The main goal of the proposed research is to investigate the possibility of allowing below-ground support systems to respond to strong seismic shaking by going beyond a number of thresholds that would conventionally imply failure and are today forbidden by codes. Such thresholds include : (a) sliding at the soil-foundation interface ; (b) separation and uplifting of a shallow foundation from the soils ; (c) mobilization of bearing capacity failure mechanism for shallow foundations ; (d) structural yielding of pile foundations ; (e) combination of some of the above. Whereas under static loading conditions a slight exceedance of such thresholds leads to failure, the oscillatory nature of seismic shaking will allow such exceedances for a short period of time, with perhaps no detrimental or irreparable consequences. The latter take the form of permanent foundation displacements, rotations, or injuries , which the designer will aspire to confine within rational limits. The motivation and the need for this research has come from : (i) observations of actual behaviour in a variety of earthquakes ; conspicuous examples : the permanent tilting , overturning, and often survival of numerous buildings on extremely soft soil in Adapazari during the Kocaeli 1999 earthquake ; (ii) the foundation design of a number of critical structures (e.g., major bridge pier, air control tower, tall monuments, elevated water tanks,) against large seismic actions ; the disproportionately large overturning moment and/or base shear force of such slender structures can hardly be faced with today s conventional foundation methods, (iii) the need to seismically retrofit and rehabilitate older structures and historical monuments; (iv) structural yielding of pile foundations is now detectable (thanks to technological advances), thus eliminating one of the reasons for avoiding it.
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