Chul-Woo Kim

Kyoto University | Kyodai · Department of Civil and Earth Resources Engineering

Structural health monitoring (SHM) is of great significance to maintain the safe operation of infrastructure, particularly for historic structures such as masonry arch bridges, as their material properties are deteriorating under effects such as climate change, but the demands of modern transport systems increase significantly. Vibration-based SHM...

A specific damage-sensitive feature (DSF) is usually sensitive to damage in a certain area, and the specific location of damage in a specific area can be detected by selecting appropriate DSFs. However, damaged components are seldom known before inspections. This makes it difficult to find an appropriate DSF, and damage identification is sometimes...

This study proposes the new condition monitoring concept of using features in the measured rotation, or ‘pitch’ signal, of a crossing vehicle as an indicator of the presence of foundation scour in a bridge. The concept is explored through two-dimensional vehicle–bridge interaction modelling, with a reduction in stiffness under a pier used to repres...

In bridge weigh-in-motion systems, the vehicle speed is a fundamental input parameter for the weighing algorithm. The speed is generally obtained by processing structural responses measured at different locations along the bridge length. For this purpose, the convoluted reciprocity relationship was derived and utilized as the basis for a novel spee...

Vibration-based structural health monitoring aims to not only detect the occurrence of the damage but also identify the location of damage. The pseudo-local flexibility method (PLFM) is a vibration-based approach that only requires the identified modal parameters of the structure to perform damage detection. Thus, the cost of constructing a finite-...

In recent years, a rapid bridge health monitoring technology has been developed using an instrumental moving vehicle. Using recorded vehicle vibration data, bridge frequencies are identified for bridge health monitoring or finite element model updating. Target bridge frequencies with significant amplitudes in the vehicle’s vibration frequency spect...

Infusing deep learning with structural engineering has received widespread attention for both forward problems (structural simulation) and inverse problems (structural health monitoring). Based on Fourier neural operator, this study proposes VINO (Vehicle-Bridge Interaction Neural Operator) to serve as a surrogate model of bridge structures. VINO l...

This paper proposes a natural frequency and displacement ratio-based probabilistic damage identification method for bridges using the finite element (FE) model update. When the damage location is known, it can be detected from an appropriate damage-sensitive feature (DSF). However, damaged components are seldom known before inspections. This makes...

Indirect structural health monitoring of bridges using vehicle-mounted sensors offers a promising approach for the continuous assessment of structures. Full-scale modelling of complex structures, however, is computationally intensive. In order to optimize the required computational expenses, a two-dimensional simplified numerical model whose respon...

This paper proposes a natural frequency and displacement ratio-based probabilistic damage identification method for bridges using the finite element (FE) model update. When the damage location is known, it can be detected from an appropriate damagesensitive feature (DSF). However, damaged components are seldom known before inspections. This makes i...

This study aims to propose a roadway roughness profile identification using the acceleration responses of a vehicle by means of a dynamic regularized least square minimization (DRLS). The DRLS is a method comprising the least square minimization whose cost function is the error between simulated and measured accelerations, a regularization techniqu...

Over the last decade, the use of drive-by inspection technology for bridge damage assessment has been widely studied by scholars. It consists of identifying bridge damage from the response of an instrumented sensing vehicle. Most current methods are based on identifying bridge properties and supervised learning techniques. However, these approaches...

This study aims to investigate the vibration serviceability and impact coefficient of a seven-span continuous cable-stayed bridge planned for the extension of a highway. In the design of the bridge, the deflection under the design live load of the continuous cable-stayed bridge would not meet the deflection limit specified in “Japanese Design Speci...

Damage localisation is an important issue in bridge health monitoring. It helps to develop further maintenance strategies. For long-term monitoring, the traditional method is to install sensors on the bridge of interest. Then, by checking the vibration frequencies, mode shapes or some other indices, the damage location was expected to be identified...

Drive-by bridge inspections are attracting attention because they reduce the time and labor required for bridge damage detection, compared to the conventional direct method of installing sensors on bridges. However, there are difficulties in realizing the drive-by-bridge inspection: the dynamic response from the vehicle’s accelerometer is strongly...

This study explores a change detection method in modal properties to automate and generalize in-service damage detection for vibration-based structural health monitoring of bridges. The noisy conditions caused by ambient loading pose difficulty for in-service damage detection because the load-induced noise often masks the difference in the modal pr...

This paper presents a probabilistic damage detection for bridges from displacement ratio through the finite element (FE) model update. Live-load displacement is crucial to understand the integrity of bridges while it depends on loads. Instead, the displacement ratio is useful because it is independent of loads. This study focuses on probability den...

