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The appropriate maintenance of highway roads is critical for the safe operation of road networks and conserves maintenance costs. Multiple methods have been developed to investigate the surface of roads for various types of cracks and potholes, among other damage. Like road surface damage, the condition of expansion joints in concrete pavement is important to avoid unexpected hazardous situations. Thus, in this study, a new system is proposed for autonomous expansion joint monitoring using a vision-based system. The system consists of the following three key parts: (1) a camera-mounted vehicle, (2) indication marks on the expansion joints, and (3) a deep learning-based automatic evaluation algorithm. With paired marks indicating the expansion joints in a concrete pavement, they can be automatically detected. An inspection vehicle is equipped with an action camera that acquires images of the expansion joints in the road. You Only Look Once (YOLO) automatically detects the expansion joints with indication marks, which has a performance accuracy of 95%. The width of the detected expansion joint is calculated using an image processing algorithm. Based on the calculated width, the expansion joint is classified into the following two types: normal and dangerous. The obtained results demonstrate that the proposed system is very efficient in terms of speed and accuracy.

The need for maintenance is increasing due to the aging of facilities. In this study, we proposed a crack width measurement method for images collected at safe distances using UAVs (Unmanned Aerial Vehicles). It is a method of measuring the widths of cracks using a high-resolution (VDSR) algorithm, which measures by increasing the resolution of images taken at 3 m intervals on the wall where cracks exist. In addition, the crack width measurement value was compared with a general photographed image and a high-resolution conversion image. As a result, it was confirmed that the crack width measurement of the image to which the high resolution was applied was similar to the actual measured value. These results can help improve the practical applicability of UAVs for facility safety inspections by overcoming the limits of camera resolution and distances between UAVs and facilities introduced in the facility safety inspection. However, more detailed image resolution is required to quantitatively measure the crack width; we intend to improve this through additional studies.

In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the “Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges.” Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.

In a previous paper, ambient vibration tests were conducted on a cable stayed bridge with resilient-friction base isolation systems (R-FBI) to extract the dynamic characteristics of the bridge and compare the results with a seismic analysis model. In this paper, a nonlinear seismic analysis model was established for analysis of the bridge to compare the difference in seismic responses between nonlinear time history analysis and multi-mode spectral analysis methods in the seismic design phase of cable supported bridges. Through these studies, it was confirmed that the seismic design procedures of the “Korean Highway Bridge Design Code (Limit State Design) for Cable Supported Bridges” is not suitable for cable supported bridges installed with R-FBI. Therefore, to reflect the actual dynamic characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure is proposed that applies the seismic analysis method differently depending on the seismic isolation effect of the R-FBI for each seismic performance level.

Recently, in the building and infrastructure fields, studies on defect detection methods using deep learning have been widely implemented. For robust automatic recognition of defects in buildings, a sufficiently large training dataset is required for the target defects. However, it is challenging to collect sufficient data from degrading building structures. To address the data shortage and imbalance problem, in this study, a data augmentation method was developed using a generative adversarial network (GAN). To confirm the effect of data augmentation in the defect dataset of old structures, two scenarios were compared and experiments were conducted. As a result, in the models that applied the GAN-based data augmentation experimentally, the average performance increased by approximately 0.16 compared to the model trained using a small dataset. Based on the results of the experiments, the GAN-based data augmentation strategy is expected to be a reliable alternative to complement defect datasets with an unbalanced number of objects.

