The aerodynamic characteristics of train/vehicles under cross winds depend on not only the shapes of the vehicles but also those of infrastructures. Accordingly three kinds of wind tunnel tests were made to evaluate the aerodynamic characteristics of typical configurations of the vehicles on typical configurations of infrastructures such as bridges and embankments. The main results obtained from the wind tunnel tests are summarized below. 1. The aerodynamic side force coefficient of the vehicle increases more as the thickness of the bridge girder becomes larger. It also increases more as the roof of the vehicle becomes edgier. 2. The aerodynamic characteristics of the vehicle on the embankment depend on the distribution of the boundary layer on the ground. The aerodynamic side force coefficient of the vehicle on a high embankment is larger than that on a low embankment.

Aerodynamic Characteristics of Train/Vehicles under Cross Winds

Data-driven methods in structural health monitoring (SHM) is gaining popularity due to recent technological advancements in sensors, as well as high-speed internet and cloud-based computation. Since the introduction of deep learning (DL) in civil engineering, particularly in SHM, this emerging and promising tool has attracted significant attention among researchers. The main goal of this paper is to review the latest publications in SHM using emerging DL-based methods and provide readers with an overall understanding of various SHM applications. After a brief introduction, an overview of various DL methods (e.g., deep neural networks, transfer learning, etc.) is presented. The procedure and application of vibration-based, vision-based monitoring, along with some of the recent technologies used for SHM, such as sensors, unmanned aerial vehicles (UAVs), etc. are discussed. The review concludes with prospects and potential limitations of DL-based methods in SHM applications.

Data-Driven Structural Health Monitoring and Damage Detection through Deep Learning: State-of-the-Art Review.

In 2004, Yang and co-workers proposed the extraction of bridge frequencies from the dynamic response of a moving test vehicle [Y B Yang, C W Lin and J D Yau, Extracting bridge frequencies from the dynamic response of a passing vehicle, J Sound Vib 272 (2004) 471–493] and verified the technique by a field test [C W Lin and Y B Yang, Use of a passing vehicle to scan the bridge frequencies — An experimental verification, Eng Struct 27(13) (2005) 1865–1878] This technique was extended to construction of mode shapes [Y B Yang, Y C Li and K C Chang, Constructing the mode shapes of a bridge from a passing vehicles: A theoretical study, Smart Struct Syst 13(5) (2014) 797–819] and damage identification of bridges It was referred to as the indirect method for bridge measurement because no vibration sensors are needed for installation on the bridge, but it only requires one or few vibration sensors on the test vehicle When compared with the conventional direct method that relies fully on the

State-of-the-Art Review on Modal Identification and Damage Detection of Bridges by Moving Test Vehicles

In the last two decades, a significant number of innovative sensing systems based on optical fiber sensors have been exploited in the engineering community due to their inherent distinctive advantages such as small size, light weight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability. A lot of optical fiber sensor-based monitoring systems have been developed for continuous measurement and real-time assessment of diversified engineering structures such as bridges, buildings, tunnels, pipelines, wind turbines, railway infrastructure, and geotechnical structures. The purpose of this review article is devoted to presenting a summary of the basic principles of various optical fiber sensors, innovation in sensing and computational methodologies, development of novel optical fiber sensors, and the practical application status of the optical fiber sensing technology in structural health monitoring (SHM) of civil infrastructure.

https://downloads.hindawi.com/journals/tswj/2014/652329.pdf

Structural health monitoring of civil infrastructure using optical fiber sensing technology: a comprehensive review.

Review on the new development of vibration-based damage identification for civil engineering structures: 2010-2019

Research on detecting structural damage at the earliest possible stage has been an interesting topic for decades. Among them, the vibration-based damage detection method as a global technique is especially pervasive. The present study reviewed the state-of-the-art on the framework of vibration-based damage identification in different levels including the prediction of the remaining useful life of structures and the decision making for proper actions. This framework consists of several major parts including the detection of damage occurrence using response-based methods, building reasonable structural models, selecting damage parameters and constructing objective functions with sensitivity analysis, adopting optimization techniques to solve the problem, predicting the remaining useful life of structures, and making decisions for the next actions. For each part, the commonly used methods were reviewed and the merits and drawbacks were summarized to give recommendations. This framework is aimed to guide the researchers and engineers to implement step by step the structure damage identification using vibration measurements. Finally, the future research work in this field is recommended.

https://www.mdpi.com/2076-3417/7/5/497/pdf

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

The dynamic response of moving vehicles on a bridge carries the vibration information of the bridge, which a few researchers have studied to extract the bridge modal properties such as natural frequencies and mode shapes. However, the vehicle response contains not only the frequency characteristics of the bridge and vehicle, but also other information such as the driving-related frequencies and road roughness effects, which makes the extraction difficult. To this end, the present study proposes a method using a specialized test vehicle consisting of a tractor and two following trailers, which can eliminate those effects and more efficiently extract the bridge modal properties. The two trailers towed by the tractor moving along the bridge were used as dynamic response receivers. In order to eliminate the effects previously discussed, the responses of one trailer were subtracted by the responses of the other with a time shift to obtain the residual responses. The residual responses were then process...

