• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.225-232
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• 2008

The object of this paper is to study the flexural strengthening effectiveness on the construction method of bonding of the FRP. The existing FRP flexural strengthening methods were divided into FRP sheet strengthening and FRP plate strengthening according to the FRP condition. For improving the existing construction method, this paper proposed the velcro type anchorage system for temporary bonding material, and flexural strengthening effects were tested. Test variables were bonding methods of the FRP strengthening materials, and total 4 specimens were tested. Following to the test results, it is shown that FRP-plate strengthening method using the velcro can get better workability than existing construction methods, and have excellent strengthening performance including flexural strength, stiffness, ductility and failure aspect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.84-92
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• 2008

This study is to investigate the flexural performance of Near Surface Mounted (NSM) strengthening method using Fiber reinforced Polymer (FRP) materials to concrete structures. For this study, the inverse-shaped trapezoid CFRP composite material which has been registered as New Excellent Technology (NET) 351 was adopted to the concrete structure. In this study, two types of the CFRP types were considered; Type A ($15{\times}13{\times}6mm$) and Type B ($4{\times}3{\times}10mm$) with different strengthening ratio. In the result of the test, it was proved that NSM strengthened specimens had more flexural performance of 20-100% than that of the unstrengthened specimen. With this test result, the structural efficiency was investigated based on the coefficient of ductility and coefficient of crack resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.151-159
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• 2015

In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (CFRP sheet, AFRP sheet, embedded CFRP rod) in existing reinforced concrete structure. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens LBCJ-CRUS, designed by the retrofitting of CFRP Rod and CFRP Sheet in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.54 times and its energy dissipation capacity by 2.36 times in comparison with standard specimen LBCJ for a displacement ductility of 4 and 7. And Specimens LBCJ-CS, LBCJ-AF series were increased its energy dissipation capacity each by 2.04~2.34, 1.63~3.02 times in comparison with standard specimen LBCJ for a displacement ductility of 7.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.451-458
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• 2004

This study describes the basic concept and the applicability of Hybrid Reinforcement System using conventional steel reinforcing bars and Fiber Reinforced Polymer bars. The concrete bridge decks are assumed to be supported by beams and reinforced with two layers of reinforcing bars. In concrete bridge deck using HRS, the top tensile force for negative moment zone on beam supports is assumed to be resisted by FRP reinforcing bars, and the bottom tensile force for positive moment zone in the middle of hem supports is assumed to be resisted by conventional steel reinforcing bars, respectively. The FRP reinforcing bars are non-corrosive. Thus, the steel reinforcement is as far away as possible from the top surface of the deck and protected from intrusion of corrosive agent. HRS concrete bridge deck has sufficient ductility at ultimate state as the following reasons; 1) FRP bars have lower elastic modulus and higher ultimate strain than steel re-bars have, 2) FRP bars have lower ultimate strain if provided higher reinforcement ratio, 3) ultimate strain of FRP bars can be reduced if FRP bars are unbonded. Test results showed that FRP and HRS concrete slabs are not failed by FRP bar rupture, but failed by concrete compression in the range of ordinary reinforcement ratio. Therefore, in continuous concrete bridge deck using HRS, steel reinforcing bars for positive moment yield and form plastic hinge first and compressive concrete fail in the bottom of supports or in the top of the middle of supports last. Thus, bridge deck consumes significant inelastic strain energy before its failure.

• The Journal of the Acoustical Society of Korea
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• v.33 no.3
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• pp.191-199
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• 2014

Wave reflection and transmission characteristics in waveguides are an important issue in many engineering applications. A combined spectral element and finite element (SE/FE) method is used to investigate the effects of local non-uniformities but limited at relatively low frequencies because the SE is formulated by using a beam theory. For higher frequency applications, a method named a combined spectral super element and finite element (SSE/FE) method was presented recently, replacing spectral elements with spectral super elements. This SSE/FE approach requires a long computing time due to the coupling of SSE and FE matrices. If a local non-uniformity has a uniform cross-section along its short length, the FE part could be further replaced by SSE, which improves performance of the combined SSE/FE method in terms of the modeling effort and computing time. In this paper SSEs are combined to investigate the characteristics of waves propagating along waveguides possessing geometric non-uniformities. Two models are regarded: a rail with a local defect and a periodically ribbed plate. In the case of the rail example, firstly, the results predicted by a combined SSE/FE method are compared with those from the combined SSEs in order to justify that the combined SSEs work properly. Then the SSEs are applied to a ribbed plate which has periodically repeated non-uniformities along its length. For the ribbed plate, the propagation characteristics are investigated in terms of the propagation constant.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.23-31
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• 2007

Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.

