Search

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]

The National Research Council Canada recently developed a Semi-Quantitative Seismic Risk Screening Tool (SQST) for seismic risk screening of existing buildings in Canada. This paper presents the structural scoring system that is part of the SQST. The structural scoring methodology is based on FEMA P-154, but has been substantially modified to suit Canadian seismicity and seismic design and construction practices. Structural scores are obtained by adding structural basic scores and applicable score modifiers. For an existing building, a structural basic score is determined by calculating the probability of collapse on the basis of a number of assumptions. Then a series of score modifiers are calculated to address the effects of applicable building characteristics on the building's seismic performance. The structural score is compared with an acceptable structural threshold to determine whether the structural seismic risk is acceptable. The objective of the structural scoring system is to ensure an acceptable and consistent seismic risk in building portfolios while minimizing life safety threats. [ABSTRACT FROM AUTHOR]

The last version of the National Building Code of Canada was issued in 2010. The next version will be issued in 2015. In the code cycle between 2010 and 2015 significant changes have taken place in the seismic design provision. The main factor that drives these changes is an improved understanding of the seismic hazard across the country. Changes have also been introduced in the site effect factors. The structural design provisions have been appropriately adjusted to respond to changes in the estimates of hazard and the new site effect factors. There are also new provisions related to design in regions of low hazard, buildings with flexible diaphragms, buildings with inclined columns, passive energy dissipation systems, base isolation, rocking foundations, glazing systems, racks, and elevators. Some of the changes are briefly discussed. The main focus of the paper is, however, on the revisions to the structural design provisions. [ABSTRACT FROM AUTHOR]