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Seismic Behaviour and Design of Two-Bay Steel Multi-Tiered Braced Frames and Other Special Steel Concentrically Braced Frames in Single-Storey Buildings

Christophe Comeau

Masters thesis (2020)

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Cite this document: Comeau, C. (2020). Seismic Behaviour and Design of Two-Bay Steel Multi-Tiered Braced Frames and Other Special Steel Concentrically Braced Frames in Single-Storey Buildings (Masters thesis, Polytechnique Montréal). Retrieved from https://publications.polymtl.ca/5435/
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Abstract

«RÉSUMÉ:Pour les structures de bâtiments en acier de grande hauteur comme les centres sportifs, les hangars d’avions, les bâtiments industriels ou les entrepôts, il est courant d’utiliser des contreventements concentriques en treillis à segments multiples (CCSM). Ces CCSM sont constitués de plusieurs panneaux contreventés superposés sur la hauteur de l’étage. Chacun de ces panneaux est appelé un segment. Cette configuration de contreventements résulte en l’utilisation de diagonales plus courtes, ce qui permet généralement de minimiser l’aire des sections choisies et de respecter plus facilement les critères d’élancement et de rapport largeur sur épaisseur. Des bielles intermédiaires sont placées entre chaque segment contreventé, afin de résister aux efforts axiaux débalancés des diagonales qui surviennent lorsque les diagonales flambent en compression. La redistribution de ces efforts axiaux débalancés au moyen des bielles permet d’éviter un comportement de cadre contreventé en « K », pour lequel les colonnes doivent résister d’importantes sollicitations flexionnelles dans le plan du cadre. Dans des CCSM, les colonnes sont généralement constituées de profilés en I orientés de tel manière à ce que le flambement hors plan survienne autour de l’axe fort du profilé, sur toute la hauteur de l’étage.» et «----------ABSTRACT: In tall single-storey steel structures such as sports facilities, airplane hangars, industrial buildings or warehouses, multi-tiered concentrically braced frames (MT-CBFs) are commonly used. MT-CBFs consist of a bracing system where multiple braced panels are stacked over each other along the storey height. Each panel is referred to as a tier. This bracing configuration results in shorter braces, which typically leads to minimized brace sections and easier compliance with slenderness and width-to-thickness requirements. Intermediate struts are provided at tier levels, to resist unbalanced brace axial loads that develop after the compression braces have buckled. This redistribution of unbalanced axial loads through struts prevents undesirable K-braced frame behaviour, where the columns must resist large in-plane flexural demands. The columns typically consist of I-shaped members oriented such that strong-axis bending is utilized to resist out-of-plane bending moments over the frame height. Struts allow the columns to be laterally braced at tier levels for weak-axis buckling. Results from previous studies showed that under seismic loading inelastic deformations in MT-CBFs tend to concentrate in one critical tier. Two major concerns arise from this phenomenon. On one hand, significant inelastic deformations can occur in the bracing members of the critical tier, which may result in brace fracture due to low cycle fatigue. On the other hand, concentration of inelastic drifts in one tier leads to in-plane bending demands in the columns, which may cause instability. Both Canadian and American seismic design provisions require MT-CBFs to be designed for seismic loading assuming a concentration of inelastic deformations in one tier.»

Open Access document in PolyPublie
Department: Département des génies civil, géologique et des mines
Academic/Research Directors: Robert Tremblay and Ali Imanpour
Date Deposited: 10 Nov 2020 10:50
Last Modified: 10 Nov 2020 10:50
PolyPublie URL: https://publications.polymtl.ca/5435/

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