9.地震による構造物の非線型振動について : その1・構造物力学特性の必然的非線型化過程

Abstract

For the establishment of the rational aseismic design of structures, it is necessary, at first, to study the following problems qualitatively. That is, what measure we should adopt for the destructive force of the earthquake, what pattern of the seismic wave we should take up for the object of the final aseismic design, and what sort of quantity we should prescribe as the limit value of the final aseismic calculation. Here, we must consider that the seismic waves are irregular and mingled with unstationary waves and that the mechanical character of structures varies inevitably from linear state to nonlinear state when subjected to the destructive seismic wave. Under these considerations we find the most dangerous wave for each structure from various seismic waves assuming the certain measure of the destructive force of the earthquake, and analyze the final nonlinear behavior of structures subjected to such a wave. Mathematically, these problems reduce to simultaneous ordinary second order nonlinear differential equations if structures are assumed to be a mass-system, so that we can solve them graphically by using our improved method induced from the phase-plane-delta method of L.S. Jacobsen. Thus we can reach the following conclusions. 1. The measure of the destructive force of the earthquake should be the constant seismic displacement. 2. The most dangerous pattern of the seismic wave has the period nearly equal to that of each structure under the constant seismic displacement- 3. Horizontal relative displacements of structures should be prescribed as the limit value in final seismic calculation.