| A type of replaceable energy dissipation connector – precast concrete frame(REDC-PCF),which may promote the development of industrial construction in China,is proposed in this dissertation.The REDC-PCF can simplify the construction procedure of the building,while a high seismic performance and rehabilitation performance can be realized as well.The replaceable energy dissipation connector(REDC)can be regarded as a part of the reinforcement in the beam,which could bear the bending moment under elastic condition.The shear force is borne by the pin sharft system.The construction method is chosen as dry connection.The REDCs remain elastic and bear bending moment when the frame works under gravity or frequent earthquakes.Once a moderate earthquake or rarely met earthquake happens,the REDCs can yield first and dissipate the inputted energy by the post-yield deformation,in which a high ductility and energy dissipation capacity can be obtained.The main structural members,such as beams and columns,can remain elastic under the strong earthquake.The rehabilitation of the frame can be achieved by replacing the damaged REDCs,while both the mechanical mechanism and seismic performance can be recovered completely.In this dissertation,the theoretical research,experimental and numerical study are conducted on the mechanical mechanism of the REDC and its seismic performance in precast concrete frame.The main works are listed as follow:(1)The REDC-PCF is proposed to solve the problems in the common reinforcement concete frame,as the ductility is limited by the compressive capacity of the concrete,while the seisimic rehabilitation is difficult to achieve.The concrete of the beam and the column is separated,while the crushing of the concrete of the beam end and the joint could be eliminated.The REDC is settled in the upper and lower side of the beam end to resist the moment and the pin shaft system is selected as the shear resisting component of the joint.The seismic principle is convinent to achieve.The damage of the structure under a strong earthquake is concentrated in the REDCs,while the main members remain elastic.The seismic rehabilitation is convenient to achieve by replacing the REDCs.The construction of the joint is easy,in which a reasonable accuracy requirements can be obtained.(2)The demand of the beam-column joint rotational stiffness and the construction of the REDCs are analyzed through the formula derivation,which is based on the mechanical mechanism of the semi-rigid beam-column joint.The relationship between the relative angle of beam and column and inter-story drift of the frame is obtained based on the semi-rigid connection theory.The relationship between the rotational stiffness of the joint and the axial stiffness of the REDCs is obtained through the parameter of relative angle of beam and column.The calculation method of the REDC axial stiffness is derived based on the series stiffness method,then the joint rotational stiffness can be obtained.Combining the lateral magnification factor of the semi-rigid frame,the length demand of the REDC is derived.Besides,the construction details of the REDCs are illustrated.(3)Experimental study on the REDC specimens are conducted.A total of 12 specimens were tested by low-cycle reversed axial-load on the mechanical test system(MTS).The test results reveal that the REDC specimens can perform a stable hysteretic property and high energy dissipation capacity.The core member of the REDC exhibited a high-order buckling modes,while a full-length yield can be observed on the core member.The construction method between the transition segment and the yield segment is a key factor affecting the low-cycle fatigue capacity,the circular chamfering specimens exhibited a higher low-cycle fatigue performance.Additionally,the strain amplitude on the specimens is a factor affecting the mechanical property of the specimens.(4)Theoretical and numerical analyses are conducted on the REDC specimens.The buckling mode of the REDC core member is formula derived,in which the influence of the friction between the core member and the restrainer was taken into consideration.The formula for obtaining the compression strength adjustment factor of REDC is derived by considering the contact force and friction.The demand of the out-of-plane stiffness of the restrainer is analyzed,while the formula for its stiffness demand is derived based on the effective constraint ratio of the metal-yield buckling-restrained member.The strength demand and the space demand of the bolt connection is also derived.The parametric analysis on the REDC specimens is conducted.The results reveal that the core member thickness,yield segment length,the clearance between the core member and the restrainer can affect the amplitude of the non-uniform strain distribution under the large deformation.(5)The shear bearing mechanism of the REDC-PCF and its effect on the mechanical performance of the REDC core member is theoretical analyzed,and the design suggestion is proposed.The theoretical analysis on the deformation property and the global stability of the REDCs embedded in the beam end.The results reveal that moment and shear force is existed in the ends of REDC core members,which may affect the working conditions of the welds.This effects could be reduced to the lowest by optimizing the location of the pin shaft.Additionally,the length of the restrainers can affect the buckling mode of REDCs in the joint.The rotational property of the core member can affect the working property of the connection between the core member and the connection block.(6)Experimental study on the exterior joints of the REDC-PCF is conducted,in which 4specimens were tested.The seismic performance and rehabilitation property of the joints are the key study objects.The test results reveal that the plastic deformation was concentrated in the REDCs embedded on the joints,while the beam and the column remained elastic,revealing that the damage concentration could be realized.Stable hysteretic curves without pinch or negative stiffness were observed in the test,while a high energy dissipation capacity could be obtained.The failure mode of the joint was the fracture of a REDC core member,in which the fracture position was near the middle of the yield segment.A no-less-than 5.0% interstory drift could be observed during the test,while the necking phenomenon could be seen in the fracture position.After the seismic rehabilitation,the mechanical and seismic property of the specimens could remain nearly the same as the initial working condition,in which the initial stiffness,loading cycles,failure modes and fracture position remained the same.The numerical analysis on the REDC-PCF joint is conducted by OpenSees.The design method of REDC-PCF joint is proposed in the end. |
PDF Full Text Request