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Ikeda Y.,Kajima Technical Research Institute
Earthquake Engineering and Structural Dynamics | Year: 2016

This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full-scale four-story steel building at E-Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single-input-four-output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc-Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single-input-single-output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent-linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure. © 2016 John Wiley & Sons, Ltd.

Takaoka E.,Kajima Technical Research Institute | Takenaka Y.,Kajima Corporation | Nimura A.,Kajima Technical Research Institute
Earthquake Engineering and Structural Dynamics | Year: 2011

This paper describes the results of shaking table tests to ascertain the ultimate behavior of slender base-isolated buildings and proposes a time history response analysis method, which can predict the ultimate behavior of base-isolated buildings caused by buckling fracture in laminated rubber bearings. In the tests, a base-isolated structure model weighing 192 kN supported by four lead rubber bearings is used. The experimental parameters are the aspect ratio of height-to-distance between the bearings and the shape of and the axial stress on the bearings. The test results indicate that the motion types of the superstructure at large input levels can be classified into three types: the sinking type; the uplift type; and the mixed type. These behaviors depend on the relationship between the static ultimate lateral uplifting force on the superstructure and the lateral restoring characteristics of the base-isolated story. In the analysis method, bearing characteristics are represented by a macroscopic mechanical model that is expanded by adding an axial spring to an existing model. Nonlinear spring characteristics are used for its rotational, shear, and axial spring. The central difference method is applied to solve the equation of motion. To verify the validity of the method, simulation analysis of the shaking table tests are carried out. The results of the analysis agree well with the test results. The proposed model can express the buckling behavior of bearings in the large deformation range. Copyright © 2010 John Wiley & Sons, Ltd.

Ikeda Y.,Kajima Technical Research Institute
Earthquake Engineering and Structural Dynamics | Year: 2016

This study proposes a new design method for an active mass damper (AMD) that is based on auto-regressive exogenous models of a building structure. The proposed method uses the results of system identification in the field of active structural control. The uncontrolled structure is identified as auto-regressive exogenous models via measurements under earthquake excitation and forced vibration. These models are linked with an equation of motion for the AMD to introduce a state equation and output equation for the AMD–structure interaction system in the discrete-time space; the equations apply modern control theories to the AMD design. In the numerical applications of a 10-degree-of-freedom building structure, linear quadratic regulator control is used to understand the fundamental characteristics of the proposed design procedure. The feedback control law requires the AMD's acceleration, velocity and stroke; the structure's acceleration; and the ground acceleration as vibration measurements. The numerical examples confirm the high applicability and control effectiveness of the proposed method. One remarkable advantage of the proposed method is that an equation of motion for the structure becomes unnecessary for designing controllers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

We have reported an active seismic response control system by making use of an energy conversion in damping devices. In this paper, we propose a system where energy conversion and reuse are interacted, we call it 'interaction system' here, and evaluate its characteristics through seismic response analyses. In the 'interaction system', responses are drastically reduced by the control gain where energy input and output are balanced. In addition, in comparison with an 'independent system' shown in Part 1, the 'interaction system' shows the similar response reduction effect by this control gain. The damping force and velocity of the passive devices are about 60% of the 'independent system', and the control force and velocity of active devices are equivalent. The 'interaction system' shows a possibility that it can construct the total system compactly compared with the 'independent system'. The proposed system can realize the active seismic response control system against large earthquakes where its application in the actual stage is supposed to be difficult.

Fukumoto T.,Kajima Technical Research Institute
Journal of Structural and Construction Engineering | Year: 2016

This paper proposes a new formulation for ultimate shear strength considering restriction stress for concrete in perfobond strip shear connections. The formulation provides ultimate shear strength by multiplying shear cracking strength by the ratio of ultimate shear strength to shear cracking strength. In the investigation, a regression formula for the relationship between the ratio and restriction stress is proposed based on a database including previous test results using no-cover simple-specimen loaded restriction force. This paper proposes a method of transforming the effect of restraining concrete around a steel plate hole by reinforced concrete cover and penetrating rebars, and transforming it into restriction stress in the ultimate shear strength formulation. Predictions from the proposed formulation almost agree with test results.

