Dionysius Siringoringo - Academia.edu (original) (raw)

Papers by Dionysius Siringoringo

Research paper thumbnail of Influence of movable bearings performance on the dynamic characteristics of a cable-stayed bridge : insights from seismic monitoring records

An investigation on seismic response characteristics and modal parameters of a cablestayed bridge... more An investigation on seismic response characteristics and modal parameters of a cablestayed bridge with movable bearings using vibration records obtained from a seismic monitoring system is presented in this paper. The object of this study is the Tokachi cablestayed bridge, a single plane prestressed cable-stayed bridge that is equipped with moveable spherical frictional plate (SFP). The bridge seismic responses subjected to various levels of earthquake including the 2003 Tokachi Great earthquake were obtained from a permanent seismic monitoring system. The bridge dynamic characteristics that include frequency and damping were estimated by both the time-invariant and time-variant recursive subspace identification methods. The identification results reveal that damping ratios of the low order modes estimated during the largest earthquake can reach more than 10% of the critical damping, which is higher than what usually assumed in the seismic design code. Supplementary damping caused by friction force at the movable SFP bearings was identified as the main source of the large damping, and it was quantified by a modal-based inverse analysis using the sparse regularization method. Results of the analyses confirm the influence of moveable SFP bearings performance with its Coulomb-friction type stick-slip behavior on the dynamic characteristics of the bridge. The bearings remain stuck at smaller excitation causing higher stiffness of the structure and slip during a larger excitation resulting in stiffness reduction. The sliding process induces friction force between contacting surfaces of the SFP bearings which results in the increase of damping as the excitation level increases. The damping, however, does not increase continuously, but becomes steadier after a certain level of excitation.

Research paper thumbnail of クタイ・カルタネガラ橋のクランプ・ピンのせん断破壊に関する一考察

Research paper thumbnail of Wavelet-Based Analysis for Detection of Isolation Bearing Malfunction in a Continuous Multi-Span Girder Bridge

Journal of Earthquake Engineering, 2021

This paper describes techniques for detecting bearing malfunction directly from the seismic respo... more This paper describes techniques for detecting bearing malfunction directly from the seismic response of the bridge using wavelet transform time varying identification. Instantaneous frequency of continuous wavelet and detail components of discrete wavelet transform are utilized as structural features, and they characterize isolation bearing condition via statistical clustering technique. Accuracy and efficacy of the techniques were verified in numerical simulations using analytical and finite element models. The techniques were implemented on seismic records from long-term monitoring of multi-span continuous-girder isolated bridge. Results demonstrate that wavelet-based features can effectively characterize the condition of the isolation bearing directly from seismic responses of girder and piers.

Research paper thumbnail of Seismic Response Analysis of Hakucho Suspension Bridge from Long-term Monitoring System

IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016

Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspe... more Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspension bridge in northeastern Japan with the total span length of 1380m. The bridge has permanent seismic monitoring system consisting of 27 channels of accelerometers placed on fourteen locations on the deck, tower and free-field. Since opened to public on June 13, 1998 until 2006 the monitoring system has recorded various scales of earthquakes, including the major ones such as the 2003 Tokachi and 2004 Kushiro earthquakes. To investigate dynamic characteristics during various level of seismic excitation in more detail, multi-input multi-output time-domain system identification was conducted. Vibration characteristics of structural members such as girder and tower for different amplitude of excitation are investigated and compared with previous results from ambient response analysis and finite element.

Research paper thumbnail of Seismic Response Analysis of Hakucho Suspension Bridge from Long-term Monitoring System

IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016

Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspe... more Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspension bridge in northeastern Japan with the total span length of 1380m. The bridge has permanent seismic monitoring system consisting of 27 channels of accelerometers placed on fourteen locations on the deck, tower and free-field. Since opened to public on June 13, 1998 until 2006 the monitoring system has recorded various scales of earthquakes, including the major ones such as the 2003 Tokachi and 2004 Kushiro earthquakes. To investigate dynamic characteristics during various level of seismic excitation in more detail, multi-input multi-output time-domain system identification was conducted. Vibration characteristics of structural members such as girder and tower for different amplitude of excitation are investigated and compared with previous results from ambient response analysis and finite element.

