FREE FIELD WAVE MOTIONS BASED ON TWO COMPONENTS OF DESIGN EARTHQUAKE GROUND MOTION

To study the free field wave motions of plane half-space based on design earthquake, a new approach synthetically considering the horizontal and vertical design earthquake ground motions is proposed. This approach can connect the design earthquake and free field wave motions based on oblique incident P, SV waves with arbitrary angles. Firstly, on the basis of previous researchers' works, the contribution of oblique incident P, SV and their reflected waves to the two components of design earthquake is discussed. Then, based on the assumption that the P and SV waves have the same frequencies with design earthquakes, the amplitude and phase spectrum of P and SV waves are obtained. The time history of P and SV wave is obtained by inverse Fourier transform. Finally, the horizontal and vertical motions of any points in plane half-space are obtained by studying the propagation of P and SV waves and their reflections. The method proposed in this paper could be applied on horizontal and vertical design earthquake ground motions with arbitrary amplitude and phase information. The obtained P and SV waves have respective spectrum information. And the motions in the plane half-space are non-uniform. The motions of points obtained by incident P and SV waves considering ground boundary conditions could be used in structure analysis for multiple-support excitation.