The net tensile/shear area of a 20 mm nominal diameter ISO metric steel bolt at the threaded section (in mm2) is approximately equal to:

The strength and size specification of a butt weld is primary specified by its:

As per IS 800, the maximum bending moment for the design of purlins can be taken as (where W is the total distributed load including wind load on purlins and L is the effective span/centre distance of supports):