Research paper thumbnail of Seismic Monitoring of Seismically Isolated Bridges and Buildings in Japan—Case Studies and Lessons Learned

Seismic Structural Health Monitoring, 2019

Monitoring of seismic response of structures has been widely employed for decades in Japan. From ... more Monitoring of seismic response of structures has been widely employed for decades in Japan. From the structural point of view, the objectives of seismic monitoring are mainly to verify designed load assumption, evaluate seismic response and structure performance during large earthquake, detecting possible damages due to earthquake and monitoring for verification of structural retrofit. Seismic monitoring is very important for large, important structures and structures with specific features and innovative technologies such as seismic isolation or response control systems. This paper describes several case-studies and lessons learned of seismic monitoring on seismically isolated bridges and buildings in Japan.

Research paper thumbnail of Investigation on vehicle lateral instability when crossing a curved highway bridge during an earthquake

Structure and Infrastructure Engineering, 2020

This paper describes a numerical study on the vehicle instability when crossing curved highway br... more This paper describes a numerical study on the vehicle instability when crossing curved highway bridge during an earthquake. Analytical framework using two-axle vehicle dynamics model is developed to describe vehicle vibration when moving under seismic excitation from the curved bridge girder. The model includes out-of-plane and in-plane motion along with the effect of curved girder with specific radius, camber angle and longitudinal grade. Two criteria for critical vehicle stability are evaluated namely the rollover and sideslip stability. As case study, numerical simulations were conducted using three-dimensional finite element model of an elevated highway junction consisting of four curved sections and two straight sections. Effects of curved bridge radii, level of earthquake, vehicle velocity and driver reaction on the vehicle stability were investigated. It was found that a vehicle moving on a curved bridge during earthquake has a larger possibility for rollover and sideslip instability than a vehicle moving on a straight section for the same driving velocity and level of earthquake. Results of simulations demonstrate that normal forces on vehicle's wheels are significantly influenced by the curved bridge effects, steering angle, effect of road camber at the curved section. These conditions contributed to reduction of normal forces on vehicle's wheels and increased the risk of vehicle instability.

Research paper thumbnail of Wind-induced responses and dynamics characteristics of an asymmetrical base-isolated building observed during typhoons

Journal of Wind Engineering and Industrial Aerodynamics, 2017

Responses of an asymmetrical base-isolated building during the passage of Typhoon Roke 2011, Typh... more Responses of an asymmetrical base-isolated building during the passage of Typhoon Roke 2011, Typhoon Guchol 2012 and a bomb cyclone strong-wind event on April 3, 2012 were investigated in this paper. Windinduced accelerations of the building were recorded by dense array permanent monitoring system and analyzed in detailed by spectra analysis, time-frequency wavelet analysis and system identification. Results of analysis revealed that wind-induced responses of the buildings were dominated by the first mode which is the fundamental flexural mode coupled with torsion of the upper stories. Building responses demonstrated nonlinear characteristics of natural frequencies, damping ratio and mode-shapes. Natural frequencies of fundamental modes decreased with the increase of acceleration amplitude, with the maximum reduction of 8-10% of natural frequencies observed during the peak wind speed. Damping estimates of the fundamental modes increased with the increase of accelerations, while characteristics of mode-shapes were also found to be dependent on the wind speed. Further analysis revealed that non-linear characteristics of building responses are related to isolator deformations caused by wind-induced static force.

Research paper thumbnail of Along-wind almost-harmonic vibration observed at Hakucho-Bridge pylons and its wind tunnel experiments

Journal of Wind Engineering, 2016

This paper describes an along-wind vibration of frame-type pylons of Hakucho Suspension Bridge fo... more This paper describes an along-wind vibration of frame-type pylons of Hakucho Suspension Bridge found from longterm vibration monitoring data. It is shown that the vibration is very harmonic although its amplitude is small and it occurs under certain ranges of wind direction (10~30 degree from the bridge perpendicular axis) and of wind velocity (13~25 m/s). The dominant frequency of the vibration is either 0.6 Hz or 0.8 Hz depending on the wind velocity and these correspond to the natural frequencies of the in-plane pylon dominant modes of the suspension bridge. A series of the wind tunnel experiments using a spring-supported scaled model are conducted under uniform flow and the alongwind pylon vibration was observed and its vibration characteristics is found to be consistent to those observed in Hakucho Bridge. It is also found that the vibration is very sensitive to the incident angle of wind and to the distance between the two columns.

