Bridges In Korea Research Articles

Forecasting Nighttime Frost-induced Black Ice Formation on Bridges Using Atmospheric Data

Background Faced with the tragedies caused by black ice in winter, especially on bridges, it is imperative to forecast black ice for preventive maintenance and to notify drivers approaching the dangerous spots. Methods In this study, three different machine learning algorithms—Deep Neural Network (DNN), Random Forest (RF), and Support Vector Machine (SVM)—were employed to predict nighttime black ice induced by frost on three bridges in Korea. Input data consisted of atmospheric data (air temperature, relative humidity, dew point, and differences between air temperature and relative humidity over two consecutive days) provided by the weather agency. Results To assess the employed models, reference data were generated based on the physical principle that ice forms when the pavement temperature is lower than the dew point temperature and negative. The pavement temperature was obtained using an infrared surface temperature sensor mounted on a maintenance patrol vehicle. Consequently, DNN and RF showed higher performance with an accuracy of 95%, followed by SVM with an accuracy of 92.5%. Conclusion Due to the use of easily obtainable atmospheric data, the findings of this study can be practically applied to preventive maintenance and driver information, thereby enhancing traffic safety.

Estimation of Water Stagnation in Asphalt-Overlaid Bridges Using Ground-Penetrating Radar

Stagnant water in asphalt-overlaid bridge decks is a primary cause of deterioration. Rainwater seeping through the asphalt layer stagnates on waterproofing membranes of the bridge deck, consequently degrading the asphalt pavement and the underlying concrete deck. Thus, identifying ponding regions under pavements potentially containing water can facilitate the prognostic maintenance of bridge decks. This study proposes a framework to estimate the subsurface ponding zone in bridge decks using ground-penetrating radar (GPR). The depth distribution of the nonpermeable layer in the subsurface of the bridge is extracted (depth map) from the GPR C-scan using a conventional thickness evaluation method and used to build a bathymetric dendrogram to model subsurface water flows. The subsurface ponding zone can be identified by considering drainage on the bathymetric dendrogram. The proposed framework is demonstrated using an in-service bridge in Korea. The estimated subsurface ponding zone is compared with damage locations of concrete observed after hydrodemolition.

Demonstrating the Test Procedure for Preventive Maintenance of Aging Concrete Bridges

Deteriorated facility maintenance is a critical social issue in advanced countries. Its cost increases when considering the social consequences in terms of asset value and direct maintenance costs. Data from Korea’s Ministry of Land, Infrastructure, and Transport shows that there were 3454 bridges aged 30 years or over in Korea in 2017; this number will increase to 10,961 by 2027. In thirty years, maintenance costs will be incurred for more than 32,000 old bridges in Korea. These trends are also observed in the US, Japan, and Korea. Diverse studies have been conducted to predict the residual life of old bridges via bridge performance evaluation and load-carrying capacity assessments. However, criteria for evaluating bridge performance and verifying the effect of bridge maintenance are yet to be established due to two reasons. First, most studies on performance evaluation, maintenance, and rehabilitation techniques have been performed on limited specimens from building elements or through small-scale simulations that do not reflect the deterioration factors of complex materials in diverse environments. Second, the performance evaluation of bridges is difficult compared to quantitative state evaluations. As a method of predicting the future performance of aged concrete bridges, it is effective to understand the actual aged bridges through experiments, and this study intends to propose the method.

Economical Inspection Methods Assisted by Unmanned Aerial Vehicle for Bridges in Korea

Economical Inspection Methods Assisted by Unmanned Aerial Vehicle for Bridges in Korea

Detection and Identification of Expansion Joint Gap of Road Bridges by Machine Learning Using Line-Scan Camera Images

Recently, the lack of expansion joint gaps on highway bridges in Korea has been increasing. In particular, with the increase in the number of days during the summer heatwave, the narrowing of the expansion joint gap causes symptoms such as expansion joint damage and pavement blow-up, which threaten traffic safety and structural safety. Therefore, in this study, we developed a machine vision (M/V)-technique-based inspection system that can monitor the expansion joint gap through image analysis while driving at high speed (100 km/h), replacing the current manual method that uses an inspector to inspect the expansion joint gap. To fix the error factors of image analysis that happened during the trial application, a machine learning method was used to improve the accuracy of measuring the gap between the expansion joint device. As a result, the expansion gap identification accuracy was improved by 27.5%, from 67.5% to 95.0%, and the use of the system reduces the survey time by more than 95%, from an average of approximately 1 h/bridge (existing manual inspection method) to approximately 3 min/bridge. We assume, in the future, maintenance practitioners can contribute to preventive maintenance that prepares countermeasures before problems occur.

