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Steel multi-tiered concentrically braced frames (MT-CBFs) represent a bracing configuration where two or more concentric bracing panels are stacked between the ground and roof levels in tall single-storey buildings. A large proportion of MT-CBFs in Canada are located in low-to-moderate seismic regions (seismic category 0–3) where limited ductility CBFs are often preferred in design. Nevertheless, brace tensile yielding may not occur in all tiers of such frames. Additionally, the analysis and design procedure adopted by the 2019 Canadian steel design standard (CSA S16-19) can become tedious in tall frames with multiple panels. In this paper, the seismic behaviour of limited ductility MT-CBFs in moderate seismic regions of Canada is examined to propose a simplified design method. A set of 16 prototype MT-CBFs is designed in accordance with CSA S16-19, excluding the design requirements prescribed for MT-CBF columns. Nonlinear dynamic analyses are then performed to examine their seismic response. Finally, an efficient design method is proposed in the framework of CSA S16-19. [ABSTRACT FROM AUTHOR]

This paper evaluates the overstrength, ductility, and response modification factors for low to mid-rise buckling restrained braced frames (BRBFs) designed as per the 2010 National Building Code of Canada. In addition to nonlinear static pushover analyses, dynamic time history analyses are performed to assess the seismic performance of four-, six-, and eight-story BRBFs. Different bracing configurations, including chevron (inverted-V) and split-X braces, are considered for the building frames with varied frame span lengths of 6 m and 8 m. The results confirm that the prescribed design values for overstrength and ductility factors provide reasonable estimations of the lower bound for these factors. The response modification factor obtained in this study ranged from 4.8 to 6 for different frames. The results also indicate that the response modification factor decreases with the increase of story height and span length. Moreover, bracing configurations may slightly affect the response modification factor for BRBFs. [ABSTRACT FROM AUTHOR]

Single-storey braced steel frame buildings (SSBSFs) are currently the most widely used commercial structures, which include strip malls, power centres, warehouses, small and medium-sized industrial plants. The lateral seismic or wind forces acting on such low-rise structures are usually transferred from a metal roof-deck diaphragm to a system of vertical bracing members. Because these flexible roof diaphragms have a considerable effect on the dynamic response of SSBSFs during an earthquake, they also play an important role in the evaluation of the fundamental vibration period, a key parameter in determining the magnitude of the design seismic forces. It is therefore of utmost importance to reliably predict the fundamental period of SSBSFs. This paper presents the results of a four-year field measurement research project on the dynamic behaviour of SSBSFs. The goal of the project was to create a reliable database for the dynamic characteristics of SSBSFs (periods, mode shapes, and damping) and to find a relationship between them and the geometric parameters (height and plan dimensions). The field tests are described, along with the selected buildings and experimental setup. The measured fundamental periods are then compared to the National building code of Canada (NBCC) empirical equations. A statistical analysis of the data, based on different regression models, yielded new proposed building geometric parameters to be used in simple equations for the prediction of the fundamental period of SSBSFs. [ABSTRACT FROM AUTHOR]