Experimental And Theoretical Research On Bolted End-plate Connection Using Shape Memory Alloys

Many traditional welded steel frames were severely damaged at the beam-to-columnconnections in the1994Northridge Earthquake and the1995Kobe Earthquake.Beam-to-column connections possess good flexural capacity and deformability after beingimproved while the unrecoverable plastic deformation on the beam ends still exists. In recentyears, attentions are payed to the connection that can avoid the unrecoverable plasticdeformation and possesses self-centering abilities. Shape Memory Alloy (SMA), with theunique and outstanding advantage of shape memory effect and superelasticty, are used todevelop a beam-column connection that possesses good flexural capacity and deformability.A Bolt extended stiffened end-plate connection using SMA bolts is introduced in thispaper. The connection is designed to have good flexural capacity under small deformationwhile form a superelasticty hinge at the beam-to-column interface by using the superelasticbehavior of SMA under large deformation, which meets the requirements of “Strongend-plate” and “Weak connection strong beam” for design guidelines. The work in this paperis as follows:(1) Two bolted end-plate connection using SMA and a high-strength bolts connectionwere analysed. Capability, energy dissipation capability, stiffness and hysteretic performanceof the connections are studied in the test. Experimental results of the bolted end-plateconnection using SMA are as follows: The ratio of its flexural capacity to plastic bearingcapacity of the beam section is0.46, the ratio of its initial stiffness to linear stiffness of thebeam is6.21and the maximum recoverable rotation is0.019rad, the bolts will form asuperelasticty hinge when the connection reachs its ultimate state, all the members willrecover elastic after uploading except the beam ends. Experimental results of thehigh-strength bolts connection are as follows: The ratio of its flexural capacity to plasticbearing capacity of the beam section is1.26, the ratio of its initial stiffness to linear stiffnessof the beam is5.37and the maximum rotation is0.07rad, a plastic hinge will be formed at200mm (1.3beam depth) away from the beam ends and local buckling will occur at the beamflange when the connection reachs its ultimate state.(2) The Finite element analysis software ANSYS14.0is used to establish a3D finiteelement model to simulate a bolted end-plate connection using SMA. Finite element analysisresults are taken to compare with the experimental results under the same loading law.Analysis results show that the3D finite element model agrees well with mechanical characteristics and failure mode of the bolted end-plate connection using SMA. Deviation inductility, strength and stiffness is within5%,5%and10%, respectively. The bolts will form asuperelasticty hinge when the connection reaches its ultimate state and the first row of boltsreach the end point stress of phase change, but all the members will recover elastic afteruploading except the rid at the beam flange.(3)203D finite element models are established for parametric analysis. Parameters,such as length, diameter and prestrain of the SMA bolts as well as thickness of the end-plate,are taken into consideration for analyzing. Analysis results show that: In constant diameter,rotation capacity of the connection increases when the length of the SMA bolts increases andmoment capacity of the connection increases when the diameter of the SMA bolts increases;prestrain of the SMA bolts and thickness of the end-plate have a certain influence on thestiffness of the connection.(4) Based on experimental results and parametric analysis of the connection, as well asthe guidance of current codes, the paper proposes the design method and a linear model ofstiffness calculation of the bolted end-plate connection using SMA. Finite element analysisresults of the connection are taken to compare with the results of theoretic calculation. Bothflexural capacity and rotation capacity of the connection calculated by theory are less thanfinite element analysis results and deviation is within7%and10%, respectively. Stiffness ofthe connection calculated by finite element model is less than that calculated by theory anddeviation is within9%.