| With the promotion of urbanization and the strong encouragement of the government,prefabricated buildings have a bright future and become one of the development trends of building structures.In order to solve the problems such as difficult construction and long construction period of cast-in-place beam column joints,which are widely used at present,and restrict the development of dress matching buildings,it is imperative to study a new type of dry connection assembly beam column joints.In this experiment,a T-shaped precast beam supported by corbel is proposed,and8 high-strength bolts are used to connect with the precast column through the cantilever lug of the beam end to form a semi-rigid dry connection beam column joint.The full-scale experimental models of precast corbel columns and precast T-beams are applied with low cycle complex loads to study the seismic failure characteristics of joints.Based on the test results,ABAQUS finite element simulation software results and mechanical theory calculation,the ductility coefficient,bearing capacity and energy consumption capacity of the new semi-rigid beam column dry-type joint are analyzed.Through this study,the main conclusions are as follows:(1)The axial compression ratio under the seismic combined axial force meets the requirements of the secondary frame.The new semi-rigid beam column dry-type connection joint studied in this experiment was finally damaged at the beam column joint,and the concrete near the upper and lower areas of the T-shaped beam end of the frame column was crushed;the bolts and nuts were greatly deformed;there were deep cracks near the intersection of the T-shaped beam end lug and the main beam;there were derivative cracks at the T-shaped beam end extending to about two thirds of the beam cantilever end;there was no crack at the beam cantilever end.There are no cracks on the column end,bracket column and node core.The experimental results show that the plastic hinge of the new fabricated beam column semi-rigid joint appears on the beam,which can make the frame column not produce plastic hinge except the bottom column base,and meet the requirements of strong column and weak beam.The support platform of prefabricated corbel column makes the bolt group bear tension to balance the bending moment of the main beam.The joint is small in shear,more reliable and meets the requirements of strong shear and weak bending.(2)When the inter story displacement angle of the structure is large,the screw at the connection part has great bearing capacity after contacting with the hole wall.The friction damping effect of the two contact surfaces of the beam and the corbel column,the ultimate strength pin bolt effect of the internal longitudinal reinforcement of the lug at the end of the beam,the irregular inclination of the internal longitudinal reinforcement to resist the bending moment of the main beam,and the length of the beam supported on the corbel is more than 250 mm.Even if the connection fails under the big earthquake,this experimental section Points can still prevent the structure from collapsing.In addition,the aggregate biting force and thick steel plate at the end of the beam when the fracture section of the lug is closed are not considered to be more conducive to improving the joint resistance,which makes the bolt group tension tend to be evenly distributed.(3)When the experimental displacement reaches 125 mm,the failure load is greater than 0.85 times of the maximum load,the bearing capacity of the structure is excellent,and the ductility coefficient of the joint is greater than 3.(4)The maximum bearing capacity of the new semi-rigid beam column dry joint is 27.27% higher than that of the cast-in-place joint.The energy consumption of the cast-in-place joint mainly depends on the plastic deformation of the reinforcement and concrete in the core area of the joint and the bending deformation of the beam end.The energy consumption of the assembled semi-rigid joint mainly depends on the plastic deformation of the cantilever lug reinforcement and concrete at the beam end,the aggregate biting force when the fracture surface is closed,the bending deformation at the beam end,the plastic deformation of the bearing high-strength bolt and the damping effect of the contact surface between the corbel column and the beam end.The types of energy consumption of experimental joints are more than that of cast-in-place joints.Furthermore,the improvement of joint properties(strength,stiffness,ductility)and the improvement of seismic resistance of energy dissipation technology are studied by numerical analysis.Furthermore,the seismic damper is set on the corbel,and the numerical analysis shows that adding the damper can form the energy dissipation joint and the assembled frame structure into three lines of defense;the design of "strong joint" is deepened through the damping.Through this study,the main conclusions are as follows:(5)The size of the cantilever lug at the beam end is sensitive to the deformation of the joint and improves the bearing capacity of the joint.If the deformation of the structure needs to be controlled,the size of the cantilever lug at the beam end can be changed to control the P? effect.(6)It is sensitive to the bearing capacity of the joint,insensitive to the deformation of the joint,and increased the energy consumption of the joint.(7)The load and displacement ductility of the semi-rigid energy dissipation joint are obviously improved,the hysteretic curve is very full,and the seismic absorption capacity is very strong.(8)The semi-rigid energy dissipation joint changes the stress mode of the joint,effectively reduces and controls the development of the beam end lug and the T-shaped beam end crack,and reduces the strain value of the beam end lug longitudinal reinforcement and the bearing high-strength bolt.The damping effect obviously reduces the external effect of the earthquake on the joint,and prevents the beam column joint from being broken.(9)If the dead load and floor live load of the slab are considered,the pressure on the contact surface between the lower end of the T-beam and the corbel is greater,and the energy dissipation effect of the damper is more obvious.There is a space of 20 mm between the damper and the column to make it have enough shear lag deformation so as to consume more energy.Figure [62] table [21] reference[ 88]... |
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