HIGH TEMPERATURE BEHAVIOR OF H-SHAPED STEEL BEAM WITH CIRCULAR OPENINGS IN WEB (PART 2): REPRODUCTION OF EXPERIMENTS BY FINITE ELEMENT ANALYSIS AND ANALYSIS OF FIRE RESISTANCE UNDER VARIOUS CONDITIONS

In order to investigate the behavior of protected steel beams with multiple circular openings at high temperatures under fire conditions, full-scale load-heating experiments were discussed in the previous paper. In this paper, an analysis procedure using ABAQUS FEM code to accurately reproduce the experimental results of the previous paper is developed. Furthermore, using the developed analysis method, perforated H-beams with various hole diameters, hole spacings, and fire protection thicknesses were analyzed. The findings of this paper are as follows: 1) In order to analyze the behavior of perforated H-shaped steel beams at high temperatures using a general-purpose finite element code, an analysis method including boundary conditions, an FEM mesh model, and an appropriate method for setting the mechanical and thermal properties of the materials used, such as steel, and thermal conditions including configuration factors of various surfaces, has been developed.2) The behavior of a protected perforated H-shaped steel beam with multiple circular openings having the diameter of half of the beam height under ISO 834 standard heating, as reported in the previous paper, was analyzed using the analysis method described above.3) It was found that the fire resistance improved as the hole spacing increased, but the improvement became smaller when the hole spacing exceeded 2.5 times the hole diameter.4) The results of the analysis with the hole diameter varied in the range of 1/2 to 1/4 of the beam height and the hole spacing was either 1.5 or 2.5 times the hole diameter showed that there was no significant difference in fire resistance when the hole spacing/hole diameter ratio was the same.5) As for the fire protection thickness, when the hole spacing/hole diameter ratio is 1.5, the fire performance of the beam does not approach that of a non-hole beam of the same specification even if the fire protection thickness is doubled. However, when the hole spacing/hole diameter ratio is 2.5, the fire resistance of the beam is almost equal to that of the non-hole beam when the fire protection thickness is increased by a factor of 1.4.6) When holes with a diameter of less than 1/2 the beam length are installed in the web at intervals of 2.5 times the hole diameter or more, the fire resistance of the beam can be maintained at least as high as that of a non-hole beam, even if the inner surface is not fire protected, if the thickness of the fire protection is not less than 1.4 t