研究者詳細 - 小檜山　雅之

論文 - 小檜山　雅之

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溝淵陸大，小檜山雅之，山下拓三

日本地震工学会論文集（日本地震工学会） 25 （ 4 ） 97 - 108 2025年03月

研究論文（学術雑誌）, 査読有り, ISSN 1884-6246

繰り返し地震動が入力し木造建物が倒壊して人的被害が発生することを防ぐため，構造ヘルスモニタリングシステムによる迅速な損傷評価が期待されている．ニューラルネットワークは建物応答から倒壊の危険性を判別する有力な手法であるが，未学習の損傷パターンの判別を苦手としている．本研究では，ニューラルネットワークを用いた木造建物の損傷判別器の構築において，学習データを作成する際に対象建物モデルの応答解析の入力にパルス性模擬地震動を用いることで損傷パターンの多様性を考慮する手法を提案し，判別精度を比較することでその有効性を検証した．

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Damage Classifier for Wooden Buildings Based on Hysteresis Loop Images Using CNN

Chiba, S., Kohiyama, M., and Yamashita, T.

Proc. of the 18th World Conference on Earthquake Engineering 2024 (WCEE2024) 2024年06月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Structural health monitoring (SHM), which evaluates building damage based on seismic response data, is useful for rapidly assessing damage due to earthquakes. If a reliable damage assessment system for houses can be developed, the loss of human lives caused by the aftershocks of major earthquakes can be reduced. When a target building is damaged by strong seismic ground motions, the shape of the restoring force–story drift angle curve (hysteresis loop) changes. Therefore, based on the hysteresis loop images of wooden buildings, this study proposes a method to classify the risk of collapse because of future seismic ground motions using a convolutional neural network (CNN). To develop training data, structural response analysis is conducted using “wallstat”, which is a numerical analysis software for wooden structures. SHM has more severe consequences when it misclassifies an unsafe condition as safe (miss) than when it misclassifies a safe one as unsafe (false alarm). Therefore, we propose the usage of a dataset that does not contain safe model data near the threshold value of major damage for training to decrease the possibility of misses, and we verify the effect of this. In creating the hysteresis loop images, we examine the range of the axes using two methods: fixing it at specific values and matching it to the range of the minimum and maximum values. The investigation results suggest that the trained CNN learns the changes in structural characteristics, such as stiffness reduction, damping increase, and residual displacement.

サーバ地震応答の故障閾値超過確率に基づくウォームスタンバイ

木田祐輔，平岡笑暢，小檜山雅之

地域安全学会論文集（地域安全学会）（ 43 ） 19 - 27 2023年11月

研究論文（学術雑誌）, 共著, 最終著者, 査読有り, ISSN 1345-2088

This study proposes a new warm standby method for computer servers based on seismic response. The proposed method triggers a warm standby in the case that the exceedance probability of the safety limit of seismic response predicted by the last two-second observation record exceeds a preset threshold. Numerical simulations showed that the proposed method reduced the loss cost by 1.64% compared to conventional methods. To validate this method, we conducted shaking table tests. When a simulated earthquake motion was input, the loss cost was reduced by 60.6%. However, when observed records were input, the loss cost was increased by 3.89%. The results suggest that it is necessary improve the input ground motion model.

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次世代火山防災リーダーの育成を目的とした住民による自律的な対面・遠隔両形式の机上訓練を可能にするツールの開発

小檜山雅之，高島帆風，山内壮泰，吉本充宏，久保智弘

地域安全学会論文集（地域安全学会）（ 43 ） 315 - 325 2023年11月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り, ISSN 1345-2088

To reduce volcanic disasters, it is important for residents to practice mutual support under the leadership of voluntary disaster reduction groups. However, many communities lack the human resource for their future leaders. To address this issue, we proposed a digital tool for residents to develop leaders by themselves. The system requirements were determined to enable residents to conduct autonomous and effective tabletop exercise in both in-person and remote formats. The usefulness of the tool was confirmed through workshops with residents of the areas at the foot of Mt. Fuji.

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Study on a Simplified Model of a High-Rise Shear-Type Building for Evaluation of Q-Δ Resonance

Anamizu R., Kohiyama M.

