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According to the characteristics of a reinforced concrete beam-supporting column transfer structure, two types of beam-supporting column joint unit specimens are designed, and fire resistance tests are conducted on the specimens. Adopting the ISO 834 international standard heating curve for temperature control, the temperatures at the measuring points on the concrete and rebar inside each joint unit specimen and the vertical deformation at the feature position of each joint unit specimen are recorded, the corresponding curves are drawn, and the fire resistance rating is obtained. After the specimens are naturally cooled, the damage to the specimens after reaching the fire resistance rating is observed. The experimental results show the following attributes: After the reinforced concrete beam-supporting column transfer structure joint unit specimen reaches the fire resistance rating, the bending deformation of the transfer girder becomes more concentrated; the damage modes of the beam sections are bending failure; the cracks are largely located approximately 400–500 mm from the maximum bending moment section; and the longitudinal rebar in the crack section of the transfer girder could break under high temperatures. Under the coupling of fire with a constant load, the distribution of internal forces along the axis of the transfer girder changes, causing the girder to deform differently on the two sides of the supported column. Therefore, the influence of a change in the internal force distribution on the fire behavior due to the arrangement of the supported column must be considered. [ABSTRACT FROM AUTHOR]

With high strength and good seismic performance, T-shaped steel reinforced concrete column is widely used in high-rise building structure. Three T-shaped steel reinforced concrete columns were tested under high temperature and vertical load, to simulate fire effect. The test results indicate that failure characteristics, distribution of temperature field, vertical deformation characteristics and fire resistance were comparatively analyzed under different axial compression ratios and different eccentricity. The test also indicated that the cracks increased with the increase of axial compression ratio and eccentricity. The damages of web were severer than the flange. The cracks were mainly distributed on the eccentric side and mostly inclined cracks in specimen. The vertical expansion became more obvious as the eccentricity decreased. The fire resistance decreased as the axial compression ratio increased. Compared with, the fire resistance of large axial compression specimens (the axial compression ratio is 0.6) were decreased by 57% than small axial compression specimens (the axial compression ratio is 0.2). The fire resistance decreased by about 30min as eccentricity increased by 20mm. [ABSTRACT FROM AUTHOR]

Steel reinforced concrete (SRC) columns in a special shape are widely used in high-rise buildings. Due to their higher ratio of embedded steel members and larger fire exposure area compared to SRC rectangular or circular columns, SRC special-shaped columns always experience severer damage in fire. This paper experimentally and analytically investigated the residual strength of SRC cross-shaped columns after exposure to high temperatures. Experiments were conducted on eight column specimens which were heated first and loaded to failure after cooling down to room temperature. The influencing factors include heating duration, loading eccentricity and loading angle. The experimental results showed that all specimens subjected to shear failure, and their bearing capacity decreased significantly after high temperatures. With the increase of heating duration from 60min to 180min, the bearing capacity decreased by 20–27%. The bearing capacity decreased by 12–22% and 4–12% with the increase of eccentricities and loading angles, respectively. A simplified calculation method was proposed to determine the residual bearing capacity of SRC cross-shaped columns after exposure to fire. Its accuracy was validated against experimental results, which provided a reference for the post-fire assessment of SRC columns. [ABSTRACT FROM AUTHOR]