Modeling sensitivity analysis of special concentrically braced frames under short and long duration ground motions

This article focuses on evaluating the adequacy of a seismic rehabilitation technology which adds rocking cores to deficient steel concentrically braced frames in near-fault regions. Two demonstration buildings were rehabilitated with the technology. Seismic performance of the rehabilitated buildings was evaluated through numerical simulations. Analysis results suggest that the code-compliant concentrically braced frames may be vulnerable to collapse under the fault-normal components of the near-fault ground motions, approximately having a probability of exceedance of 10% in 50 years. It is found that the Rocking Core technology is effective in reducing the inter-story drift responses of the demonstration buildings under near-fault earthquakes. The rehabilitated systems can further benefit from the use of hysteretic energy dissipating links between the rocking cores and existing concentrically braced frames. This article also addresses the influence of the rocking cores on modal properties of the rehabilitated buildings. It is found that the rocking core with moderate stiffness does not significantly alter the modal properties of a rehabilitated concentrically braced frame.

Download Full-text

Evaluation of 2D concentrically braced frames with cylindrical dampers subjected to near-field earthquake ground motions

Numerical Methods in Civil Engineering ◽

10.52547/nmce.4.3.21 ◽

2020 ◽

Vol 4 (3) ◽

pp. 21-30

Author(s):

M. Mirtaheri ◽

M. Salkhordeh ◽

S. M. S. Kolbadi ◽

H. Mirzaeefard ◽

M. R. Razzaghian ◽

...

Keyword(s):

Ground Motions ◽

Near Field ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Earthquake Ground Motions ◽

Concentrically Braced

Download Full-text

SEISMIC COLUMN SPLICE DEMANDS IN BRACED FRAMES WITH BUCKLING CONTROLLED BRACES

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.2021.8(1).str-54 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Mahmoud Faytarouni ◽

Laura Micheli ◽

Jiehua Shen ◽

Onur Seker ◽

Bulent Akbas

Keyword(s):

Seismic Design ◽

Ground Motions ◽

Substantial Reduction ◽

Experimental Tests ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Earthquake Ground Motions ◽

Concentrically Braced ◽

Margin Of Safety ◽

Hollow Structural Sections

Numerous experimental tests showed that ductile square hollow structural sections (HSS) are susceptible to premature fracture under design-level earthquake ground motions. In addition, recent research has highlighted the vulnerability of column splices to reach their full strength once ductile square HSS braces experience a fracture in braced frames. In this study, the performance of column splices in 5-and 13-story special concentrically braced frames (SCBFs), with X-bracing configuration, located at a distance permitted by the seismic design provisions (i.e., four feet over the concrete floor level), is evaluated under a large number of ground motion excitations. The performance of identical SCBFs with conventional HSS braces and innovative buckling controlled HSS braces is compared. Overall, results from this research indicate that the prevention of brace buckling in SCBFs yields a substantial reduction in the seismically induced bending demands on the column splices, leading to a large margin of safety to remain elastic.

Download Full-text