EXPERIMENTAL RESEARCH ON DYNAMICAL PROPERTIES OF HRBF500 RC BEAM AFTER FIRE AND NUMERICAL MODELING OF TEMPERATURE FIELD

The hot rolled bar of fine grains 500 MPa is a new material which has high strength and good ductility.For promoting its application,through the flame test,the fire behavior of HRBF500 reinforced concrete beams was studied in fire,under the ISO834 standard fire curve.Considering the thermal properties of concrete and using ANSYS program,the transient temperature distribution within the cross-section of the concrete beams was studied at the high temperatures and the data were compared and analyzed with the experimental results.It was also conducted the vibrator test of four fine grain reinforced concrete beams after fire to study their dynamic properties.With different time under fire and when the beams were cooled to room temperature naturally,their self-resonant frequencies were investigated through the vibrator test.The results show that the self-resonant frequency of concrete beam is seriously affected by fire.Some conclusions are drawn out: The longer it is exposed to fire,the smaller is its self-resonant frequency.And also,the smaller is bar ratio,the bigger is its self-resonant frequency．