A. Biddah et Ac. Heidebrecht, Evaluation of the seismic level of protection afforded to steel moment resisting frame structures designed for different design philosophies, CAN J CIV E, 26(1), 1999, pp. 35-54
Steel moment resisting frames have been considered as excellent systems for
resisting seismic loads. However, after recent earthquakes (e.g., Northrid
ge, California, in 1994 and Kobe, Japan, in 1995) the confidence in this st
ructural system was reduced as a result of various types of damage that mom
ent resisting steel frames suffered. This paper presents the results of the
evaluation of seismic level of protection afforded to steel moment resisti
ng frame buildings designed in accordance with the National Building Code o
f Canada. Six- and 10-storey office buildings located in a region of interm
ediate seismic hazard are designed in accordance with the current Canadian
code provisions. Three different design philosophies are considered, namely
strong column - weak beam (SCWB), weak column - strong beam (WCSB), and st
rong column - weak panel zone (SCWP). The performance of these frames is ev
aluated dynamically by subjecting an inelastic model to an ensemble of 12 a
ctual strong ground motion records. The model takes into account both conne
ction flexibility and panel zone shear deformation. The results are present
ed in terms of response parameters determined from static pushover analyses
, as well as statistical measures of the maximum response parameters determ
ined from the inelastic dynamic analyses. The computed performance of the f
rames is evaluated in order to assess both the overall level of protection
of the frames and the preferred design philosophy. It is concluded that a w
ell-designed and well-detailed ductile moment resisting frame designed usin
g either the SCWB or SCWP design philosophy can withstand ground motions of
twice the design level with very little likelihood of collapse, whereas a
frame designed using the WCSB approach is ill-conditioned and may develop a
collapse mechanism at an excitation level well below twice the design leve
l.