Earthquakes pose a persistent and formidable natural threat, prompting decades of extensive research aimed at mitigating their destructive impact on built infrastructure. The seismic input energy transferred to a structural system is critically governed by both the dynamic properties of the structure and the frequency content of the ground motion. Among the available protective strategies, passive control systems have proven to be highly effective, offering robust solutions for both seismic design of new structures and retrofitting of existing substandard buildings, particularly those with deficient lateral load-resisting systems such as precast concrete frames. Within this category, metallic yielding dampers are widely employed to suppress structural responses by capitalizing on the post-elastic deformation capacity and stable hysteretic behavior of metals. These devices are particularly advantageous due to their ease of fabrication, stable and repeatable cyclic performance, and inherent insensitivity to environmental variations, which collectively ensure long-term operational reliability.
Steel pipe dampers, as a specific subclass, have demonstrated significant capability in dissipating seismic energy through inelastic deformations, thereby protecting primary load-bearing elements from severe damage, while also offering considerable flexibility in their integration within beam-to-column connections. As an advanced refinement of conventional metallic dampers, multi-level yielding mechanisms have been developed to provide adaptive performance under various seismic hazard intensities.
In this context, the present study investigates the efficacy of a novel dual-level steel pipe damper in enhancing the seismic behavior of steel moment-resisting frames (MRFs). To this end, three prototype structures of 4, 8, and 12 stories were analyzed using the SAP2000 software to comprehensively evaluate the influence of the proposed damper on the structural response. Numerical results reveal a marked improvement in the dynamic performance of retrofitted frames, attributable to the adaptive, multi-stage operational characteristics of the damper when subjected to ground motions with diverse frequency contents and strong-motion durations.
Quantitatively, the proposed device achieved substantial average reductions in maximum lateral displacements by 69%, 61%, and 46% for the 4-, 8-, and 12-story frames, respectively. Furthermore, significant enhancements were observed in other critical response parameters, including average base shear reductions of 63%, 78%, and 81%, and peak roof acceleration decreases of 24%, 19%, and 29% for the corresponding frames, all attained despite an inherent increase in structural stiffness and a consequent reduction in the fundamental vibration period. Additionally, the incorporation of the dampers led to a pronounced reduction in inter-story drift, averaging 62%, 60%, and 56% across the three structural configurations, effectively minimizing the potential for cumulative structural damage. In conclusion, the findings substantiate that the proposed dual-level steel pipe damper is highly effective in reducing global and inter-story drifts, base shear, and roof acceleration. Nevertheless, the ultimate efficiency of this passive control strategy remains contingent upon the intrinsic characteristics of the seismic input, the spatial distribution and number of dampers, and the specific dynamic properties of the host structure.