5 - Modern Steel Construction

Typical mill buildin8 construction in Ne'w Zealand IlSt"S a !Iigh-bay. moment-resisting
steel frame braced m the lon8 direction. 11 the mill shown at top. the castellated beams
framing tile bu ilding experienced some permanent deformation. Pictu red above is lite
Tasmau mill. where several masonry walls collapsed, resulting in damage to ti,e adjacent
structures and equipment. As irl the other mills, tlte steel was ill good COllditioll .
16 I Modem Steel Construction J September-October 1990
City, the soft soil conditions in the •
portion of the city overlying an old
lake resulted in amplification and
filtration of the ground motion. Instrumentation
recorded almost a
perfect harmonic motion with a
period of approximately two seconds
and an amplitude of approximately
0.20g, which lasted almost
two minutes. This motion proved
extremely damaging to mid- and
high-rise structures, with natural
frequencies in a range that permitted
resonance with the ground motion.
Over 300 buildings in Mexico
City were severely damaged to a
collapse or near-collapse state.
Only 12 of these had steel frames,
and most of these were constructed
prior to the restrictive
seismic design provisions adopted
following a damaging earthquake
in 1957. Dozens of modern steel
structures, constructed in the 19605
or later and located within the soft
soil zone, were undamaged .
The Conjunto Pi no Suarez, a •
five building complex of 14- and
21-story steel-frame buildings, is
noteworthy for the collap e of two
of these structures and nea r-collapse
of another. These structu res
were a combination of moment-resisting
and braced-frame construction.
Because larger hot-rolled
shapes are not commonly available
in M exico, main frame members in
these buildings were built-up box
column and tubular truss girder
sections. Beam-