Japan Architectural Review （Wiley） 6 （ 1 ） 1 - 16 2023年10月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り, ISSN 2475-8876

To evaluate Q–Δ resonance, which is a torsional resonance phenomenon caused by geometric nonlinearity, a simplified model for a multistory non-eccentric building with a shear-type structure was proposed. A four-story small-scale specimen was designed and fabricated, assuming a non-eccentric steel structure with a height of 324 m, and conducted shaking table tests of the specimen. Q–Δ resonance was confirmed as predicted by the simplified model. In addition, the simplified model reproduced the resonance amplitude calculated using a finite element model of the specimen with constrained out-of-plane slab rotation. The simplified model can be used to predict the Q–Δ resonance response when the bending deformation of an entire building is very small.

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Probability Distribution of Torsional Response by Q–Δ Resonance of Multi-Story Building under Long-Period Seismic Motion

Kohiyama M.

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP14) 2023年07月

研究論文（国際会議プロシーディングス）, 単著, 筆頭著者, 責任著者, 査読有り

When the torsional moment owing to geometric nonlinearity synchronizes with the torsional mode response, an internal resonance phenomenon occurs in a building structure system. The author’s research group calls this phenomenon Q–Δ resonance. The probability distribution of the torsional response was evaluated using Monte Carlo simulations on a 60-story building model, the input wave being simulated using nonstationary colored-noise ground motion. The results showed that the torsional response greatly increased the horizontal acceleration response and the response amplification ratio between the center and corner of the top floor could exceed 1.2 when the model satisfied the Q–Δ resonance condition that the natural frequency of the torsional second mode matched the sum of the first natural frequencies in the x- and y-directions. It was also evident that closer proximity to the resonance condition increased the amplification ratio. These results suggest that Q–Δ resonance may need to be considered in seismic design.

BAYESIAN UPDATING OF WOODEN STRUCTURAL PARAMETERS AND SEISMIC DAMAGE CLASSIFIER USING NEURAL NETWORK

Mizobuchi R., Kohiyama M., Yamashita T.

Proceedings of the 9th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2023) 1 2335 - 2347 2023年06月

研究論文（国際会議プロシーディングス）, 共著, 査読有り, ISSN 26233347

Structural health monitoring is an effective way to quickly and efficiently detect earthquake damage to a building. However, its applications to wooden buildings are still limited. One of the challenges in predicting the seismic response of a wooden structure is that the effect of variance in its material and structural properties is relatively significant. To handle this problem, we propose a method to update the damage classifier using Bayesian system identification. The damage classifier is constructed using neural network (NN) and machine learning techniques. The method utilizes the weighted loss function for the NN to reflect the updated probability distribution of the structural parameters. The NN is tuned using backpropagation, where the training data are consequently weighed by the weighed loss function, directly using the value of the posterior probability, according to the data obtained from the numerical model of a target structure with the corresponding parameters. Using the result of the Bayesian updating, the tuned NN damage classifier achieved a higher accuracy than before tuning by reflecting the posterior probability distribution of the structural parameters.

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THREE-DIMENSIONAL FRAME ANALYSIS OF Q-Δ RESONANCE OF CENTER-CORE BIAXIALLY SYMMETRICAL HIGH-RISE BUILDING UNDER LONG-PERIOD EARTHQUAKE MOTION

Kohiyama M., Maki S.

COMPDYN Proceedings 1 961 - 970 2023年06月

研究論文（国際会議プロシーディングス）, 共著, 筆頭著者, 査読有り, ISSN 26233347

When large displacements occur in buildings with different stiffnesses in the two horizontal directions, torsional moments are generated owing to geometric nonlinearities. Consequently, when the sum or difference of the translational mode natural frequencies in the two horizontal directions is close to the torsional mode natural frequency, the torsional mode is excited. This is known as Q-? resonance. Therefore, we created a three-dimensional frame model of a center-core high-rise building with a biaxially symmetrical plane that satisfied the Q-? resonance condition and examined whether the torsional response was excited by long-period design waves. A time-history response analysis was conducted assuming elastic response and considering geometric nonlinearities. It was confirmed that the torsional mode could be induced.

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EXPERIMENT AND SIMULATION OF Q-Δ RESONANCE USING FOUR-LAYER BENDING-SHEAR TYPE SPECIMEN

Kai R., Kohiyama M.

