2005 Volume 43 Issue 11 Pages 12-17
First, this paper explains the characteristics of vertical ground motions, mainly based on the recorded data obtained during 1994 Northridge earthquake. Ratios of peak vertical to horizontal ground motions are discussed together with illustrated accelerograms and spectral acceleration of vertical ground motions. Ratios of peak vertical to horizontal acceleration at roof of buildings are also discussed with the illustration of behaviors of parking concrete buildings during 1994 Northridge earthquake. Second, the seismic provisions regarding vertical ground motions in each building code of Japan, China and U.S.A. are introduced. In the Japan building code, no special provisions are provided except the precast beams of PC building structures. In China, special provisions are given for high-rise buildings (more than 9 storied buildings) calculated based on spectral acceleration and the distribution of inverted triangle as well as for large span beams. In U.S.A., special provisions are given for strength design method, taking into considerations the effects of vertical ground motions on load factors. Finally, suggestions are given for design methods regarding vertical ground motions induced by big earthquakes in the near future.
