Pushover Analysis of Steel Seismic Resistant Frames with Reduced Web Section and Reduced Beam Section Connections

The widespread brittle failure of welded beam-to-column connections caused by the
1994 Northridge and 1995 Kobe earthquakes highlighted the need for retrofitting
measures effective in reducing the strength demand imposed on connections under
cyclic loading. Researchers presented the reduced beam section (RBS) as a viable
option to create a weak zone away from the connection, aiding the prevention of
brittle failure at the connection weld. More recently, an alternative connection known
as a reduced web section (RWS) has been developed as a potential replacement,
and initial studies show ideal performance in terms of rotational capacity and ductility.
This study performs a series of non-linear static pushover analyses using a modal
load case on three steel moment-resisting frames of 4-, 8-, and 16-storeys. The
frames are studied with three different connection arrangements; fully fixed moment
connections, RBSs and RWSs, in order to compare the differences in capacity curves,
inter-storey drifts, and plastic hinge formation. The seismic-resistant connections
have been modeled as non-linear hinges in ETABS, and their behavior has been
defined by moment-rotation curves presented in previous recent research studies.
The frames are displacement controlled to the maximum displacement anticipated
in an earthquake with ground motions having a 2% probability of being exceeded
in 50 years. The study concludes that RWSs perform satisfactorily when compared
with frames with fully fixed moment connections in terms of providing consistent
inter-storey drifts without drastic changes in drift between adjacent storeys in low- to
mid-rise frames, without significantly compromising the overall strength capacity of
the frames. The use of RWSs in taller frames causes an increase in inter-storey drifts
in the lower storeys, as well as causing a large reduction in strength capacity (33%).
Frames with RWSs behave comparably to frames with RBSs and are deemed a
suitable replacement.