| Eccentrically braced steel frame is an ideal aseismic structure,which is often used in medium and strong earthquake areas.Its action mechanism is to use some components of the structure as a defense line for earthquake resistance and dissipate earthquake energy,thus weakening the seismic response.However,for the traditional eccentrically braced frame,in order to ensure that the energy dissipation beam section is elastic-plastic while other members remain elastic under the earthquake action,sometimes the section of the beam column and the brace has to be increased,which leads to the increase of steel consumption and is not economical.Therefore,the replaceable shear links and the frame beam are designed separately to form an eccentrically braced steel frame structure with the replaceable shear links,and the inelastic deformation of the structure is concentrated on the replaceable shear links to facilitate replacement and repair after the earthquake.In this paper,firstly,a small shaking table test is carried out on three scaled models eccentrically buckling restrained braced steel frames with replaceable shear links with different layers under unidirectional earthquake action,and the correctness of the finite element method is verified.Then,the nonlinear dynamic time-history analysis of 27 structures with different parameters is carried out,and the effects of the shear links length,section size,number of stiffening ribs and structural height on the mechanical properties such as acceleration amplification coefficient,displacement response and base shear of the eccentrically buckling restrained braced steel frames with replaceable shear links are analyzed and studied.After research,the following conclusions are obtained:(1)Under the action of frequent earthquakes,the replaceable shear links can be used as an energy dissipation element to dissipate earthquake energy by its own elastic-plastic deformation,thus ensuring that the buckling-restrained brace and the frame are in an elastic working state.Under the action of rare earthquakes,the replaceable shear links dissipate seismic energy by using the full cross-section shear yielding of the web plate,so as to ensure that the beam and column of the frame structure have sufficient strength and rigidity,do not suffer from instability and collapse,and still have sufficient lateral resistance capability.(2)Model tests show that the deformation of the replaceable shear links is mainly shear dislocation,which increases with the increase of seismic intensity and decreases with the rise of floors.The shear links at the bottom of the frame have the highest stress.Acceleration amplification coefficient increases with the rise of floors,and decreases with the increase of earthquake intensity in the same floor.(3)The finite element method is used to compare the ccentrically buckling restrained braced steel frames with replaceable shear links with the traditional eccentrically braced steel frame.Under the same earthquake action,the displacement response and acceleration response of the traditional eccentrically braced steel frame are both large,and the deformation of the energy dissipation beam section has obvious influence on the surrounding members.The addition of replaceable shear links reduces the lateral displacement of each layer of the frame,alleviates the seismic response of each layer,ensures that other components are not affected while yielding in full section,and improves the overall seismic performance of the frame.(4)Through parameter analysis of finite element numerical simulation,the longer the length of the replaceable shear links,the larger the deformation of the steel frame,and the greater the interlayer displacement and the column top acceleration response.Increasing the ratio of height to thickness and decreasing the spacing of stiffening ribs can properly improve the lateral stiffness of the structure and make the distribution of stress and strain more uniform.When the length of the replaceable shear link is 1.11~1.34 times Mp/Vp,and the spacing between stiffening ribs is 0.53~0.73 times the web height,the plastic deformation of the shear connector is sufficient,and the stress on the frame and brace is reasonable.(5)The sequence of plastic hinges for the eccentrically buckling-restrained braced steel frame with replaceable shear links under earthquake action is as follows: when the interlayer displacement angle reaches 1/250,the replaceable shear links produce local plasticity.When the interlayer displacement angle reaches 1/50,the full section of the web of the replaceable shear connector yields into plasticity.When the interlayer displacement angle reaches 1/30,the replaceable shear connector produces plastic hinge,the buckling-restrained brace produces plastic deformation locally,and the foot of the frame column produces local yield,while the plastic hinge is not completely formed. |
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