Development of BIM-Based Bridge Maintenance System Considering Maintenance Data Schema and Information System

Due to the significant increase in the age of infrastructure globally, maintenance of existing structures has been prioritized over the construction of new structures, which are very costly. However, many infrastructure facilities have not been managed efficiently due to a lack of well-trained staff and budget limitations. Bridge management systems (BMSs) have been constructed and operated globally to maintain the originally designed structural performance and to overcome the inefficiency of maintenance practices for existing bridges. Unfortunately, because most of the current BMSs are based on 2D information systems, bridge maintenance data and information are not utilized effectively for bridge management. To overcome these problems, studies of BMSs based on building information modeling (BIM) have significantly increased in number. Most previous studies have proposed comprehensive frameworks containing approximate and limited information for maintenance to utilize BIM technology. Moreover, the utilization level of the maintenance information is less efficient because detailed information regarding safety diagnosis and maintenance are not included in data formats that are interpretable by computer algorithms. Therefore, in this study, a BIM-based BMS, including detailed information relating to safety diagnosis and maintenance, was constructed for the sustainability of bridge maintenance. To consider detailed information in the BMS, a maintenance data schema and its information system were established via the compilation of detailed information for safety diagnosis, repair and strengthening, remaining life, and valuation. In addition, a web data management program (WDMP) was developed using the maintenance data schema and information system, and was connected with the Midas CIM, which is a 3D modeling program. Finally, a prototype of the proposed BMS was established for an actual bridge in Korea. The proposed BMS in this study may be expected to improve the existing management practices for maintenance, and to reduce maintenance cost and information loss.

Broken Bridges and Breathless Images: Circulating Wirephotos in Midcentury America

This article examines the association between Wirephotos – the brand name that became a generic term for news photographs sent by telegraph, telephone or radio, also sometimes described as radiophotos – and objectivity. It suggests that many wirephotos functioned by making visible not places or events, but the drama of communication, understood as the challenging process of articulating messages across space and time. The article also considers Edward Steichen’s use of Associated Press photographer Max Desfor’s wirephotos in the exhibition Korea – The Impact of War, at the Museum of Modern Art in New York in 1951. It thinks through Steichen’s use of the metaphor of ‘bridging’ to describe the work of press photography and asks what it can tell us about photographic circulation and communication, particularly in mid-twentieth-century USA. By playing on the repertoire of meanings associated with bridges, Desfor’s Flight of Refugees Across Wrecked Bridge in Korea can be read as reflecting on its own medium’s limitations. As it circulated and recirculated in different formats, Desfor’s bridge photograph dramatised communication’s difficulty, and the always-present potential of failure in press photography’s effort to bridge distance.

Dynamic Displacement Estimation for Long-Span Bridges Using Acceleration and Heuristically Enhanced Displacement Measurements of Real-Time Kinematic Global Navigation System.

In this paper, we propose a dynamic displacement estimation method for large-scale civil infrastructures based on a two-stage Kalman filter and modified heuristic drift reduction method. When measuring displacement at large-scale infrastructures, a non-contact displacement sensor is placed on a limited number of spots such as foundations of the structures, and the sensor must have a very long measurement distance (typically longer than 100 m). RTK-GNSS, therefore, has been widely used in displacement measurement on civil infrastructures. However, RTK-GNSS has a low sampling frequency of 10–20 Hz and often suffers from its low stability due to the number of satellites and the surrounding environment. The proposed method combines data from an RTK-GNSS receiver and an accelerometer to estimate the dynamic displacement of the structure with higher precision and accuracy than those of RTK-GNSS and 100 Hz sampling frequency. In the proposed method, a heuristic drift reduction method estimates displacement with better accuracy employing a low-pass-filtered acceleration measurement by an accelerometer and a displacement measurement by an RTK-GNSS receiver. Then, the displacement estimated by the heuristic drift reduction method, the velocity measured by a single GNSS receiver, and the acceleration measured by the accelerometer are combined in a two-stage Kalman filter to estimate the dynamic displacement. The effectiveness of the proposed dynamic displacement estimation method was validated through three field application tests at Yeongjong Grand Bridge in Korea, San Francisco–Oakland Bay Bridge in California, and Qingfeng Bridge in China. In the field tests, the root-mean-square error of RTK-GNSS displacement measurement reduces by 55–78 percent after applying the proposed method.

