Assessment of shear capacity of bridge beams with non-standard anchorage-an experimental study

This paper considers the effect of inadequate or damaged anchorage regions on the shear strength of bridge beams. This research is motivated by the occurrence of theoretical deficiencies in the assessed shear capacity of existing reinforced concrete bridges. The provisions for dealing with damaged or non-standard RC details as prescribed in CS455 (2020) can be con-servative, as such low shear strength assessed capacities may lead to expensive and potentially unnecessary repairs. The aim is to identify if changes are needed to the provisions currently adopted in the UK for the assessment of shear capacity for beams with non-standard anchor-age. The paper presents preliminary results from a series of off-set 3-point tests on beam speci-mens specifically constructed to replicate the types of anchorage defects commonly found in aging UK infrastructure. This includes the effects of insufficient anchorage length, prior slip in the longitudinal reinforcement and corrosion affecting longitudinal bars, links and concrete cover. A unique two-stage beam casting system has been implemented to produce specimens with known prior anchorage slip and corrosion. Beams with either plain or deformed bars and both with and without stirrups, have been tested, representative of typical bridge reinforcement detailing within the UK infrastructure. CS455 (2020) does not provide full guidance on RC elements affected by prior anchorage slip, the higher-than-expected resistances obtained to date (particularly for deformed bars) seem to suggest that the current limited provisions may lead to overconservative assumptions. However, further study is needed for beams containing plain bars, which are expected to exhibit significantly much lower bond capacities.