Proceedings of the 9th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2023) 1 971 - 981 2023年06月

研究論文（国際会議プロシーディングス）, 共著, 最終著者, 査読有り, ISSN 26233347

Torsional vibration of buildings subjected to earthquake motion has been studied for many years, but the torsional vibration of high-rise buildings has not yet been clarified. Many previous studies have focused on eccentricity, the mismatch between the center of gravity and the rigid center, as the cause of torsional vibration. However, in buildings with no eccentricity, torsional vibrations could be observed. The authors' research group focused on the “Q-Delta effect,” a phenomenon in which torsional torque is generated due to geometric nonlinearity and “Q-Delta resonance,” a phenomenon in which resonance occurs when the period of torsional torque generation coincides with the natural period of the torsional mode. In order to analyze the characteristics of Q-Delta resonance, a small-scale specimen was designed and fabricated from an 81-story high-rise building with biaxially symmetrical plans, which was reduced to four stories. As a result, the torsional response of the experimental and simulation results generally agreed, confirming that the torsional response increases when the Q-Delta resonance condition is satisfied. In addition, a comparison of the torsional response with a specimen with a smaller tower ratio and less bending deformation was conducted, and it was confirmed that the peak of the torsional response was steeper in the present study case.

せん断型超高層建物のQ－Δ共振評価用簡易モデルに関する研究

穴水亮輔，小檜山雅之

日本建築学会構造系論文集（日本建築学会） 88 （ 803 ） 59 - 70 2023年01月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 13404202

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Torsional behavior of a non-eccentric structure considering the effect of shear deformations in vertical members

Maki S., Kohiyama M.

Japan Architectural Review （Wiley） 5 （ 4 ） 404 - 431 2022年10月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2475-8876

Torsional moments can occur in a column owing to the geometric nonlinearity when the top of the column undergoes a large displacement in two horizontal directions. Periodically generated torsional moments can excite the torsional mode of a building owing to the internal resonance. For high-rise buildings, there is a risk that long-period seismic motions can cause a non-negligible torsional response due to this phenomenon. To investigate this risk, this study focuses on non-eccentric single-story and two-story shear-type structural models with an aggregate column, which is assumed to be an elastic Timoshenko beam. We derived the equations of motion for the models under horizontal ground motions and confirmed that the equations were identical to those of the models with an aggregate column of an elastic Euler beam. We then performed time-history response analyses of the models satisfying the internal resonance conditions under the input ground motions of harmonic waves, Gaussian white noise acceleration, acceleration records of previous earthquakes, and a long-period design wave. The results showed that the maximum horizontal acceleration at the corner of the top floor slab could be increased by more than 60% of the acceleration at the center of the slab in the worst case.

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振動台実験および有限要素解析による高次モードを考慮したＱ—Δ共振の基礎的検討

穴水亮輔，小檜山雅之

構造工学論文集（日本建築学会） 68B 386 - 396 2022年04月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0910-8033

The Q–Δ effect is a phenomenon that a column with different lateral stiffness generates a restoring torsional moment owing to geometric nonlinearity when its top displaces in two horizontal directions simultaneously. The Q–Δ resonance that is resonance of a torsional mode induced by the periodic torsional moment due to the Q–Δ effect could cause considerable torsional vibration even in non-eccentric buildings. However, the Q–Δ resonance in higher-order modes has not been investigated well. We first constructed a model of a two-story non-eccentricity structure and derived the conditions of the Q–Δ resonance considering higher-order modes. Then, we conducted shaking table experiments and finite element analysis to reproduce the experiments. As a result, it was confirmed that the second mode in the torsional direction was excited as predicted by the derived Q–Δ resonance condition. Moreover, the finite element analysis could reproduce the experimental result with high accuracy.

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Torsional response of a bisymmetric structure induced by bending–torsion interaction in vertical members

Kohiyama M., Yokoyama H., Maki S.

