Jungwhee Lee

Necessity of the bridge health monitoring system to mitigate natural and man-made disasters

In Korea, there has been a wide consensus about the necessity of bridge monitoring systems. This is primarily due to a chain of accidental bridge collapses over the past decade. The first generation bridge monitoring system originated from an instrumentation system introduced upon the reconstruction of the New-Haengju Bridge after its sudden collapse in 1995. After that, on-line instrumentation systems were installed in existing cable-supported bridges including Namhae, Jindo and Dolsan Bridges. These systems can be considered the second generation bridge health monitoring systems (BHMSs). These were then followed by the development of the third generation bridge monitoring systems installed and currently in service on the Seohae and Yeongjong Bridges. This study tracks the background and advent of Korean bridge monitoring systems and their developmental history up to the present time. It also investigates current associated studies in progress and the limitations of contemporary BHMS technologies, and suggests possible remedial solutions for a follow-up bridge monitoring system.

Structural performance evaluation of a precast prefabricated bridge column under vehicle impact loading

In this study, the numerical analysis method was proposed to analyse the structural behaviour of bridge columns under various impact loading conditions. A parametric study of vehicle impact simulation was carried out to determine the impact loading-time functions. According to the impact simulation results, five-point piecewise linear approximation is proposed and validated. The proposed loading function was applied to the material nonlinear finite element analyses of two different types of bridge piers, the cast-in-place reinforced concrete bridge columns and the prefabricated bridge columns, which were designed under the same loading conditions. The dynamic performances of the considered bridge piers are compared using the results of dynamic numerical analyses. Also, the static design loadings of a vehicle crash defined in the Korean bridge design code and AASHTO LRFD Bridge Design Specifications were applied to analyse the results of the dynamic analyses of the piers.

Dynamic Characteristics of High-speed Railway Steel Bridges

The dynamic behavior of two steel bridges crossed by the Korean High Speed Train(KHST) has been investigated experimentally and the results are compared with the specification requirement of BRDM and other typical PSC Box bridge`s responses. The investigated bridges are a 2-girder steel bridge of 1@40m span length(E-Won Bridge), 2@50m span length (Ji-Tan Bridge), and a PSC Box girder bridge of 2@40m span length (Yeon-Jae Bridge). A set of experimental tests were performed during operation of KHST, and a number of accelerometers, LVDTs and ring-type displacement transducers were utilized for measurement of three kinds of dynamic responses (acceleration, deflection, and end-rotation angle). Measured responses show that the vertical deflections and end-rotation angles of the three bridges are all satisfying the spec. requirement with large margin, but it was also found acceleration responses which are very close or exceed the limit value. Most of the excessive acceleration responses were found when the passing velocity of the KHST is close to the critical velocity () which causes resonance. No noticeable differences of dynamic responses due to the different materials(steel or concrete) could be found within these experimental results.

Development and Optimization of a Reverse Transcription Hemi-Nested PCR Primer for the Detection of Potato Mop - Top Virus at Quarantine Inspection Sites in Korea

Potato mop-top virus (PMTV) is classified as a plant quarantine virus in Korea. It is tested at import inspection sites. In this study, two sets of reverse transcription-hemi-nested polymerase chain reaction primers were developed to diagnose PMTV. In addition, modified- positive control plasmid was developed for the identification of false positive results in plant quarantine. The assay is expected to be useful for improving the detection and diagnosis of PMTV.

Assessment of Impact Resistance Performance of Post-tensioned Curved Wall using Numerical Impact Analysis

Abstract In this study, the effect of wall curvature and post-tension force on impact resistance is evaluated by numerical analysis method. A total of twelve cases with two parameters such as wall shape of flat and curved, and consideration of post-tensioning force were included in this study. A 3D detailed finite element model of commercial passenger plane engine is utilized as projectile. The depths of penetration and central displacement calculated from the numerical simulations were compared and analysed. As the results of the numerical simulations of this study, penetration depth was reduced approximately 60∼80% due to the application of post-tension force, but the decrease of maximum central displacement was not remarkable. Also, the effect of curvature was relatively insignificant. Keywords :impact resistance, impact analysis, curvature, post-tension, penetration depth, maximum displacement † Corresponding author: Tel: +82-31-8005-3511; E-mail: jwhee2@dankook.ac.krReceived November 2 2015; Revised November 9 2015;Accepted November 10 2015Ⓒ2016 by Computational Structural Engineering Institute of KoreaThis is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Impact performance evaluation of MASH TL4 bridge barrier

Many roadside safety features such as traffic barrier systems, end treatments, crash cushions, breakaway devices, truck-mounted attenuators, and other hardware are used to achieve the highest levels of highway safety. A goal of a highway safety feature is to provide a forgiving roadway and roadside that reduces the risk of a serious accident when a vehicle leaves the roadway. Among various evaluation methods, full-scale crash test has been and will continue to be the most common method of evaluating the impact performance of safety hardware, therefore there are many countries that have the full-scale crash test procedures and evaluation criteria including the US, EU, and South Korea. The recommended procedures for the full-scale crash test of safety hardware have been developed in the US starting from Highway Research Correlation Services Circular 482 in 1962. During the subsequent decade, the evolution of roadside safety concepts, technology, and practices necessitated an update to previous recommendations. In 2009, the American Association of State Highway and Transportation Officials (AASHTO) published Manual for Assessing Safety Hardware (MASH) for the purpose of evaluating new safety hardware devices and this publication marks the first time that AASHTO has officially adopted crash-testing procedures for use in assessing roadside hardware. However, the evaluation of a bridge barrier in accordance with MASH has not been performed until 2012. Within the scope of this research, a bridge barrier system that meets the MASH criteria has been developed and evaluated, and the procedures and the results are described in this paper. The developed bridge barrier with the target safety level of TL4 is first designed using the plastic failure mechanism approach presented in AASHTO LRFD Design Specifications as a static manner and then the impact performance is pre-evaluated by the three-dimensional crash analysis software, LS-DYNA. Finally, the full-scale crash test is performed at Texas Transportation Institute for tests 4-10, 4-11, and 4-12 using 2005 Kia Rio passenger car, 2008 Dodge Ram pickup truck, and 1998 International 4700 single-unit truck, respectively. The full-scale crash test results meet the evaluation criteria presented in MASH, hence the developed bridge barrier in this research is ready for the field application.

Effect of Support Rotational Stiffness on Tension Estimation of Short Hanger Ropes in Suspension Bridges

ABSTRACT Tension force of hanger ropes has been recognized and utilized as an important parameter for health monitoring of suspension bridges. Conventional vibration method based on string theory has been utilized to estimate tension forces of relatively long hanger ropes without any problem, however it is convinced that the vibration method is not applicable for shorter hanger ropes in which the in-fluence of flexural stiffness is not ignorable. Therefore, as an alternative of vibration method, a num-ber of feasibility studies of system identification(SI) technique considering flexural stiffness of the hanger ropes are recently performed. In this study, the influence of support condition of the finite element model utilized for the SI method is investigated with numerical examples. The numerical ex-amples are prepared with the specification of the Kwang-Ahn bridge hanger ropes, and it is revealed that the estimation result of the tension force can be varied from -21.6 % to +35.3 % of the exact value according to the consideration of the support condition of FE model. Therefore, it is concluded that the rotational stiffness of the support spring should be included to the list of the identification parameters of the FE model to improve the result of tension estimation.