| In recent years,prefabricated reinforced concrete structure have been widely employed because of their simple construction,energy saving and environmental protection,the commonly used structural systems include wallboard systems,frame systems,etc.The beam-column joint is a key component in the prefabricated reinforced concrete frame structure,and its safety has an important impact on the overall safety of the structure.During the service period,the fabricated structure will be subjected to the lateral impact of accidental loads such as heavy impacts.Although a large number of low speed impact tests have been carried out on RC columns,RC beams and beam-column joints of steel structure,few experiments have been performed to clarify the dynamic behaviors of PC beam-column joints subjected to impact loading.But the impact performance of prefabricated beam-column joints under impact loading is seldom studied,so it is urgent to carry out systematic research.In this paper,the side beam-column joints of precast reinforced concrete frame structure were selected as experimental research objects.Based on the experimental study on the impact resistance of RC beams and RC columns,the simplified beam-column joints test model was designed.By adding butterfly springs and hydraulic jacks to the original drop hammer impact test device to improve the test device,the low-speed impact test of PC beam-column joints and RC beam-column joints with pre-axial loading was designed and conducted.Three prefabricated columns and PC beam-column joints assembled with composite beams and three ordinary RC beam-column joints were subjected to the drop-weight impact test with pre-axial force on the column end and concentrated force on the beam end,respectively.The failure mode,impact force,support force,energy dissipation capacity,deformation and stress characteristics of beam-column joints.Furthermore,through numerical simulation,further parameter analysis of the impact performance of the two types of joints was carried out.It is found that the crack developments and failure modes of two types of beam-column joints are resemble under the impact energy of 25.313 kJ,and there is no obvious failure at the interface between PC beam-column joints prefabrication and post-casting.Within the impact energy range of energy is 39.513kJ-55.193 kJ,the failure mode of PC beam-column joints is more serious than that of RC beam-column joints,especially at the interface between precast and post-cast,where the post-cast sitting slurry layer area of the concrete falls off in a large area and the cracks are concentrated at the core area and the interface.Within the impact energy range of 39.513kJ-55.193 kJ,there is no significant difference in the deflection and force response process between PC beam-column joints and RC beam-column joints under the same impact loading.Within the impact energy range of 25.313kJ-39.513 kJ,both PC specimens and RC specimens maintain good energy dissipation capacity,and the integrity and energy dissipation capacity of PC specimens are lower than that of RC specimens.With the increase of impact energy,the difference between the energy dissipation capabilities of the two types of joints is increase.The FE parametric analysis shows that with the increase of axial pressure ratio,the peak of displacement of the specimens are reduced and the peak of impact force is increased under the impact energy of 25.313 kJ. |
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