As you are aware, MiTek Designs and Design software conform 100% to the required standards for rational design in South Africa, using loading from SANS 10160 and timber design requirements from SANS 10163. The use of Limit State Design has been the standard in the Steel and Concrete Industry for at least the last 10 years, and this is the standard taught at tertiary Institutions.
There has been a request from the Joint Structural Division of the South African Institute of Civil Engineers, that the timber Industry generally align themselves with the standard design methodology, namely limit state design, and with this in mind, have requested the SABS to encourage the use of Limit State Design from 2017.
MiTek has had the Limit State Option available in 20/20 with the introduction of Ultra Span Limit State Design with version 5.65, and this has also been implemented in our Timber Design offering with the release of V5.66 in the second quarter of 2016.
We have had some very positive feedback from our fabricators and the difference in design is completely transparent to the end user. Internally, the limit state design uses load factors on the applied loads together with material factors, which can model the actual design situation with greater reliability. This has the advantage, generally, of better timber and plate designs. The change in the design process of using load factors and different duration of load factors (K – factors are now gamma factors) can influence individual truss designs, and as such these should not be compared against the allowable stress designs, but the overall results will generally be the same or better.
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