Experimental Study On Seismic Performance Of Buckling-restrained Braces With In-line Steel Plate Core

Since the last century, destructive earthquakes around the world have caused heavycasualties and huge economic loss. Many countries have paid more and more attentionson earthquake engineering and the energy-dissipation technique is rapidly developedthese years. The original intention of buckling-restrained braces(BRBs) is to prevent thebuckling behavior of common braces under cyclic seismic loadings but researches showthat the BRBs can not only enhance the lateral stiffness of the structure but alsodissipate the seismic energy. The existing researches mainly focus on BRBs which usereinforced concrete, concrete-filled steel tube, square or circular steel tube as the outerunit and no concrete research achievements are found about the impact of BRB usingdifferent core materials on reinforced concrete frames in domestic. This paper mainlydid some physical and numerical experiments on a new type of BRB which takes anin-line steel plate as the core and a double-web wide flange steel member as the outerunit, the main work and conclusions are presented as follows:First, eight BRBs using two different kind of core materials, i.e. LY225and SN490,were tested to investigate their hysteresis performance and failure mechanism in orderto compare the difference of performance with different core materials. Results showthat the low cycle fatigue property, the plastic deformability, the additional dampingratio and the ductility of BRBs using LY225as the core material is much better that theones using SN490as the core material. The above performance is weakened and thestrengthening of compression becomes more obvious when the length of BRB isincreased.Secondly, finite element analysis software ABAQUS is used to simulate the BRBs.Because of the strengthening of steel, the widely used bilinear or trilinear model can notaccurately simulate the hysteresis behavior of steel under cyclic loading thus the energydissipation and bearing capacity are underestimated. Here the writer used a combinedplastic metal model which includes kinematic hardening model and isotropic hardeningmodel. The hysteresis curves of BRBs using different core materials are preciselysimulated and these model parameters are to be used in the elastoplastic analyses of BRB frames.Finally, two reinforced concrete frames are designed and BRBs using three kindsof core materials, i.e. SN490, LY225and LY100, are added into the frame to form BRBFrames(BRBFs). Time history analyses are conducted under various ground motions ofdifferent intensities to investigate the diversity of the seismic performance among theoriginal frame and the BRBFs. Results show that when the stiffness of BRBs is certain,using SN490as core material have better performance for low or multistory structuresbut for high-rise structures, LY100is a better choice. When the yield force of BRBs iscertain, using LY100as core material can achieve the minimum story displacement. Themiddle of the beams where the chevron BRBs are installed take risks of getting intoplasticity.