Study On Seismic Behavior Of Precast High Ductile Concrete Beam-Column Joints

The development of precast concrete structure is the indispensable way for the industrialization of the building.The precast structure can improve the level of mechanization,speed up the construction progress,accomplish the low power,low emissionconstruction process,and achieve the green development of the construction industry.Beam-column joint is the key component which links beam and column.Under semic actions,joint core zone is in shear-compression composite stress state which is caused by tension on one diagonal direction and compression on other diagonal direction of joint core zone,so shear failure occurred in joint core zone,and energy-dissipation capacity is rather low.High ductile concrete(HDC)is a new structural material with high toughness,high crack resistance,high durability and high resistance to damage the ability,especially it is able to with multiple fractures and strain hardening characteristics under tension together shear loads.HDC used as precast beam-column joints,it can improve the brittleness of conventional concrete materials significantly,improve seismic performance and deformability of concrete structures.In addition,High ductile concrete used in assembly field with easy construction,material saving,low comprehensive cost and other obvious advantages,has broad applied prospect.In this paper,the connection performance of sleeve grouting in the precast HDC beam-column joints is studied firstly,on this basis,precast HDC beam-column joints are designed,experimental study is carried out and theoretical analysis.The main studies are as follows:(1)Based on the theoretical research,the construction technology of the precast high ductile concrete beam-column joint is designed.Three pull-out tests of sleeve joint specimen were carried out.Five precast high ductile concrete beam-column joints and one precast concrete beam-column joint as a comparative specimen were designed and fabricated.(2)Tests by low cycle reversed loading,the specimen failure process and failure modes,hysteretic property,load-carrying capacity,deformation capacity,ductility,stiffness,energy dissipation capacity and shear capacity of the core zone are studied.The results indicates that the use of HDC in precast beam-column joints can improve the load-carrying capacity,deformation capacity and energy dissipation capacity;the use of HDC in precast beam-column joint core zone can substitute shear-sturrups partly;Beam end using HDC can improve ductility the load-carrying capacity and energy dissipation capacity;the increase of axial load rations of text axial load rations can improve shear capacity of joint core zone.(3)Based on the analysis of the test results,by analyzing shear bearing mechanism of precast HDC beam-column joints,the diagonal strut mechanism and the truss mechanism would be existed in joint core zone.By analyzing the proportion of shear capacity undertaked by the diagonal strut mechanism and the truss mechanism to the total shear capacity,considering the HDC strain-hardening characters,the calculation model of shear bearing capacity of precast HDC beam-column joint core zone was put out.The calculated value has a good agreement with the test results,there it can provide a reference for practical engineering.