PERMISSIBLE STRESSES IN AXIAL TENSION

It is related to the guaranteed minimum yield point of steel with an appropriate factor of safety. Most of the codes assume a factor of safety of 1.67.

The direct stress in axial tension or the effective net area should not exceed  given by the equation,

Where, = minimum yield stress of steel in  (MPa).

Indian Standard IS: 226

It stipulates the following permissible stress in axial tension for steel,

(i)

Plates, angles, tees, I-beams, channels and flats

 

upto and  including 20mm thickness

150 MPa

 

above 20mm thickness to 40mm

144 MPa

 

Over 40 mm thickness

138 MPa

(ii)

Bars (round, square and hexagonal)

 

Upto and including 20mm diameter

150 MPa

 

Over 20mm diameter

144 MPa

Permissible Combined Stress

When tension members are subjected to both axial loading and bending moment, then the permissible stress is governed by the formula,

Where, = axial tensile stress,

 = permissible axial stress in tension,

 = calculated bending stress in tension in the extreme fibre, and

 = permissible bending stress in tension.