Evaluation of hysteretic behavior of eccentrically braced frames with zipper-strut upgrade

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Evaluation of hysteretic behavior of eccentrically braced frames with
zipper-strut upgrade

 

Seyed Mehdi Zahrai a, Milad Pirdavari b,⁎, Hamid Momeni Farahani b
a Center of Excellence for Management and Engineering of Civil Infrastructures, School of Civil Engineering, College of Engineering, The Univ. of Tehran, P.O. Box 11365/4563, Tehran, Iran
b Ati-Naghsh Hamraz Consultants, Inc. Suite 8, No. 73, Jalale Ale Ahmad, P.O. Box 1446665718, Tehran, Iran
a r t i c l e i n f o a b s t r a c t
Article history:
Received 28 August 2012
Accepted 28 December 2012
Available online xxxx
Keywords:
EBF
Zipper strut
Hysteretic behavior
Pushover analysis
Finite-element
Cyclic loading
This paper describes the seismic behavior of Eccentrically Braced Frames (EBF) upgraded using zipper-struts
which connect the mid-point of shear links in all stories.
The numerical modeling of the zipper-strut-equipped model is conducted using finite-element method software
under cyclic load, with the goal of evaluating the behavior of shear links. The interaction of shear links
and zipper-struts is also studied. Furthermore, the prototypes are subjected to nonlinear static (Pushover)
analysis in two configurations; one with moment-resisting connections and one with pinned connections. Finally,
the increase of ductility coefficient for the prototypes with zipper-strut is studied. The prototypes are
also subjected to time-history analysis using scaled earthquake records, with the purpose of studying the energy
parameters of the models.
The unbalanced shear force is distributed among all stories due to the added continuity among shear links.
This results in the extension of structural displacement capacity according to acceptance criteria. Moreover,
a noticeable delay occurs until shear links experience enough rotation to meet Collapse Prevention acceptance
criteria. By imposing acceleration on the structure and conducting time history analysis, it is observed
that the zipper-strut-equipped system shows a stronger tendency to form shear links, leading to greater dissipation
capacity in plastic zone

 

Journal of Constructional Steel Research 83 (2013) 10–20

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