• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3280-3286
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• 2011

In recent years, many efforts have steadily been allocated to develop a new deck system in terms of its materials and structures in order to make up for the shortcomings of reinforced concrete deck. This study implemented and analyzed the verification for concrete composite beam with perfobond FRP as a permanent formwork and the tensile reinforcement, using non-linear finite element analysis program. Approximately 8-15% difference of ultimate failure load between numerical and experimental results were found and showed a similar figure of strain distribution in failure state.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.677-685
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• 2015

In a will to subdue the brittleness as well as the low tensile and flexural strengths of ordinary concrete, researches are being actively watched worldwide on steel fiber-reinforced Ultra High Performance Concrete (UHPC) obtained by admixing steel fibers in ultra high strength concrete. For the purpose of maximizing advantage of UHPC, this study removes the upper flange of the steel girder to apply an inverted T-shape girder for the formation of the composite beam. This paper intends to evaluate the behavior of the shear connectors and the flexural characteristics of the composite beam made of the inverted T-shape girder and UHPC slab using 16 specimens considering the compressive strength of concrete, the mixing ratio of steel fiber, the spacing of shear connectors and the thickness of the slab as variables. In view of the test results, it seemed that the appropriate stud spacing should range between 100 mm and 2 or 4 times the thickness of the slab. Moreover, the relative displacement observed in the specimens showed that ductile behavior was secured to a certain extent with reference to the criteria for ductile behavior suggested in Eurocode-4. The specimens with large stud spacing exhibited larger values than given by the design formula and revealed that the shear connectors developed larger ultimate strength than predicted owing to the action of UHPC and steel after non-composite behavior. Besides, the specimens with narrow stud spacing failed suddenly through compression at the upper chord of UHPC before reaching the full capacity of the shear connectors.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.182-182
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• 2011

현재 국내에서 PSC 거더의 제작은 주로 포스트텐션방식을 사용하고 있다. 포스트텐션방식은 콘크리트 양생 후 긴장력을 도입하여 제작회전율이 높은 특성을 가지나 쉬스, 그라우팅, 정착장치 등이 요구되어 조립과정이 복잡하고 제작단가가 높다. 교량에 적용되는 PSC 거더를 포스트텐션방식 대신에 프리텐션방식으로 제작한다면 제작단가를 대폭 감소시킬 수 있을 것이나, 교량용 PSC 거더의 길이가 일반적으로 30~50m이므로 공장에서 제작하여 현장으로 운반하는 것은 운반비용의 상승 및 운반 가능한 크기의 제한을 받게 된다. 운반의 문제를 해결하기 위해서는 현장에서 PSC 거더를 제작하여야 하는데 현장에 긴장대를 고정식으로 설치하는 것은 제작단가의 상승으로 이어져 경제성을 잃게 된다. 따라서 현장에서 사용할 수 있도록 이동식 긴장대를 제작한다면 경제성을 갖춘 프리텐션방식의 PSC 거더 생산이 가능할 것이다. 50m급 이동식 긴장대에는 약 10MN에 이르는 매우 큰 긴장력이 가해져 이동식 긴장대가 콘크리트 양생전까지 이 긴장력을 저항하여야 한다. 본 논문에서는 유한요소 해석프로그램인 ABAQUS를 사용하여 50m급 PSC 거더를 생산할 수 있는 이동식 긴장대를 모델링하여 약 10MN에 이르는 긴장력이 가해질 때에 이동식 긴장대의 각 구성요소의 거동특성 및 하중에 대한 안전성 및 좌굴에 대한 안정성 확보 여부를 해석적으로 파악하고자 한다. 이동식 긴장대는 구성요소인 정착블럭(긴장BOX)과 중간연결블럭으로 나누어 모델링하였다. 정착블럭(긴장BOX)은 다수의 강판을 4절점 쉘요소(S4R)를 사용하여 직육면체의 BOX 형상에 내부를 보강한 단면으로 구성하였고, 중간연결블럭은 H형강 2개를 일체화한 긴장대 거더와 콘크리트 바닥판 블록이 볼트로 합성된 구조이며, H형강은 4절점 쉘요소(S4R), 바닥판블럭은 8절점솔리드요소(C3D8R)를 사용하였다. 긴장대거더와 바닥판블럭은 합성거동을 하도록 weld option을 사용하여 부분적으로 결합하였다. 정적해석결과 이동식 긴장대에 발생하는 응력은 도로교 설계기준에 SS400 강재의 허용응력 140MPa 보다 작으며 선형탄성좌굴 해석결과 가력하중의 2.22배 약 21MN의 하중이 가력되어야 전체좌굴이 발생하게 될 것으로 추정된다. 해석결과를 보아 50m급 PSC 거더를 생산할 수 있는 이동식 긴장대는 하중에 대한 안전성 및 좌굴에 대한 안정성을 확보하고 있는 것으로 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.139-148
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• 2008