Japan Architectural Review （Wiley） 5 （ 1 ） 3 - 19 2022年01月

研究論文（学術雑誌）, 共著, 筆頭著者, 最終著者, 責任著者, 査読有り

The biaxially symmetric column induces torsional moment owing to the bending–torsion interaction when the top of the column is given horizontal displacement in the two directions of the principal axes of the cross section and the rotation of the column ends around the axes is constrained. Hence, horizontal ground motions in two directions can cause non-negligible torsional vibration in a high-rise building owing to autoparametric resonance. To investigate this phenomenon, in this study, we focus on a single-story structure with an aggregated column, which is a model for columns or core structures in tall buildings and is assumed to be an elastic Euler beam; subsequently we derive the equations of motion under horizontal ground motions in two directions. The resonance condition in the torsional direction is also investigated. Time-series response analyses are performed for input ground motions of harmonic waves, white noise, acceleration records of prior earthquakes, and a long-period design wave, and the relationship between the ratio of two translational natural frequencies and the increase in maximum responses is explained. The results demonstrate that the absolute acceleration response to the long-period design wave could increase by more than 50% in the worst-case scenario.

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火山災害対応における認知バイアスを克服するための訓練ツール

今野裕三，高島帆風，小檜山雅之，吉本充宏，久保智弘

地域安全学会論文集（地域安全学会）（ 39 ） 233 - 243 2021年11月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 1345-2088

近年の災害をみると，避難勧告が出ていたにも関わらず逃げ遅れる人や事前準備を適切に行っていなかった人の事例が多数挙げられる．この原因の一つとして考えられるのが，認知バイアスによる影響である．しかし，これまで地域住民の災害対応における認知バイアスへの対策は十分取られてこなかった。本研究では，火山災害の対応において起こりうる認知バイアスについて知識を身につけ，対策を議論することで認知バイアスを克服する訓練ツールをウェブアプリケーションの形式で開発した。富士吉田市で2回のワークショップを開催し，訓練ツールの有効性を検証した。開発した訓練ツールはビデオ会議システムを用いることにより、住民自身で訓練を実施することが可能である。

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Experiment of torsional response induced by the Q–delta resonance

Mizutori F., Kohiyama M.

The Structural Design of Tall and Special Buildings （Wiley） 30 （ 4 ） 2021年03月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 15417794

Because of geometric nonlinearities, vibrations in two horizontal directions can generate a torsional moment that induces a torsional response, even in a structure with no eccentricity; we term this phenomenon Q–Δ effect. In this study, the torsional response caused by the Q–Δ resonance was investigated by performing a shaking table test that involves a single-layer symmetric specimen. The specimen was designed and fabricated by focusing on one of two resonance conditions. Its moment of inertia was adjustable by changing locations of weights, and the natural frequency in the torsional mode could be modified. We developed a numerical model of the specimen, in which the columns connected to the slab were integrated into an elastic Euler beam. It was confirmed that the torsional response increased near the predicted Q–Δ resonance point. In addition, the acceleration at the corner of the slab was significantly increased. The formulated equations of motion provided a better prediction of the actual phenomena. Because the specimen corresponds to a stiff and slender high-rise building when converted into a full scale, the result suggests a need to be aware of the risk of torsional response increase due to the Q–Δ resonance.

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Deep neural network for detecting earthquake damage to brace members installed in a steel frame

Yamashita T., Kohiyama M., Watanabe K.

Japan Architectural Review （Japan Architectural Review） 4 （ 1 ） 56 - 64 2021年01月

研究論文（学術雑誌）, 共著, 査読有り

We are developing an artificial intelligence system for structural health monitoring that can detect local damage in a building structure by using the E-Simulator numerical simulation system that is being developed by the Japanese National Research Institute for Earth Science and Disaster Resilience. In this study, we confirmed the applicability of a multiclass classifier using a deep neural network to address the problem of identifying damage patterns in braces installed in a steel frame. Experimental data obtained from shaking table tests were used for training and testing. Cross-validation tests were conducted for several cases with different numbers of sensors, sensor degrees of freedom, and nodes in the hidden layers of the network. The results demonstrated that the accuracy of the damage pattern detection from the constructed classifier exceeded 77% when the appropriate hidden layers were selected and reached 87.9% for the best case.

