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Capacity design of welded steel MRF connections
Published in Federico M. Mazzolani, Stessa 2003, 2018
Jaswant N. Arlekar, C.V.R. Murty
Seismic design of connections for steel moment resisting frame (MRF) buildings has received considerable attention over the past decade. The inability of MRF buildings to perform to the expected level during the 1994 Northridge and the 1995 Hyogo-Ken Nanbu earthquakes was attributed to the early failure of beam-to-column connections, which prevented the formation of energy dissipating plastic hinges at the beam-column joint. Extensive experimental and analytical research was initiated after these earthquakes under the SAC joint venture. Recommendations for improved seismic design criteria to achieve better performance of steel MRF buildings, particularly for the beam-column joints and its connections, were compiled in FEMA 350 [FEMA 350, 2000]. The FEMA 350 recommended criteria were intended to be a resource document for the development of building codes and design standards. Even though procedures to formally adopt the same into the design codes are underway, they are already being used by the steel construction industry in the USA in the design of new steel MRF buildings.
Parametric Study on a Self-Centering Beam-Column Joint Equipped with Arc-Shaped Steel Plate Damper
Published in Journal of Earthquake Engineering, 2023
Yangchao Ru, Liusheng He, Huanjun Jiang
Traditional welded and bolted connections have been widely used in steel moment-resisting frame structures. In general, steel frames with these connections and joints dissipate seismic energy by sacrificing preselected “plastic hinge” regions under earthquake action. By adopting the method, structural collapse can be largely avoided and life safety is ensured basically. However, since some parts of the structure (e.g. beam ends and column ends) are susceptible to plastic deformation, the deterioration of both strength and stiffness of the structure as well as irreversible damage is caused, which may result in unacceptable post-earthquake economic losses and repair costs. This has been confirmed by previous earthquake phenomena, such as the 1994 Northbridge earthquake (Mahin 1998), the 1995 Kobe earthquake (Nakashima, Roeder, and Maruoka 2000), and the 2011 Christchurch earthquake (Bruneau and MacRae 2017). Therefore, the traditional seismic design method based on the “plastic hinge” concept is no longer adequate to meet the seismic requirements of modern building structures, and there is a need to propose more advanced seismic-resistant structures and design methods to improve the resilience and sustainability of building structures.
Effect of Damper Sub-System Stiffness on the Response of a Single Degree of Freedom System Equipped with a Viscous Damper
Published in Journal of Earthquake Engineering, 2022
R. Xie, G. W. Rodgers, T. J. Sullivan
Some insight into the significance of damper sub-system stiffness for nonlinear viscous dampers has been provided by Dong, Sause, and Ricles (2016) as part of a large-scale experimental investigation of a multi-story steel frame building. The test structure underwent both design basis and maximum considered ground motions using real-time hybrid simulation. Results from this experimental study concluded that a steel frame would perform significantly better during all levels of seismic events than a bare conventional steel moment resisting frame. Additionally, this literature also provided the interesting observation that the deformations of structural components and connections adjacent to the dampers caused the local deformations of the nonlinear viscous dampers to be different to the story drift. This phenomenon, referred to as the “brace flexibility” effect by the authors, caused the damper responses to be partially out-of-phase with the structural responses, and as a result, the brace flexibility effect added stiffness to the steel frame equipped with viscous dampers (Fig. 1). The term “brace” in the work of Dong et al. indicates the damper sub-system that provides connection between the damper and the main structure. Furthermore, Dong (2016) used an equivalent linear elastic-viscous model to simulate a damper-sub-system component in order to further investigate the effect of sub-system stiffness on the response of a frame structure. This study stated that a more flexible sub-system stiffens a structure and the sub-system stiffness also affects the effective damping of the structure.