Parametric studies and design recommendations for assembled steel rod energy dissipaters

A recently proposed assembled steel rod energy dissipater (ASRED) has been demonstrated to have distinctive hysteretic behavior and satisfactory low-cycle fatigue performance for mitigating seismic effects by experimental tests. However, design recommendations and fatigue model for the ASRED have not been established, thus hindering its practical applications in earthquake -resistant engineering structures. To solve this dilemma, parametric analysis via calibrated nu-merical models was carried out in this paper. Numerical models were reinforced by the newly proposed cyclic constitutive model and the cyclic Bai-Wierzbicki ductile model (CBWM) to enable high-fidelity simulations on the full-life hysteretic behavior of the energy dissipaters. Four key design parameters including the length of dissipation segment, clearance size, friction coefficient, and the length of middle stopper, which generate 54 cases in total, were considered in the parametric studies. The influences of these parameters on the hysteretic behavior of an ASRED were comprehensively analyzed. It was found that increasing the dissipation segment length and friction coefficient would impair the fatigue life and increase the cyclic hardening rate of the energy dissipater. Comparatively, an increased stopper length had no influence on the cyclic curves and the fatigue life. Besides, an excessive clearance size would cause pitching effects and tensile strength deterioration of the hysteretic loops. Based on the numerical results, the optimal stopper length for an ASRED with a diameter of, say, 18 mm, is 20 mm, and the corresponding clearance size should be no larger than 1.5 mm. Moreover, the length-diameter ratio and the clearance-diameter ratio are identified as the key parameters to affect the deformation nonuni-formity of the energy dissipater. Finally, a design-orientated fatigue model was proposed to predict the fatigue life of the ASRED with varied yield strength and length.