As the significant number of European bridge stock comprises more than 100 years old masonry arch bridges, restrictions to the operation of these bridges or their closure due to increased traffic load can result in network disruptions with subsequent economic losses. Apparently, most of these bridges are carrying loads above those envisaged by thei...

Physics-informed neural networks (PINNs) have been rapidly developed for solving partial differential equations. The Exact Dirichlet boundary condition Physics-informed Neural Network (EPINN) is proposed to achieve efficient simulation of solid mechanics problems based on the principle of least work with notably reduced training time. There are fiv...

Infusing deep learning with structural engineering has received widespread attention for both forward problems (structural simulation) and inverse problems (structural health monitoring). Based on Fourier Neural Operator, this study proposes VINO (Vehicle-bridge Interaction Neural Operator) to serve as the digital twin of bridge structures. VINO le...

In order to develop an efficient and quantitative bridge inspection method using sensors, this study investigates feasibility of bridge damage detection using Bridge Weigh-In-Motion (BWIM) and deflection of the bridge. As deflection influence line changes due to damage in BWIM, a virtual axle is introduced to the vehicle and the process of axle wei...

This paper studies the problem of bridge health monitoring in an unsupervised manner utilizing only the measured responses from a vehicle passing over a bridge. A half-car model along with a simply supported beam is adopted for numerically simulating vehicle–bridge interaction (VBI). Multiple bridge states including healthy bridge and damaged bridg...

Recently, due to low cost and convenience, the concept of estimating the bridge's first natural frequency through indirect measurements of a passing vehicle has gained increasing attention-known as drive-by bridge structural health monitoring. As the vehicle acts as a moving mass added to the bridge, this system is nonstationary with time-varying c...

Indirect bridge monitoring provides an economical procedure to ensure reliable operation of the bridges by utilizing the vehicle responses passing over the bridge. The present work proposes a unified framework for damage detection, assessment, and localization using adversarial autoencoder and wavelet transform in an unsupervised manner. Vehicle ac...

This study aims to investigate feasibility of a drive-by bridge inspection method using dynamic vehicle force. The dynamic vehicle force is identified using accelerations of a traveling vehicle. Dynamic vehicle forces when the vehicle travels on healthy and damage states of bridges are first identified. Differences of the identified dynamic vehicle...

This study aims to discuss vibration extraction of a pole structure from a video processing as a preliminary investigation utilizing video footage from an inspection vehicle. The proposed method transforms the video footage into frequency domain, magnifies the featured frequency bands and then reconstructs it. The vibration patterns of the target p...

This study intends to investigate the application of model updating based on forced vibration data to a simply-supported truss bridge. A fast Bayesian FFT method was used to perform the modal identification obtained from field tests, and the Transitional Markov Chain Monte Carlo (TMCMC) algorithm is employed to generate samples. Although updating a...

This study is intended to examine changes in modal parameters PC box girders due to defective grouting and failures in PC tendons through a laboratory experiment. In the laboratory experiment, three PC box girders, which have different damage scenarios, are examined. Both static loading and vibration experiments were conducted. The static loading e...

A road roughness profile of pavement surface is one of the important indicators for status of bridges and roads, and regular pavement monitoring and repairing directly link to the life span of the bridge and road. This research proposes a dynamic regularized least square minimization to identify the road roughness profile directly by regularized le...

This study aims to investigate ambient vibration based modal analysis and cable tension estimation with Bayesian approaches, associating with an ambient vibration testing in a cable-stayed bridge. Firstly, a Bayesian fast Fourier transform (FFT) is introduced to the target bridge for operational modal analysis using ambient vibration data. Consider...

Developing robust bridge health monitoring (BHM) frameworks based on the vehicle-mounted sensing, or so-called indirect structural health monitoring (SHM) or Drive-by Bridge Inspection is currently a rapidly growing research area. The goal is to monitor any change in the structural integrity of a bridge using the vibration responses measured from s...

Automated and intelligent structural design optimization has been a heated research topic in structural engineering community. The automated structural design may learn from existing design drawings and finite element models of previous design, infuse design experts' knowledge with design standards and codes, and notably reduce the time and difficu...

This study investigates the concept that when localized bridge superstructure damage is present, the weights of passing vehicles inferred from a rotation-based bridge weigh-in-motion (B-WIM) system will deviate from those predicted by a strain-based B-WIM system. Rotation measurements were gathered from a 5.4-m simply supported laboratory model bri...

For bridges with surface foundations, scour is one of the main reasons for bridge failures. In regard to structural health monitoring, vibration-based scour detection techniques have received increasing attention over the past two decades. Scour occurs below the water surface in rivers or sea, leading to difficulty in equipment installation and mai...

