E‐Defense, which is operated by the Japanese National Research Institute for Earth Science and Disaster Resilience, currently contains the world's largest 3‐dimensional shaking table (size: 20 × 15 m, maximum loading capacity: 12 000 kN). This facility has already implemented over 80 full‐scale or large‐scale experiments since its operation commenced in 2005. During these research activities, E‐Defense has encountered many challenges in the successful execution of various types of experiments within the designed experimental capacity and under the guidance of safe operational management. The experience gained in the past years using E‐Defense has led to the accumulation of knowledge on loading/shaking techniques, measurements for large‐scale specimens, table maintenance and operation, safety management, and specimen construction. This article highlights the major technical issues that have been encountered during the operation of E‐Defense and introduces the solutions that have been achieved. This is followed by brief summaries of some of the major experiments conducted since E‐Defense was commissioned.

Nonlinear signal‐based control (NSBC) is very powerful for controlling structural systems with parameter variations and has the advantage that the controllers can be designed using classical control theory and expressed by transfer functions. This report describes the first application of NSBC to shake table tests with nonlinear specimens and compares the performance of NSBC with that of a basic control approach that relies on the inverse transfer function of the controlled system. NSBC and the basic approach were numerically applied to shake table tests to excite a nonlinear single‐degree‐of‐freedom system with earthquake acceleration motion, considering the nonlinear specimen characteristics and estimation errors associated with the table dynamics. NSBC achieved excellent control with near 100% accuracy, whereas the basic approach provided insufficient control. Although inaccurate estimation of the pure time delay in the controlled system causes instability at the practice of NSBC, proper design of the nonlinear signal feedback controller prevented instability. In experimental examinations, controllers for the two approaches were designed on the basis of the table dynamics with/without a specimen, which were preliminarily identified by performing tests using a random wave with small amplitude excitations. With no specimen present, both approaches yielded the expected acceleration motion on the table with high accuracy. However, with the specimen present, only NSBC successfully achieved excellent control of the shake table with near 100% accuracy, whereas the basic approach did not because of the specimen nonlinearity. These results numerically and experimentally demonstrate the efficiency and practicality of NSBC for shake tables supporting nonlinear structures.

In this paper, we propose a free-standing structure that is unanchored to its foundation and has a cost-efficient interface consisting of common construction materials (steel, mortar, and iron) with graphite lubrication; this structure is expected to behave as an earthquake-resistant structure during small earthquakes and a base-isolated structure during large earthquakes. To realize the structure, this study examined the frictions of the interfaces in shaking table tests. In addition, the seismic responses of the free-standing structures based on the interfaces were examined via incremental dynamic analyses with 44 ground motions and a simple model of typical Japanese steel structures.