Steel in Housing Acknowledgements

Steel Construction New Zealand Inc. wish to acknowledge the support of OneSteel NZ Ltd who allowed the use of data and graphics from the Onesteel Market Mills publication Structural Steel in Housing, First Edition. The span and load tables in that publication were then reviewed and updated to reflect common practice in New Zealand with respect to deflection under serviceability loads and connection details. Structural engineers, Chambers Consultants Ltd, were engaged to develop revised load span tables to the criteria agreed with Steel Construction New Zealand Inc. and the New Zealand Heavy Engineering Research Association Inc. The design criteria used are summarised in the Design Data section and in the Design Certification. The On-line Steel in Housing web application looks up the revised load span tables to determine the answer to the user's query.

Design Limitations

In compiling the Online Steel in Housing web application, the solutions developed have been calculated in accordance with accepted principles of structural mechanics and design. All requirements of the relevant standards and codes have been adopted along with established New Zealand practice for domestic housing structures.

In particular the following New Zealand Standards and criteria have been applied:

  1. Dead, live and wind loads are in accordance with AS/NZS 1170:2002 Structural Design Actions.
  2. Steelwork conforms to the requirements of NZS 3404: 1997 Steel Structures Standard.
  3. All structural steel sections are G300 in accordance with AS/NZS 3679.1 Hot Rolled Sections.
  4. Timber member strength conforms to the requirements of NZS 3602: 1993 Timber Structures Standard using MSG8 or VSG8 timber.
  5. Reinforced concrete slab thickening and footing strengths conform with the requirements of NZS 3101:1995 Concrete Structures Standard using concrete with 17.5 MPa at 28 days concrete cylinder compressive strength.
  6. Foundation Soils assumed are in accordance with the definition of "good ground" in NZS 3604:1999. That is, "any soil or rock capable of permanently withstanding an ultimate bearing capacity of 300 kPa..."
  7. All applied loads are evenly distributed along the span of the member.
  8. A span upper limit of 8.0 m has been applied, as rarely do spans exceed 7.0 m in housing situations.
  9. Applied load arrangements are as shown in each diagram associated with each condition.
  10. Wind loads have been derived based on a roof pitch between 5° and 45° to give maximum internal pressures of -0.3 and +0.2, and maximum external roof pressures of -1.3 or +0.5. The On-line Steel in Housing web application does not apply to wind zones that are designated as "Specific Design" in NZS 3604.
  11. Wind zone classification conforms with wind zones defined in NZS 3604: 1999 Timber Framed Buildings.
  12. A deflection limit at mid-span of the lesser of Span/350 or 15 mm has been applied to bearers, beams, and lintels for serviceability load case G+Q.
  13. Where there are loads applied from cantilever rafters or joists, the cantilever should be no greater than half the main span of the rafter or joist.
  14. All loads are static and are applied vertically.
  15. All members are simply supported single spans except for the continuous span floor bearer / beam option.
  16. End support bearing distance for single spans is assumed to be at least that of the width of the member. For continuous spans, internal support bearing is to be at least 2 times the width of the member.
  17. Care must be taken in determining appropriate supports for beams and that adequate bracing has been provided on the line of that beam. Refer to the appropriate standard for non-specific bracing design (NZS 3604 for timber structures or NZS 4229 for masonry buildings).

Applications not complying with the above conditions are outside the scope of the Online Steel in Housing web application and advice should be sought from a Chartered Professional Engineer with structural engineering experience.