Research On Mechanical Properties Of Two New Types Of Shear Connectors In SRC Columns

The composite structure of the steel-concrete column has the advantages of both reinforced concrete and steel structure,and is widely used in high-rise and super high-rise structures.In steel-concrete columns,there are usually too many stirrup arrangements,complicated installation,and low initial stiffness.Steel and concrete are two common materials,and the bonding effect between the two is small.In order to exert the performance of the two materials,it is very necessary to arrange shear connectors on the contact surface of the steel and concrete in the steel-concrete column.At present,the shear connectors arranged in steel-concrete composite columns mainly include studs and bolt connectors.Under the action of a small force,relative slippage occurs between steel and concrete.In order to reduce the relative slip between steel and concrete,A practical and effective method is needed to achieve shear force transfer between columns.To this end,two new types of shear connectors are proposed by the research group.They areπ-type perfobond shear connector and π-type crestbond shear connector.For the π-type perfobond shear connector,6 groups of 10 test pieces were pushed out tests,and the failure mode,load-slip curve,and stress development law of the new perforated plate shear connector were studied.Analyzed the effects of penetration steel bars,web spacing,flange plate arrangement direction,longitudinal arrangement number of connectors,and loading methods(monotonic loading,repeated loading)on the initial stiffness,shear bearing capacity and other mechanical properties of π-type perfobond shear connector influences.The results show that the initial stiffness of the π-shaped perforated plate connector is relatively large,and the presence of the flange plate bears most of the shear force,prevents the development of longitudinal penetration cracks,and improves the ultimate bearing capacity;the placement of penetration steel specimens The load-slip curve drops gently,showing good ductility;with the decrease of the web spacing,the restraint effect of the concrete between the webs of the connecting piece increases,and the ultimate bearing capacity of the specimen increases;under repeated loads,The connector shows good mechanics and energy consumption.The finite element software ABAQUS is used to analyze the parameters of the π-type perfobond shear connector,and it is concluded that as the web spacing decreases,the confinement effect of the concrete below the flange plate of the π-shaped aperture plate connector increases;Plate thickness,connector web thickness,steel strength,steel bar yield strength,and flange plate width have little effect on the ultimate bearing capacity of the specimen;when the concrete strength increases from C40 to C50,C60,C70,the bearing capacity of the specimen increases When the specimen is damaged,it is limited by the strength of the concrete;the ultimate bearing capacity of the specimen with penetrating steel bars is significantly improved than that of the specimen without penetrating steel bars.When the diameter of the steel bar increases slowly,the ultimate bearing capacity of the specimen slowly increases;Finally,the force transmission model of the connector is established through the comparison of finite element and experiment,and the design method of the connector and the calculation formula of the bearing capacity are put forward.For the π-type Crestbond shear connector,5 groups of 9 specimens were pushed out tests with varying parameters such as the arrangement of the penetrating steel bars,the spacing of the webs,the orientation of the flange plate,the height of the connector and the loading mode.The results show that the penetrating steel bars have little effect on the ultimate bearing capacity and significantly improve the ductility of the specimen;reducing the web spacing increases the ultimate bearing capacity and ductility of the specimen,and the web restricts the expansion of the concrete below the flange plate The smaller the spacing,the greater the limiting effect;the orientation of the flange plate of the π-type Crestbond shear connector has a greater impact on the ultimate bearing capacity of the test piece.When the flange plate of the connecting piece is down,the ductility of the test piece is significantly reduced;the height of the connecting piece is on the limit The bearing capacity has a greater influence.As the height increases,the initial stiffness and ductility increase;under repeated loads,the specimen still has a higher bearing capacity.The connector has good energy consumption and ductility under repeated loads.The finite element software ABAQUS is used to analyze the parameters of the π-type Crestbond shear connector,and it is concluded that the web spacing,web thickness,height and concrete strength of the connector have a greater impact on the mechanical properties of the connector.Reducing the web spacing,increasing the height of the connecting piece,and increasing the concrete strength significantly increase the ultimate bearing capacity of the connecting piece;changing the thickness of the flange plate of the connecting piece,the yield strength of steel bars,the yield strength of steel and the width of the flange plate affect the ultimate bearing capacity of the connecting piece smaller;the ultimate bearing capacity of the specimens with increased penetration steel bars is not much different than that of the specimens without penetration reinforcements;as the diameter of the reinforcement increases,the bearing capacity of the connectors increases slowly.It can be seen that when the diameter of the reinforcement slowly increases,the ultimate bearing capacity of the specimens The force increases slowly;In this paper,the shear force transmission mechanism of the connector is analyzed.And put forward suggestions on the design method of the connecting piece and the calculation formula of the bearing capacity.the shear force transmission mechanism of the connector is analyzed.