Seismic Fragility Assessment Method for RC Bridges in Korea using a Representative Bridge

Seismic Fragility Assessment Method for RC Bridges in Korea using a Representative Bridge

Assessment of historic stone arch bridge characterisation: experiments and numerical model

The importance of historic stone arch bridges in Korea is based on their very long period of use and their ability to change the landscape. The inherent variations in a bridge's constituent materials, its deterioration over time and other types of damage directly affect the structural response of these heritage structures. In order to characterise the structural components and behaviour of a masonry arch bridge in Korea, a series of full-scale experiments including dynamic measurements, non-destructive tests and advanced geomatics techniques were conducted. Three-dimensional (3D) models of Hongye-gyo Bridge were created using commercial finite-element (FE) software and various modifications were also made to enhance the computer model. Using experimental and numerical results obtained with advanced technologies, a rational definition of the material properties and structural geometry was simulated with a 3D FE model. It was found that, despite the complexity of masonry stone arch bridges, reasonable assumptions of material properties and the friction angle between the voussoir's interfaces enable a good prediction of a bridges’ actual performance with a margin of 12%.

State-of-the-practice of constructed bridges in Korea

This paper presents the state-of-the-practice of constructed bridges in Korea, focusing on historical development, performance and recent achievements in rehabilitation technologies. The most commonly erected bridge types and trends over the last 100 years are identified. Dramatic changes occurred in the 1960s, when significant economic development in Korea began, evidenced by the replacement of traditional reinforced concrete T-girder bridges with prestressed concrete I-girder bridges. High-performance systems, such as preflex bridges, were introduced in the 1990s. The evolution of rehabilitation techniques indicates that engineers have sought more durable materials for more functional structural systems and have employed these to extend the longevity of constructed bridges. State-of-the-art strengthening techniques are discussed, with potential applications, and a case study is detailed. Suggestions are provided to advance bridge technologies.

Advances in Smart Technologies for Structural Health Monitoring of Cable-stayed Bridges

This study deals with the general problem of developing smart technologies for vibration and impedance-based structural health monitoring (SHM) of cable-stayed bridges. The following approaches are implemented to achieve the objective. Firstly, vibration- and impedance-based SHM methods suitable for cable-stayed bridge are briefly outlined. Secondly, smart sensors are designed for vibration- and impedance-based SHM. Thirdly, the practicality of the smart sensor system is evaluated on a real cable-stayed bridge, Hwamyung Bridge in Korea. The system's performance is experimentally analyzed under various cable forces and weather conditions. Finally, the experimental modal parameters are identified by numerical modal analyses of the target bridge. Also, its structural parameters are estimated from the vibration-based structural identification using experimental modal parameters.

Development of a High Precision Displacement Measurement System by Fusing a Low Cost RTK-GPS Sensor and a Force Feedback Accelerometer for Infrastructure Monitoring.

A displacement measurement system fusing a low cost real-time kinematic global positioning system (RTK-GPS) receiver and a force feedback accelerometer is proposed for infrastructure monitoring. The proposed system is composed of a sensor module, a base module and a computation module. The sensor module consists of a RTK-GPS rover and a force feedback accelerometer, and is installed on a target structure like conventional RTK-GPS sensors. The base module is placed on a rigid ground away from the target structure similar to conventional RTK-GPS bases, and transmits observation messages to the sensor module. Then, the initial acceleration, velocity and displacement responses measured by the sensor module are transmitted to the computation module located at a central monitoring facility. Finally, high precision and high sampling rate displacement, velocity, and acceleration are estimated by fusing the acceleration from the accelerometer, the velocity from the GPS rover, and the displacement from RTK-GPS. Note that the proposed displacement measurement system can measure 3-axis acceleration, velocity as well as displacement in real time. In terms of displacement, the proposed measurement system can estimate dynamic and pseudo-static displacement with a root-mean-square error of 2 mm and a sampling rate of up to 100 Hz. The performance of the proposed system is validated under sinusoidal, random and steady-state vibrations. Field tests were performed on the Yeongjong Grand Bridge and Yi Sun-sin Bridge in Korea, and the Xihoumen Bridge in China to compare the performance of the proposed system with a commercial RTK-GPS sensor and other data fusion techniques.

