This research reviews attenuation of peak ground acceleration(PGA), statistical characteristics of vertical ground motion, expected value of PGA and relation between design coefficient and PGA, all of which are the basis for the present design standard of port structures. This review was conducted because of the serious damage of Kobe port, etc. due to the Hyogo-ken Nanbu Earthquake of Jan 17, 1995. After the reviews, new phirosophy of aseismic design force for port structure is presented. Following conclusions are obtained in this research.
(1)Attenuation relations for corrected PGA, PGA of SMAC-B2 type accelerograph(SMAC PGA), PGV, PGD on base layer are newly obtained through statistical analysis of strong ground motion. Attenuation relation for SMAC PGA gives larger value in the near field than conventional attenuation relation presented by Noda et. al.(1975) and consistent value in the far field (over several 10km ) with conventional relation.
(2)According to statistical analysis of vertical ground motion, effect of vertical seismic motion is found to be small on the safety factor for sliding of rigid structure.
(3)Expected values of PGA, etc. on base layer in Japanese coastal area for the return period of 75 years are computed based on newly derived attenuation relations. Newly obtained expectedvalues of SMAC PGA are larger than the values obtained byKitazawa et. al. (1984) in the range of large PGA.
(4)Relation between PGA, etc. and seismic coefficient for gravity type quaywall and anchored sheet-piling quaywall are investigated. Relation between PGA and the upper limit of seismic coefficient presented by Noda et. al.(1995) is confirmed to be valid for gravity-type quaywall. The same relation is almost applicable also for anchored sheet-piling quaywall.
(5)New phirosophy of aseismic design force for port structure is presented.