Research paper thumbnail of The needs for advanced sensor technologies in risk assessment of civil infrastructures

Smart Structures and Systems, 2009

ABSTRACT Civil infrastructures are always subjected to various types of hazard and deterioration.... more ABSTRACT Civil infrastructures are always subjected to various types of hazard and deterioration. These conditions require systematic efforts to assess the exposure and vulnerability of infrastructure, as well as producing strategic countermeasures to reduce the risks. This paper describes the needs for and concept of advanced sensor technologies for risk assessment of civil infrastructure in Japan. Backgrounds of the infrastructure problems such as natural disasters, difficult environment, limited resource for maintenance, and increasing requirement for safety are discussed. The paper presents a concept of risk assessment, which is defined as a combination of hazard and structural vulnerability assessment. An overview of current practices and research activities toward implementing the concept is presented. This includes implementation of structural health monitoring (SHM) systems for environment and natural disaster prevention, improvement of stock management, and prevention of structural failure.

Research paper thumbnail of 訂正：2011年東北地方太平洋沖地震における横浜ベイブリッジの応答［土木学会論文集A1（構造・地震工学）, Vol. 69, No. 2, pp. 372-391, (2013)］

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2014

Research paper thumbnail of 2011年東北地方太平洋沖地震における横浜ベイブリッジの応答

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2013

高密度地震応答計測システムを有する横浜ベイブリッジでは，2011年3月11日東北地方太平洋沖地震M w 9.0の本震と余震による周辺地盤の地震動と地震応答の記録が収録された．本論文はその記録を多... more 高密度地震応答計測システムを有する横浜ベイブリッジでは，2011年3月11日東北地方太平洋沖地震M w 9.0の本震と余震による周辺地盤の地震動と地震応答の記録が収録された．本論文はその記録を多面的に 解析し1) 主桁の振動は橋軸直角方向の応答が卓越した(最大応答変位62cm)，2) 橋軸方向の主桁と主塔 および端部橋脚の応答記録から，主塔と端部橋脚位置のリンク支承が所要の免震性能を発揮した，3) 主塔 と端部橋脚のウィンド沓は橋軸直角方向に衝突していた形跡がある，4) 本震時の大振幅応答時には，主桁 の橋軸直角方向水平たわみ1次モードや主桁の鉛直方向たわみ1次モードの固有振動数が変化しただけでな く，それぞれのモード形において，小振幅時には見られない連成挙動が同定されたことを明らかにしてい る．

Research paper thumbnail of クタイ・カルタネガラ橋のクランプ・ピンのせん断破壊に関する一考察

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2013

Research paper thumbnail of Long-term seismic monitoring of base-isolated building with emphasis on serviceability assessment

Earthquake Engineering & Structural Dynamics, 2014

Seismic monitoring system provides opportunities to observe possible damage or failure and weaken... more Seismic monitoring system provides opportunities to observe possible damage or failure and weakening of structural components and to evaluate serviceability performance of a structure during an earthquake. This can be achieved by comparing structure recordings before and after the event or by identifying significant change in characteristics of structural response that may serve as indicators of failure or damage in progress. Excessive vibration on some parts of structure may become a serviceability concern for some buildings, and this also can be detected from continuous monitoring. Several factors such as characteristics of ground motion, soil condition, and geometry of the structure could cause excessive localized structural vibration, and by evaluating the responses, one can take remedial action. For a base-isolated building in particular, reduction of response of upper stories is critical to protect nonstructural elements or sensitive equipments on the building. In this paper, we describe a case study on seismic monitoring of a base-isolated building with the main focus on evaluation of serviceability performance. The study emphasizes on a influence of building asymmetricity on the seismic response. Results of the study are based on a long-term building seismic monitoring program for over 3 years between 2010 and 2012 under various amplitudes of earthquake including the March 11, 2011 Great East-Japan Earthquake.

Research paper thumbnail of Strategies for structural health monitoring of bridges

From Materials to Structures: Advancement through Innovation, 2012

Abstract: The needs for structural health monitoring in Japan originally come from its geographic... more Abstract: The needs for structural health monitoring in Japan originally come from its geographical conditions such as severe environment for deterioration and frequent natural disasters. Monitoring of the environment and loading conditions with respect to natural hazards and severe environmental conditions have been conducted for several decades. In the last decade, bridge monitoring has extended its function as an instrument for efficient stock management. Accumulation of bridge stock built within the same period around ...

