fire resistance; tubular column; high strength steel; numercial analysis; HSS; experimental test; validation
Abstract :
[en] High strength steels (HSS) have specific chemical compositions, which primarily depend on rolling
tempering techniques, element thickness and the producer. Nonetheless, EN1993-1-12 related to HSS
up to S700 grade does not provide any additional note on the design of steel structures subjected to
fire and the designer is referred to EN1993-1-2 valid up to S460 grade. This paper presents the results of a numerical analysis on the behaviour at elevated temperature of Circular Hollow Sections (CHS) columns made of HSS. In details, three full-scale HSS CHS columns with average measured yield strength of 822 MPa and 3.15 m long were tested under the standard ISO fire with constant
eccentric compression load. Two members were made of a cross section 323.9 mm x 10 mm and one of a cross section 355.6 mm x 12 mm. The constant applied loads during the tests were respectively equal to 10%, 14% and 19% of the axial capacity of the columns at ambient temperature. Then, a nonlinear thermomechanical finite element model made of solid elements was developed by means of ABAQUS. A fully-coupled analysis using Geometrically and Materially Nonlinear Imperfect
Analysis (GMNIA) was employed meaning that the temperature field was determined together with
the stress-displacement fields. The calibration of the numerical model was carried out against
experimental data by exploiting the thermal and the mechanical properties of steel provided in EN1993-1-2. A sensitivity analysis was performed to highlight the main parameters that affect the
simulation results, i.e. mesh size, residual stresses, geometrical imperfections etc. The calibration process showed a good agreement between the numerical results and the experimental outcomes both in terms of failure temperature and of failure mode. With the calibrated model, it was finally possible to perform a preliminary parametric analysis by varying the applied load and the column relative slenderness to assess the appropriateness of the buckling curve included in EN1993
-1-2 to predict the fire resistance of HSS CHS columns.