• Journal of the Society of Disaster Information
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• v.20 no.3
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• pp.549-562
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• 2024

Purpose: In this study, numerical analysis was conducted to verify the vibration reduction effect of installing vibration barriers under various installation conditions to mitigate train-induced vibrations from the GTX. Method: To identify the factors influencing vibration reduction among the installation conditions, the stiffness ratio of the filling material and the installation depth of the barrier were varied. Result: The study results indicated that using ductile filling materials provided superior vibration reduction compared to hard filling materials. The vibration reduction effect was found to be more significant when the stiffness ratio between the ground and the filling material was closer to zero. Additionally, the deeper the installation depth of the barrier, the better the vibration reduction effect. Conversely, if the barrier was installed too shallowly, vibration at the measurement point was amplified. Conclusion: The optimal installation condition for vibration reduction was found to be a stiffness ratio of 0.08 and an installation depth of 15 meters, resulting in a vibration reduction rate of 60.34% at a measurement point 10 meters away from the vibration source.

• The Journal of the Petrological Society of Korea
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• v.6 no.3
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• pp.244-244
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• 1997

The Janggunbong area(this study area) at the central-south part in the North Sobaegsan Massif, Korea, consists mainly of Precambrian(Wonnam and Yulri Formations)-Paleozoic [Joseon Supergroup(Jangsan Quarzite, Dueumri Formation and Janggum Limestone) and Pyeongan Group(Jaesan and Dongsugok Formations)] metasedimentary rocks and Mesozoic granitoid(Chunyang granite.) This study is to interpret geological structure of the North Sobaegsan Massif in the Jang-gunbong area by analysing rock-structure and microstructure of the constituent rocks. It indicates that its geological structure was formed at least by four phases of deformation after the formation of gneissosity(S0) in the Wonnam Formation and bedding plane(S0) in the Paleozoic metasedimentary rocks. The first phase deformation(D1) formed tight isoclinal fold(F1). Its axial plane(S1) strikes east-west and steeply dips north. Its axis (L1) subhorizontally plunges east-west. The second phase deformation(D2), which was related to ductile shear deformation, formed stretching lineation(L2) and shear foliation(S2). The sense of the shear movement indicates dextral strike-slip shearing(top-to-the east shearing). The third phase deformation(D3) formed open inclined fold(F3). Its axial plane(S3) strikes east-west and moderately or gently dips north. Its axis(L3) subhorizontally plunges east-west. The F3 fold reoriented the original north-dipping S1 foliation and D2 shear sense into south-dipping S1 foliation(top-to-the west shear sense on this foliation) at its a limb. The four phase of deformation(D4) formed asymmetric-type open inclined fold(F4) of NE-vergence with NW striking axial plane(S4) and NW-NNW plunging axis(L4). The F4 fold partly reoriented pre-D4 structural elements with east-west trend into those with north-south trend. Such reorientation is recognized mainly in the Paleozoic metasedimentary rocks.

• The Journal of the Petrological Society of Korea
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• v.6 no.3
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• pp.224-259
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• 1997

The Janggunbong area(this study area) at the central-south part in the North Sobaegsan Massif, Korea, consists mainly of Precambrian(Wonnam and Yulri Formations)-Paleozoic [Joseon Supergroupuangsan Quarzite, Dueumri Formation and Janggun Limestone) and Pyeongan Group (Jaesan and Dongsugok Formations)l metasedimentary rocks and Mesozoic granitoid(Chunyang granite). This study is to interpret geological structure of the North Sobaegsan Massif in the Janggunbong area by analysing rock-structure and microstructure of the constituent rocks. It indicates that its geological structure was formed at least by four phases of deformation after the formation of gneissosity(S0) in the Wonnam Formation and bedding plane(S0) in the Paleozoic metasedimentary rocks. The first phase deformation(D1) formed tight isoclinal fold(F1). Its axial plane(S1) strikes east-west and steeply dips north. Its axis(L1) subhorizontally plunges east-west. The second phase deformation(D2), which was related to ductile shear deformation, formed stretching lineation(L2) and shear foliation(S2). The sense of the shear movement indicates dextral strike-slip shearing(topto-the east shearing). The third phase deformation(D3) formed open inclined fold(F3). Its axial plane(S3) strikes east-west and moderately or gently dips north. Its axis(L3) subhorizontally plunges east-west. The F3 fold reoriented the original north-dipping S1 foliation and D2 shear sense into south-dipping S1 foliation(top-to-the west shear sense on this foliation) at its a limb. The four phase of deformation(D4) formed asymmetric-type open inclined fold(F4) of NE-vergence with NW striking axial plane(%) and NW-NNW plunging axis(L4). The F4 fold partly reoriented pre-D4 structural elements with east-west trend into those with north-south trend. Such reorientaion is recognized mainly in the Paleozoic metasedimentary rocks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.95-98
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• 1991