In areas of civil engineering, the resilient friction base isolator (R-FBI) system has been used due to its enhanced isolation performance under seismic excitations. However, because nonlinear behavior of the R-FBI should be reflected in seismic design, effective stiffness (Keff) of the R-FBI is uniformly applied at both peak ground acceleration (PGA) of 0.08 g and 0.154 g which use a multimodal response spectrum (RS) method analysis. For rational seismic design of bridges, it should be required to evaluate the dynamics of the R-FBI from in-field tests and to improve the seismic design procedure based on the performance level of the bridges. The objective of this study is to evaluate the dynamics of the R-FBI and to suggest the performance-based seismic design method for cable-supported bridges with the R-FBI. From the comparison between the experiments&rsquo, results and modal shape analyses, the modal shape analyses using primary (Ku) or infinite stiffness (fixed end) showed a great agreement with the experimental results compared to the application of Keff in the shape analysis. Additionally, the RS or nonlinear time history method analyses by the PGA levels should be applied by reflecting the dynamic characteristics of the R-FBI for the reasonable and efficient seismic design.

Long span cable supported bridges are important transport infrastructure and exposed to number of different hazards such as fire, strong wind, and earthquake. In 2015, a cable-stayed bridge in Korea, Seohae Bridge, experienced uncommon cable fire due to a lightning strike. A fire caused full and partial failure of three stay cables. The Seohae Bridge was closed to traffic for 15 days and repaired by replacing three damaged cables. After reopening, the extensive retrofit works were carried out to prevent and mitigate damages from fire and lightning. A fire hydrant system and a lightning protection system were newly installed on the Bridge. The Korean Highway Bridge Design Code (Limit State Design Method) for Cable-supported Bridges introduced the performance-based design provisions for seismic design in 2016. Three seismic performance level, operational, Long- term repairable, and collapse prevention, was defined and corresponding return periods. The seismic performance of the Bridge, which was designed using force-based method, was recently verified using a detailed non-linear analysis considering material and geometric nonlinearity according to the displacement-based seismic design concept. The results showed that the bridge can satisfy the required seismic performance levels and safety using progressive increment analysis, under the earthquake with very low frequencies of occurrence.

The study presented in this paper developed a sequential and universal bridge fire risk assessment procedure for constructed bridges, as well as countermeasures to reduce the risk level. Of interest were concrete and steel bridges on highways, except for certain special types of bridges. The fire risk assessment procedure consisted of three steps: ( a) preliminary risk analysis (PRA), which was a screening step to determine the likelihood of bridge fire events; ( b) simplified risk analysis (SRA), which was performed with the use of bridge inventory databases and checklists; and ( c) detailed risk analysis (DRA), which made use of computer simulation and collected data. A PRA determines whether a bridge requires an SRA on the basis of bridge clearance height and roadway conditions under the bridge. An SRA has three parts: analysis of fire occurrence, vulnerability to fire, and bridge importance. Itemized details were developed to evaluate the three parts and determine risk scoring. The SRA procedure identified which parts contributed to the resultant risk level. Reliability indexes concurrent with the latest ISO DP 10252 design code were used to determine the score of a given bridge and to perform an analysis to determine the risk level of 8,267 bridges in South Korea. The DRA was the final step, a detailed analysis of occurrence and vulnerability of a bridge mainly on the basis of computer simulation. This study provided guidelines to determine the DRA levels. Countermeasures also were developed for each of three risk levels (i.e., occurrence, vulnerability, and importance); the application of the countermeasures depended on the factors causing the risk.

The simultaneous presence of multiple heavy trucks on road bridges causes a higher stress to the structural members of bridges than the presence of a single heavy truck. Truck traffic data acquired using weigh-in-motion systems are typically used to assess the multiple-presence probability for side-by-side and following trucks. A number of high-speed weigh-in-motion (HS-WIM) systems are installed in the Korean Expressway Network to control overloaded vehicles and obtain long-term truck weight data. In this study, the multiple-presence probabilities for following and side-by-side trucks were determined using data from two HS-WIM sites. The correlation probability between the gross vehicle weights (GVWs) of successive trucks was also calculated. To determine the characteristics of heavier truck loads, the multiple-presence probabilities for the overweight trucks, which exceed the legal weight limit, were calculated separately. The analysis of the HS-WIM data showed that the multiple-presence probabilities of the trucks increased with the headway distance of following or side-by-side trucks, and the probability of following truck events was lower than that of side-by-side truck events. The probability of side-by-side truck events increased with the increase of daily truck traffic (DTT), whereas the probability of following truck events was only slightly affected by the DTT. The full correlation probabilities of the GVW for the following and side-by-side trucks were low.