Research paper thumbnail of Failure Analysis of the Hanger Clamps of the Kutai-Kartanegara Bridge from the Fracture Mechanics Viewpoint

Journal of JSCE, 2014

,the Kutai-Kartanegara Suspension Bridge in Indonesia collapsed. The collapse was triggered by fa... more ,the Kutai-Kartanegara Suspension Bridge in Indonesia collapsed. The collapse was triggered by failure of the clamp of cable band that connects the hanger with the main cable in the middle of the centerspan. The national investigation team report cited the failure as a result of stress accumulation on the clamps that have been weakened by fatigue, initial fracture and corrosion. In this paper, we investigated in more detail the possibility of shear brittle fracture of the clamp's pin from the viewpoint of linear fracture mechanics by utilizing the measured Charpy absorbed energy. Several possible scenarios of defect sizes and combined stress conditions were assumed. The analysis shows that the shear brittle fracture could occur even under low shear stress level when several unfavorable conditions occur simultaneously.

Research paper thumbnail of The importance of dense monitoring of long-span bridges for its performance re-evaluation

IABSE Congress, Chicago 2008: Creating and Renewing Urban Structures – Tall Buildings, Bridges and Infrastructure, 2008

Monitoring of structures is expected to offer rich information on structural performance evaluati... more Monitoring of structures is expected to offer rich information on structural performance evaluation. While the performance of existing structures may differ from their designs, monitoring of dynamic behaviors potentially provides indications of how close or far the performance is to the designs and unexpected differences that might be important to the safety. In this paper, monitoring of two bridges in Japan as well as dynamic and structural analyses of the monitoring data is presented. Ambient vibration and seismic response records are utilized in performance evaluation of these bridges. The dense sensor instrumentation on the bridges and long-term monitoring provides exceptional opportunities to obtain insight into the behaviors of the bridges and performance of their components.

Research paper thumbnail of Yokohama-Bay Bridge Response Characteristics in the 2011 Great-East Japan Earthquake

IABSE Conference, Rotterdam 2013: Assessment, Upgrading and Refurbishment of Infrastructures, 2013

Yokohama Bay Bridge with the total span length of 860m (200-460-200) is the second longest span c... more Yokohama Bay Bridge with the total span length of 860m (200-460-200) is the second longest span cable-stayed bridge in East Japan and one of the most densely instrumented bridges in Japan. On March 11, 2011, northeastern Japan was shaken by the Great East Japan earthquake and at the bridge location seismic intensity with PGA 1.40–2.50 m/s² was recorded. This paper describes response analysis of the bridge by focusing on the following subjects: 1) temporal and spectral analysis of the bridge responses, 2) system identification and observation of the changes in modal parameters with respect to earthquake amplitude, 3) performance evaluation of link-bearing connection –a seismic isolation device, during the earthquake and 4) post-earthquake field observation.

Research paper thumbnail of Seismic Response Analysis of an Instrumented Base-Isolated Building in the 2011 Great East-Japan Earthquake

IABSE Congress, Seoul 2012: Innovative Infrastructures – Towards Human Urbanism, 2012

This paper describes a study on seismic response of a base-isolated building in Tokyo Bay area. T... more This paper describes a study on seismic response of a base-isolated building in Tokyo Bay area. The building is instrumented with triaxial accelerometers at twenty-four locations and seismic responses were recorded since October 2010. The building experienced strong shaking during the March 11, 2011 Great East-Japan Earthquake. Series of aftershocks that follow the large main shock earthquake were also recorded and they provide a comprehensive database on the building seismic responses. Response analysis shows that base isolation system performed as intended during the main shock. In addition, rotational motion had a great influence on the structure motions since the building has asymmetrical shape. We also observe the change in modal parameters, especially reduction of the first few natural frequencies of the building after the March 11, 2011 main shock.

Research paper thumbnail of Vibration Mechanisms and Controls of Long-Span Bridges: A Review

Structural Engineering International, 2013

Dynamic performance is an important consideration in long-span bridge design. Owing to its flexib... more Dynamic performance is an important consideration in long-span bridge design. Owing to its flexibility an d low damping, various types of vibration from different sources of excitation could occur during the lifetime of a long-span bridg e. This paper reviews important studies and developments on long-span bridge vibration mechanism an d control under wind, seismic,traffic and human-motion excit ations. Types of vibration commonly observed on the long-span bridge are discussed from the viewpoint of structure engineering. Discussion for each subject is commenced by describing the vibration mechanism followed by the survey on observed phenomena in many long-spa n bridges associated with the type of vibration. The paper also describes the engineering solutions adopted as countermeasures for each type of bridge vibration problem.

