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PVC Pipe Fitting Information
The criterion for the design of foundations of earthquake resisting
structures is that the foundation system should be capable of supporting the
design gravity loads while maintaining the chosen seismic energy dissipating
mechanisms of the structure. The foundation system in this context includes
the foundation structure, consisting of reinforced concrete construction, piles,
caissons and the supporting soil.
It is evident that for this criterion a suitable foundation system for a given
superstructure can be conceived only if the mechanisms by which earthquake actions
are disposed of are clearly defined. In most structures inelastic deformations
during large earthquakes are expected. Consequently for these
structures provisions are to be made for energy dissipation, usually by flexural
yielding. It is vital that energy dissipation be assigned by the designer
to areas within the superstructure or within the foundation structure in such
a manner that the expected ductility demands will remain within recognized
capabilities of the selected components. It is particularly important to ensure that
any damage that might result in the foundation structure does not lead to a
reduction of strength that might affect gravity load carrying capacity.
After defining design criteria in general for foundations
of earthquake resisting reinforced concrete structures, principles
are set out which govern the choice of suitable foundation systems
for various types of shear wall structures. The choice of
foundation systems depends on whether the seismic response of the
superstructure during the largest expected earthquake is to be elastic
or inelastic. For inelastically responding superstructures, preferably
the foundation system should be designed to remain elastic.
For elastically responding superstructures, suitable foundation systems
may be energy dissipating, elastic or of the rocking type. Design
criteria for each of these three foundation types are suggested.
