Modular construction refers to the use of factory prefabricated integrated module units. The modular steel construction unit SHS (Square Hollow Section) group column is a structure composed of four independent steel column units. Due to its compositional characteristics with voids, the fire resistance performance differs from ordinary steel columns, necessitating specific study. This paper employed a sequentially coupled thermal–mechanical analysis to investigate this. The effectiveness of the simulation model was first validated by comparing the simulated time–temperature curves and fire resistance limits with experimental results. A parametric analysis was then conducted to evaluate the influence of various factors, including the load ratio, cavity spacing, insulation type, gypsum board thickness, slenderness ratio, steel yield strength, and inner panel type, on the fire resistance limit. The results show that when the gypsum board thickness increased from 10 mm to 30 mm, the fire resistance limit correspondingly increased by 126%, 120%, 130%, and 130% for load ratios of 0.4, 0.5, 0.6, and 0.7, respectively. When the steel yield strength increased from 235 MPa to 690 MPa, the fire resistance limit increased by 20%, 21%, 24%, and 43% for load ratios ranging from 0.4 to 0.7. For inner panels of Glass Fiber, Rock Wool, Mineral Wool, and Plasterboard, the corresponding fire resistance limit ratios for load ratios of 0.4 to 0.7 were 1:1.13:1.24:1.45, 1:1.14:1.23:1.46, 1:1.11:1.2:1.42, and 1:1.08:1.18:1.41, respectively. It can be found that the best way to increase the fire resistance of the modular column is to increase the thickness of the gypsum board. A simplified calculation formula for the fire resistance limit of SHS group columns was derived through regression analysis, and recommendations for fire protection design were proposed, providing valuable insights for the future design and application of SHS group columns in steel modular construction.
Liu et al. (Wed,) studied this question.