The direct inspection of the outward aspects by field engineers is the important and critical part for structural safety assessment according to the related reports. This study presents an improved method of the state assessment for concrete floor slab by separating and evaluating the individual damage types. First, the various types of damage symptoms are separated, which have been included and dealt in a group. Secondly, they are weighted and scored independently based on the present guide and references. Overall procedures other than the above are retained as same as possible to avoid the confusion. The proposed method is applied and tested to a performed assessment project for a bridge for validation. The result shows that it is reasonable and applicable in respect that it is able to make up for the controversial points of the present guide revealed in practices. Careful check of excessively deteriorated parts in addition to the reasonable assessment of system by this method grants the structural repair and reinforcement propriety and economy, and assures of more safety. Twofold appraisal of this approach expands the applicable areas of value engineering to the structural maintenance.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.25-36
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• 2017

In the 1994 Northridge earthquake, connection damage initiated from the beam bottom flange was prevalent. The presence of a concrete slab and resulting composite action was speculated as one of the critical causes of the prevalent bottom flange fracture. In this study, four seismic retrofit schemes are proposed in order to salvage welded steel moment connections with composite floor slabs in existing steel moment frames. Because top flange modification of existing beams is not feasible due to the presence of a concrete floor slab, three schemes of bottom flange modification by using welded triangular or straight haunches or RBS(reduced beam section), and beam web strengthening by attaching heavy shear tab were cyclically tested and analyzed. Test results of this study show that haunch and web-strengthened specimens can eliminate the detrimental effect caused by composite action and ensure excellent connection plastic rotation exceeding 5% rad. Design recommendations for each retrofit scheme together with supplemental numerical studies are also presented.

• Korean Architects
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• no.8 s.388
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• pp.85-91
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• 2001

10년도 넘었을까 모처럼 유럽을 여행할 기회가 있었다. 우리나라는 온 국토가 공사장이나 진배없던 시절이라 그곳의 풍경이 오히려 이채로웠다. 자동차를 타고 한참을 가야 그것도 별로 크지 않은 공사장을 볼 수 있었고, 그나마 신축공사 보다는 오래된 건물을 보수하는 것들이 더 많았다. 더구나 희한한 것은 대로에 면한 고색 창연한 건물의 외벽만을 텔레비전 세트처럼 남겨두고 그 뒤편에서는 전혀 새로운 공사를 하는 것도 눈에 들어왔다. 조상들의 유적을 외관만이라도 보존하도록 법제화되었으므로 여기저기 떨어져 위치한 100년도 넘은 집에다 따로따로 최신형 공작기계를 설치한 공장에서 제품을 생산하는 비능률을 감수하는 것도 볼 수 있었다. 물론 변두리 신시가지에서는 현대 감각이 물씬한 건물도 신축하고 있었는데, 대체로 리모델링 사업규모가 전체 건축 물량의 50% 정도는 될 것이라는 설명이었다. 필자는 그때 우리도 머지 않아 그런 시절이 도래할 것이라는 확신이 있었다. 더구나 그들의 건물들이 100년 이상을 버티는데 반하여 우리네 것들은 수명이 고작 20~30년 밖에 되지 못할 정도로 부실하기 때문이다. 그때부터 기존 건물의 내력 부족분을 보완하고 용도를 변경하거나 증축을 할 때 어떤 방법이 합리적일까 하는 것에 관심을 가지고 연구하게 되었다. 바닥 슬래브나 보를 잘라버리거나 새로 덧붙이기도 하고 심하면 기둥을 솎아낼 필요가 있을 수도 있다. 그러나 유감스럽게도 대부분의 경우는 그동안 열심히 고안한 방식을 실무현장에 적용할 수 있도록 받아들이는 당사자가 별로 없었다. 첫째 이유는 처음하는 일이라 말하자면 겁이 난다는 것이고, 둘째로는 새로운 방식을 믿고 시행하려 해도 실제로 책임지고 시공하겠다고 나서는 업체를 만날 수 없어서였다. 그래서 그동안 설계뿐만 아니라 시공까지 일일이 간섭하여 어렵게 시행했던 현장 경험들을 소개하여 앞으로 비슷한 조건을 만날 경우 참고할 수 있게 한다. 우선 기둥을 솎아 내는 것을 알아보고 앞으로 기둥, 보, 슬래브, 기초 등의 새로운 보강방법을 소개하고자 한다.

