Unbiased rank selection for automatic hysteretic response extraction
Reference : Yeow TZ & Kusunoki K. (2021), Unbiased rank selection for automatic hysteretic response extraction of RC frame buildings using acceleration recordings for post-earthqauke safety evaluations. Earthquake Eningeering and Structural Dynamics.(online access)
This research consists of two major parts. Firstly, an existing method to derive a building's capacity curve using acceleration data by applying the wavelet transform method is further refined using E-Defense test data. In the latter, an E-Defense test of a reinforced concrete building with spandrel walls casted to be monolithic with frame elements was performed to evaluate its ability to satisfy stringent performance objectives recently proposed for important buildings in Japan, and its resilience is evaluated using loss-estimation techniques. This research is supported by the Tokyo Metropolitan Resilience Project of the National Research Institute for Earth Science and Disaster Resilience (NIED).
It has been observed from past significant seismic events that recovery may be hindered by (i) disaster management centers being damaged which decreases the effectiveness of emergency response and recovery planning, and (ii) a long building-inspection process being required to evaluate a building’s safety; among other reasons. This research, which is part of a larger Tokyo Metropolitan Resilience Project, involves evaluating the effectiveness of a new building solution to enhance the resiliency of disaster management centers, as well as developing a health monitoring system to rapidly and reliably predict the building’s safety. As part of this research, an earthquake simulation experiment of a 3-story reinforced concrete building has been performed at the E-defense facility in December 2019.
“Seismic ratcheting” describes the phenomenon of structures predominantly deforming inelastically in a single direction during a seismic event. Structures with eccentric gravity loading may be prone to such behavior due to potentially having unbalanced strength in the forward and backward directions. Shake-table tests of steel frames exhibiting such behavior were performed to evaluate if structural health monitoring methods and conventional structural analyses are capable of capturing seismic ratcheting effects.
Post-earthquake visual damage inspection is a resource-intensive and subjective procedure that could result in occupants being unnecessarily displaced from safe buildings or for severe damage to be misidentified. To address this issue, our laboratory has instrumented a large number of buildings both within Japan and internationally. The sensor data is used to monitor the building’s dynamic properties and safety condition in real-time. Within minutes of a sizeable earthquake occurring, our system is able to produce reports detailing the response and potential damage level of each monitored building in the affected area which provide rapid building safety information while reducing resources required for post-earthquake evaluations. Research is ongoing to improve the accuracy of the damage classification method and to increase the efficiency of the system to perform the calculations for a large number of buildings.
One issue with using acceleration data in the described approach is that residual displacement information cannot be captured, which could cause the peak displacement response to be underestimated. An alternative approach could be to explicitly use sensors capable of measuring a building’s displacement or inter-story drift. In this research, the potential to use the building’s displacement response data directly into the capacity curve-based evaluation method instead of calculating it from acceleration response was investigated.
In the residual seismic performance grasping technique using acceleration sensors, performance curves are calculated by extracting acceleration components of a frequency band (rank) corresponding to a primary mode of a building using wavelet-transform method.Although the effectiveness of performance curve calculation methods using wavelet-transform mehtod has been verified, it has been found that it is difficult to determine the rank in a wooden structure in which the frequency band of a primary mode changes with plasticization or in a tower-shaped building showing relatively large higher-mode vibrational properties. Therefore, the purpose of this study is to conduct analysis and vibration experiments with changing parameters of the frequency bands of primary and secondary modes that interfere with the boundary of the Nyquist frequency, then the effect of the vibration property on the calculation of the performance curve is considered.
In Japan, the capacity spectrum approach is wildly used to predict the structure’s response. One major aspect of this is to predict a reduction factor, Fh, which accounts for hysteretic damping. In order to have a more reliable prediction of Fh, there is a need to estimate the yield displacement accurately. However, it is common practice to only consider flexural deformations when estimating yield displacement, and bar slippage and shear effect are often ignored. Therefore, there is a need to consider three effects for a more accurate prediction of yield response.
This study aims to investigate the lateral stiffness and ultimate shear strength of a new type structural system, thick wall-thick slab structure by calibrating finite element analyses based on a cyclic loading experimental study performed at Yamaguchi University and performing parametric finite element analyses. This type of structural system is developed based on flat plate floor strucrure which composed of column-slab joints and reinforced concrete wall structure which consisting mainly of walls to provide flexibility for interior design and high seismic performance simultaneously.
details coming soon
To better understand the dynamic properties and behavior of structures of cultural importance for preservation purposes, two 5-story pagodas located in the Shikoku region of Japan were instrumented with accelerometers. These pagodas were located at Zentsuji Temple and Motoyamaji Temple, both of which are part of the Shikoku 88 Temple Pilgrimage. Seven sensors were placed within each pagoda at various locations along their height, and visitors to the site can access real-time acceleration readings via a QR code. The monitoring of the pagodas is a joint effort with Professor Kaori Fujita of the University of Tokyo’s Graduate School of Engineering and is supported by the Motoyamaji Maintenance Committee (本山寺整備委), the National Research Institute for Earth Science and Disaster Resilience (防災科学技術研究所), and the SECOM Science and Technology Foundation (セコム科学技術振興財団).
details coming soon
There are two investigations for buildings damaged by earthquakes. One is the damage classification method and the other is damage evaluation for seismic insurance. However, they have some issues such as the required time for investigations. Therefore, the research for conducting these surveys by using capacity curves obtained from accelerometers installed in buildings has proceeded. To conduct these investigations, it is necessary to compare capacity curves and these investigations. As part of this, the objective of this research is to find out the issue and to modify damage evaluation by comparing two investigations.
We are interested in developing innovative technologies for structural health monitoring. We are currently working on sesnor capable of measuring directly inter stroey strcutural displacements, which can be used to improve the earthquake damage estimation of buildings and bridges.