As the finite element (FE) model has become increasingly important in engineering, the model updating method has also received much attention as a means of improving the structural FE model accuracy. However, the objectives of many earlier studies have been laboratory experiments and numerical simulations. Actual structures have not been adequately...

This guide is developed by ISWIM volunteers to assist bridge engineers and inspectors interested in using truck weight and size data collecting by WIM systems. It describes what is considered a good practice in the use of weigh-in-motion (WIM) data for bridge-related applications and assumes no prior knowledge of WIM. The guide focuses on the use o...

This study investigates feasibility of bridge damage detection using BWIM and deflection of the bridge. A virtual axle is introduced to the vehicle so that increase of identified wheel loads caused by changes in deflection influence line due to damage can be distributed to the virtual axle. Investigating the identified wheel load of the virtual axl...

This study aims to improve accuracy of the road profile identification utilizing accelerations of a moving vehicle. There exist road profile identification methods: one identifies the vehicle force by dynamic programming and convert it into road profile and the other identifies road profile directly by pseudo inverse matrix. This study proposes a n...

To investigate the driving safety of vehicles travelling on bridges which cross the sea in cold regions, this study presented a dynamic analysis framework for a vehicle–bridge–soil interactive system subjected to stochastic ice loads. Time histories of the stochastic ice loading based on real ice loading spectrum were obtained to consider them as e...

This study proposes a damage detection method for bridges using a damage indicator that is automatically derived from vehicle induced vibrations. To extract damage-sensitive features, the principal component analysis is applied to the characteristic polynomials of auto-regressive models estimated from measured acceleration. A stochastic distance be...

This paper presents results of numerical and experimental investigations for the feasibility assessment of drive-by bridge inspection, where the health status of a bridge is solely identified from the dynamic response of an inspection vehicle, passing over a target bridge. To this aim, a novel metric based on the transmission performance between th...

Ambient and vehicle-induced bridge vibration tests are two important ways of collecting data for the purpose of system identification and performance evaluation of bridges. A common bridge form that has been very popular over the past number of decades is the steel truss bridge; this paper presents the vibration data of a steel truss bridge situate...

Scour is a significant issue for bridges worldwide that influences the global stiffness of bridge structures and hence alters the dynamic behavior of these systems. For the first time, this paper presents a new approach to detect bridge scour at shallow pad foundations, using a decentralized modal analysis approach through re-deployable acceleromet...

This study presents an approach to detect loosening bolts in steel bridges by image processing. High-tensioned bolts have been adopted to connect members of steel bridges. Insufficient axial tension of bolts by bolt-loosening leads to bolt joint failure and reducing load carrying capacity of steel bridges. There are also possibilities of accidents...

This paper presents the work on developing a frequency domain method for damage detection using ambient vibration data. Bayesian factor is used to construct a new damage detection indicator utilizing the concept of Fast Bayesian FFT (Fast Fourier Transform) method. Based on Bayes factor and the properties of FFT data, the prior probability density...

This study is intended to discuss feasibility of scour detection for railway bridges by means of remote microtremor monitoring. The impact test that applies impact force to the bridge pier by dropping a hammer so as to measured vibrations of the bridge pier is a laborious and time-consuming method, and has difficulties in real time monitoring durin...

This study is intended to investigate how the local damage and varying temperature affect changes in modal frequencies of a steel plate girder bridge. A damage experiment on a real bridge was conducted. Artificial cracks were applied to the lower flange and web plate near base plate of shoe, which models fatigue cracks observed in actual steel plat...

Damage detection is one important target in structural health monitoring (SHM). Vibration‐based damage detection has attracted more attention in the past decades by tracking the modal parameter changes of objective structures. This paper presents the work on developing a novel Bayesian fast Fourier transform (FFT) method for damage detection using...

This paper presents one of the first attempts of indirect Bridge Health Monitoring (BHM) for cable damage identification in a cable-stayed bridge. The premise of the work is to identify the location and the severity of a sustained structural damage to the cables, measured solely by vibration response of a moving vehicle passing over the bridge. To...

The development of a fully automated system identifier without the need for human intervention, is a key step for real-time vibration-based Structural Health Monitoring (SHM). In this paper a novel approach based on the Dirichlet Process Gaussian Mixture Model (DP-GMM) is developed in order to analyze the stabilization diagram. The aim is to separa...

This article uses extracted bridge mode shapes to detect bridge damage, including both local damage such as that due to a bridge strike and global damage such as that due to foundation scour. Typically, only one accelerometer is required, which is mounted on an instrumented vehicle passing over the test bridge. This concept is referred to as 'drive...

