Geotechnical aspects of the January 17, 1995 Hyogoken-Nambu earthquake: investigation and analysis of a landing pier of steel pipe piles damaged by the 1995 Hyogoken-Nambu earthquake

A detailed investigation was made of a landing pier constructed of steel pipe piles that was damaged during the 1995 Hyogoken-Nanbu earthquake. The external force which acted on the pier and the mechanism of failure were inferred. The pier was of an open type supported by vertical and batter piles and was constructed in front of the sea wall caisson. The investigation covered the displacement and inclination of the sea wall and the pier, and the buckling and deformation of the steel pipe piles were examined after the piles were extracted. In the vicinity of the area near the investigated pier, a horizontal acceleration of 327 gal had been recorded, so a large inertial force may have acted on the sea wall caisson and the pier. In addition, the replacement sand below the caisson may have undergone liquefaction, causing the sand and the rubble to shift, and imposing a horizontal force directly upon the piles, thus causing their breakage. Hence, in the present analysis, a total of eight cases were studied under various conditions, including the presence/absence of horizontal force due to ground movement, the loading direction and the magnitude of the horizontal load, in addition to the inertial force of the structure generated by the earthquake. As a result, it was found that the case where the inertial force of the structure was in the direction opposite to that of the ground deformation load most correctly explained the condition of the actual damage.