The influence of the parameter ϕ/ρ_eff on crack widths

Many formulae for the prediction and control of crack widths in reinforced concrete members assume that the transfer length over which force is transferred by bond from the reinforcement to the concrete on either side of a crack is proportional to the parameter ϕ/ρ_eff, where ϕ is the bar diameter and ρ_eff is an effective reinforcement ratio. This paper aims to examine the validity of this assumption by comparing the predictions of the theory which leads to the derivation of the parameter ϕ/ρ_eff to data from experimental programmes where crack widths were measured. These comparisons strongly suggest that ϕ/ρ_eff has minimal influence on crack widths.