Experimental Investigation On The Fire Resistance Performance Of Cross-Special-Shaped Steel Reinforced Concrete Columns

Steel reinforced concrete special-shaped columns are structural members which configure section steel and appropriate amount of longitudinal reinforcement and stirrup in cross section, then outsourcing concrete. This structure has high bearing capacity and economic cost is relatively low. However, this structure is exposed to a large area under fire, and the steel skeleton is high in steel content. Therefore, the cross-shaped column structure is more easily damaged than concrete columns of other cross section under the same fire load. Current research mainly focus on the fire resistance of specially shaped columns after high temperature, and there are few studies on the fire resistance of special-shaped columns under high temperature. In this paper, the fire resistance of the SRC cross-shaped columns is studied from two aspects of experiment and numerical simulation. The main work and conclusions are as follows:This experiment design and pour 16 steel reinforced concrete columns, and experiment with them on four sides fire under constant load by using self-made electric heating furnace. Relative data of eccentricity ratio and load ratio are analyzed and compared. The following conclusions are obtained:(1) The axial deformation degree of the member increases with the increase of load ratio and eccentricity ratio. Each column shows milky white and a large number of irregular small cracks. Vertical cracks appear along the column with the load and the eccentricity increases, which is about 2cm in width.(2) Seen from distribution of temperature field in the column section limbs, the heating rate of 7 members are basically the same. Heating rate of partial measuring points accelerate at 100 minute after members cracking.(3) Seen from distribution of temperature field at the steel web, temperature of measuring points at member limb web are basically the same, and the heating rate of the seven members are roughly the same.(4) There is a large increase in the displacement of the eccentric loading end. On the other side, the change of displacement is very small, and the displacement curve tends to level.(5) With the increase of load ratio, the fire resistance limit of the member decreases by about 30min.(6) When the load eccentricity is 40mm, the decrease of fire resistance limit is larger than that of that of 60mm and 80mm.The decrease increases by about 50%.(7) As the load ratio increases, the fire resistance limit of the member is decreased, and the decrease range under different eccentricity is basically the same. The temperature field of the cross-shaped column is simulated using the finite element software ABAQUS. The simulation of temperature field doesn’t consider cracking and evaporation of water vapor in concrete and other practical factors,so some values of heating curves are slightly different from the experimental values.The heating trend of computer simulation value is basically the same with temperature field measured by experiment, which can reflect the general heating law of the section.