Research On Seismic Performance Of New Fabricated Beam End Strengthened And Weakened Joints

With the increasing improvement of the national economy and the quality of the people,people are deeply aware of the social concepts of green buildings and environmental protection.The traditional extensive buildings have been difficult to adapt to the development of the times due to serious environmental pollution and waste of resources.Concrete structure and fabricated steel structure have the advantages of light weight,good seismic performance,recyclable resources,and reduced environmental pollution.The processing plant can realize modularization of components and standardized production.It is an inevitable choice for liberating labor,adhering to sustainable development and green concepts.The current research on frame beam-column joints is mostly concentrated in a single field of reinforced or weakened type,and there is less research on reinforced and weakened joints.In actual situations,reinforced and weakened joints have the advantages of both reinforced and weakened joints.It has broader application value and application prospects.This paper proposes a new type of fabricated beam end strengthening and weakening joint connection node.The node is strengthened by the outer ring plate at the column end and the beam end flange is weakened by the dog-bone type.Then the new node is combined with the other three types of nodes(only enhanced nodes,only weakened nodes,and ordinary nodes that are neither strengthened nor weakened).The seismic performance of this new type of node is compared to that of the other three types of nodes.It has a huge performance advantage under seismic loads.Finally,the geometric parameters of the beam-column node are changed.Single parameter analysis,the geometric single parameters changed in the study include: beam flange dog-bone weakened length,beam flange dog-bone weakened depth,square steel tube column wall thickness,additional internal diaphragms,and compared the seismic performance between different variable parameter nodes.The following main conclusions are obtained:(1)The four types of nodes(both enhanced and weakened nodes,only enhanced nodes,only weakened nodes,and ordinary nodes)hysteresis curves all present a "spindle shape",the hysteresis loop shape is full of outer drum,and it has good shock resistance and energy consumption,Which shows the rationality of the node design.Taking JD-1 as a reference node,the area of JD-2 hysteresis loop and the height of a single hysteresis loop are slightly reduced compared to it.The area of hysteresis loop and the height of the hysteresis loop of JD-3 and JD-4 are obviously lower than those of JD-1,and the degree of fullness is obvious.No,it is judged that the only weakened joints designed in this paper,ordinary joints are obviously inferior to JD-1 in load-bearing capacity and deformation capacity,and seismic energy dissipation capacity,which highlights the strength and weakened joints designed in this thesis in load-bearing capacity and deformation energy consumption.Obvious advantages in ability.(2)Comparing the peak bearing capacity of different nodes,it is concluded that the addition of outer ring plates can greatly improve the bearing capacity;the setting of the beam flange dog-bone weakened section reduces the load-bearing capacity to a certain extent;the weakened length of the beam flange dog-bone weakened section increases The impact on the peak bearing capacity of the joint shows a trend of first increasing and then decreasing,but the overall numerical difference is small,indicating that this parameter has little effect on the bearing capacity;the increase in the weakened depth of the dog-bone weakened section of the beam flange significantly weakens the load-bearing capacity of the joint;square steel pipe The increase in column wall thickness has a certain increase in the bearing capacity of the joint,but the enhancement is not obvious;the increase in the inner diaphragm of the square steel tube column also has a significant improvement in the bearing capacity of the joint.(3)The increase in the wall thickness of the square steel tube column,the increase in the column inner partition,the increase in the weakened depth of the beam flange dog-bone section,and the increase in the weakened length of the beam flange dog-bone section all increase the energy dissipation capacity,and the weakened depth is more sensitive.,The effect of improving energy dissipation capacity is the best.(4)The node failure position is finally near the junction of the outer ring plate flange and the beam flange dog-bone section end.The yield range of the node members has a similar development trend,all of which are first in the contact area of the square steel tube column and the outer ring plate.The end of the beam(or the weakened part of the beam dogbone)appears,gradually extending radially to the surroundings over time,and finally the penetration of the yield range appears.Due to the existence of the dog-bone weakened section of the reinforced and weakened joints,the node failure area is transferred from the proximal column end to the beam dog-bone weakened section,which can effectively transfer the position of the plastic hinge and better realize the "strong column and weak beam" Anti-seismic design concept.(5)The reinforced and weakened joints have the characteristics of being recoverable after the earthquake.During the whole process of the joints,the square steel tube column has a small yield area,and most of the column area does not reach the yield stress.After the earthquake,the column yield area will be removed.Appropriate repair welding and replacement of the remaining damaged components of the node can complete the quick repair after the earthquake.