Abstract: The methods of taking half or 2/3 of shear response spectrum as vertical seismic action, recommended or prescribed compulsorily in many engineering codes at home and abroad, are used to design buildings. But how to rationally consider this effect is one of the most important tasks. Firstly, these research advancements are reviewed. The necessary of equivalent linear method of 2D wave motion explicit FEM ELPSV program with characteristic of high efficiency, real phase, actual radiation damping, is discussed. Then, strength of vertical strong ground motion influencing on response spectrum of slope site surface, equivalent response history and PGD and PGV in site section, seismic response of soft slope site are analyzed; and draw some primary conclusions as follows: There are certain influences on shear seismic response spectrum when the period less than 0.3 s, but it is very light over 0.3 s. Vertical seismic response of slope site was distinctly changed by vertical strong ground motion. Moreover, value of vertical seismic action in code for seismic design for buildings is apt to unsafety. Simultaneously, vertical response of the right site is great than the left’s. The slope top’s shear response is much stronger than slope feet’s for slope topography condition, while vertical seismic response is not obvious. Magnified effect in strong ground motion is more than in weak motion when ratio of horizontal to vertical component(av/ah) is 2/3, which agrees with the knowledge of nonlinear response. Interestingly, Interface effects make the response is lower than ambient site response. And soft site response is essentially consistent with phenomena of the hard site, except for vertical seismic response is increased previously and then decreased from site bottom to the top. At last, concise epilogue is given. All of conclusions and study results reflected quantitatively effect extent of vertical strong ground motion, provide beneficial basement for rational considering vertical strong ground motion in aseismic design of buildings and constructions in slope site.

Key words: vertical strong ground motion, slope site, nonlinear seismic response, effect and analysis