| Green High-performance Fiber-reinforced Cementitious Composites(GHPFRCC)is a new type of cement-based material modified with a large amount of fly ash to replace cement partly and optimal mix design,which has excellent mechanical properties and is environment friendly.For advantages in its remarkable crack control ability,high performance in tension toughness,ductility and energy dissipation,GHPFRCC can be applied in structure seismic strengthening and durability improvement.Besides,the mechanical properties of structure would be enhanced when GHPFRCC is applied in complex loaded areas.Prefabricated concrete frame structure is widely constructed in civil engineering,which has features in efficient construction,intensive manufacturing,resources conservation and environment protection.Prefabricated beam column joints play a vital role in component connection,load transmission and force distribution,which bear complex stress under seismic action,joints failure may lead to the collapse of the whole structure.Based on the equivalent cast-in-place design principle,this paper investigates the seismic performance of GHPFRCC prefabricated beam column joints by tests and numerical simulation,in which GHPFRCC are poured in the core area and secondary casting place,plus,division design and interface methods are used in these joints,the detailed contests are as follows:(1)present a summary of research progress on prefabricated beam column joints and research status on prefabricated beam column joints with ECC,then put forward new forms about GHPFRCC prefabricated beam column joints.(2)conduct a series of bending tests on interface bonding between GHPFRCC and concrete or the interface bonding between old GHPFRCC and new GHPFRCC to investigate the effect of different interface bonding forms on the flexural behavior correspondingly,then select the bestperformed form about bending strength and flexural ductility,exposed aggregate interface or bubble film keyway,to apply on construction progress of prefabricated beam column joints.(3)make a design on prefabricated beam column joints with 2 different assembly methods according the principles of seismic rules-“Stronger column and weaker beam,stronger shear and weaker bend,stronger joint and weaker member”,and the construction principles of assemblyconstruction friendly and increasement of assembly rate,then low cycle repetitive loading tests are conducted on 5 full scale specimens,including 3 GHPFRCC prefabricated beam column joints with grout sleeves,1 C30 prefabricated joint with grout sleeves and 1 cast-in-place beam column joint.(4)employ the Open Sees to conduct variable parameters analysis on GHPFRCC beam column joints and calculate the influence of axial compression ratio and length of GHPFRCC on its seismic performance.The tests and simulation come to the following conclusions:(1)the seismic behavior of prefabricated beam column joints is better than that of cast-inplace concrete beam column joint.(2)the core of joints with GHPFRCC performs excellent in improving the capacity of shear resistance so that the core has less possibility to be destroyed.(3)joints with grouts sleeves or core with added rebars can enhance the capacity of energy dissipating and damage resistance.(4)the application of exposed aggregate method and keyway bubble film method in interface connection of beam column joints can satisfy the need of beam column joints under seismic condition,so that superposed beams may not necessary for prefabricated beam column joints.(5)the simulation to the prefabricated beam column joints with Open Sees performs well,and the simulated results agree well with test results. |
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