Seismic Response Observation of Super High-Rise Buildings Throughout their Construction Stage and Development of Long-Stroke Shaking Table for Tracing Long-Period Floor Response

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In this research project, the fundamental dynamic properties of super high-rise buildings are investigated based on a large quantity of data observed during their construction stage. To understand the differences in structural response between structurally similar buildings with different numbers of floors, observations can be carried out in a single building during its construction, as earthquakes are likely to occur throughout the construction period when different numbers of floors have been completed. In this research, three super high-rise buildings have been observed. We clarify that the natural period is approximately proportional to the building height, while the damping ratio is inversely proportional. In the case of long-period buildings with small damping, when the natural period is close to the predominant period of soil, the seismic response of the building is enormously amplified for long-duration seismic ground motion. This phenomenon is explained from both observations … More and a simple analysis of a system with one degree of freedom. The changes in natural periods and damping ratios were obtained from microtremor records for a 47-story building while under construction. The natural period increases almost linearly with building height, both for the first and second modes, while the damping ratio is scattered around 0.5%. This damping value corresponds to the material damping of the steel itself.To promote countermeasures for super-high-rise buildings against long-period ground motions arising from predicted massive earthquakes, it is necessary to inform structural designers and building owners that buildings might suffer from an unexpectedly large response due to resonance. To ensure that structural designers and building owners are aware of this risk, it is necessary for them to experience the amount of floor response. They will then understand the necessity of safety measures for indoor areas and the importance of the addition of dampers to reduce the response.Conventional shaking tables are unable to reproduce this movement because of the displacement limit of the dynamic actuator used to drive the table. We developed a new shaking table named the 'Triple-L shaker,' which stands for he 'Long-stroke Long-period Linear shaker,' to reproduce the response of super-high-rise buildings. The innovation in this idea is the use of two servo-motors that pull the rope connected to the shaking table on the rail from both sides, as shown in Figure 13 and Photo 2. Compared with ordinary shaking tables, this system doesn't require a large space or special power supplies. The table reproduces amplitudes of displacement of up to 3 m, velocities of 5m/s, and acceleration of 2G. Using this table, people can easily experience the arbitrary response of various buildings upon different soil conditions. Less