Structural performance and design of high strength steel welded H-section members under combined compression and bending in fire

• Experimental investigation into the fire resistance of high strength steel H-section columns under combined compression and bending. • 9 specimens were tested. • Elaborated FEM was developed and validated based on the test results. • New design approach was recommended. An experimental investigation into the overall buckling behaviour of high strength steel (HSS) H-section columns under combined compression and bending in fire, to support the assessment and development of structural fire design, is presented. Three grades of high strength steel - Q460, Q690 and Q960 and two H-sections, covering two different cross-sectional slenderness, were examined. Nine (minor- and major-axis) eccentric compression tests were conducted under fire conditions. Suitable finite element models were then developed to simulate the behaviour of tested columns and were validated against test results. After the model was validated, parametric studies were subsequently carried out to generate further numerical data. The results from tests and parametric studies were compared with the design recommendations provided in European and Chinese specifications to assess the accuracy and safety of the fire design standard. A new design approach was proposed to be used to more accurately estimate the critical temperature of HSS welded H-section columns under combined compression and bending.