| Precast reinforced concrete structure is one of the significant trends of building structure development in China,because it is the representative of modern industrial production mode which adopts standardized design,industrial production,prefabricated construction,information management and intelligent application.The precast reinforced concrete structure system is not perfect enough,and the research on its overall stress and seismic performance is not systematic enough,which to some extent limits its wide application,especially in high seismic region.Beam-column joints,connection configuration and seismic performance of precast reinforced concrete frame structures are the core components and key problems of precast structure systems.In this paper,the seismic performance of steel connection beam ends,two-stage energy dissipation joints and fully precasted reinforced concrete frame is studied.Referring to the assemblability of steel connection,the steel ends of beam-beam connection and combined rotational friction and flexural yielding metallic dampers are proposed.The steel column end,the column-column steel reinforced concrete columns are proposed,and the reinforced concrete column-column and column-beam steel tube joints are formed.On the basis,a new frame structure system with steel connection between beams and columns of reinforced concrete frame and two-stage energy dissipation joints of combined rotational friction and flexural yielding metallic dampers is established,which not only facilitates the prefabrication and assembly of reinforced concrete frame,but also realizes the “whole process” energy dissipation structure system with controllable design of strong columns and weak beams.Not only could friction pinfuse joint undertake vertical loading,but also it provided energy-dissipating by rotational friction in low deformation/rotation.The corresponding frame structure,elasto-plastic analysis model and design method are established.The main research contents and innovate achievements of this paper are as follow:(1)The beam-beam connection by steel ends in non-energy dissipation area is proposed,and the calculation method of critical length of embedded steel connector is established.The non-energy-dissipation areas are mainly composed of precast concrete beams,steel connectors welded with studs on the flange surfaces.The steel end plate should be welded with longitudinal steel bars in the beam and the ends of steel connectors with equal strength to ensure its reliable connection with the main structure and transfer the internal force.The welding studs on the flange surface of steel connectors strengthen the bonding force with concrete and embedded length is important parameters that influence the bearing capacity of precast concrete beam ends.According to the mechanical characteristics of concrete beams,a formula for calculating the critical embedded length of steel connectors is proposed.The mechanical properties of steel connectors with different lengths were compared.It is suggested that the length of steel connectors should be 0.5-1.0 times of the critical length,and its bearing capacity should be 1.1-1.5 times higher than that of cast-in-place structures.It is economical and suitable for popularization and application.(2)A new novel type of connection in beam with the rotational fiction and flexural energy-dissipating is proposed.Not only could friction pin-fuse joint undertake vertical loading,but also it provided energy-dissipating by rotational friction in low deformation/rotation.Then composite channel steel plates(top and bottom channel steel plates)could primarily contribute to energy dissipating with plastic deformation in conditions of large deformation/rotation.The rotational fiction damper is composed of steel ear plates and circle friction pads.The pre-tightening force is applied to this system due to bolt nuts.The disc springs are a significant design consideration to prevent prestress relaxation.The experiment results show that a new type of connection has good bearing capacity and comprehensive energy dissipation performance.(3)On the basis of the above research,the reinforced concrete steel column ends,column-column steel tube reinforced concrete connections and beam-column joints are put forward.The requirements of "strong column and weak beam" and "strong connection and weak bar" are realized,and the rapid assembly of precast beams and columns on site is solved.The key of prefabricated beam-column joints is the composite steel sections in the core region.Through the overall stress analysis of precast beam and column,the calculation and design method of precast beam and column section is formed.The hysteretic behavior and failure mode of fully prefabricated cross-shaped beam-column joints are studied by using the column end loading method.Compared with the cast-inplace structure,the bearing capacity of the joints is improved and the failure mode of the structure is changed.The experiment results show that the core area of cast-in-place structural joints is finally sheared,while the core area of precast beam-column joints remains intact.There is a small amount of slip between the precast column and the core area,and there is no obvious damage,which verifies the effectiveness of column-column and column-beam steel reinforced concrete joints.(4)Based on the above research,the "whole process" energy dissipation and vibration reduction structure system with controllable design of strong column and weak beam,rotational friction dissipates in a small earthquake and the composite channel steel plates yield in a large earthquake.According to the different requirements of seismic performance,three types of energy dissipation systems of frame structures suitable for different seismic intensity regions are put forward,and the design method of precast beam-column connection with rotational fiction and flexural energy-dissipating frame structures are formed accordingly.Based on Pushover and dynamic time-history analysis,the seismic performance of cast-in-place concrete frame(CCFS)and fully prefabricated concrete frame(PCFS)under a small,medium,large and super-large earthquakes are comparatively studied.The results show that the overall performance of PCFS is better than CCFS,and the seismic performance of PCFS structure is significantly improved. |
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