Study On Seismic Performance Of Precast Concrete Frame Beams With Large-diameter Steel Bars

The precast concrete beam-column joints with small-diameter steel bars lead to the cumbersome installation procedures and the lack of compactness of concrete pouring,which are hard to ensure the quality of concrete pouring and construction efficiency.The largediameter and large-spacing steel bars are used to the precast concrete beam-column jointsreduce,which reduce the number of mechanical connections with steel bars during field splicing,improve the efficiency of project construction and the quality of joint connections,save steel consumption,reduce energy consumption,and promote the healthy development of prefabricated concrete structure.At this stage,however,the research and application of largediameter steel bars are relatively few.Therefore,it is very important to study the performance of these components.This paper proposes a precast concrete frame beam with HRB500 large-diameter steel bars,which adopted the beam end assembly method.The longitudinal reinforcement of the beam was D40-D32 and D32-D25.By the full-scale low-cyclic experiment and finite-element analysis,the behavior of precast concrete frame beam with large-diameter steel bars such as failure mode,bearing capacity,hysteretic performance and stress mechanism was analyzed.The main contests are listed as follows:Firstly,connection performance of precast frame such as connection mode by shear key and full grouting sleeve,and anchorage mode of steel bar by welding anchorage was analyzed.The research shows that: the whole performance of the specimen can be ensure by adopting the construction measure with full grouting sleeve,shear key and anchorage at the end of the steel bars.Secondly,full-scale low-cyclic experiment were carried out to study the failure mode of the precatst frame beam with large-diameter.The effects of two factor(diameter of steel bar,presence or absence of additional web reinforcement)on crack propagation,bearing capacity,stiffness degradation,energy dissipation capacity and other hysteretic performance were studied by the connection mode of plus and the end on the connection performance of prefabricated frame beam is studied.The test research shows that: the failure mode of the specimens were bending failure at the beam end,and the cracking load and flexural capacity of the large-diameter reinforced prefabricated members can be calculated according by the current code.The ultimate load,yield load and energy dissipation capacity were inceresed by rebar steel bars D40-D32.The crack propagation was crack limited by setting of additional web reinforcement.Thirdly,by means of finite analysis of ABAQUS,the behavior of stress mechanism and failure mode of the precast concrete frame beam with large-diameter steel bars were study.The results was compared between numerical analysis and test.The results show that: the properties such as failure mode,the development of plastic damage of concrete were in good agreement with test,the difference was small between the load eigenvalues.Fourthly,the mechanical properties between the precast concrete frame beam with largediameter,the monolithic concrete frame beam with large-diameter steel bars,and the monolithic concrete frame beam with small-diameter steel bars wrew compared.The results show that: the bearing capacity of large-diameter precast reinforced concrete frame beams was basically consistent with cast-in-place concrete frame beams.