Two kinds of model tests of suction foundations, such as shaking table tests and monotonic horizontal loading tests, were conducted to investigate their stability and to examine the proposed design method. It was found that the suction foundations with the larger penetration depth showed larger resistance against horizontal loads. And the proposed design method was validated by these model tests. The following results were obtained.
1) The suction foundations have larger resistance against horizontal loads when the penetration depth of the foundations becomes large.
2) Horizontal displacements are larger than vertical ones at the crown of the structures on the suction foundations. However, difference between the horizontal displacements and the vertical ones becomes small when the penetration depth becomes larger.
3) Although the foundations are open at the bottom, the weight of the inside soils contributes to the resistance against the external loads.
4) The displacements of the suction foundations are different with the same horizontal maximum acceleration if the seismic waveforms are different.
5) The critical loads obtained with the proposed design method can normalize the loads applied to the suction foundations because the applied loads divided by the critical loads have almost unique relationship with the displacements of the foundations.