Search

This paper proposes an experience-based lecture style that offers dual-scale experiments in combination. Lectures for vibration engineering were designed based on the proposed style and offered to undergraduate students. In the proposed style, experiments on free vibration on a seismic building for second-year students and advanced vibration control using an effective device for fourth-year students are examined in combination. The lecture style trials were repeated twice, once each in 2015 and 2016, with about two hundred second-year students; the students felt the free vibration of the five-story building which had a 6,100 ton weight inside and witnessed the mechanism of the base-isolated layer. To follow the demonstration steps, we developed an experimental device. The experimental device is composed of a vibration component corresponding to a building, and a motor cart with a handle corresponding to the ground. These are connected via a linear actuator that can exert one-dimensional force on the vibration component as a function of the input voltage. In the lectures conducted in 2017 and 2018, the students oscillate the cart and observe the motion of the vibration component. In addition, the virtual reality cameras for offering students a visually rich experience attracted students' interest. The questionnaire results showed that almost all of the students valued the lectures as useful. Since most of the students answered that the combination of the large-scale demonstration and scale-down experiment was useful, the proposed lecture style achieved the expected overall goals.

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.

The present study describes the important factors (period, duration, and intensity) involved in evaluating input ground motion and structural response for the design of long-period structures such as high-rise buildings and base-isolated buildings. First, the fundamental dynamic properties of high-rise buildings are explained based on the results of newly introduced vibration observations programs. Next, the distribution of the predominant period and duration of seismic ground motion within the Nobi Plain, one of the largest sedimentary plains in Japan, is discussed with respect to the possibility of resonance of long-period structures. Finally, we introduce a recently developed long-stroke shaking table that is intended to convince structural engineers and building owners to take adequate countermeasures against large floor response in high-rise buildings because of resonance.

By use of a newly developed network connected vibration measuring system which is suitable for continuous observation at construction sites, dynamic characteristics of high-rise buildings and their change during construction are discussed. Hundreds of ambient vibration data and several seismic response records were obtained at two neighboring high-rise buildings in approximately twenty months of construction. Observed response characteristics, estimated natural periods and damping ratios are shown with the change of building height under the same soil and foundation condition. Characteristics of higher modes and soil-structure interaction effect are also discussed. By use of forced and ambient vibration data, amplitude-dependent characteristics are clearly displayed as a relation with the velocity response which is proved to be highly correlated with the average deformation angle of stories.

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.