| Ultra High Performance Concrete(UHPC)as a new type of building material with ultra-high strength and durability,its "light weight" and "high strength" advantages are obvious,and it can be effectively used in assembled structures improve assembly efficiency and enhance structural durability.Therefore,this paper studies the mechanical properties of UHPC precast beams and columns and the seismic performance of UHPC beam-column joints through finite element analysis.The main work and conclusions are as follows:(1)By changing the cross-sectional dimensions of beams and columns in the frame structure,the effect of beam-column cross-sectional dimensions on the bending moment distribution of beam ends and column ends of different nodes was studied,and find the range of beam-to-column stiffness ratio that makes the beam-column joint distribution bending moment more balanced and reasonable(2)Using numerical simulation method to analyze the failure process of UHPC precast beam and column members,and to study the influence of longitudinal reinforcement ratio,stirrup spacing and protective layer thickness on the mechanical properties of UHPC precast beam and column members.The results show that: The change of the longitudinal reinforcement ratio can affect the ultimate bending failure shape of the beam.It is recommended that the longitudinal reinforcement ratio of the beam is 0.68% ? 2.59%;The recommended range of stirrup spacing in the beam is 60 ? 150mm;If the thickness of the protective layer of the beam is greater than 30 mm,the beam will first yield steel bars,and the thickness of the protective layer is recommended to be 15 mm ? 25 mm.The increase of the reinforcement ratio of the longitudinal reinforcement in the UHPC column can enhance its ultimate failure load.It is recommended that the reinforcement ratio of the longitudinal reinforcement in the column should be 0.79% ? 3.80%;The yield load,ultimate load and maximum peak strain all increase first and then decrease as the thickness of the protective layer of the column increases.It is recommended that the thickness of the protective layer of the column be 15 mm ? 25 mm.(3)Establish different finite element models of UHPC beam-column joints,and explore different influencing factors on UHPC prefabricated beam-column joints by changing the axial compression ratio of members,the stirrup reinforcement ratio in the core area of the joints and the longitudinal reinforcement ratio of beams and columns.The influence law of seismic performance,the results show that: The ductility coefficient of UHPC beam-column joint members increases with the increase of axial compression ratio,but the energy dissipation capacity and ultimate bearing capacity decrease first and then increase with the increase of axial compression ratio.It is recommended that the axial compression ratio should not be greater than 0.5;The ultimate load and energy dissipation capacity of UHPC beam-column joint members are significantly enhanced with the increase of the reinforcement ratio in the core area of the joint.The overall stiffness,ultimate load and corresponding displacement of UHPC beam-column joint members increase with the increase of beam longitudinal reinforcement,but the ductility of the members decreases slightly.It is recommended that the longitudinal reinforcement of UHPC beam-column joint member beams The rate is preferably 1.00% ? 3.99%.The ductility coefficient and structural energy dissipation capacity of UHPC beam-column joint members increase first and then decrease with the increase of the column longitudinal reinforcement ratio.It is recommended that the UHPC beam-column joints have a longitudinal reinforcement ratio of 1.54% ? 3.82%.(4)The PTED node form was applied to the assembled prestressed node connected by UHPC beam and column,and the seismic performance of the node was compared with the cast-in-place UHPC node and cast-in-place ordinary concrete C50 node.The results show that the skeleton curve of the PTED node only exists in two stages,and the ultimate load borne by the loading process is between the two types of cast-in-place nodes.In terms of node ductility,the ductility of the PTED node is significantly better than the other two nodes. |
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