• Steel and Composite Structures
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• 제35권4호
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• pp.509-525
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• 2020

Steel-concrete composite slabs with profiled steel sheeting are widely used in the execution of floors in steel and composite buildings. The rapid construction process, the elimination of conventional replaceable shuttering and the reduction of temporary support are, in general, considered the main advantages of this structural system. In slabs with the spans currently used, the longitudinal shear resistance commonly provided by the embossments along the steel sheet tends to be the governing design mode. This paper presents an innovative reinforcing system that increases the longitudinal shear capacity of composite slabs. The system is constituted by a set of transversal reinforcing bars crossing longitudinal stiffeners executed along the upper flanges of the steel sheet profiles. This type of reinforcement takes advantage of the high bending resistance of the composite slabs and increases the slab's ductility. Two experimental programmes were carried out: a small-scale test programme - to study the resistance provided by the reinforcing system in detail - and a full-scale test programme to test simply supported and continuous composite slabs - to assess the efficacy of the proposed reinforcing system on the global behaviour of the slabs. Based on the results of the small-scale tests, an equation to predict the resistance provided by the proposed reinforcing system was established. The present study concludes that the resistance and the ductility of composite slabs using the reinforcing system proposed here are significantly increased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.201-204
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• 2006

The shear resistance of RC beams is subject to the amount of shear-reinforcing bars ($p_w$) and yield strength ($f_{wy}$) as well as their interactive influence ($p_wf_{wy}$). Thus, it is reasonably expected that high-strength steel bars can greatly reduce the necessary amount of shear-reinforcing bars. On the other hand, although the bond strength is influenced by the amount of shear reinforcing bars, it is not affected by the yield strength. Thus, there is often an issue that bond failure occurs before shear failure depending on the arrangement of shear reinforcing bars. It is a common practice to set sub-ties for the transverse confinement of the main re-bars as a method to prevent the bond failure. However, it can also become a factor in decreased work efficiency due to the complexity of the construction. This study experimented with simultaneous use of high-strength transverse reinforcing bars ($f_{wy}=800MPa$) and U-shaped transverse reinforcing bars of regular strength ($f_{wy}=300MPa$) in an attempt to decrease the necessary quantity of shear reinforcing bars. The effect of this attempt was investigated through fundamental experimental research in terms of the improvement in shear resistance and bond strength as well as the ease of construction.

• 대한치과보철학회지
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• 제44권1호
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• pp.29-39
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• 2006

Statements of problem: Zirconia core is used for posterior fixed partial dentures because it's good mechanical properties. Stress is concentrated on connectors in fixed partial dentures, so the proper design of connector areas is needed for adequate mechanical long-term properties of any prosthesis. The area of connector is critical, but tooth size and surrounding soft tissue limit the connector design. Purpose: The purpose of this study is to compare fracture strengths between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system and determining the optimal connector design satisfying strength and hygiene. Material and method: The following four groups of 40 posterior fixed partial denture specimens(each group 10) were fabricated as followed; group 1 vertical height of connector is 3mm (control group, all groups have the same condition); group 2, lingual vertical 1mm reinforcement on connector; group 3, lingual vertical 2mm reinforcing on connector and group 4, lingual vertical 3mm reinforcing on connector. Specimens were subjected to compressive loading on the central fossa of pontic by instron. SEM was used to identify the initial crack and characterize the fracture mode. Results: The results were as follows: 1. The mean fracture load of the non-lingual reinforcing group was 1212N and the lingual vertical 1mm reinforcing group was 1510N, the lingual vertical 2mm reinforcing group was 1882N, the lingual vertical 3mm reinforcing group was 1980N. 2. The reinforcing groups were statistically significant compared to non-reinforcing groups(P<0.001). 3. There were 2, 3mm reinforcing groups that were statistically significant compared to 1mm reinforcing groups(P<0.001), and the 3mm reinforcing group was not statistically significant compared to 2mm reinforcing groups(P>0.05) 4. Fractures were initiated in gingival embrasures of connectors and processed to the loading site. Conclusion: In this study, lingual reinforcement of connector for improved strength of zirconia based fixed partial denture is nessasary. And long-term study for clinical application is required

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.602-605
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• 2006

