Height Effect on Response Modification Factor of Open Chevron Eccentrically Braced Frames

Purpose An analytical investigation is performed on zipper-braced frames. Zipper-braced frames are an innovative bracing system for steel structures. Conventional inverted-V-braced frames exhibit a design problem arising from the unbalanced vertical force generated by the lower story braces when one of them buckles. This adverse effect can be mitigated by adding zipper columns or vertical members connecting the intersection points of the braces above the first floor. Design/methodology/approach This paper critically evaluates over strength, ductility and response modification factors of these structures. To achieve the purpose of this research, several buildings of different stories are considered. Static pushover analysis, linear dynamic analysis and nonlinear incremental dynamic analysis are performed by OpenSees software concerning ten records of past earthquakes. Findings Also, ductility factor, over strength factor and response modification factor, has been calculated for zipper-braced frames system. The values of 3.5 and 5 are suggested for response modification factor in ultimate limit state and allowable stress methods, respectively. Originality/value The fragility curves were plotted for the first time for such kind of braces. It should be mentioned that these curves play significant roles in evaluating seismic damage of buildings.

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Response modification factor of suspended zipper braced frames

Steel and Composite Structures ◽

10.12989/scs.2015.18.1.165 ◽

2015 ◽

Vol 18 (1) ◽

pp. 165-185 ◽

Cited By ~ 3

Author(s):

Gholamreza Abdollahzadeh ◽

Mehdi Abbasi

Keyword(s):

Braced Frames ◽

Response Modification Factor ◽

Modification Factor

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Response modification factors for steel buckling restrained braced frames designed as per the 2010 National Building Code of Canada

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2014-0014 ◽

2016 ◽

Vol 43 (8) ◽

pp. 702-715 ◽

Cited By ~ 2

Author(s):

Moniruzzaman Moni ◽

Saber Moradi ◽

M. Shahria Alam

Keyword(s):

Time History ◽

Building Code ◽

Braced Frames ◽

Response Modification Factor ◽

Building Frames ◽

Modification Factor ◽

Design Values ◽

Nonlinear Static ◽

Buckling Restrained Braced Frames ◽

Dynamic Time

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.

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