Nobuo Fukuwa

Field measurement of damping and natural frequency of an actual steel-framed building over a wide range of amplitudes

Abstract In order to understand the dynamic characteristics of a prefabricated steel building, several vibration tests with a wide range of amplitudes were carried out. Under excitation with relatively small amplitude levels, four different construction stages are prepared. The dynamic properties such as natural frequencies and damping ratios are evaluated using several identification methods based on observation records. The variability in the results due to the differences in identification methods and excitation conditions is examined. By comparing the results at different construction stages, the effect of non-structural members on the structural stiffness and damping ratio is studied. Using a mechanical exciter, forced vibration tests were carried out for several high excitation levels (100–3000 kgf). Free vibration tests using a wire cutting method were also carried out for several initial displacement levels (5–25 tonf, as initial tensile force levels). Based on the results of these vibration tests with various amplitude levels, the effect of non-structural members on dynamic characteristics is studied from the view point of amplitude dependence.

A knowledge-based approach to the structural analysis of large spacestructures

Analysis is one of the key issues in realizing large space structures. In spite of the fact that a huge amount of accumulation has been done in the field of structural analysis, there is still a need to include newly developed methodologies into analysis codes for production use. This paper introduces an attempt which implements a knowledge-based approach to structural analysis based on the idea that numerical analysis programming can be thought of as a particular type of engineering design. A system is proposed which first accepts the users description of a problem, then generates a program, along with input data, and finally to give a result to the user. In order to test the possibility of this approach, a problem solving model called Organizational Model is introduced and is implemented based on the object-oriented program development.

Synthesis of Earthquake‐Like Sound Using Seismic Ground‐Motion Records

Abstract Listening to a sound representing ground motion is valuable to intuitively understand an earthquake, compared with conventional methods such as observing waveforms, Fourier spectra, and response spectra. In this study, we propose a new method for generating sound representing an earthquake, which has several differences in comparison with existing methods. In our new method, an earthquake‐like sound is generated by modifying the frequency information of a generating function based on the symmetric Fourier analysis theory. Applying the method to existing seismograms illustrates three features of the sound generated by this method: the sound has the same duration as the seismogram, the sound pitch corresponds to the instantaneous frequency of the seismogram, and the sound volume corresponds to the envelope amplitude of the seismogram. Furthermore, we constructed a web‐based earthquake‐like sound generating system called Naion. Other applications will be implemented in the future.

Conceptual Design of a Cable Driven Parallel Mechanism for Planar Earthquake Simulation

Earthquake simulation is helpful in order for society to experience real seismic waves in safe environment. Cable-driven parallel mechanisms have advantages over conventional serial and parallel mechanisms. Prototype simulator which covers 1 m stroke in each direction has been built. In this paper, conceptual design of an earthquake simulator using cable driven parallel mechanism is presented. Spatial arrangement of cables is investigated in terms of the stability and safety of the simulator by dynamic analysis of the simulator. It was revealed that increasing the vertical angle of the cables with the ground while connecting them closer to the center of mass of the output link with low coefficient of friction between the ground ensures the most stable motion.

620 Maybe the World's First Attempt on Vibration Engineering Lecture : Report of Experience-Based Program : Building to Perform a Lecture Vibrated Freely

Susumu HARA, Nobuo FUKUWA, Toshihiro NODA, Takashi TASHIRO, Jun TOBITA, Takuya NAGAE, Kazumi KURATA and Tsuyoshi INOUE Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan

Erratum to Synthesis of Earthquake-Like Sound Using Seismic Ground-Motion Records Notice of Partially Redundant Publication

The Bulletin of the Seismological Society of America wishes to inform its readers of the following incident of a partially redundant publication. Hirai and Fukuwa (2014) contains substantial data also reported in the previously published article in the Journal of the Seismological Society of Japan (Hirai and Fukuwa, 2012) without referencing the prior publication. Although Hirai and Fukuwa report additional findings not contained in Hirai and Fukuwa (2012), The Bulletin of the Seismological Society of America regrets that the previous publication was not referenced by the authors. The editors of The Bulletin of the Seismological Society of America were not informed by the authors of the prior publication and discovered the redundancy only after the paper was submitted, accepted, and published. The previous article (Hirai and Fukuwa, 2012) introduces the basic idea and discusses the theoretical aspects of the sound synthesis method. On the other hand, the …

ANALYSIS OF THE DYNAMIC CHARACTERISTIC OF A BASE ISOLATED BUILDING AFFECTED BY PARTIAL SOIL IMPROVEMENT UNDER SEISMIC EXCITATION

This paper investigates dynamic characteristics of a base-isolated building affected by partial soil improvement under seismic excitation. An analysis model is made in order to estimate the behavior of such structures under seismic excitations. Comparisons were made between the results from analysis model and observed data. Dynamic properties of impedance and foundation input motion are also analyzed in this paper. It is found that the torsional response is generated due to the partial improved soil. With the increase of the depth and scale of the soil improvement, impedance shows an upward trend, at the same time, foundation input motion decreases.

Ground Vibration Caused by Tunnel Construction and its Effect on an Electron Microscope

Abstract In this study, we observed the vibrations caused by the construction of a roadway tunnel excavated using the New Austrian Tunneling Method (NATM) in an urban area. We analyzed the resulting vibrations and disturbances and their effect on a high-voltage electron microscope (HVEM). The characteristics of the construction equipment, various construction tasks, wave propagation and attenuation in the soil, along with the transmission of vibration forces to adjacent buildings were also clarified. These findings were combined and the effects on the HVEM were examined to model vibration-induced disturbances. The accuracy of these findings was confirmed by comparing the results obtained with actual observations that were recorded later. The findings of this study are expected to enhance the ability to distinguish between the many factors involved in vibration-induced disturbances caused by equipment. The findings could also be applied to monitoring construction activities and predicting the effects of vibration-induced disturbances on high-precision equipment.

SUMMARY OF BASIC DESIGN OF BASE ISOLATION RETROFIT FOR AICHI PREFECTURAL OFFICE

As seismic retrofit for Aichi prefectural office building, base isolation retrofit method was recognized by Aichi prefectural assembly and we started further study for basic design. We had to budget the seismic retrofit cost for coming year and we investigated important matters for cost such as building foundation level, necessary volumes of soil improving and so on. And we had to decide seismic criterion of retrofit building. We had to study about tender method in addition. This report is summary of basic design.