Research paper thumbnail of Influence of movable bearings performance on the dynamic characteristics of a cable-stayed bridge : insights from seismic monitoring records

An investigation on seismic response characteristics and modal parameters of a cablestayed bridge... more An investigation on seismic response characteristics and modal parameters of a cablestayed bridge with movable bearings using vibration records obtained from a seismic monitoring system is presented in this paper. The object of this study is the Tokachi cablestayed bridge, a single plane prestressed cable-stayed bridge that is equipped with moveable spherical frictional plate (SFP). The bridge seismic responses subjected to various levels of earthquake including the 2003 Tokachi Great earthquake were obtained from a permanent seismic monitoring system. The bridge dynamic characteristics that include frequency and damping were estimated by both the time-invariant and time-variant recursive subspace identification methods. The identification results reveal that damping ratios of the low order modes estimated during the largest earthquake can reach more than 10% of the critical damping, which is higher than what usually assumed in the seismic design code. Supplementary damping caused by friction force at the movable SFP bearings was identified as the main source of the large damping, and it was quantified by a modal-based inverse analysis using the sparse regularization method. Results of the analyses confirm the influence of moveable SFP bearings performance with its Coulomb-friction type stick-slip behavior on the dynamic characteristics of the bridge. The bearings remain stuck at smaller excitation causing higher stiffness of the structure and slip during a larger excitation resulting in stiffness reduction. The sliding process induces friction force between contacting surfaces of the SFP bearings which results in the increase of damping as the excitation level increases. The damping, however, does not increase continuously, but becomes steadier after a certain level of excitation.

Research paper thumbnail of クタイ・カルタネガラ橋のクランプ・ピンのせん断破壊に関する一考察

Research paper thumbnail of Wavelet-Based Analysis for Detection of Isolation Bearing Malfunction in a Continuous Multi-Span Girder Bridge

Journal of Earthquake Engineering, 2021

This paper describes techniques for detecting bearing malfunction directly from the seismic respo... more This paper describes techniques for detecting bearing malfunction directly from the seismic response of the bridge using wavelet transform time varying identification. Instantaneous frequency of continuous wavelet and detail components of discrete wavelet transform are utilized as structural features, and they characterize isolation bearing condition via statistical clustering technique. Accuracy and efficacy of the techniques were verified in numerical simulations using analytical and finite element models. The techniques were implemented on seismic records from long-term monitoring of multi-span continuous-girder isolated bridge. Results demonstrate that wavelet-based features can effectively characterize the condition of the isolation bearing directly from seismic responses of girder and piers.

Research paper thumbnail of Seismic Response Analysis of Hakucho Suspension Bridge from Long-term Monitoring System

IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016

Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspe... more Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspension bridge in northeastern Japan with the total span length of 1380m. The bridge has permanent seismic monitoring system consisting of 27 channels of accelerometers placed on fourteen locations on the deck, tower and free-field. Since opened to public on June 13, 1998 until 2006 the monitoring system has recorded various scales of earthquakes, including the major ones such as the 2003 Tokachi and 2004 Kushiro earthquakes. To investigate dynamic characteristics during various level of seismic excitation in more detail, multi-input multi-output time-domain system identification was conducted. Vibration characteristics of structural members such as girder and tower for different amplitude of excitation are investigated and compared with previous results from ambient response analysis and finite element.

Research paper thumbnail of Seismic Response Analysis of Hakucho Suspension Bridge from Long-term Monitoring System

IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016

Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspe... more Hakucho Suspension Bridge (HSB) located in Muroran Gulf, Hokkaido Prefecture is the longest suspension bridge in northeastern Japan with the total span length of 1380m. The bridge has permanent seismic monitoring system consisting of 27 channels of accelerometers placed on fourteen locations on the deck, tower and free-field. Since opened to public on June 13, 1998 until 2006 the monitoring system has recorded various scales of earthquakes, including the major ones such as the 2003 Tokachi and 2004 Kushiro earthquakes. To investigate dynamic characteristics during various level of seismic excitation in more detail, multi-input multi-output time-domain system identification was conducted. Vibration characteristics of structural members such as girder and tower for different amplitude of excitation are investigated and compared with previous results from ambient response analysis and finite element.

