Model-Free Design of Aseismic Structures

The specifications of earthquake resistance for a structure must inevitably include some assumptions concerning the nature of a typical expected disturbance. Current thinking tends towards specifying a probabilistic model for this disturbance. As an alternative, it is proposed that specification be based on the least favorable excitation, i.e., on one which will induce the most undesirable response characteristics in the structure under study. The execution of this idea is presented, subject to the following assumptions: (1) the response of the structure to any excitation is governed by a linear operator; (2) the energies of all excitations under consideration have a known upper limit; and (3) the magnitude of the response peak is the critical measure of the response of the structure. Several cases are analyzed. The least favorable excitations are determined and the magnitudes of the response peaks are derived. Some of the extensions and limitations of the approach are considered.