Effects of Foundation Tipping on Dynamic Response

When subjected to severe ground shaking, a slender building may begin to tip about the edge of its foundation. Methods have been presented which allow the influence of tipping to be considered in the dynamic analysis of single-mass models of structures. Solutions have been obtained for the response of tipping systems subjected to simple transient ground motion. Two main effects of tipping on dynamic response have been identified. First, in comparison to fixed-base behavior, tipping leads to a favorable reduction in the maximum transverse deformation suffered by a structure. By contrast, the second effect is potentially dangerous. After a period of tipping when the foundation slams into renewed contact with the ground, collision impulses are generated in the superstructure and the supporting soil. These short duration high intensity normal forces could conceivably endanger the stability of the structure's compression members or lead to foundation failure.