Shape memory alloy bending bars as seismic restrainers for bridges in seismic areas

In general, shape memory alloy (SMA) cables do not resist in compression and, thus, their applications are limited. This study suggests a superelastic SMA bar in bending to be used to overcome the above problem. The objectives of this study are to analyze the characteristics of the bending behavior of an SMA bar and to prove its seismic applicability, especially to restrain openings in bridges. Single and double bending tests are conducted with varying loading speeds and maximum displacements. The loading and the unloading stiffness are estimated from the force-displacement curves, and the equivalent damping ratio of each test is assessed. The SMA bar shows the same stiffness hardening, during bending and under tension which appears to be due to stress-induced-martensite hardening. Increasing the loading speed does not influence the stiffness of the SMA bar with a single bend, but the stiffness of the double bending bar is about five times that of the single bending bar. This study also introduces the use of SMA bending bars as a seismic restrainer for bridges. The SMA bars are assessed as seismic restrainers for a three-span-simply-supported bridge in a zone of moderate seismic activity. The bars reduce the openings at the internal hinges and the pounding force on abutments. Thus, the SMA bending bars are assessed to prevent the unseating at internal hinges and cracks on abutments. This study shows the applicability of the SMA bending bars as a seismic restrainer.

[1]  E. J. Graesser,et al.  Shape‐Memory Alloys as New Materials for Aseismic Isolation , 1991 .

[2]  Howard H. M. Hwang,et al.  Seismic Fragility Analysis of Highway Bridges , 2001 .

[3]  Brian Maroney,et al.  Experimental Testing of Laterally Loaded Large Scale Bridge Abutments , 1993 .

[4]  Ken Gall,et al.  The role of texture in tension–compression asymmetry in polycrystalline NiTi , 1999 .

[5]  Donatello Cardone,et al.  Implementation and testing of passive control devices based on shape memory alloys , 2000 .

[6]  Kim-Ho Ip.  Energy dissipation in shape memory alloy wires under cyclic bending , 2000 .

[7]  Reginald DesRoches,et al.  CYCLIC PROPERTIES OF SUPERELASTIC SHAPE MEMORY ALLOY WIRES AND BARS , 2004 .

[8]  A. Pelton,et al.  An overview of nitinol medical applications , 1999 .

[9]  Y. K. Wen,et al.  Uniform Hazard Ground Motions for Mid-America Cities , 2001 .

[10]  Gunther Eggeler,et al.  Structural fatigue of pseudoelastic NiTi shape memory wires , 2004 .

[11]  Reginald DesRoches,et al.  Comparison between Shape Memory Alloy Seismic Restrainers and Other Bridge Retrofit Devices , 2007 .

[12]  B. T. Berg,et al.  Bending of Superelastic Wires, Part I: Experimental Aspects , 1995 .

[13]  S. Unjoh,et al.  Development of a Shape Memory Alloy Damper for Intelligent Bridge Systems , 2000 .

[14]  Hisaaki Tobushi,et al.  Fatigue Properties of TiNi Shape Memory Alloy , 2000 .

[15]  Shuichi Miyazaki,et al.  Fatigue life of Ti–50 at.% Ni and Ti–40Ni–10Cu (at.%) shape memory alloy wires , 1999 .

[16]  T. W. Duerig,et al.  Engineering Aspects of Shape Memory Alloys , 1990 .

[17]  C Lexcellent,et al.  Pseudoelastic behaviour of shape memory alloy beams under pure bending: experiments and modelling , 2002 .

[18]  Reginald DesRoches,et al.  Seismic fragility of typical bridges in moderate seismic zones , 2004 .

[19]  B. T. Berg.  Bending of Superelastic Wires, Part II: Application to Three-Point Bending , 1995 .

[20]  Krzysztof Wilde,et al.  Base isolation system with shape memory alloy device for elevated highway bridges , 2000 .

[21]  Roberto T. Leon,et al.  Steel Beam-Column Connections using Shape Memory Alloys , 2004 .

[22]  Reginald DesRoches,et al.  Seismic retrofit of simply supported bridges using shape memory alloys , 2002 .