• Journal of Korean Society of Steel Construction
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• v.26 no.5
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• pp.385-396
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• 2014

Traditionally, domestic steel design and construction practice has provided extra shear studs to moment frame beams even when they are designed as non-composite beams. In the 1994 Northridge earthquake, connection damage initiated from the beam bottom flange side was prevalent. The upward moving of the neutral axis due to the composite action between steel beam and floor deck was speculated to be one of the critical causes. In this study, full-scale seismic testing was conducted to investigate the side effects of the composite action in steel seismic moment frames. The specimen PN700-C, designed following the domestic connection and floor deck details, exhibited significant upward shift of the neutral axis under sagging (or positive) moment, thus producing high strain demand on the bottom flange, and showed a poor seismic performance because of brittle fracture of the beam bottom flange at 3% story drift. The specimen DB700-C, designed by using RBS connection and with the details of minimized floor composite action, exhibited superior seismic performance, without experiencing any fracture or concrete crushing, almost identical to the bare steel counterpart (specimen DB700-NC). The results of this study clearly indicate that the beams and connections in seismic steel moment frames should be constructed to minimize the composite action of a floor deck if possible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1687-1694
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• 2014

Recently FRP of carbon fibers is utilized as a repairing and reinforcing material for concrete structures. In this study, the bond performance between CFRP planks and ductile fiber reinforced cementitious composites was evaluated in order to develop a new system of concrete bridge deck to take advantage of the FRP planks of carbon fiber using as a permanent formwork. In order to strengthen the bonding between the FRP and cast-in-place concrete, an epoxy resin circulated in the market generally was fitted with a silica sand. The bond stress of ordinary concrete appeared in 2.11~5.43MPa and the bond stress of ductile fiber reinforced cementitious composites DC1 (RF4000) and DC2 (PP) respectively were 3.91~5.60MPa, 2.92~5.21MPa and the average bond stress of DC3 (RF4000+RSC15) and DC4 (PP+RSC15) were 4.80~5.58MPa, 5.57~5.89MPa.

• Journal of the Korean GEO-environmental Society
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• v.24 no.8
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• pp.13-20
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• 2023

Tunnelling through the geological anomalies has widely known to have many difficulties such as bottom heave, crack of lining, squeezing and so on. To stabilize the tunnel during the construction or after construction, various reinforcing methods have been introduced and applied such as micropiling at the bottom of tunnel to prevent the bottom heave. In this study, long-term behavior of tunnel in the presence of geological anomalies was predicted using numerical analyses. To this end, material properties for swelling rock model capable of representing the rock swelling behavior was obtained using matching process with measured data to validate the adopted model. After the model validation, simulations were performed to predict the long-term behavior of tunnel in the geological anomalies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.245-253
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• 2021

RC slab bridges account for the largest portion of deteriorated bridges in Korea. However, most RC slabs are not included in the first and second classes of bridges, which are subject to bridge safety management and maintenance. The highest damaged components in highway bridges are the subsidiary facilities including expansion joints and bearings. In particular, leakage through expansion joints causes deterioration and cracks of concrete and exposure of reinforced bars. Therefore, this study analyzed the effect of adhesion damage at expansion joints on the response of the deck in RC slab bridges. When the spacing between the expansion joints at both ends was closely adhered, cracks occurred in the concrete at both ends of the deck due to the resistance rigidity at the expansion joints. Based on the response results, the correlation analysis between displacements in the longitudinal direction of the expansion joint and concrete stress at both ends of the deck for each damage scenario was performed to investigate the effect of the occurrence of damage on the bridge behavior. When expansion joint devices at both sides were damaged, the correlation between displacement and stress showed a low correlation of 0.18 when the vehicles proceeded along all the lanes. Compared with those in the intact state, the deflections of the deck in the damaged case at both sides showed a low correlation of 0.34 to 0.53 while the vehicle passed and 0.17 to 0.43 after the vehicle passed. This means that the occurrence of cracks in the ends of concrete changed the behavior of the deck. Therefore, data-deriven damage detection could be developed to manage the damage to expansion joints that cause damage and deterioration of the deck.