Effect of steel fibres on the shear behaviour of SCC dry joints in precast segmental bridges

The purpose of connections in precast concrete segmental bridges (PCSBs) is to transmit significant compressive and shear forces, ensuring the stability and stiffness of the structure. Castellated dry joints are increasingly used for the connection of precast concrete elements in these regions of discontinuity. Due to the low tensile strength of concrete, the use of steel fibres to improve the shear strength of this joint type has become widespread. In addition, in recent decades self-compacting concrete (SCC) has become popular in the precast industry due to its workability and ease of placement. Although there are experimental campaigns that studied the influence of steel fibres on the shear capacity of castellated dry joints, experimental tests using normal strength self-compacting concrete (NS-SCC), with and without steel fibres, have not been found. Therefore, this research analyses the influence of adding steel fibres to NS-SCC to improve the mechanical behaviour and shear strength of castellated dry joints in PCSBs. An experimental campaign of 37 push-off-type tests was conducted to assess their effect on the cracking, failure mode, shear strength and residual strength of the joint. The study revealed improvements in post-peak behaviour and shear capacity, which became more significant for higher steel fibre contents. A comparison to other authors' experimental results was made and indicated lower shear strength when using SCC. Additionally, the AASHTO formulation overestimated the shear strength of the NS-SCC joints tested in this study, except for the specimens with 80 kg/m3 of steel fibres.