eBook writers: Masahiro SHIRATO, Jiro FUKUI and and Junichi KOSEKI
Right after the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake) in Japan, the Specifications for Highway Bridges and commentaries were revised in 1996[1, 2]. The specification has introduced ductility design of foundations of piers as standard seismic design against severe and rare scale earthquakes. It should be noted that the aseismic design of piers based on the ductility design itself was not new, but had been already introduced before the 1995 Hyogo-ken Nanbu earthquake against large earthquakes which correspond to type I motions of level 2 earthquake motions defined in detail later.
Nevertheless, abutments and their foundations have been exception in applying the ductility design even in the 1996 version of the specification, and the specification still required to check that they behave elastically against level 1 earthquake motions which are small to middle (or frequent scale) earthquakes as it had demanded in the past. The reasons for this judgment are the following. First, because of the lack of knowledge on a proper evaluation method of their performances, including the seismic active earth pressure at high seismic loads, it is difficult to establish any verification methods of seismic performance of abutments and their foundations against severe earthquakes. Second, there has been no case history in Japan where the damage to abutments or their foundations causes unseating of girders. Third, a bridge abutment is a structure resisting against the earth pressure exerted from the backfill at any moment, and thus it would be just pushed forward by the seismic earth pressure even if it suffers residual displacements during earthquakes, which would not directly result in the unseating of supporting girders.
Download Ductility Design of Foundations of Highway Bridge Abutments.pdf for FREE. (15 pages, 800KB)
0 comments:
Post a Comment