RESEARCH ON FIRE RESISTANCE AND ON CALCULATION METHOD FOR FIRE PROTECTION THICKNESS OF SPECIAL-SHAPED CONCRETE-FILLED STEEL TUBULAR (CFST) COLUMNS

To investigate the calculation method for the fire protection thickness of special-shaped concrete-filled steel tubular (CFST) columns subjected to eccentric loading, six multi-cell special-shaped CFST columns with non-expansive fireproof coating were designed. The fire resistance test was carried out and the parameters investigated include the cross-sectional shape and the thickness of fireproof coating. The test results indicate that the more the number of fire surfaces in each chamber of concrete-filled steel tubular special-shaped columns, the higher the central temperature of concrete. The cross section has little influence on the fire resistance of specimens with the same thickness fireproof coating. As the thickness of coating increases, the heating rates of specimens become lower, and the fire resistance becomes much longer. When the thickness of the fireproof coating exceeds 16 mm, the special-shaped CFST columns can meet the requirements of the specification for the first grade refractory component. The thermal and structural models were established using ABAQUS and the models were validated by the test results. Parametric study was then conducted on the fire performance of special-shaped CFST columns with different thickness fireproof coating. Then, the design method for predicting the thickness of the fire protection layer was proposed.