Until recent years stainless steel has been viewed in much the same way as normal carbon steel and with its reduced strength and increased fabrication cost its true potential as a structural material has not been exposed. However with increases in carbon steel prices due an demand that way out exceeds the supply mainly due to the economic boom currently underway in China and as more research is been undertaken to develop a true understanding of its material properties coupled with its pleasing aesthetics and low maintenance costs stainless steel is becoming ever more popular as a structural material.It can be clearly seen from Fig. 1 that stainless steel possesses a significantly different stress strain relationship to that of carbon steel. Unlike carbon steel whose stress-strain relationship can sufficiently described by the idealised elastic, perfectly-plastic model for materials such as stainless steel that exhibit non-linearity below the yield point this idealised model becomes significantly inaccurate (Gardner & Ashraf 2005). This has led to the development of a new model for materials that portray such behaviour. In the case of stainless steel the model currently accepted by most design codes is the modified Ramberg-Osgood formula proposed by Hill (Ashraf et al. 2006). In recent years it is becoming more accepted that a two tier formula best describes the full stress-strain relationship as it has been found that the current Ramberg-Osgood formula becomes highly inaccurate past the 0.2% proof stress....