Experiences, accomplishments, lessons, and challenges of E‐defense—Tests using world's largest shaking table

Nakashima, Masayoshi; Nagae, T.; Enokida, Ryuta; Kajiwara, Koichi

doi:10.1002/2475-8876.10020

Cited by 56 publications

(39 citation statements)

References 52 publications

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“…E‐Defense is currently the largest three‐dimensional shake table in the world (size: 20 m × 15 m, maximum loading capacity: 12,000 kN). Over 80 full‐ or large‐scale experiments have been implemented since its commencement in 2005 . Its basic approach is a three‐variable control method using the acceleration, velocity, and displacement of the table .…”

Section: Introductionmentioning

confidence: 99%

“…Over 80 full-or large-scale experiments have been implemented since its commencement in 2005. 10 Its basic approach is a three-variable control method using the acceleration, velocity, and displacement of the table. 2 When the table dynamics are affected by a specimen, traditional input compensation is applied to enhance the shake table control.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Enokida

Kajiwara

2019

Struct Control Health Monit

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Summary 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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Enokida

Kajiwara

2019

Struct Control Health Monit

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“…However, the damage limit states of expansion joints and the safety factors required to avoid failure are not well considered in current design practice. 2,20,21 In keeping with these campaigns, guidelines for expansion joints were recently published by the Japanese Society of Seismic Isolation (JSSI) 22 and the Japan Expansion Joint Association (JEJA), 23 an association consisting of six expansion joint manufacturers. Expansion joints on apartment buildings dropped off during the 2005 Fukuoka earthquake 12 and the 2016 Kumamoto earthquake, 13 while 90 of 327 expansion joints on base-isolated buildings were heavily damaged during the 2011 Tohoku earthquake.…”

Section: Introductionmentioning

confidence: 99%

Fragility function development and seismic loss assessment of expansion joints

Otsuki

Kurata

Skalomenos

et al. 2019

Earthq Engng Struct Dyn

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Summary Expansion joints are used as a special connection equipment between adjacent buildings to accommodate the relative motions generated by wind, thermal, or earthquake loads, but they often exhibit damage during severe earthquakes. The level of damage and safety factors required to avoid loss of function are not well considered in current design practices. The objective of this paper is to provide quantitative information on the seismic damage probability of common expansion joints and the associated repair costs. The designer and engineer can refer to this information as a basis for decision making in the selection of expansion joints. Four common types of expansion joints are considered: high‐ and standard‐performance floor and wall expansion joints, whose damage states have been evaluated recently by the authors through shaking table tests. First, the fragility functions of expansion joints for seven damage patterns are developed utilizing the test results. Next, the vulnerability of expansion joints installed between adjacent building models is assessed via incremental dynamic analysis. The recommended level of safety factor to ensure the function of expansion joints is discussed. Finally, a procedure for cost‐effective selection of expansion joints is introduced, where case studies are examined using buildings with different characteristics. The presented results are deemed to be beneficial for improving the design practice of expansion joints and for reducing future seismic loss.

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“…Mitigation of the seismic response of structures subjected to large earthquake ground motion is one of the major challenges in structural engineering. 1 Over recent decades, the base isolation system has been shown to effectively protect structures and facilities against earthquakes. 2,3 The friction pendulum system (FPS) isolator is a commonly used base isolation system.…”

Section: Introductionmentioning

confidence: 99%

Development of a tunable friction pendulum system for semi‐active control of building structures under earthquake ground motions

Pan

Zhang

Zeng

et al. 2018

Earthq Engng Struct Dyn

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Summary The Friction Pendulum System (FPS) isolator is commonly used as a base isolation system in buildings. In this paper, a new tunable FPS (TFPS) isolator is proposed and developed to act as a semi‐active control system by combining the traditional FPS and semi‐active control concept. Theoretical analysis and physical tests were carried out to investigate the behavior of the proposed TFPS isolator. The experimental and theoretical results were in good agreement, both suggesting that the friction force of the TFPS isolator can be tuned to achieve seismic isolation of the structure. A series of numerical simulations of a base‐isolated structure equipped with the proposed TFPS isolator and subjected to earthquake ground motions were also conducted. In the analyses, the linear quadratic regulator (LQR) method was adopted to control the friction force of the proposed TFPS, and the applicability and effectiveness of the TFPS in controlling the structure's seismic responses were investigated. The simulation results showed that the TFPS can reduce the displacement of the isolation layer without significantly increasing the floor acceleration and inter‐story displacement of the superstructure, confirming that the TFPS can effectively control a base‐isolated structure under earthquake ground motions.

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Experiences, accomplishments, lessons, and challenges of E‐defense—Tests using world's largest shaking table

Cited by 56 publications

References 52 publications

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Fragility function development and seismic loss assessment of expansion joints

Development of a tunable friction pendulum system for semi‐active control of building structures under earthquake ground motions

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