How do old structural steels behave compared with modern grades?
A. Old structural steels are very similar to modern day mild steels. On a pro-rata basis they do not lose their strength at elevated temperatures quicker than Grade 275 for example. Since the design loads in use at the time when old mild steels were manufactured were somewhat lower by proportion, they would under the same fire conditions behave slightly better. Further information is given in the research publication ‘The application of BS5950: Part 8 on fire limit state design to the performance of old structural mild steel’.