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拡張現実を用いた富士山火山ハザードマップ

小檜山雅之，赤堀竜海，吉本充宏，久保智弘

地域安全学会論文集（地域安全学会）（ 37 ） 147 - 155 2020年11月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 1345-2088

火山災害には多種多様なハザードがあり，ハザードによって避難が必要な地域や適切な避難のタイミングが異なる．被害を軽減するためには起こりうる現象とそれに対する対策行動を正しく理解しておくことが重要となる．火山ハザードマップは，ハザードの影響が及ぶ恐れのある範囲を地図上に特定し，避難等の防災対策をとるべき範囲を視覚的に捉えやすいよう作成されている．しかし，ハザードが一つのマップに重複して描かれ複雑になっていることなどからその内容は一般の人々にとって必ずしも容易ではない．そこで，紙媒体や静止画によるハザードマップを補完し，ハザードマップへの興味や関心を高め，各家庭や自主防災会におけるハザードマップを活用したコミュニケーションを活性化するツールとして，拡張現実(AR)を用いた富士山AR火山ハザードマップを開発した．市民等や高校生によるワークショップを開催し，アンケート調査を行ってその有効性を検証した．その結果，開発した富士山AR火山ハザードマップは紙媒体の火山ハザードマップを補う効果があることが明らかになった．とくに，各ハザードを表示切り替えできる機能はハザードマップの理解に役立つことが確認できた．また，AR特有の立体感は，地形によってハザードの動きが変わる火山災害をイメージしやすくする効果があることが明らかになった．

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次世代火山防災リーダーの育成を目的とした住民主体の災害机上訓練のフレームワーク

高島帆風，小檜山雅之，吉本充宏，久保智弘

地域安全学会論文集（地域安全学会論文集）（ 37 ） 175 - 185 2020年11月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 1345-2088

In order to reduce volcanic disasters, it is important for residents to practice mutual assistance, which can be led by a voluntary disaster reduction group. However, many communities lack the human resources for their future leaders. To address this issue, we created a framework of disaster imagination game to develop next-generation leaders. The effectiveness of the game was verified through workshops held in Fujiyoshida City. The framework allows residents to train independently by using a web application software.

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Detection method of unlearned pattern using support vector machine in damage classification based on deep neural network

Kohiyama M., Oka K., Yamashita T.

Structural Control and Health Monitoring （Wiley） 27 （ 8 ） 2020年08月

研究論文（学術雑誌）, 共著, 筆頭著者, 最終著者, 責任著者, 査読有り, ISSN 15452255

深層ニューラルネットワーク（DNN）は、対象構造物の損傷パターンを高精度で分類および認識するのに役立つ特徴量を自動的に識別できるため、構造ヘルスモニタリングの強力なツールである。しかし、未学習の損傷パターンの入力データを、学習済みの損傷パターンのいずれかに誤って分類する可能性がある。この欠点に対処するため、本論文では、サポートベクトルマシン（SVM）の多数決を使用して、未学習の損傷パターンを検出する方法を提案した。SVMは、学習用データにおいてDNNの出力層に格納されている特徴ベクトルを使用して構築される。提案手法を検証するため、2つの異なるデータセットを使用した。1つは鉄骨構造の振動台実験データ、もう1つは木造住宅のシミュレーションおよび振動台実験データである。いずれの場合も、学習済みと未学習の両方の損傷パターンのデータを正しく識別できることを確認した。これより提案手法は、構造ヘルスモニタリング（SHM）の有効性を向上できることが示唆される。また、SHM固有の特性を使用していないため、画像処理や音声処理など、さまざまなパターン認識アプリケーションの未学習のパターンの問題解決にも応用できる。

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摩擦を考慮した動的解析結果の強化学習に基づくコンピュータビジョンを用いたキャスタ付き機器の地震応答制御

若林憲人，河西洋亮，小檜山雅之，江口僚，髙橋正樹

構造工学論文集（日本建築学会） 66B 305 - 314 2020年03月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0910-8033

We developed a computer vision system to control the seismic response of medical equipment with casters in a building subjected to earthquake excitation. The controller employs a neural network and the reinforced learning was conducted based on dynamic simulations of a controlled equipment under building floor motion. In the dynamic simulations, we used Open Dynamics Engine, which is a simulator library of three-dimensional rigid body dynamics, and we introduced a friction model to simulate the dynamic behavior of the casters. To validate the proposed system, we conducted shaking table tests and it was confirmed that the proposed control could successfully suppress the response of the equipment.

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