2068 Bhadra (old course) · 6 marks

Permissible stresses as per IS 800

Short answer

Permissible stresses per IS 800:1984: axial tension 0.6f_y, bending 0.66f_y (laterally supported), average shear 0.4f_y, maximum shear 0.45f_y, bearing 0.75f_y. For f_y=250 N/mm², these are 150, 165, 100, 112.5, and 187.5 N/mm² respectively.

For a steel of yield stress as $f_y$ , what are the permissible stresses in tension, compression, bending, shear and bearing according to IS 800?

As per IS 800:1984 (working stress method), with $f_y$ the yield stress of steel (the 2007 code uses limit states instead):

Stress	Clause	Permissible value
Axial tension, $\sigma_{at}$	4.1	$0.6f_y$
Axial compression, $\sigma_{ac}$	5.1	$0.6\dfrac{f_{cc}f_y}{[(f_{cc})^n+(f_y)^n]^{1/n}}$ with $n=1.4$ , $f_{cc}=\pi^2E/\lambda^2$ ; maximum $0.6f_y$
Bending, tension & compression, $\sigma_{bt},\sigma_{bc}$	6.2	$0.66f_y$ (laterally supported); lower for a compression flange with high slenderness (table)
Average shear, $\tau_{va}$	6.4.2	$0.4f_y$
Maximum shear (in web of I-section), $\tau_{vm}$	6.4.1	$0.45f_y$
Bearing, $\sigma_p$	6.3	$0.75f_y$

For $f_y=250$ N/mm²: tension 150, bending 165, average shear 100, maximum shear 112.5 and bearing 187.5 N/mm². For connections (IS 800:1984), black bolts of grade 4.6 have permissible shear 80 N/mm² and bearing 250 N/mm², and shop fillet welds have permissible shear 108 N/mm².

✓ Answer checked by Claude Opus 5.5 (high effort)

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