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Steel Checks to SANS 10162-1

The steel design check supports the SANS 10162-1:2011 edition.

Input data​

All cases provided to the checker are assumed to be ultimate limit state (i.e. the member forces are fully factored). Any non ULS cases – e.g. unfactored wind load – will be treated as if they are ULS, and so will result in non-conservative utilizations.

Effective Section Properties

Members are classified as Class 1, Class 2, Class 3 and Class 4 sections in accordance with SANS 10162-1:2011 Table 3 and 4.

Effective section area is calculated in accordance with SANS 10162-1:2011 clause 13.3.3.

Effective section modulus for the section with class 3 or better web and class 4 flange is calculated in accordance with SANS 10162-1:2011 clause 13.5. If the web is class 4 and flange is class 3 or better then the revised factored moment of resistance is calculated in accordance with SANS 10162-1:2011 clause 14.3.4. Checker doesn’t support the section if both the flange(s) and web are class 4.

Local Checks​

Sections are checked at the ends of every sub-span of the member for the moments and forces acting on it.

Members with Angle sections are treated as strut and tie only member and the shear and moment capacities are assumed as zero.

Shear

For the webs of section with two flanges shear capacity is calculated using elastic analysis in accordance with SANS 10162-1:2011 clause 13.4.1.1. This clause applies for I,Channel sections with shear acting along the web and also for RHS sections.

For all other cases maximum shear stress is calculated in the section and compared with 0.66ϕfy0.66\phi f_y. The effect of shear buckling is not considered and this is non-conservative.

Bending moment

Moment capacity at a section is calculated in accordance with SANS 10162-1:2011 clause 13.5 and clause 14.3.4. See Effective Section Properties for details on calculation of effective section modulus. Moment capacity of a section is assumed as zero whose flanges and web are class 4

Moments are conservatively enhanced if slenderness or end connection leads to the effective centroid of the section moving, and axial force is present.

Axial force

Compression capacity at a section is calculated in accordance with SANS 10162-1:2011 clause 13.3.1 and 13.3.4 and assuming member length as zero. See Effective Section Properties for details on calculation of effective area of section.

Tension capacity at a section is calculated in accordance with SANS 10162-1:2011 clause 13.2. Sections in tension use the user defined ‘Net Area Ratio’.

Torsion

At present, any significant torsional moment (greater than 5% of the torsional capacity) produces a warning.

Combined local effects

The section is checked for interaction of axial and moments in accordance with SANS 10162-1:2011 clause 13.8.2 (b) and 13.8.3 (b).

Moments used in the local interaction check include the moments due to eccentricity in axial force. Eccentricity may be due to end connection and to shift in neutral axis.

Buckling Checks​

Axial buckling

The member is checked along its length for major axis axial buckling and minor axis axial buckling according to SANS 10162-1:2011 clause 13.3.1

Singly symmetric and unsymmetrical sections are also checked for torsional and flexural torsional buckling according to SANS 10162-1:2011 clause 13.3.2. Doubly symmetric sections are checked for torsional buckling in accordance with SANS 10162-1:2011 clause 13.3.2 (a).

SANS 10162-1:2011 Annex E (Figure E.1) is referred to estimate effective length factor using the restraint condition.

Bending laterally unsupported members

Lateral torsional buckling is checked in accordance with SANS 10162-1:2011 clause 13.6.

If the member has an Equivalent Uniform Moment Factor override specified, this is used in place of ω2\omega_2 in lateral torsional buckling calculations.

Buckling interaction

Interaction checks are carried out according to SANS 10162-1:2011 clause 13.8.2 and 13.8.3

Limitations​

  • Clause 15.3.4 suggest that “The factored resistances of the first compression web member and its connection shall be determined with their respective resistance factors, ϕϕ, multiplied by 0.85”. To account for this user should explicitly enter the reduced yield strength in the steel design property.
  • Web buckling, yielding and crippling checks are not implemented.
  • Section with class 4 flange and class 4 webs are not supported.
  • Design of cold formed sections are not supported.

Refer to BS5950-1:2000 for other limitations.