This paper experimentally investigates a vibration-based scour monitoring approach applicable to bridges with multiple simply supported spans on shallow foundations. A monitoring strategy based on the relative changes in pier-mode shape amplitudes due to scour is postulated. The first global mode shape of a bridge structure with multiple spans is e...

This study assesses the seismic responses of viaduct structures in the Japanese high-speed rail system under moderate earthquake forces considering the slip between tracks and wheels. Equations of motion for the train-bridge interaction system were derived, where the track-wheel interaction was described by the Coulomb friction law. A full train-br...

Long term structural health monitoring has gained wide attention among civil engineers in recent years due to the scale and severity of infrastructure deterioration. Establishing effective damage indicators and proposing enhanced monitoring methods are of great interests to the engineering practices. In the case of bridge health monitoring, long te...

This paper presents a unified framework for dynamic analysis of vehicle-bridge interaction (VBI) systems using a commercial finite element software suite (ABAQUS®). This framework can provide bridge designers and engineering practitioners with a general platform to analyze the coupled system with high modeling efficiency and accuracy in modeling an...

This study examines results obtained experimentally from two post-tensioned concrete beams subjected to static and dynamic tests. The static tests results were used to evaluate the level of flexural performance in the beams. Data obtained from the dynamic tests were used to identify the change in modal parameters that occurred after different perfo...

This study is intended to disucuss and compare accuracy of road profile identification methods utilizing measured accelerations on a moving vehicle. The accuracy of road profile identification is discussed focusing on ways of deriving a state-space equation and the parameters to be identified by the inverse problem. Vehicle accelerations obtained b...

Multivariate information of soil parameters is quite important for the design and risk assessment of geotechnical engineering problems. It is necessary to have an accurate and realistic statistical multivariate model for representing the soil properties and thus evaluating the soil conditions. Thus, advanced multivariate modeling of soil parameters...

Dynamic features are often used for structural damage diagnosis. Besides the features from the modal analysis, some other features describing the wave propagation in the structure are usually concerned, like the wave’s intensity, speed, etc. In the data processing of experiment on the pre-stressed concrete (PC) box girders with artificial damages,...

Bridge modal parameters play an important role in bridge engineering; they can serve as useful indices for many applications such as numerical mode calibration and updating, and bridge structural health monitoring. Recently, the indirect monitoring of bridges is increasingly investigated and developed as it avoids the need for instrumentation on al...

This study is intended to verify validity of an efficient damage detection method by means of a Bayesian ap-proach. A Bayesian inference was adopted to the regressive model representing bridge vibration. The posterior distribution for the regressive coefficients provides reasonable damage-sensitive features. Bayesian hypothesis testing is formulate...

Drive-by bridge inspection method is a method by which the bridge’s dynamic characteristics or health status are identified from the dynamic responses of an inspection vehicle when passing over the target bridge. In this study, a homemade trailer being tailored for capturing bridge vibrations more effectively was designed and as-sembled. After the...

This study is intended to discuss a vibration-based scour monitoring of railway bridges under in-service condi-tion. A long-term vibration monitoring was conducted on a railway bridge to investigate feasibility of the vibra-tion-based scour monitoring in real-time. A high-precision three-axis wireless accelerometer was installed on the pier top to...

This study aims to investigate a way to select sub-sensor groups for reduction of radio communications of whole system by confining radio communication within sensors inside sensor groups so as to save power of wireless sensor networks. Sparse-like system matrix is reconstructed for system identification utilizing the opti-mal sensor groups decided...

Wireless sensors in structural health monitoring are useful to simplify deployment and to realize a remote control of deployed sensors. However, wireless sensors operate in significant constraint on power consumption. Re-duction techniques of radio communications in sensor networks are useful to extend the battery life. This study is intended to a...

A vibration-based bridge scour detection procedure using a cantilever-based piezoelectric energy harvesting device (EHD) is proposed here. This has an advantage over an accelerometer-based method in that potentially, the requirement for a power source can be negated with the only power requirement being the storage and/or transmission of the data....

The natural frequencies of coupled vehicle-bridge systems change with vehicle position. These changes are generally attributed to the contribution of the additional mass of the vehicle. However, other mechanical properties of the vehicle influence the evolution of the vehicle-bridge system frequencies, an aspect that has rarely been addressed. The...

In this research, the model of hierarchical structure from universe theory is imported into the general probability system which helps logically and subordinately describing, measuring, and evaluating the hierarchical probabilistic system. To clearly classify the hierarchy, “fayer” is proposed as the unit of hierarchy. Then, discussions on the rela...