The objective of this research is to evaluate of global and local damage for steel-concrete composite structures under highway bridge exposed to fire loading. To enhance the accuracy and efficiency of the numerical analysis, the proposed transient nonlinear thermal structure interaction(TSI) parallel fire analysis method is implemented in ANSYS. To validate the TSI parallel fire analysis method, a comparison is made with the standard fire test results. The proposed TSI parallel fire analysis method is applied to fire damage analysis and performance evaluation for Buchen highway bridge. The result of analysis, temperature of low flange and web are exceed the critical temperature. The deflection and deformation state show good agreement with the fire accident of buchen highway bridge.

After years of research and development, the structural health monitoring system for the Seohae Bridge was installed in 2000 in South Korea. This steel–concrete composite cable-stayed bridge has a main span of 470 m. To monitor the long-term structural behavior and anomalies of the bridge, the system was composed of hundreds of sensors, including accelerometers, anemometers, and strain gauges. These sensors were installed on critical elements of the bridge, such as the stay cables, a stiffening girder, and the main pylons. After the development and stabilization phase, which lasted almost a year, the system has been successfully operated and has helped in understanding the structural characteristics and long-term behavior of the bridge. After more than 9 years of operation, however, the system started to show signs of aging and deterioration. Some gauges and sensors have worn out and have become malfunctioning. To fix these problems and upgrade the system, the renovation work was planned and carried out with a budget estimated at US$2 million. The main goals of the renovation work were to optimize sensor deployments, improve graphical user interfaces, and deploy state-of-the-art sensors and technologies. Although the number and types of sensors were minimized, a monitoring system based on a global navigational satellite system was newly installed to monitor deformation and geometry change of the bridge.

Trapezoidally corrugated steel plates have been used as the web of pre-stressed concrete box girder bridges to reduce dead load and increase structural efficiency. Due to an applied shear stress, the trapezoidally corrugated web can fail by three different shear buckling modes: local, global, and interactive shear buckling. Local buckling involves a single panel, whereas global buckling involves multiple panels, with buckles extending over the entire depth of the web. The interactive buckling is rather complex and is an intermediate type of shear buckling between local buckling and global buckling, which involves several panels. In this study, a series of finite element analyses was carried out to study the geometric parameters affecting interactive shear buckling modes and strength. Based on the analysis results, the interactive shear buckling strength formula is proposed. The proposed formula agreed well with the experimental data.

Super Long Span Bridge R&D Centre of Korea has established design standards with the use of a limit state design method and carried out studies on new materials and new construction methods to be used for cable bridges since 2009, and are now in preparation for its practical use as well as its use as a test bed.The Super Long Span Bridge Project aims at securing the design and construction technology of the Long Span Bridge Cable on the cost effectiveness and technical competitiveness bases and is the technology study project executed in total 4 disciplines (1~4 vital disciplines); Design, Material, Construction and Test Bed. In addition, the purpose of 4th vital assignment is to secure international reliability and cost effectiveness on the Super Long Span Bridge Project by applying the individual technology studied from the design, material and construction of 1, 2 and 3 assignments to the integrated Test Bed. In addition, safety in each Limit State has been confirmed and accordingly cost effectiveness on loads in each life, a resistance correction coefficient by the reliability index and member forces of main members has been checked and compared by applying the Cable Bridge Design Specification (Limit State Design Method) to the concrete cable stayed bridge with the main span of 350m selected as the test bed bridge.

