Evaluation of Displacement-Based Analysis and Design Methods for Steel Frames with Passive Energy Di

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Evaluation of Displacement-Based Analysis and Design Methods for Steel Frames with Passive Energy Dissipators.
 
De la Universidad de Queensland - Australia
Civil Engineering Research Bulletin No. 24
M.S. Williams and F. Albermani
 

Abstract
This report investigates the use of displacement-based, or pushover methods of analysis in the
design of frames incorporating passive dissipative devices. An extensive analysis and design
study of 3-, 6- and 10-storey frames, both undamped moment-resisting frames (MRFs) and
retrofitted with hysteretic and frictional dissipators has been performed. Frames were
modelled using the finite element program Sap2000 and were analysed using both non-linear
static pushover analysis and non-linear time history analysis. The principal aims were to
assess the degree of improvement in performance achieved through use of the devices, and the
suitability of various displacement-based analysis methods for estimating the seismic
response of frames fitted with dissipative devices.
It was found that both dissipative systems led to substantial improvements in frame
performance, in terms of plastic hinge formation (reduced to virtually zero) and deformation
(reduced by a factor of more than 2). Base shears remained similar to those for the undamped
MRFs.
Pushover analyses were found to be a useful design tool for the unretrofitted frames, giving
good estimates of the overall displacement demands, base shears and plastic hinge formation.
However, the various pushover approaches proved less successful at estimating the
performance of the dissipative frames, where they appeared to underestimate the beneficial
effects of energy dissipation.
Of the various pushover methods assessed, the FEMA 356 approach appears to offer the most
accurate and realistic estimate of seismic performance, with the exception of the inter-storey
drift distribution.
For the 6- and 10-storey frames (both ductile MRFs and dissipative frames), pushover
methods using fixed, single load patterns gave rather poor estimates of the distribution of
inter-storey drift with height. Far better drift estimates were obtained using the modal
pushover method, in which pushover results obtained using force distributions based on the

first three modes are combined by the SRSS method.
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