Flood fragility analysis for bridges with multiple failure modes

Bridges are one of the most important infrastructure systems that provide public and economic bases for humankind. It is also widely known that bridges are exposed to a variety of flood-related risk factors such as bridge scour, structural deterioration, and debris accumulation, which can cause structural damage and even failure of bridges through a variety of failure modes. However, flood fragility has not received as much attention as seismic fragility despite the significant amount of damage and costs resulting from flood hazards. There have been few research efforts to estimate the flood fragility of bridges considering various flood-related factors and the corresponding failure modes. Therefore, this study proposes a new approach for bridge flood fragility analysis. To obtain accurate flood fragility estimates, reliability analysis is performed in conjunction with finite element analysis, which can sophisticatedly simulate the structural response of a bridge under a flood by accounting for flood-related risk factors. The proposed approach is applied to a numerical example of an actual bridge in Korea. Flood fragility curves accounting for multiple failure modes, including lack of pier ductility or pile ductility, pier rebar rupture, pile rupture, and deck loss, are derived and presented in this study.

국내 고속도로 교량의 차량 충돌 위험도 평가

차량충돌은 가장 빈도가 높은 교량 붕괴의 원인 중 하나로 알려져 있으며, 최근 재해에 대하여 대책 수립 및 관리의 필요성이 공익 안전을 위해 제기되고 있다. 본 연구에서는 차량 충돌로 인한 교량 피해에 대하여 위험도 분석을 실시하였다. 위험도 분석 단계는 세 단계로 구분하였고, 예비위험분석 단계에서는 충돌의 발생가능성을 확인하며, 기본위험분석 단계에서는 발생가능성, 취약성, 중요도에 대한 위험도 점수평가를 통한 위험도 등급을 산정하였다. 마지막 상세위험분석 단계에서는 위험도가 높은 등급에 대하여 상세분석을 실시한다. 본 연구에서는 예비위험분석과 기본위험 단계에 집중하여 위험도 등급 구분을 위한 네 가지의 급간분류법을 적용하였다. 충돌 사례와 분석 결과를 비교하여 적절한 급간분류법을 결정하고자 하였다. 본 연구에서 사용된 위험도 분석법은 유사한 재난에 대한 대책수립을 위해 사용될 수 있을 것이다. Vehicle collision to bridges has been known as one of the causes of bridge collapse, and the emergency plans and disaster management has been recently emphasized to secure public safety. This study conducted risk assessment of vehicular collision to bridges for highway bridges in Korea. Risk assessment consists of three steps; preliminary risk analysis(PRA), simplified risk analysis(SRA) and detailed risk analysis(DRA). The PRA firstly screens out the possibility of occurrence of the event. The SRA identifies influencial factors to risk of the event and evaluates risk scores to determine risk levels and necessity of DRA that investigates the risk of the bridge in detail. This study focuses on the methodology of the risk assessment, especially the SRA, and the stratification methods which evaluate risk levels of vehicular collision. The analysis results were compared to the reported vehicular collision accidents. The proposed method can be utilized in similar disaster management area.

