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Structural Engineering and Mechanics
  Volume 64, Number 2, October25 2017, pages 195-204

Improving cyclic behavior of multi-level pipe damper using infill or slit diaphragm inside inner pipe
Seyed Mehdi Zahrai and Abdullah Cheraghi

    Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.
Key Words
    multi-level damper; metal infill; slit diaphragm; cyclic performance; ductility; numerical analysis
Seyed Mehdi Zahrai: Center of Excellence for Engineering and Management of Civil Infrastructures, School of Civil Engineering, College of Engineering, The University of Tehran. P.O. Box 11155-4563, Tehran, Iran
Abdullah Cheraghi: 2Department of Civil Engineering, Arak branch, Islamic Azad University, Arak, Iran

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