Chae S.,Kajima Technical Research Institute | Yoshida T.,Kajima Technical Research Institute
Automation in Construction | Year: 2010

This paper describes the application of RFID (Radio Frequency Identification) technology to prevention of collision accidents with heavy equipment such as hydraulic excavators and cranes. Past disasters involving heavy equipment are evaluated to clarify the causes of accidents, and the functions of support systems for preventing collisions are defined. A system design is proposed with a working area obtained using RFID technology that is given a role from defined functions. A prototype has been developed using an active type RFID tag for the functions of a support system. RFID tag data were obtained from an actual construction site, and it is clarified that the prototype is applicable to estimation of working areas for the prevention of collision accidents. © 2009 Elsevier B.V. All rights reserved.

Mahaboonpachai T.,University of Tokyo | Matsumoto T.,Hokkaido University | Inaba Y.,Kajima Technical Research Institute
International Journal of Adhesion and Adhesives | Year: 2010

This paper aims to investigate interfacial fracture toughness between concrete and polymer-cement mortar (PCM) in an external wall tile structure under various shear to tensile stress ratio by using interface elements in a finite element method (FEM). A constitutive material model of interface elements was developed, and its corresponding values that have a relation to the interfacial fracture toughness were calibrated with three four-point bending set-ups and one high shear test. Then, the developed interface element was verified by applying to analyze the failure of tiles in the tiled column compression test. With this method, the interfacial fracture toughness of the current interface was successfully obtained for the whole range of the shear to tensile stress ratio. Finally, the result is further discussed with the other interfaces, consisting of cementitious materials. © 2009 Elsevier Ltd. All rights reserved.

Fukumoto T.,Kajima Technical Research Institute
Journal of Structural and Construction Engineering | Year: 2015

This paper proposes a new practical model of a restoring force characteristic on the panel zone within steel beam-to-concrete filled circular steel tube column moment connections for predicting the elastoplastic behavior of the panel zones including strength reduction after ultimate strength. The proposed model for a skeleton curve is provided as a multi-linear model having a cracking strength point, a yield strength point, an ultimate strength point and strength reduction points for 95%, 90% or 80% of ultimate strength. The skeleton curve model up to the ultimate strength point is based on the previous shear force-deformation model proposed by the writer, while the deformations of these strength reduction points is provided as new regression formulations obtained from previous test results. The writer proposes a new hysteresis loop model including stiffness reduction. The proposed models agree approximately with experimental results up to large deformations.

Sakagami K.,Kobe University | Fukutani Y.,Kobe University | Yairi M.,Kajima Technical Research Institute | Morimoto M.,Kobe University
Applied Acoustics | Year: 2014

As for the sound absorbing system using an MPP (microperforated panel), a double-leaf MPP sound absorber has been studied so far. However, this structure uses two MPPs, which are still expensive, and is disadvantageous when its cost is concerned. Therefore, it is considered that it can be advantageous if one of the leaves can be replaced with a less expensive material keeping high sound absorption performance. In this study, the possibility of producing a useful sound absorbing structure with an MPP and a permeable membrane as an alternative less expensive material is examined. The acoustic properties of this MPP and permeable membrane combination absorber are analysed theoretically with a Helmholtz integral formulation. The absorption performance and mechanism are discussed through the numerical examples. Also, the effect of a honeycomb in the air cavity, which is to be used for reinforcing the structure, is also discussed through a theoretical analysis. © 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

Imai M.,Kajima Technical Research Institute
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

As an optical fiber is able to act as a sensing medium, a Brillouin-based sensor provides continuous strain information along an optical fiber. The sensor has been used in a wide range of civil engineering applications because no other tool can satisfactorily detect discontinuity such as a crack. Cracking generates a local strain change on the embedded optical fiber, thus Brillouin optical correlation domain analysis (BOCDA), which offers a high spatial resolution by stimulated Brillouin scattering, is expected to detect a fine crack on concrete structures. The author installed the surface-mounted optical fiber on a concrete deck and periodically monitored strain distribution for seven years. This paper demonstrates how a BOCDA-based strain sensor can be employed to monitor cracks in a concrete surface. Additionally, focusing on another advantage of the sensor, the natural frequency of the deck is successfully measured by dynamic strain history. © 2015 SPIE.

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