Q. Longitudinal steel – an enhancement of shear strength ?

Furthermore to shear resistance provided by shear reinforcement, shear forces in a concrete section is also resisted by concrete compression force (compressive forces enhances higher shear strength), dowel actions and aggregate interlocking. Presence of longitudinal steel contributes to enhancement of shear strength of concrete section in the subsequent ways: 

(i)  Dowelling action performed by longitudinal reinforcement directly contributes considerably to the shear capacity.

(ii)  Provision of longitudinal reinforcement also indirectly controls the crack widths of concrete section that consequently affects degree of interlock between aggregates.