Structural design of stainless steel

Design strengths

The basic design strength, py, is usually taken as the minimum specified 0.2% proof strength, given in the relevant product standard. Values for 0.2% proof strength and ultimate tensile strength for stainless steel sheet/strip and plate for grades typically used in structural applications are given below.


Minimum specified mechanical properties to BS EN 10088-2

Type Designation Product form1 Maximum thickness 0.2% proof strength (N/mm2) Ultimate tensile strength (N/mm2)
304 1.4301 C 6 230 540/750
H 12 210 520/720
P 75
304L 1.4307 C 6 220 520/670
H 12 200
P 75 500/650
316 1.4401 C 6 240 530/680
H 12 220
P 75 520/670
316L 1.4404 C 6 240 530/680
H 12 220
P 75 520/670
Duplex 2205 1.4462 C 6 480 660/950
H 12 460
P 75 640/840
Note
1) C=cold rolled strip, H=hot rolled strip, P=hot rolled plate

The modulus of elasticity of each of the grades given in the table is 200kN/mm2, Poissons ratio can be taken as 0.3 and the shear modulus is 76.9kN/mm2.

Physical properties

Physical properties of grades typically used in structural applications are given below.

Room temperature physical properties to BS EN 10088-1 (annealed condition)

Grade Steel designation Density (kg/m3) Thermal expansion 20 - 1000C (10-6/K) Thermal conductivity (W/mK) Heat capacity (J/kgK)
304 1.4301 7900 16 15 500
304L 1.4307
316 1.4401 8000
316L 1.4404
duplex 2205 1.4462 7800 13

Designing stainless steel in structures

In most respects, structural design in stainless steel is similar to design in carbon steel and requires comparable design checks and considerations. The only significant difference stems from the different shape of the stress-strain curve for stainless steels. Whereas carbon steel typically exhibits linear elastic behaviour up to yield stress and a plateau before strain hardening, stainless steel has a more rounded response with no well-defined yield stress.

This difference in stress-strain behaviour has implications on the buckling resistance (both local, flexural and lateral torsional) and deflections for stainless steel members. Buckling curves which are appropriate to the grade of stainless steel must therefore be used. Suitable methods must also be used for deflection calculations.

There is a comprehensive set of references for designing in stainless steel at:

Online Information Centre for Stainless Steel in Construction

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