The appropriate expression in assessing development length is:
1
\({L_d} = \frac{{\phi {\sigma _s}}}{{4{\tau _{bd}}}}\)
2
\({L_d} = \frac{{\phi {\sigma _{bc}}}}{{{\tau _{bd}}}}\)
3
\({L_d} = \frac{{{\sigma _s}}}{{4{\tau _{bd}}}}\)
4
\({L_d} = \frac{{\phi {\sigma _s}}}{{8{\tau _{bd}}}}\)