Insights from large-scale shake table testing: Key criticisms and potential solutions

Abstract

This article presents the authors' experience with large-scale shaking table tests conducted in Japan using the E-Defense shaking table. The discussion focuses on four criticisms often addressed regarding the utilities of large-scale shaking table tests. Potential solutions to mitigate such criticisms are discussed based on shaking table tests conducted for a pair of three-story wooden houses. The first criticism is that the test specimen anchored rigidly to a rigid shaking table is not a reproduction of actual structures supported by soils and foundations. A model ground was developed in a large sandbox, which occupied about 85% of the total specimen weight, supported the house, and the entire soil-structure system was shaken. Considerable sliding occurred, having lessened the earthquake forces exerted and resultant damage to the superstructure. The second criticism is that a single specimen test, regardless of its size, cannot provide sufficient information for generalizing the behavior and performance. Empirical equations between the maximum story drift and the change in the natural frequency were developed from a series of shaking table tests. Using such empirical equations might promote quick damage assessment of individual houses when suffering from actual earthquakes. The third criticism is the importance of public appeal and eventual support from the general public to secure the budget to operate large-scale testing facilities. The example test featured two nearly identical specimens placed on the table with different support conditions. The apparent difference in response revealed the effect of support conditions on seismic performance. The fourth criticism is the importance of increasing the number of experimental projects to balance the operation budget. Most of the preparation in the example test was accomplished in an open yard adjacent to the shaking table, and the test specimens were quickly assembled on the table using indoor cranes. The table occupation was four out of 35 weeks of the entire test duration.