2015 Volume 15 Issue 6 Pages 6_77-6_90
Shrine buildings were considered to be constructed on the platforms which were mainly consisted of piled up “shicras”, stones wrapped in vegetable fiber baskets, of the ancient sanctuaries in coastal Peru. Authors reported the shicras foundations have a potential for earthquake response reduction. Each shicra exhibited rotational motion like one of the current base-isolation technologies by the shaking table test using platform-modeled specimens. This study aims to investigate repeatability and stability of the earthquake response reduction properties of old foundations with shicras so as to think about significance of old technology dating up to 5000 years ago from the view point of engineering. A complete set of shaking table tests were conducted to investigate impact and variation due to possible test parameters like randomness in production and piled up of shicras and type of shaking waves. The test results arrive following conclusions. 1) Every shaking tests of shicras foundations with different parameters exhibited earthquake response reduction effects. Variations of test results due to manufacturing of shicras and construction of shicras foundations were within 25% of the acceleration on the shicras foundation. Stable properties of shicras foundation in earthquake response reduction were observed by the shaking table test. 2) In case of sine waves input, ratio of the acceleration on the shicras foundation to that on the shaking table reduces in proportion to increase of acceleration on the table due to the rotational motion of each shicra. When the accelerations on the shaking table were 4.0m/s2 and 6.0m/s2, average response acceleration on the shicras foundation were 3.05m/s2 and 3.8m/s2, which were 76% and 63% in reduction, respectively. In case the acceleration on the shaking table increased beyond 6.0m/s2, the response acceleration on the shicras foundation never exceeded 4.0m/s2. 3) In case of earthquake waves input, the accelerations on the shicras foundation were 40 to 80% of those on the shaking table. These indicate remarkable reductions obtained compared to the case of sine waves. Since the shicras foundations of the ancient sanctuaries experienced many events including earthquakes for their long-time existence, and they derived from natural materials which have no impact on the earth environment, there may be lessons we should learn from the old technologies. Hereafter, research progresses on this matter are expected by cooperation with archaeology and humanities. Change of human view for technologies will bring out a trend of viewpoint for future technologies which we s hould have. Much progresses of this field are expected.
