Research On Seismic Performance Of Precast Concrete Beam-to-Column Connections With Anchored Bottom Longitudinal Bars In Precast Beams

In the transforming and upgrading process of the construction industry in China,precast concrete structures can fulfill the demands of China's modernization of construction industry,and have been becoming one of the most important directions and breakthrough points of China's industrialization of construction industry.They are also being regarded a hotpot of research in the construction industry.In the all kinds of precast concrete structures,the emulative system has been widely applied for the relatively easy realization.However,there are some problems like high precision requirement,low applicability,inconvenient construction,in the applied precast concrete frames,which counteract the merits of precast concrete structures.In the developing trend of highly efficient construction of industrialized structures,further improvement of precast concrete structures is needed.For the sake of improving the construction efficiency,reducing the cost and realizing highly efficient construction of precast concrete frames further,the new system of combining anchored reinforcing bars and lap-spliced additional reinforcing bars was studied in the terms of seismic performances,which adopted the idea of "large diameter and small quantity".A new precast concrete beam-to-column connection partially reinforced with high-strength rebars was proposed and the seismic performance of it was researched.It adopted the idea of "high strength and small diameter",aimed to break through the technical bottleneck and promote the precast concrete frames being applied more widely.The main work and conclusions are as follows:(1)On the basis of the internal force transmission way,a new classification of precast concrete beam-to-column connections was put forward,that was directly force transmitting connection,indirectly force transmitting connection and mixedly force transmitting connection,and the kinds of exsting precast beam-to-column connections were classied and summurised.(2)Cyclic loading tests of the two kinds of precast concrete beam-to-column connections with anchored bottom longitudinal bars in precast beams were conducted,including a monolithic reference specimen,two specimens of combining anchored reinforcing bars and lap-spliced additional reinforcing bars and two specimens partially reinforced with high-strength rebars.The experimental results were analyzed,including failure pattern,hysteresis curves,skeleton curves,strength,deformation capacity,stiffness,energy dissipation.It is showed that both the two kinds of precast concrete beam-to-column connections with anchored bottom longitudinal bars in precast beams exhibit satisfactory seismic performance corresponding to the monolithic connections.(3)Finite element models reflecting the tested specimens in this paper were established and the analysis results were compared to the measured results to prove the accuracy of the finite element models.Parametric analysis based on established finite element model was conducted to study the influence of the different parameters on the seismic performance.(4)Based on the results of the cyclic loading test in this paper,the plastic hinges of test specimens were researched.Considering the characteristics of cyclic loadings,a method of measuring the plastic hinge length was proposed.A new modified plastic hinge length model was put forward,which could be applied for precast concrete components and filled in the gap of the current research on the plastic hinges of precast components.(5)On the basis of theoretical analysis and numerical fitting method,the static force calculating model and restoring force mathematic model were established.By comparing the test results and calculating results,it can be concluded that the established models have good accordance with the measured results,reflecting well the structural performance of precast concrete beam-to-column connections with anchored bottom longitudinal bars in precast beams.The seismic performance of precast concrete beam-to-column connections with anchored bottom longitudinal bars in precast beams was studied and understood deeply based on the accomplished experiment and analysis work.Some basic experimental datum and preliminary theoretical models were obtained,laying a foundation for further research and application.