As will be discussed and illustrated later, one of the basic guidelines or principles in the seismic-resistant design and construction of structures is that the whole structure-foundation system should work as a unit, and that the superstructure be tied or anchored properly to the foundation. The need for following this guideline is illustrated by Slides J19-J21.
THE M = 6.7 COALINGA, CALIFORNIA, EARTHQUAKE (May 2, 1983)
A survey of single-family dwellings conducted in the City of Coalinga showed that nearly 300 houses, 15% of the total surveyed, were thrown off their foundations as illustrated in Slides J19 and J20 [14, 15]. Most of these dwellings were more than 20 years old and were supported on cripple studs without adequate lateral bracing, and several had been moved into the city from nearby oil fields and were placed directly on the smooth surface of concrete foundations without proper anchorage. These examples illustrate the need for inspecting the way that older buildings are supported on their foundations.
J19. This two-story wood frame dwelling underwent a lateral displacement of more than 0.5 m as illustrated by the slant in the porch columns, and also fell more than 0.5 m from its foundation due to lack of adequate anchorage and support during the 1983 Coalinga Earthquake.
J20. This one-story wood frame dwelling slid on its foundation by approximately 1.0 m during the 1983 Coalinga Earthquake.
THE M = 6.5 SAN FERNANDO, CALIFORNIA, EARTHQUAKE (February 9, 1971)
During this earthquake, structural sliding on foundations occurred not only in houses, but also in parts of some modern engineered buildings. This was the case of the reinforced concrete walls surrounding the service core of the five-story Medical Treatment and Care Unit of the Olive View Hospital. As illustrated in Slide J21, these walls shifted on their supports at first floor level because they were purposely separated by a steel plate from the reinforced concrete supporting floor frame at first floor level [Vol. I, Part A of Ref. 6].
J21. The reinforced concrete walls surrounding the service core of the five-story Olive View Hospital shifted on its supports during the 1971 San Fernando Earthquake.
The University of California, Berkeley Copyright 1997, The Regents of the University of California. Structural Engineering Slide Library, W. G. Godden, Editor Set J: Earthquake Engineering, V. V. Bertero
