STUDY ON THE SEISMIC PERFORMANCE OF REINFORCED CONCRETE BEAM-COULUMN JOINTS UNDER DIFFERENT STRAIN RATES

In the circumstances of dynamic loading，the reinforced concrete beam-column joint exhibits different properties with those presented in the case of quasi-static loads，due to the effect of strain rate． The majority of previous studies were focused more on the beam-column joint model as well as axial load ratio，concrete strength， longitudinal reinforced ratio etc，but less on the strain rate effect on the beam-column joint performance． Considering the strain rate effect，three beam-column joint specimens with displacement control loading were studied，respectively at the beam-end loading speed of 0. 4 mm/s，4 mm/s and 40 mm/s． Comparing the impact of different loading rates， the failure mode，carrying capacity，stiffness degradation and energy dissipation of the joint are discussed in detail． The results show that with the increasing of the strain rate，the failure mode of the beam-column joint does not changed essentially，but the number of crack within the joint continues to decline with the tendency to a single main crack damage． The higher the strain rate，the higher the yield carrying capacity and ultimate carrying capacity of the joint，and the degree of yield carrying capacity improvement is more obvious than that of ultimate carrying capacity． Within a certain range，the carrying capacity，stiffness and energy dissipation capacity of the joint are enhanced with the increase of strain rate． Beyond a certain range，the carrying capacity and stiffness decline sharply，and energy dissipation capacity is reduced as well，then the increase of strain rate will have adverse affect． Therefore，in the practical design，it is significant to consider the effect of strain rate on the beam-column joint．