• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.47-53
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• 2014

The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated in the model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developed to account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.1-11
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• 2021

As the aging of large domestic SOC facilities accelerates, facility maintenance is also changing from safety evaluation based on the current condition to performance-oriented preventive and preemptive maintenance based on the prediction of the level of future obsolescence. In particular, in the case of bridges, class 1 and 2 bridges are systematically managed along with many studies, but for small and medium-sized class 3 bridges there is no collection and utilization of historical data presenting performance degradation during their service life. Therefore, in this study, 3D model-based demonstration DB system was designed and developed to intuitively check the damage change rate at the damage location by registering the maintenance history by life cycle for each member's exterior damage in the 3D bridge object and to enable API-based comprehensive performance evaluation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.153-173
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• 1993

폭약은 탄광에서 석탄이나 각종 광물을 캐거나, 건설토목현장에서 암반 제거를 위해서 주로 사용되었다. 전쟁에서 군사용으로 파괴를 위한 목적으로 사용되기도 하였으나, 최근의 동서화해 분위기와 남북통일이 무르익는 시대적 조류로 볼때 더이상 파괴용으로의 사용은 제어될 것이고 이제는 평화를 위하여, 건설을 위하여, 산업발전을 위하여 더 많이 사용되어지고 응용되어질 것이다. 작금의 첨단산업의 발달과 산업의 고도화로 우리 화약 업계에도 첨단발파기술의 개발에 많은 관심과 연구.개발을 진행중이다. 첨단발파기술의 응용사례를 소개하면, 건축토목 분야에서 노후 고층빌딩 및 굴뚝의 철거, 노후 교량 및 공장시설의 철거등에 활용되고 있으며, 위락서비스 분야에서 응용으로는 불꽃놀이를 들 수 있다. 최근에는 첨단 과학 장비를 이용하여 각종 꽃불의 모양이 음악과 미술등 예술적인 기능을 기억시킨 컴퓨터를 활용하여 보다 고차원의 공예술품(공학-예술)을 만들어낸다. 아울러 각종 기공식 발파시에도 예술적 기능과 웅장함을 가미하여 그 화려함을 극치에 다다르게 한다. 그외에도 로켓트 발사추진제등의 우주 개발에의 응용, 석유시추등 해양개발에의 응용, 각종 공학 실험연구에의 응용, 폭발 가공에의 응용, 의학에의 응용, 철강산업에의 응용 등으로 그 숫자를 이제는 일일이 나열하기 힘들 정도로 광범위해졌다.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.615-620
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• 1997

Further to static test on aged RC bridge slabs strengthened with TYFO glassfibers, fatigue tests have been done on aged RC bridge slabs with and without glassfibers. It can be seen from the test that fatigue behaviors of aged RC bridge slabs stiffened with TYFO glassfibers have been by and large improved comparing with those of aged RC bridge slabs without TYFO, but fatigue failure modes have not been changed become of bonding failure between tensile reinforcements and concrete. It is in particular noted from the test that bonding failure between concrete surface and TYFO have been observed. Further tests are strongly necessiated to develop appropriate anchoring method for improving fatigue life of aged RC bridge slabs strengthened with TYFO glassfibers.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.621-626
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• 1997

Recently, TYFO glassfibers have been used for strengthening n aged RC bridge slabs because of low material cost and easy repairing work. The purpose of this study is to experimentally and analytically investigate the effect of TYFO glassfibers for enhancing the capacity of aged RC bridge slabs. Tes result shows that yield and ultimate strength of RC slabs with TYFO are increased as 11~18% and 25~35% comparing with those for RC slabs without TYFO, respectively, Also, ductility of RC slabs strengthened with TYFO have been significantly increased. Further tests have been performing on aged RC bridge slabs strengthened with carbon fiber strips.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.3
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• pp.194-204
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• 1998

This study was performed to suggest the proper maintenance method for the deteriorated gerber type PC box girder bridge by using the long term displacement monitoring data. For this study, the monitoring system which can measure the long term displacement and the concrete surface temperature was designed and operated. From the measurement and structural analysis results, the cause of the permanent deformation which the bridge has already was estimated, and based on this result, the allowable permanent displacement value at the hinge was suggested. From this study, it was known that the long term monitoring system can be applied to the active maintenance of the deteriorated bridge and the suggested allowable permanent displacement could be used for the maintenance of the bridge.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.206-216
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• 2020

As the number of aging railway bridges in Korea increases, maintenance costs due to aging are increasing and continuous management is becoming more important. However, while the number of old facilities to be managed increases, there is a shortage of professional personnel capable of inspecting and diagnosing these old facilities. To solve these problems, this study presents an improved model that can detect Local damage to structures using machine learning techniques of AI technology. To construct a damage detection machine learning model, an analysis model of the bridge was set by referring to the design drawing of a non-ballasted plate-girder railroad bridge. Static strain data according to the damage scenario was extracted with the analysis model, and the Local damage index based on the reliability of the bridge was presented using statistical techniques. Damage was performed in a three-step process of identifying the damage existence, the damage location, and the damage severity. In the estimation of the damage severity, a linear regression model was additionally considered to detect random damage. Finally, the random damage location was estimated and verified using a machine learning-based damage detection classification learning model and a regression model.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.352-358
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• 2005

For non-destructive testing of concrete structures, time and frequency domain method were applied to detect cavity in underground model and pier model. To interpret the measured data, time domain method made use of tomography which was completed with first arrivaltime and inversion method. In this steady, frequency domain method using Fourier transform was tried. Maximum frequency in the frequency domain was analyzed to calculate location of cavity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.86-93
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• 2023

A bridge health monitoring technology is under development for the safety management of aged bridges. The bridge health monitoring technology has been developed mainly for single bridge management at a large scale, so it uses wire-based systems for power supply and data transfer. However, the wire-based systems need to be improved for the sporadically distributed small-sized bridges on local roads. This study proposed a wireless structural health monitoring system for small-sized bridges. The proposed monitoring system overcomes the limitations of wired systems by providing wireless power through solar power and utilizing LTE technology to transmit measurement data. In addition, a remote control system and power management plan were proposed to ensure the stability of the bridge measurement system. The proposed measurement system was installed on 32 bridges on fields and verified the operability by collecting 80.6% of measurement data for one year. The proposed system can support the health monitoring of aged bridges on local roads.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.355-363
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• 2023

In safety assessment of a aged bridge, dynamic characteristics and displacement are directly related to the rigidity of the structural system, especially displacement is the most important factor as the physical quantity that the bridge user can directly detect. However, in order to measure the displacement of the bridge, it is difficult to install displacement sensors at the bottom of the bridge and conduct traffic blocking and loading tests, resulting in increased costs or impossible measurements depending on the bridge's environment. In this study, a method of measuring the displacement of a bridge using only accelerometers without installing displacement sensors and ambient vibration without a loading test was proposed. For the analysis of bridge dynamic characteristics and displacement using ambient vibration, the mode shape and natural frequency of the bridge were extracted using a TDD technique known to enable quick analysis with simple calculations, and the unit load displacement of the bridge was analyzed through flexibility analysis to calculate static displacement. To verify this proposed technology, an on-site test was conducted on C Bridge, and the results were compared with the measured values of the loading test and the structural analysis data. As a result, it was confirmed that the mode shape and natural frequency were 0.42 to 1.13 % error ratio, and the maximum displacement at the main span was 3.58 % error ratio. Therefore, the proposed technology can be used as a basis data for indirectly determine the safety of the bridge by comparing the amount of displacement compared to the design and analysis values by estimating the displacement of the bridge that could not be measured due to the difficulty of installing displacement sensors.