DEVELOPMENT OF HYSTERETIC DAMPERS FOR CONCENTRICALLY BRACED FRAMES

Date

2025-6-25

Author

Dursun, Süleyman Eren

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Moment-resisting frames (MRFs) and concentrically or eccentrically braced frames (CBFs or EBFs) are commonly used in steel structural systems to resist lateral loads from wind and earthquakes. CBFs dissipate energy through the yielding and buckling of diagonal brace members. In the past two decades, buckling-restrained braces (BRBs) have been developed and commercialized to improve the energy dissipation capabilities of CBFs. Over the last decade, seismic resilience has become a critical focus, with modern structures expected to perform satisfactorily during major seismic events and be repairable in a reasonable amount of time. However, BRBs have two significant limitations related to the resilience of structural systems. First, replacing BRBs in an existing structure is a challenging task due to their size and weight. Second, BRB systems often experience residual drifts after a seismic event. Ongoing research aims to address these challenges, including the development of hysteretic energy dampers that can be mounted at the ends of conventional brace members to improve replaceability. Additionally, self-centering systems are being explored to minimize or eliminate residual drifts, though they tend to be complex and costly. Previous numerical studies have shown that using systems with high post-yielding stiffness can significantly reduce residual drifts. This study aims to develop solutions that address both of the major disadvantages of BRBs. To achieve this, five types of hysteretic dampers were developed. These dampers are shorter in length compared to typical BRBs, facilitating easier replacement after a seismic event. Furthermore, the load-displacement characteristics of these dampers feature a hardening branch with much higher stiffness than typical BRBs, which theoretically reduces the residual drifts following an earthquake. To evaluate the performance of these dampers, both experimental and numerical studies were conducted. Full-scale experiments were conducted on the developed dampers, beginning at the element level and progressing to their integration at the ends of brace members in frame systems. Three distinct test setups were used: two for element-level experiments and another for frame-system-level experiments. The experiments employed various loading methods, including monotonic loading, stepwise cyclic loading, low-cycle fatigue (LCF) loading, and the AISC341 BRB loading protocol. These tests provided valuable load-displacement data critical for evaluating damper performance. To complement the experimental work, comprehensive numerical analyses using 2D and 3D models in ABAQUS and ANSYS were performed. These analyses helped identify critical parameters, such as the maximum displacement capacity of the dampers, and contributed to a deeper understanding of their behavior.

Subject Keywords

Concentrically Braced Frames, Damper, Bolted and Welded Connections, Experimental Testing, Finite Element Analysis

URI

https://hdl.handle.net/11511/115413

Collections

Graduate School of Natural and Applied Sciences, Thesis