where hi = distance from the centroid of tension steel to the neutral axis and
h2 = distance from the extreme tension fiber to the neutral axis.
N0-Slip Theory
Base et al of the Cement and Concrete Association proposed a fundamentally different approach in which they assumed that for the range of
crack widths normally permitted in reinforced concrete, there is no slip
of the steel relative to the concrete. The crack is therefore assumed to have
zero width at the surface of the reinforcing bar and to increase in width as
the surface of the member is approached. This means that the crack width is
dependent on the deformations of the surrounding concrete. The theory of
elasticity can be used to determine the distribution of stresss and strain in the
concrete between the cracks. The stresses so calculated indicate when further
cracking is likely; the strains indicate the deformed shape of the concrete