A number of bridges on Korean highways have been damaged by fires in recent years. Most of these fires were caused by tanker trucks. In 2010, a gasoline tanker truck parked under a steel box girder bridge caught fire and caused partial collapse of the bridge. To protect bridges against fires, a bridge fire risk assessment procedure and fire-resistant design guidelines were developed in this study. The fire risk assessment procedure is composed of three main steps: Preliminary Risk Analysis (PRA), Simplified Risk Analysis (SRA), and Detailed Risk Analysis (DRA). The fire occurrence probability, vulnerability, and importance of bridges are considered in the risk assessment procedure. For high-risk bridges, fire-resistant designs must be implemented. Two important design considerations are bridge clearance height and under-bridge conditions.

The Yongjong Grand Bridge includes a self-anchored suspension bridge with inclined cable planes. The bridge uses splay bands (cable collars) to flare the main cables at the anchorage, which is located at the end of a stiffening truss. During cable erection, some of the wires at the splay band were expected to experience lateral displacement and/or lift phenomena because of the large flare angles at the splay band. Mockup cable erection tests at the anchorage were carried out to find the degree of displacement of the wires and to determine appropriate measures to deal with these problems. Through these tests, methods to arrange wires at the splay bands were devised and tried, and the selected method was successfully used for the actual bridge.

This paper presents the results of mock-up cable erection tests for the Yong Jong Grand Bridge, Inchon, Korea. The Grand Bridge includes the world's first self-anchored spatial suspension bridge whose main cable planes are inclined in the transverse direction. Cable erection problems were expected to occur at the pylon saddle and the splay band due to the self-anchored cable system and the difference between the erection and completed layout of the main cable. The mock-up tests were performed prior to actual cable erection. Through the tests, cable erection problems at the saddle, lateral displacement, and bending of the wires inside the saddle were identified, and measures to deal with the problems were devised and tested. The tested measures were successfully implemented for the construction of the bridge.

The statistically processed results are sometimes not intuitive for the structural health monitoring systems of cable-stayed bridges which process voluminous data from a lot of sensors. For this reason, the signals-image recognition algorithm using images more intuitive than numerical values is presented in this study. The signals-image here means not a photograph taken by any camera but the artificial image which consists of measured signals and their process results. It is applied to extract the features from signals and identify the cable vibrations. Consequently, identifying and classifying signals-images have been successfully performed.

The Yong Jong Grand Bridge in South Korea is part of the new road and rail links between Seoul and the new Inchon International Airport now being constructed. The main design principles of the bridge were function, symbolic expression of Korean culture, and visual harmony with the surrounding environment. The 4.42km long bridge has an upper deck carrying a six-lane highway, and a lower deck carrying a four-lane highway and two railway lines. The main part of the bridge is its 550m long suspension bridge, with 300m main span, two 125m side spans, and a 60m cable sag. It is one of the few self-anchored suspension bridges that have yet been built. It has 35m clearance above the sea, steel box girders for its decks, and 104m diamond-shaped steel towers, whose wind-resistance properties were tested using a 1:150 scale model. The main cables are shaped in three dimensions. The bridge's design wind speed is 40m/s. The approach viaducts have a double-deck truss configuration with three-span continuous sections; each span is 125m long and 36.1m wide. The whole superstructure, which is almost all made of steel, is being constructed on steel bents. Cables will be erected on top of the superstructure, which they will then support. By April 1998, about 40% of the construction work had been completed.

Trapezoidally corrugated steel webs are composed of a series of flat and inclined subpanels and have been used as the webs of prestressed concrete box girder bridges to reduce superstructure weight and increase the effectiveness of prestressing. Because of accordion effects, the corrugated web resists only the shear stress, and the flanges resist most of the bending stress. The shear stress in the web can cause three different modes of shear buckling: local, global, and interactive (zonal) buckling. Several studies have been performed to determine buckling formulas for each mode. However, there are differences regarding the buckling strength, and some of the formulas are found to overestimate it. The results of a study are presented; a series of experiments was done with large corrugated plates. The specimens were designed to fail by the local, global, or interactive buckling mode in elastic and inelastic states. The effect of geometric parameters on the shear buckling strength was also studied. Nonlinear...