Abstract
M.Ing.
Grade 350W structural steel was introduced into the South African steel market to replace its predecessor 300W structural steel. 350W structural steel has a 50 MPa increase in its minimum yield strength. Currently, little or no experimental data exists that describes the behaviour of full scale 350W structural sections. No extensive comparisons between 350W and 300W, as to their structural behaviour, exist.
The main aim of this investigation was firstly to determine if the minimum yield strength was fully realised throughout typical sections and if the increase in yield strength changed the yielding behaviour of the material. Secondly, the effect that the increased yield strength has on the structural resistance of axial compression members.
The investigation largely consisted of an evaluation of firstly the material and then secondly the structural behaviour of full scale member sections as axial members.
It was found that all the sections tested complied with the minimum specified yield strength of 350 MPa. In general, 350W hot rolled structural steel yields more gradually than 300W hot rolled structural steel. This increase is small and seems to be of little significance as far as the overall behaviour is concerned. In general, the increase in minimum yield strength from 300 MPa to 350 MPa has realised an increase in critical buckling strength well into the medium slenderness ratio region and is beneficial for members of short and intermediate lengths. The data seems to indicate that SANS 10162-1:2005 can be used with confidence when designing axial compression members in 350W hot rolled structural steel.