• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.67-73
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• 2003

The present seismic analysis of Road-Bridge Design Standard is on a basis of load-based analysis which lets structures have the strength over load. In this study, the capacity spectrum method, a kind of displacement based method, which is evaluated by displacement of structure, is presented as an alternative to the analysis method based on load. Seismic capacity is performed about the existing reinforced concrete pier which has already secured seismic design by capacity spectrum method. As a result. capacity spectrum method could realistically evaluate the non-elastic behavior of structures easily and quickly and the displacement of structures for variable ground motion level. And it could efficiently apply to an evaluation of seismic capacity about the existing structure and a verification of design for capacity target of the new structure.

• Journal of the Korean Society of Safety
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• v.30 no.6
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• pp.70-77
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• 2015

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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.139-149
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• 2000

In the preliminary design stage of prestressed concrete (PSC) box girder bridges, the design factors decided by inexperience designer could heavily affect to the results of final design. There is a possibility that the design ends up with an excessively wasteful design. To achieve an economical design with preventing an excessive design, the optimal design technique has been developed using ADS optimal program and SPCFRAME in this study. The objective function for the optimal design problem is the material cost of box girders and constrained functions are constituted with design specifications and workability. The Sequential Unconstraint Minimization Technique (SUMT) is used for the optimal design in this study. We designed an uniform cross-section bridge and an ununiform cross-section bridge in the same design condition by optimal design technique developed in this study. Analyzing the results obtained for various tendon layouts, we suggest a standard tendon layout which gives the most effective structural behavior.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.503-512
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• 2002

Generally, the girder spacing of the two-girder composite bridge is from 5m up to 15m. To ensure the structural safety according to Korean Bridge Design Specification, the deck depth should be from 33 cm upto 73 cm. Using the transversal prestressing strands in concrete deck, we can reduce its depth about 10％. However, there is little experience on the design and construction of prestressed concrete(PSC) decks in Korea. This paper focuses on the behaviors of PSC deck. A literature survey is performed widely. Considering the characteristics of the two-girder bridge and the construction conditions in Korea, a cast-in-place PSC deck is recommended for the two-girder bridge with 6m girder spacing. To examine its structural behaviors and safety, three partial model deck specimens(3 m$\times$5 m) with real scale are fabricated md tested. One(PS34-RS) is 34cm depth with the stiffness restraint in longitudinal edges for simulating the real bridge deck. Another(PS34-NS) is same depth without the stiffness restraint, and the other(PS28-NS) is 28cm depth with the stiffness restraint. Under the static patch loading, each specimen had a larger ultimate flexural strength than the design value. Specimens with the stiffness restraint (PS34-RS and PS28-RS) showed the punching shear failure mode and specimen without that(PS34-NS) showed the flexural failure mode.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.201-209
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• 2010

Generally, PSC girder bridge uses total gross cross section to resist applied loads unlike reinforced concrete member. Also, it is used as short and middle span (less than 30 m) bridges due to advantages such as ease of design and construction, reduction of cost, and convenience of maintenance. But, due to recent increased public interests for environmental friendly and appearance appealing bridges all over the world, the demands for longer span bridges have been continuously increasing. This trend is shown not only in ordinary long span bridge types such as cable supported bridges but also in PSC girder bridges. In order to meet the increasing demands for new type of long span bridges, PSC hollow box girder with H-type steel as compression reinforcements is developed for bridge with a single span of more than 50 m. The developed PSC girder applies compressive prestressing at H-type compression reinforcements using unbonded PS tendon. The purpose of compressive prestressing is to recover plastic displacement of PSC girder after long term service by releasing the prestressing. The static test composed of 4 different stages in 3-point bending test is performed to verify safety of the bridge. First stage loading is applied until tensile cracks form. Then in second stage, the load is removed and the girder is unloaded. In third stage, after removal of loading, recovery of remaining plastic deformation is verified as the compressive prestressing is removed at H-type reinforcements. Then, in fourth stage, loading is continued until the girder fails. The experimental results showed that the first crack occurs at 1,615 kN with a corresponding displacement of 187.0 mm. The introduction of the additional compressive stress in the lower part of the girder from the removal of unbonded compressive prestressing of the H-type steel showed a capacity improvement of about 60% (7.7 mm) recovery of the residual deformation (18.7 mm) that occurred from load increase. By using prestressed H-type steel as compression reinforcements in the upper part of cross section, repair and rehabilitation of PSC girders are relatively easy, and the cost of maintenance is expected to decrease.

• Journal of Korean Society of societal Security
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• v.2 no.2
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• pp.63-68
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• 2009

Seismic design of newly built bridges can be considered and carried out during construction process according to the revised road bridge design standard issued recently. While for the existing reinforced concrete bridge priers under service before new standard implements, their resistance capacity against lateral seismic loading is inferior. In this research, seismic reinforcing for existing bridge piers by nickel-chrome alloy bar has been analyzed. Based on the established model by MIDAS program, the behaviors of bridge piers including deformation and stress with and without nickel-chrome alloy reinforcing bars have been compared and discussed under lateral seismic loading. And the advantages of using nickel-chrome alloy bar as seismic reinforcement over other materials, such as good performance, good economy etc. have been demonstrated by comparison with other researches. Also the anti-seismic efficiency of nickel-chrome alloy reinforcing bars has been confirmed by MIDAS modeling analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.451-457
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• 2014

Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.389-398
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• 2010

The flexural strength of composite HSB I-girders under a positive moment was investigated using the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specifications to such girders. A total of 2,391 composite I-girder sections that satisfied the section proportion limits of the AASHTO LRFD specifications was generated by the random sampling technique to consider a wide range of section properties. The flexural capacities of the sections were calculated inthe nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels were modeled as an elasto-plastic strain-hardening material, and the concrete, as a CEB-FIP model. The effects of the ductility ratio and the compressive strength of the concrete slab on the flexural strength of the composite girders made of HSB and SM520-TMC steels were analyzed. The numerical results indicated that the current AASHTO LRFD equation can be used to calculate the flexural strength of composite girders made of HSB600 steel. In contrast, the current AASHTO LRFD equation was found to be non-conservative in its prediction of the flexural strength of composite HSB800 girders. Based on the numerical results of this study for 2,391 girders, a new design equation for the flexural strength of composite HSB800 girders in a positive moment was proposed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.369-376
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• 2016

In this study, a numerical analysis framework for investigating the nonlinear behavior of structures under fire conditions is presented. In particular, analysis procedure combining fire-driven flow simulation and thermo-mechanical analysis is discussed to investigate the mechanical behavior of fire-exposed representative volume structures made of steel and concrete, respectively. First of all, fire-driven flow analysis is conducted using Fire Dynamics Simulator(FDS) in a rectangular parallelepiped domain containing the structure. The FDS simulation yields the time history of temperature on the surface of the structure under fire conditions. Second, mechanical responses of the fire-exposed structure with respect to prescribed uniformly distributed loads are calculated by a coupled thermo-mechanical analysis using the time-varying surface temperature as boundary conditions. Material nonlinearities of steel and concrete have been considered in the thermo-mechanical analysis. A series of numerical results are presented to demonstrate the feasibility of the multiphysics structural fire analysis for investigating the structural behavior under fire conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.40-45
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• 1993

일반적으로 건물 구조물에 전달되는 기계진동을 감소시키기 위해서 기계와 기초사이에 유연한 방진소자를 삽입하여 기계가진력(exciting force)의 전달 률을 줄인다. 또한 구조물의 고유진동수와 진동원의 가진주파수가 일치할 경 우, 가진주파수를 변화시키거나, 구조물의 동특성을 변화시키는 방법을 사용 한다. 어떠한 방안을 선택하든 효과적이고 정량적인 방진 시스템을 구성하고 구조물의 정확한 진동상태를 예측하기 위해서는 진동원의 가진특성과 구조 물의 동특성에 대한 정보가 요구된다. 일반적으로 방진설계를 위해 필요한 진동원의 가진특성은 제조회사의 사양이나 측정을 통하여 비교적 쉽게 얻을 수 있다. 복합재료, 다양한 경계조건, 복잡한 대형구조물등은 수치해석을 이 용하여 해석적인 방법으로 동특성을 구할 경우, 신뢰성 있는 정보를 얻기에 는 많은 노력이 요구된다. 더우기 현장에서 발생하는 진동문제는 대부분 복 잡하고 시간적으로 시급히 해결해야 하기 때문에 효율적인 절차를 구성하여 구조물의 동특성을 해석하는 방법을 사용할 필요가 있다. 구조물의 동특성은 실험적인 방법을 통하여 구하고 그 외의 필요한 계산들은 해석을 통하여 얻 는 것이 효율적일 수 있다. 실험적 동특성해석은 입력하중에 대한 응답의 크 기와 위상 비를 주파수별로 나타내는 전달함수를 측정하는 방법으로서 가진 장치 및 여러 측정/분석 장비가 필요하며, 철교, 교량, 건물의 철골 및 콘크 리트 슬라브등 다양한 중대형의 구조물을 Signal/Noise비가 좋도록 가진 시 켜야 할 필요성이 있다. 본 연구에서는 이러한 실험적 방법의 현장 적응성과 신뢰성을 확보하기 위해 대형충격기(large impact hammer, max, peak force 약 10000N, time duration 약 20ms)를 제작하고 실험/분석 시스템 및 구조물 의 진동제어를 위한 절차를 Fig.1과 같이 구성하고 이를 철근콘크리트 건물 에 설치한 기계식 주차설비의 진동제어에 적용하였다.force response simulation)를 수행하여 임의의 좌표 공간에 대한 진동수준을 해석적으로 예측할 뿐만 아니라 구조물의 진동제어 를 위한 동적인자를 변경시킬 수 있는 정보를 제공하며 장비를 방진할 경우 신뢰성 있는 전달률을 결정할 수 있다. 실험적으로 철교, 교량이나 건물의 철골구조 및 2층 바닥 등 대,중형의 복잡한 구조물에 대항 동특성을 나타내 는 모빌리티를 결정할 경우 충격 가진 실험이 사용되는 실험장비 측면에서 나 실험을 수행하는 과정이 대체적으로 간편하다. 그러나 이 경우 대상 구조 물을 충분히 가진시킬수 있는 용량의 대형 충격기(large impact hammer)가 필요하게 된다. 이러한 동적실험은 약 길이 61m, 폭 16m의 4경간 교량에 대 하여 동적실험을 수행하여 가능성을 확인하였다. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 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 results shows a fluences on both inflection field and the maximum relaxivity value. The results shows