Research paper thumbnail of Seismic Monitoring of Seismically Isolated Bridges and Buildings in Japan—Case Studies and Lessons Learned

Seismic Structural Health Monitoring, 2019

Monitoring of seismic response of structures has been widely employed for decades in Japan. From ... more Monitoring of seismic response of structures has been widely employed for decades in Japan. From the structural point of view, the objectives of seismic monitoring are mainly to verify designed load assumption, evaluate seismic response and structure performance during large earthquake, detecting possible damages due to earthquake and monitoring for verification of structural retrofit. Seismic monitoring is very important for large, important structures and structures with specific features and innovative technologies such as seismic isolation or response control systems. This paper describes several case-studies and lessons learned of seismic monitoring on seismically isolated bridges and buildings in Japan.

Research paper thumbnail of Investigation on vehicle lateral instability when crossing a curved highway bridge during an earthquake

Structure and Infrastructure Engineering, 2020

This paper describes a numerical study on the vehicle instability when crossing curved highway br... more This paper describes a numerical study on the vehicle instability when crossing curved highway bridge during an earthquake. Analytical framework using two-axle vehicle dynamics model is developed to describe vehicle vibration when moving under seismic excitation from the curved bridge girder. The model includes out-of-plane and in-plane motion along with the effect of curved girder with specific radius, camber angle and longitudinal grade. Two criteria for critical vehicle stability are evaluated namely the rollover and sideslip stability. As case study, numerical simulations were conducted using three-dimensional finite element model of an elevated highway junction consisting of four curved sections and two straight sections. Effects of curved bridge radii, level of earthquake, vehicle velocity and driver reaction on the vehicle stability were investigated. It was found that a vehicle moving on a curved bridge during earthquake has a larger possibility for rollover and sideslip instability than a vehicle moving on a straight section for the same driving velocity and level of earthquake. Results of simulations demonstrate that normal forces on vehicle's wheels are significantly influenced by the curved bridge effects, steering angle, effect of road camber at the curved section. These conditions contributed to reduction of normal forces on vehicle's wheels and increased the risk of vehicle instability.

Research paper thumbnail of Wind-induced responses and dynamics characteristics of an asymmetrical base-isolated building observed during typhoons

Journal of Wind Engineering and Industrial Aerodynamics, 2017

Responses of an asymmetrical base-isolated building during the passage of Typhoon Roke 2011, Typh... more Responses of an asymmetrical base-isolated building during the passage of Typhoon Roke 2011, Typhoon Guchol 2012 and a bomb cyclone strong-wind event on April 3, 2012 were investigated in this paper. Windinduced accelerations of the building were recorded by dense array permanent monitoring system and analyzed in detailed by spectra analysis, time-frequency wavelet analysis and system identification. Results of analysis revealed that wind-induced responses of the buildings were dominated by the first mode which is the fundamental flexural mode coupled with torsion of the upper stories. Building responses demonstrated nonlinear characteristics of natural frequencies, damping ratio and mode-shapes. Natural frequencies of fundamental modes decreased with the increase of acceleration amplitude, with the maximum reduction of 8-10% of natural frequencies observed during the peak wind speed. Damping estimates of the fundamental modes increased with the increase of accelerations, while characteristics of mode-shapes were also found to be dependent on the wind speed. Further analysis revealed that non-linear characteristics of building responses are related to isolator deformations caused by wind-induced static force.

Research paper thumbnail of Along-wind almost-harmonic vibration observed at Hakucho-Bridge pylons and its wind tunnel experiments

Journal of Wind Engineering, 2016

This paper describes an along-wind vibration of frame-type pylons of Hakucho Suspension Bridge fo... more This paper describes an along-wind vibration of frame-type pylons of Hakucho Suspension Bridge found from longterm vibration monitoring data. It is shown that the vibration is very harmonic although its amplitude is small and it occurs under certain ranges of wind direction (10~30 degree from the bridge perpendicular axis) and of wind velocity (13~25 m/s). The dominant frequency of the vibration is either 0.6 Hz or 0.8 Hz depending on the wind velocity and these correspond to the natural frequencies of the in-plane pylon dominant modes of the suspension bridge. A series of the wind tunnel experiments using a spring-supported scaled model are conducted under uniform flow and the alongwind pylon vibration was observed and its vibration characteristics is found to be consistent to those observed in Hakucho Bridge. It is also found that the vibration is very sensitive to the incident angle of wind and to the distance between the two columns.

