An experimental study of in-plane oval damper

Abstract

This paper presents a new type of seismic metallic yielding damper referred to as the in-plane oval damper (i-POD) which consists of two circular arches with intermediate straight arms in a closed-form. It is designed to deform inelastically in an in-plane flexural mode to dissipate seismic energy for building structures. A series of component tests of five i-PODs with various dimensions was conducted to assess their energy-dissipative characteristics (e.g. initial stiffness, post-yielding stiffness ratio, ultimate strength, ultimate displacement and ductility), which in turn serves as parametric study to gain more insight of this closed-form in-plane damper. Test results indicate that the hysteresis loops of all the dampers are full and consistently stable under cyclic loadings. Moreover, the i-POD effectively minimizes the problems of displacement setback and end rotation of its previous version, the in-plane arch-shaped damper, which would otherwise lead to loss of energy-dissipative capacity. Parametric study indicates that, in general, the i-POD with a shorter length of straight arms and a smaller radius of curvature of the circular arch exhibits a larger strength and better energy-dissipative capacity, but tolerates a smaller ultimate displacement as a trade-off. Furthermore, quadratic functions representing the mechanical parameters and energy-dissipative capacity of the dampers with respect to dimensionless design parameters have been proposed for design purpose, in particular at the preliminary design stage. Good correlations between the experimental results and regression formulae have been observed, suggesting that these empirical formulae can be adopted to determine the geometric dimensions of the i-POD for desired performance specifications in terms of ultimate strength, ultimate displacement or ductility.