop new theories and methodologies to assess existing structures accurately. In this study, an experimental programme was carried out on reinforced concrete beam specimens, investigating the effects of anchorage deterioration in the longitudinal tension bars of the full-depth portion of half-joints. Corrosion-induced spalling and delamination were reproduced by casting the beams without cover and reducing the cover/diameter ratio at critical locations. The results indicate that half-joints are vulnerable to anchorage deterioration in the full-depth section. This is due to the absence of direct confining pressure from the end supports. Bond and anchorage degradation led to a progressive reduction in the overall load-bearing capacity of the beam-ends and combined bending-shear failure modes. Nevertheless, the presence of confining vertical reinforcement allowed for some residual anchorage capacity, even in the case of complete loss of cover.



Journal Title

Proceedings of the fib Symposium 2020: Concrete Structures for Resilient Society

Conference Name

fib Symposium 2020 - Concrete Structures for Resilient Society

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EPSRC (1791721)
Engineering and Physical Sciences Research Council (EP/K016148/1)
EPSRC (EP/M508007/1) EPSRC (EP/N509620/1)