Pushover Response of Multi Degree of Freedom Steel Frames

Seismic codes use the behaviour factor to consider the ductility and the structure's non-linearity to improve the system's overall performance. Generally, Steel moment-resisting frames are characterized by a relatively high period showing high deformability and, foreseen that with stringent damageability criteria, the adopted behaviour factor might not optimally be utilized for achieving better performance of the frames. The design is generally governed by stiffness, leaving behind a complex structural system where the capacity design rules are disturbed and therefore necessitates to relax the drift limits for such frames. Given this and with extensive parametric analysis, the current paper aims to examine the behaviour factor of steel Moment Resisting Frames (MRFs). The parametric analysis has been conducted on rigid steel MRFs of 9, 7, and 5 storeys with bay 4 different bay widths of 9.15 m, 7.63 m, 6.54 m, and 5.08 m. Perimeter frame configuration has been designed using 4 different behaviour factors (q = 6.5, 4, 3, and 2) for a total number of 144 cases. Static nonlinear analysis has been conducted, and consequently, the behaviour factors have been examined. It has been observed that compatibility is required while choosing the drift limit for an assumed ductility class of the code. Doi: 10.28991/cej-2020-SP(EMCE)-08 Full Text: PDF

Download Full-text

From Design to Earthquake Loss Assessment of Steel Moment-Resisting Frames

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.763.124 ◽

2018 ◽

Vol 763 ◽

pp. 124-130 ◽

Cited By ~ 1

Author(s):

Luís Macedo ◽

Antonio Silva ◽

José Miguel Castro

Keyword(s):

Seismic Design ◽

Eurocode 8 ◽

Loss Assessment ◽

Behaviour Factor ◽

Steel Moment Resisting Frames ◽

Performance Factors ◽

Moment Resisting Frames ◽

Moment Resisting ◽

Earthquake Loss ◽

Steel Mrfs

Steel moment-resisting frames (MRFs) are well known for their ductile and stable hysteretic behaviour. For this reason, they are an attractive and effective structural system for seismic resistance. Current seismic design codes, namely Eurocode 8, provide system performance factors that should be used in the seismic design under different ductility classes. However, recent research studies have shown that the use of the code-prescribed performance factors lead to stiffer and heavier structural solutions that are not consistent with the performance-based design assumptions. A new methodology, Improved Force-Based Design (IFBD), has recently been proposed with the aim of a more rational determination of the adopted value of the behaviour factor, q, instead of using the upper bound reference values provided by the design code. This paper investigates if the obtained values of q for both EC8 and IFBD concerning steel MRFs are not only adequate, but also provide sufficient margins against collapse under maximum considered earthquake (MCE) ground motions. To this end, the methodology proposed in FEMA P695 was used. Additionally, the expected direct economic seismic losses are computed according to the PEER-PBEE methodology.

Download Full-text

Seismic fragility of steel moment-resisting frames in Vancouver and Montreal designed in the 1960s, 1980s, and 2010

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2014-0492 ◽

2015 ◽

Vol 42 (11) ◽

pp. 919-929 ◽

Cited By ~ 2

Author(s):

Lucía Valentina Díaz Gómez ◽

Oh-Sung Kwon ◽

Mohammad Reza Dabirvaziri

Keyword(s):

Numerical Models ◽

Fragility Curves ◽

Time History ◽

Steel Moment Resisting Frames ◽

Moment Resisting Frames ◽

Nonlinear Time History Analyses ◽

Moment Resisting ◽

The 1960S ◽

Steel Mrfs ◽

Nonlinear Time History

Typical steel moment-resisting frames (MRF) of six-storey buildings in Vancouver and Montreal were designed for three different provisions of the National Building Code of Canada (1960s, 1980s, and 2010). Numerical models were developed in OpenSees to understand the seismic performance of the structures. These models accounted for strength and stiffness degradation through appropriate representations of the beam–column connection behaviours, which were calibrated against experimental results available in the literature. The behaviour of the buildings was evaluated through pushover and nonlinear time history analyses. The pushover analysis results showed that the 1960s and 2010 steel MRFs of both cities exhibited strong-column-weak-beam failure mode. The 1980s steel MRFs of both cities showed soft-storey mechanism. Fragility curves were developed for the steel MRFs based on the seismic demands evaluated using nonlinear time history analyses, which can be used for regional seismic impact assessment studies in the future.

Download Full-text