효율적인 도심지 교량관리를 위한 교량자산관리 체계 및 서비스수준(LOS) 개발을 위한 기초연구

사회기반시설물의 핵심 시설물 중 하나인 교량은 이용자들이 쉽게 접하고 이용하는 시설물로 일정 수준이상의 성능유지는 필수적으로 요구된다. 교량건설 역사가 상당히 오래된 호주, 뉴질랜드, 미국, 유럽 등의 최근 관련 연구보고서 등의 사례를 비추어 보았을 때, 우리나라 또한 교량의 기대수명에 도달하는 10-20년 내 교량의 유지관리 및 개축 수요가 급격하게 증가될 것으로 예상되므로 비교적 건전한 상태를 유지하고 있는 현 시점에서 한정적인 예산을 효율적으로 분배하기 위해 교량 성능을 적정 수준 이상으로 유지하며 LCC 측면에서의 비용은 최소한으로 투입하는 합리적이고 공학적인 의사결정방법론이 필요하다. 이러한 목적을 달성하기 위하여 호주, 뉴질랜드 및 미국 등에서는 오래전부터 자산관리체계를 마련하기 위하여 많은 노력이 이루어지고 있다. 본 논문에서는 모든 교량을 관리할 수 있는 범용적인 자산관리체계와 교량이 제공하는 서비스수준(Level of Service)과 이를 측정하기 위한 성능측정기준을 개발하기 위한 사전 기초연구로써 연구의 범위를 도심지의 교량으로 한정하여 그 자산관리체계와 서비스수준을 개발하고자 한다. 전문가와 이해관계자로 구성된 워크숍을 실시하여 국내 실정에 맞는 도심지 교량자산관리체계와 그 서비스수준(LOS) 및 성능 척도(PM)를 개발하고 다속성 효용이론(Multi-Attribute Utility Theory)와 AHP기법을 이용하여 성능 지표별 가치의 값과 성능 척도의 가중치 분석을 실시하였다. 도출 된 성능 척도의 가중치와 성능 지표의 가치(Value) 등의 적용 확인을 위해 <TEX>${\bigcirc}{\bigcirc}$</TEX>시의 교량 6개를 선별하여 LOS분석을 적용하고 그 결과를 고찰하였다. Bridges, which constitute one of the key facilities in a social infrastructure, are easily accessed and used by users, so that keeping their performance above a certain level is essential. According to various cases in the U.S., Japan and Europe with a long construction history, it is expected that the maintenance cost of bridges in Korea will increase continuously in the future, so a rational decision making system based on engineering factors is necessary to optimize the performance of and maintain them by allocating the limited budget efficiently. This study is a preliminary basic study for the purpose of developing a common asset management system for managing all of the bridges and maintaining the level of service provided by them. The scope of this preliminary study is limited to bridges in urban areas. The bridge asset management system for bridges in urban areas, their level of service (LOS) and performance measure (PM) were developed by carrying out a workshop consisting of both experts and stakeholders. The analysis on the weights of the value and performance measure for each performance indicator was carried out by using the multi-attribute utility theory and the AHP method. In order to confirm the application of the weight of the performance measure and value of the performance indicator, six bridges in an example city were selected, LOS analysis was applied and its results were reviewed.

실측자료에 근거한 도개교량의 거동 분석

하천 또는 해안의 선박운항을 위한 도개교는 그 희소성으로 인해 최근에는 랜드마크로의 역할을 인정받으면서, 국외의 경우 세심한 유지관리로 수십 년 이상 공용기간을 지속하고 있는 사례가 적지 않다. 국내 유일의 도개교인 영도대교는 부식과 노화로 철거 후, 2013년에 재가설 되었으며, 현재 1일 1회 도개를 실시하고 있다. 최근 교량의 안전과 유지관리에 대한 요구가 높아지면서 주기적인 안전진단이 수행되지만 도개교에 대한 계측 및 분석 사례는 거의 없는 실정이다. 이에 본 연구에서는 도개교가 상승 및 하강하는 도개과정과 상시 사용상태에서의 계측자료를 토대로 구조해석을 실시하여 도개교의 응력, 진동, 반력 등 실제 거동을 분석하고자 하였으며, 이 결과는 추후 공용연수의 증가 및 도개횟수의 증가에 따른 교량거동의 변동 추세를 분석하기 위한 초기 자료로 활용될 수 있을 것으로 기대된다. Bascule bridge, with its use to help vessels ply, has a several examples overseas of being serviced for more than decades years by careful maintenance, admitted its significance as landmarks for its rareness. Yeongdo Bridge, the sole bascule bridge in Korea was reconstructed in 2013 after being demolished because of its corrosion and aging, and now operates once in a day. Recently, safety inspections are executed thanks to demands getting higher for maintenance and safety of bridges, but measurement and analysis about bascule bridges are scarce. This study includes the analysis of the bascule bridge's behavior such as stress, vibration and reaction in normal condition and while it lifts up, based on measurement. We expect that this study will be used as an initial data to compare and confirm bridge's changes as service year and the number of operation increase.