Research paper thumbnail of The needs for advanced sensor technologies in risk assessment of civil infrastructures

Smart Structures and Systems, 2009

ABSTRACT Civil infrastructures are always subjected to various types of hazard and deterioration.... more ABSTRACT Civil infrastructures are always subjected to various types of hazard and deterioration. These conditions require systematic efforts to assess the exposure and vulnerability of infrastructure, as well as producing strategic countermeasures to reduce the risks. This paper describes the needs for and concept of advanced sensor technologies for risk assessment of civil infrastructure in Japan. Backgrounds of the infrastructure problems such as natural disasters, difficult environment, limited resource for maintenance, and increasing requirement for safety are discussed. The paper presents a concept of risk assessment, which is defined as a combination of hazard and structural vulnerability assessment. An overview of current practices and research activities toward implementing the concept is presented. This includes implementation of structural health monitoring (SHM) systems for environment and natural disaster prevention, improvement of stock management, and prevention of structural failure.

Research paper thumbnail of 訂正：2011年東北地方太平洋沖地震における横浜ベイブリッジの応答［土木学会論文集A1（構造・地震工学）, Vol. 69, No. 2, pp. 372-391, (2013)］

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2014

Research paper thumbnail of 2011年東北地方太平洋沖地震における横浜ベイブリッジの応答

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2013

高密度地震応答計測システムを有する横浜ベイブリッジでは，2011年3月11日東北地方太平洋沖地震M w 9.0の本震と余震による周辺地盤の地震動と地震応答の記録が収録された．本論文はその記録を多... more 高密度地震応答計測システムを有する横浜ベイブリッジでは，2011年3月11日東北地方太平洋沖地震M w 9.0の本震と余震による周辺地盤の地震動と地震応答の記録が収録された．本論文はその記録を多面的に 解析し1) 主桁の振動は橋軸直角方向の応答が卓越した(最大応答変位62cm)，2) 橋軸方向の主桁と主塔 および端部橋脚の応答記録から，主塔と端部橋脚位置のリンク支承が所要の免震性能を発揮した，3) 主塔 と端部橋脚のウィンド沓は橋軸直角方向に衝突していた形跡がある，4) 本震時の大振幅応答時には，主桁 の橋軸直角方向水平たわみ1次モードや主桁の鉛直方向たわみ1次モードの固有振動数が変化しただけでな く，それぞれのモード形において，小振幅時には見られない連成挙動が同定されたことを明らかにしてい る．

Research paper thumbnail of クタイ・カルタネガラ橋のクランプ・ピンのせん断破壊に関する一考察

Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering ^|^ Earthquake Engineering (SE/EE)), 2013

Research paper thumbnail of Long-term seismic monitoring of base-isolated building with emphasis on serviceability assessment

Earthquake Engineering & Structural Dynamics, 2014

Seismic monitoring system provides opportunities to observe possible damage or failure and weaken... more Seismic monitoring system provides opportunities to observe possible damage or failure and weakening of structural components and to evaluate serviceability performance of a structure during an earthquake. This can be achieved by comparing structure recordings before and after the event or by identifying significant change in characteristics of structural response that may serve as indicators of failure or damage in progress. Excessive vibration on some parts of structure may become a serviceability concern for some buildings, and this also can be detected from continuous monitoring. Several factors such as characteristics of ground motion, soil condition, and geometry of the structure could cause excessive localized structural vibration, and by evaluating the responses, one can take remedial action. For a base-isolated building in particular, reduction of response of upper stories is critical to protect nonstructural elements or sensitive equipments on the building. In this paper, we describe a case study on seismic monitoring of a base-isolated building with the main focus on evaluation of serviceability performance. The study emphasizes on a influence of building asymmetricity on the seismic response. Results of the study are based on a long-term building seismic monitoring program for over 3 years between 2010 and 2012 under various amplitudes of earthquake including the March 11, 2011 Great East-Japan Earthquake.

Research paper thumbnail of Strategies for structural health monitoring of bridges

From Materials to Structures: Advancement through Innovation, 2012

Abstract: The needs for structural health monitoring in Japan originally come from its geographic... more Abstract: The needs for structural health monitoring in Japan originally come from its geographical conditions such as severe environment for deterioration and frequent natural disasters. Monitoring of the environment and loading conditions with respect to natural hazards and severe environmental conditions have been conducted for several decades. In the last decade, bridge monitoring has extended its function as an instrument for efficient stock management. Accumulation of bridge stock built within the same period around ...

