This paper presents a new seismic design philosophy, which under-designs the foundation to act as a “fuse” in case of strong seismic shaking. A simplified bridge pier is used to illustrate the advantages and disadvantages of this new philosophy compared to conventional capacity design. For this purpose, two alternatives are compared : one with an over-designed foundation, in accordance with conventional capacity design (so that the plastic “hinge” develops in the superstructure), and one with under-designed foundation. The performance of the two alternatives is investigated through shaking table testing of reduced scale models, using real accelerograms and artificial sinusoidal motions. It is shown that the performance of both alternatives is acceptable for moderate seismic shaking. For larger intensity ground motions, that clearly exceed the design limits, the performance of the new design concept is advantageous, not only avoiding collapse but hardly suffering any inelastic structural deformation. The price to pay is mainly the increase of seismic settlements, and in some cases of permanent foundation rotation
