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Electric Power Facilities
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Bridges
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Unreinforced Masonry Buildings
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At Pardee substation, ten two-legged tubular steel 220 kV transmission towers were leaning. The leg on one nearly fractured completely above its base plate, as shown. The weld was not sufficient to develop the tubular section (5 foot square, ¾-inch plate thickness), which had been sized for stiffness.
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The La Cienega-Venice Undercrossing of the I-10 (Santa Monica) freeway was one of the seven bridges that collapsed. These non-ductile columns failed in shear and then collapsed under the weight of the bridge. The nearby Fairfax-Washington Uncercrossing failed for similar reasons. Both structures were constructed in the 1960’s.
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URM's, built before the 1933 Long Beach Earthquake, are a known hazard but few exist in the epicentral region, since it is of more recent development. Nevertheless, a number of URM's in surrounding areas were severely damaged. This shows a 4-story residential building in Santa Monica with cracked piers and a portion of a wall fallen outward.
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Nonductile Concrete Buildings
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Nonductile Concrete Buildings …
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Precast Parking Garages
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The Kaiser Permanente Building in Granada Hills suffered a complete collapse of its second story and partial collapse of the upper stories in the end bays, attributable to inadequate shear and confining reinforcements in the columns and joints.
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A number of other nonductile reinforced concrete buildings experienced shear failures in columns or piers and probably were not too far from collapse. The list includes the St. John’s Hospital in Santa Monica, above.
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Six parking garages constructed of pre-cast concrete partially collapsed, due to lack of continuity that resulted in inadequate transfer of seismic forces to lateral load carrying components. Inadequate deformation capability of members intended to carry only gravity loads, and vertical ground motion, also contributed to the collapses. A large garage at the Northridge Fashion Center almost completely failed.
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Precast Parking Garages 2
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Wood Buildings
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Nonstructural Damage
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A garage at Cal State Northridge used pre-cast moment frames, which were pulled inward by post-tensioning cables when part of the interior structure collapsed.
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This modern wood-frame residential building on Sherman Way had a central driveway, and it collapsed inward over unbraced entrances to first-story parking.
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Much damage occurred to shelving and storage racks due to overloading or code ignorance. Even where storage racks stood, contents sometimes spilled as shown at a home center type store.
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