SMA passive elements for damping in stayed cables: experimental results and simulation
2012
The use of shape memory alloy (SMA) wires as passive elements for damping the vibrations of stayed
cables requires that the essential conditions of SMA necessary for the application are well established. The
specific conditions of the cable define the appropriate characteristics of the damper, such as the length and
the number of the NiTi SMA wires. As the stayed cables in bridges remain under forces near 1 MN, the main
study is focused on SMA wires of diameter 2.46 mm that produces forces of about 2 kN. With these forces
the use of one or several wires only induces minor changes in the stress distribution within the structure. In
this work, the requirements for the SMA wires including, for instance, the fracture level, the thermal actions
and the convection, are evaluated. Furthermore, several examples of the application of SMA in laboratory
facilities and the simulation of the SMA actions in realistic cables are included. The non-linearities of the
SMA dampers are visualized by windowed Fourier transform and Morlet wavelets analysis of the oscillating
behavior. There is a change of the cable natural frequency during the damping process, the frequency
increases as amplitude decreases. From the experimental results obtained in ELSA, JRC, Ispra, Italy,
IFSTTAR, Nantes, France, and in the Pavia University, Italy, the general rules for the preparation of the
SMA dampers are also outlined.
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