회전 기기의 이상으로 인하여 발생하는 진동은 축 회전속도의 고주파 성분 (super-harmonic)이나 또는 분수조파 성분(sub-harmonic)으로 나타나는 경 우가 대부분이기 때문에 회전기기의 진동을 주파수 영역에서 해석함에 있어 파워 스펙트럼의 주파수 축을 Hz로 나타내기보다는 축 회전속도의 order로 써 나타내는 것이 매우 유용하다. 스펙트럼을 order로써 나타내기 위해서는 샘플링 시간을 축 회전속도와 동기(synchronization)시켜야 하는데 이 방법으 로는 회전축에 엔코더(encorder)를 부착하여 엔코더에서 발생하는 펄스 신호 를 이용하여 샘플링하는 방법과 order tracking 필터를 이용하는 방법이 있 다. 그러나 전자의 방법은 원하는 회전축마다 엔코더를 부착하여야 하며 경 우에 따라서는 엔코더를 부착하기가 어려운 경우도 있으며, 회전기기의 운전 개시나 종료시처럼 회전속도가 급격히 변화하는 경우에는 낮은 주파수에서 중첩(aliasig)에 의한 오차가 수반될 수도 있다. 후자의 방법은 order tracking 필터 이외에도 여러 부수장비가 필요하며 기준 주파수(즉 회전속 도)가 급격히 변화하는 경우 PLL(phase locked loop)에서 tracking 오차가 발생된다. 최근에 발표된 논문에서 일정한 시간간격으로 샘플링한 데이터들 로부터 신호를 재합성하여 회전축의 속도와 동기가 되도록 재 샘플링함으로 서 스펙트럼의 주파수를 회전속도의 order로써 나타내는 방법을 제시하였다. 그러나 위 논문에서는 신호의 재합성에 필요한 재합성 필터(reconstruction filter)의 설계 방법에 대하여 구체적인 언급이 없이 다만 결과만을 논하였다. 따라서 본 논문에서는 재합성 필터의 설계 방법에 대하여 구체적인 방법을 제시하고 또한 동기화 샘플링의 장점 및 고려 사항에 대하여 고찰하였다. 고려한 능동 소음제어 에 대해 연구하였다. 경량화 추세에 따라 지반이나 케이싱이 경량이거나 유연하여 회전축과 동적으로 연성된 경우 회전축-베어링-지반으로 이루어진 2중구조의 회전축 계 동특성을 해석할 수 있는 프로그램을 개발하므로서 회전 기계류의 진동 전반에 걸친 문제점에 대한 그 원인과 현상을 명확히 분석하여 국내의 전기 계류의 보다 신뢰성있는 설계 및 제작자료를 확보하는데 기여할 수 있게 하 였다.존의 small molecular Gd-chelate에 비해 매우 큼을 알 수 있었다. MnPC는 간세포에 흡수된 후 담도계로 배출되는 간특이성 조영제임을 확인하였다. 장비 내에서 반복 시행한 평균값의 차이는 대체적으로 유의한 차이가 없었으나, 다른 장비에서 반복 시행한 장비간의 사이에는 유의한 차이가 있는 경우가 더 많았다. 따라서 , MRS 검사를 소뇌나 뇌교의 어떤 절환에 적용하기 전에 각 장비 마다 정상 기준치를 반드시 얻은 후에 이상여부를 판 정하는 것이 필수적이라고 생각된다.EX> 이상이 적절한 진단기준으로 생각되었다. $0.4{\;}\textrm{cm}^3$ 이상의 좌우 부피차를 보이는 모든 증례에서 육안적으로도 해마위축이 뚜렷이 나타났다. 결론 : MR영상을 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The re