Numerically Extracting Bridge Modal Properties from Dynamic Responses of Moving Vehicles

The vehicles moving on a bridge excite bridge vibration and can also serve as response receivers because the vehicle dynamic response contains the vibration information of the bridge. A methodology was proposed in a previous study for extracting bridge modal properties, such as natural frequencies and modal shapes, from the vehicle dynamic responses. A specialized test vehicle consisting of a tractor and two following trailers was developed in which the two trailers towed by the tractor moving along the bridge were used as the dynamic response receivers. The responses of one trailer with a time shift were subtracted from the responses of the other to obtain the residual responses that were then processed with fast Fourier transformation (FFT) and short-time Fourier transformation (STFT) to extract the bridge modal properties. In the present paper, field test data of an existing bridge were adopted to verify the proposed methodology. In the vehicle and bridge system, a bridge finite-element (FE) model was updated using the measured accelerations and strains of the bridge; two types of test vehicle models were proposed for use in simulations of the tractor–trailer test system; and the measured surface-roughness profile was used in the numerical simulation. Parametric studies have been conducted to determine the trailer mass and stiffness. VehicleModel I shows a good capacity for extracting bridge frequencies and the first two modal shapes with a dominant vertical component. However, Vehicle Model II performed better than Vehicle Model I on the extraction of bridge modal shapes that are dominant in lateral bending. DOI: 10.1061/(ASCE)BE.19435592.0001038.© 2017 American Society of Civil Engineers. Author keywords: Moving vehicle; Vehicle dynamic responses; Field bridge; Bridge modal properties; Tractor and trailer test vehicle;

Using Dynamic Responses of Moving Vehicles to Extract Bridge Modal Properties of a Field Bridge

Research on damage detection is commonly carried out in the frequency domain using methods based on the modal data, transfer function or frequency response function, and transmissibility. The motivation for using transmissibility to detect damages relies on the fact that transmissibility measurements are local quantities that suggest high sensitivity. Nevertheless, the measurement of transmissibility requires external harmonic forces as the known input and sensors directly attached to the structure. There is a need for methods that can perform damage detection without attaching sensors and knowing the details of the input excitations. In a vehicle-bridge coupled (VBC) system the vehicle can serve as a force exciter and its dynamic response can be easily measured. In this paper, to make use of the vehicle response the transmissibility of a VBC system was first theoretically derived in a system consisting of a simply supported beam and a single-degree-of-freedom vehicle. Then, a numerical study was conducted to investigate the feasibility of detecting bridge damages using the vehicle transmissibility of the VBC system. In the numerical analysis, several damage indicators were constructed based on the transmissibility from both the bridge and vehicle responses, and compared to each other to select a proper one for damage detection. A parametric study was conducted on factors such as the measurement numbers, road roughness, and vehicle speeds and numbers to analyze the effectiveness of using such indicators for damage detection. To make use of the mobility of moving vehicles, two methods were finally proposed to measure the transmissibility of vehicle responses by using two vehicles. Method I used one reference vehicle and one moving vehicle; Method II used two moving vehicles at a constant distance in the longitudinal direction along the bridge. Using these two methods, the modal information such as natural frequencies and modal shape squares was successfully extracted for damage detections.

Damage Detection Based on Transmissibility of a Vehicle and Bridge Coupled System

Scour is one of the main causes of bridge failures. In order to measure and monitor scour depth variations including deposition (refilling) process, three designs for a scour monitoring system using fiber Bragg grating (FBG) sensors are discussed in the present study. By a comparative study, one of them is recommended in the present study and its instrumentation manufacture process is also introduced in detail. Using this recommended design, the advantages of FBG sensors for monitoring, such as immunity from electromagnetic interference and multiplexing capability, can be fully utilized. Both scour depth variations and entire scour development process including deposition process can be correctly monitored in real-time by continuously identifying the locations of emerging FBG sensors from the riverbed. A reliable sensor protection measure is also designed for FBG sensors in harsh environments, especially in floods. Finally, a verification test using a flume is carried out in the laboratory and three experimental cases are conducted to demonstrate the capability of FBG sensors and applicability of the recommended scour monitoring system. It can be concluded that the recommended scour monitoring system using FBG sensors is capable of measuring the water level, (maximum) scour depth, entire process of scour development, and deposition height due to refilling process. The advantages over other conventional scour monitoring systems are clearly demonstrated.

Xuan Kong

Papers

The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making

Numerically Extracting Bridge Modal Properties from Dynamic Responses of Moving Vehicles

Using Dynamic Responses of Moving Vehicles to Extract Bridge Modal Properties of a Field Bridge

Damage Detection Based on Transmissibility of a Vehicle and Bridge Coupled System

Instrumentation design for bridge scour monitoring using fiber Bragg grating sensors.