고정하중을 받는 다경간 현수교의 예비해석을 위한 케이블 부재의 초기평형상태 해석

본 연구에서는 고정하중을 받는 다경간 현수교의 예비해석을 위한 케이블 부재의 초기평형상태 해석방법을 제안한다. 본 연구에서 제안한 초기 평형상태 해석 알고리즘은 타 연구들에서 사용된 기존 방법들보다 간편하고 실용적이며, 3경간 현수교 및 다경간 현수교에 적용 가능하다. 제안방법의 타당성을 검증하기 위해, 3경간 현수교 예제모델과 4경간 현수교인 국내의 새천년대교 및 중국의 Yingwuzhou Bridge 모델을 사용하여 초기평형상태 해석을 수행하였다. 검증 결과, 본 연구에서 제안한 초기평형상태 해석방법에 의한 결과가 3경간 예제모델의 선행 연구결과 및 새천년대교의 설계값과 잘 일치하는 경향을 나타내었으며, 제안 방법은 Yingwuzhou Bridge에 대한 초기형상을 잘 유지하는 초기값들을 도출하였다. This paper proposes a method to determine the initial equilibrium state of cable members for preliminary analysis of multi-span suspension bridge under dead load. The proposed method is simpler and more practical than the previous methods used in other studies. The proposed method can be applied to three-span or multi-span suspension bridges. To verify the proposed method, an three-span model as well as four-span models such as New Millenium Bridge in Korea and Yingwuzhou Bridge in China are analyzed. In the verification results, the initial coordinates and tensions of the members calculated by the proposed method are good agreement with those in the previous study for the three-span model and those in the design data of New Millenium Bridge. In addition, the proposed method gives the initial values to keep the initial configuration of Yingwuzhou Bridge.

GFRP 근 보강 콘크리트 교량 바닥판의 설계지배인자

In this study, the governing design factors of GFRP-reinforced concrete bridge deck are analyzed for typical bridges in Korea. The adopted bridge deck is a cast-in-situ concrete bridge deck for the prestressed concrete girder bridge with dimensions of 240 mm thickness and 2.75 m span length from center-to-center of supporting girders. The selected design variables are the diameters of GFRP rebar, spacings of GFRP rebars and concrete cover thicknesses, Considering the absence of the specification relating GFRP rebar in Korea, AASHTO specification is used to design the GFRP-reinforced concrete bridge deck. The GFRP-reinforced concrete bridge deck is proved to be governed by the criteria about serviceability, especially maximum crack width, while steel reinforced concrete bridge deck is governed by the criteria on ultimate limit state. In addition, GFRP rebars with diameter of 16 mm ~ 19 mm should be used for the main transverse direction of decks to assure appropriate rebar spacings.

Evaluation of load and resistance factors for the reliability-based design of the main cables of earth-anchored suspension bridges

This paper presents load and resistance factors for the reliability-based design of the main cables of earth-anchored suspension bridges for the Strength I Limit State defined in the AASHTO LRFD Bridge Design Specifications. Reliability analyses are performed for three suspension bridges in Korea with main span lengths ranging from 650 m to 1545 m, and the reliability indices and the Most Probable Failure Points (MPFP) of random variables are evaluated. The strength, load and stiffness parameters are taken into account as random variables. The advanced first-order second-moment method is employed to evaluate the reliability indices and the MPFP of the random variables. The elastic catenary cable element is utilized to discretize the main cables. Load factors are proposed based on the normalized MPFP of each load component considered in the Strength I Limit State. The resistance factor that yields the reference target reliability index for the main cable is found as 0.53. Two alternative resistance factors, which give lower and higher reliability indices than the reference value, are also proposed. The proposed load and resistance factors lead to a uniform reliability level for a main cable regardless of the length of the main span of a suspension bridge.