What are the permissible stresses in Tension Steel and Concrete as per BS8110 while checking a section for crack widths?

What is the effective depth d

What are the permissible stresses in Tension Steel and Concrete as per BS8110 while checking a section for crack widths?

Permissible stress in Steel and concrete is defined as following.

Stress in steel is limited to 0.8 x fy (BS8007:1987 Appendix B2 and Cl. 3.8.3, BS8110-2:1985)

Stress in concrete is limited to 0.45 x fcu (BS8007:1987 Appendix B2)

What is the effective depth d

Permissible Stress