Abstract

The author has developed a new method for evaluating the seismic performance of existing structures from measured accelerations based on the capacity spectrum method. This involves comparing the performance curve, which is the equivalent nonlinear behavior of a simplified single-degree-of-freedom system, and the demand curve, which is the relationship between the response acceleration and displacement spectra. Two telecommunication towers in Japan were instrumented in 2016, and their responses during several earthquakes have been recorded. This paper discusses the evaluation of damage during the two earthquakes. Moreover, parameters such as the predominant period and the required performance are discussed. The proposed system evaluated both towers as being “elastic.” The damping ratios of the towers are very low, which caused the oscillations to continue for more than 5 min after the mainshock of each earthquake because of long-period components of the seismic motion

Highlights

  • In 2000, a new structural calculation method known as the “response and limit-capacity calculation” was added to the Building Standard Law of Japan as a new option for evaluating the seismic performance of buildings

  • The dynamic response of two instrumented steel telecommunication towers that were in place during two major earthquakes in 2016 was investigated

  • The demand curves associated with the base of each tower were smaller than those of the free field (KNet)

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Summary

Introduction

In 2000, a new structural calculation method known as the “response and limit-capacity calculation” was added to the Building Standard Law of Japan as a new option for evaluating the seismic performance of buildings. The current inspection method this involves structural engineers making visual assessments, which is both time consuming and subjective. To overcome these drawbacks, a new real-time method has been proposed [1-4] for evaluating building damage with inexpensive accelerometers based on the aforementioned response and limit-capacity calculation. One was the Fukushima Offshore Earthquake of magnitude 7.4 at 0559 JST on November 22, 2016. At both tower sites, the maximum seismic intensity was recorded as three on the Japan Meteorological Agency (JMA) seismic intensity scale. This paper discusses the damage evaluation results and design parameters such as the predominant period and the required performance

Outline of towers and measurements
Measured accelerations
Damage evaluated from measured accelerations
Capacity curve from the measured accelerations
Capacity curve with the Wavelet transformation
Capacity curve with measured acceleration
Demand curve with measured acceleration
Performance curves derived from measured accelerations
Concluding remarks
Findings
Hiroshi

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