Assalam o alaikum.
According to 21.5.1, width of beams must satisfy the following
1. Clear span ln ≥ 4 effective depth General
2•Width to depth ratio bw/h ≥ 0.3
3.Width bw ≥ 10 in.
It means, i can provide 10 inch thickness in zone 4, if it is satisfying above 3 clauses. Is there further limit?