Research paper thumbnail of Failure Analysis of the Hanger Clamps of the Kutai-Kartanegara Bridge from the Fracture Mechanics Viewpoint

Journal of JSCE, 2014

,the Kutai-Kartanegara Suspension Bridge in Indonesia collapsed. The collapse was triggered by fa... more ,the Kutai-Kartanegara Suspension Bridge in Indonesia collapsed. The collapse was triggered by failure of the clamp of cable band that connects the hanger with the main cable in the middle of the centerspan. The national investigation team report cited the failure as a result of stress accumulation on the clamps that have been weakened by fatigue, initial fracture and corrosion. In this paper, we investigated in more detail the possibility of shear brittle fracture of the clamp's pin from the viewpoint of linear fracture mechanics by utilizing the measured Charpy absorbed energy. Several possible scenarios of defect sizes and combined stress conditions were assumed. The analysis shows that the shear brittle fracture could occur even under low shear stress level when several unfavorable conditions occur simultaneously.

Research paper thumbnail of The importance of dense monitoring of long-span bridges for its performance re-evaluation

IABSE Congress, Chicago 2008: Creating and Renewing Urban Structures – Tall Buildings, Bridges and Infrastructure, 2008

Monitoring of structures is expected to offer rich information on structural performance evaluati... more Monitoring of structures is expected to offer rich information on structural performance evaluation. While the performance of existing structures may differ from their designs, monitoring of dynamic behaviors potentially provides indications of how close or far the performance is to the designs and unexpected differences that might be important to the safety. In this paper, monitoring of two bridges in Japan as well as dynamic and structural analyses of the monitoring data is presented. Ambient vibration and seismic response records are utilized in performance evaluation of these bridges. The dense sensor instrumentation on the bridges and long-term monitoring provides exceptional opportunities to obtain insight into the behaviors of the bridges and performance of their components.

Research paper thumbnail of Yokohama-Bay Bridge Response Characteristics in the 2011 Great-East Japan Earthquake

IABSE Conference, Rotterdam 2013: Assessment, Upgrading and Refurbishment of Infrastructures, 2013

Yokohama Bay Bridge with the total span length of 860m (200-460-200) is the second longest span c... more Yokohama Bay Bridge with the total span length of 860m (200-460-200) is the second longest span cable-stayed bridge in East Japan and one of the most densely instrumented bridges in Japan. On March 11, 2011, northeastern Japan was shaken by the Great East Japan earthquake and at the bridge location seismic intensity with PGA 1.40–2.50 m/s² was recorded. This paper describes response analysis of the bridge by focusing on the following subjects: 1) temporal and spectral analysis of the bridge responses, 2) system identification and observation of the changes in modal parameters with respect to earthquake amplitude, 3) performance evaluation of link-bearing connection –a seismic isolation device, during the earthquake and 4) post-earthquake field observation.

Research paper thumbnail of Seismic Response Analysis of an Instrumented Base-Isolated Building in the 2011 Great East-Japan Earthquake

IABSE Congress, Seoul 2012: Innovative Infrastructures – Towards Human Urbanism, 2012

This paper describes a study on seismic response of a base-isolated building in Tokyo Bay area. T... more This paper describes a study on seismic response of a base-isolated building in Tokyo Bay area. The building is instrumented with triaxial accelerometers at twenty-four locations and seismic responses were recorded since October 2010. The building experienced strong shaking during the March 11, 2011 Great East-Japan Earthquake. Series of aftershocks that follow the large main shock earthquake were also recorded and they provide a comprehensive database on the building seismic responses. Response analysis shows that base isolation system performed as intended during the main shock. In addition, rotational motion had a great influence on the structure motions since the building has asymmetrical shape. We also observe the change in modal parameters, especially reduction of the first few natural frequencies of the building after the March 11, 2011 main shock.

Research paper thumbnail of Vibration Mechanisms and Controls of Long-Span Bridges: A Review

Structural Engineering International, 2013

Dynamic performance is an important consideration in long-span bridge design. Owing to its flexib... more Dynamic performance is an important consideration in long-span bridge design. Owing to its flexibility an d low damping, various types of vibration from different sources of excitation could occur during the lifetime of a long-span bridg e. This paper reviews important studies and developments on long-span bridge vibration mechanism an d control under wind, seismic,traffic and human-motion excit ations. Types of vibration commonly observed on the long-span bridge are discussed from the viewpoint of structure engineering. Discussion for each subject is commenced by describing the vibration mechanism followed by the survey on observed phenomena in many long-spa n bridges associated with the type of vibration. The paper also describes the engineering solutions adopted as countermeasures for each type of bridge vibration problem.