Locating reinforcing bars, in particular to know their accurate depths and horizontal distances, is very important in radar inspection of concrete structures. By the way, it is not easy for an accurate depth and horizontal distance estimation of reinforcing bars in concrete structures by the radar test. This problem can be solved by synthetic aperture radar method. To improve the vertical and horizontal resolution of reinforcing bars in concrete, synthetic aperture radar method was examined in this study.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.479-480
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• 2010

콘크리트 구조물의 고성능, 고내구성화를 위해 콘크리트 뿐만 아니라 보강 재료에 대한 성능 향상이 요구되고 있다. 본 연구에서는 고성능의 보강재료를 복합적으로 적용하여 고강도 콘크리트 구조물의 성능 극대화를 도모하는 하이브리드 보강기법에 대한 연구를 수행하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.197-202
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• 1997

Recently the interest in the reinforcing steel corrosion due to the use of sea-sand and deicing salt, marine environment, and carbonation in RC structures is increasing, therefore the studies on the corrosion control of reinforcing steel in concrete are vigorously proceeding. In this study, from the viewpoint of electrochemical process of steel corrosion in concrete we applied the impressed current system among the cathodic protections to reinforcing steel in concrete and ascertained the protection effect by half-cell potential, corrosion rate, and depolarization.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.80-85
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• 1991

This experimental study was performed to derive the relationship between the measured values(corrosion potential) and the actual amount of corrosion products(reinforcing steel weight loss rate). Also the growth of crack due to the steel corrosion was oberved. First, the reinforcing steel of R/C specimen was corroded with chloride penetration and accelerated galvanostatic corrosion method. And then, the corrosion potential of reinforcing steel was measured with nondestructive tester.

• KCI Concrete Journal
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• 제13권2호
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• pp.42-48
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• 2001

The bend resistance of coated reinforcing bar is greatly influenced by both the adhesion strength between bar and coating materials, and the followed transformation of coating material as bars bend. Especially, tearing state or partial microscopic cracks are predicted on the inside and outside of bending angle, because tensile strength and elongation of polymer film are very different according to types of polymer dispersions in bar coating, and these damaged parts are rapidly corroded by penetration of corrosive factors. In this study, polymer cement slurry coated reinforcing bars with various polymer dispersions are prepared by following combined conditions, polymer-cement ratio of 50% and 100%, coating thickness of 250$\mu$m and 450$\mu$m, coating number, curing age of 3, 7, 14 and 28days. Then the specimens are tested for working life and bend resistance at bending angles $90^{\circ}$, $135^{\circ}$and $180^{\circ}$ to observe the microscopic damage effect as the bars bend. Also, epoxy-coated reinforcing bars for control experiment were used with 250$\mu$m of coating thickness. The tensile strength for polymer films is performed. From the test results, the working life of the polymer cement slurry is within 90 seconds. Among four types of polymer dispersion, polymer cement slurry coated reinforcing bar using St/BA-1 emulsion has the excellent bend resistance, which is remarkably improved than that of epoxy-coated reinforcing bar. And the bend resistance is more related to elongation than tensile strength of polymer film. Polymer cement slurry with a polymer-cement ratio of 100%, a coating thickness of $450\mu$m and one coating using St/BA emulsion is selected as a most suitable coating material for coated reinforcing bar.

• 콘크리트학회논문집
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• 제23권5호
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• pp.559-567
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• 2011

효율적인 철근콘크리트 구조물을 설계 시공하기 위하여, 최근 들어 고강도 철근에 대한 연구가 활발히 진행되고 있다. 그러나 고강도 철근은 일반강도 철근에 비하여 연신 능력이 낮은 것이 일반적이므로, 기존의 최소 연신율규격을 만족하지 못할 가능성이 있다. 또한 국내외 철근 규격의 최소 연신율 규정과 표점 거리 규정은 각 규격마다 상이하여, 동일한 철근이라도 적용하는 규격에 따라 적합 여부가 다르게 평가된다. 따라서 각 철근 규격을 비교 검토하고, 국내의 철근 규격 KS D 3504의 규정이 합리적인지 검토할 필요가 있다. 이 연구에서는 한국, 미국, 일본, 유럽, ISO 등 국내외 철근 규격의 최소 연신율 규정과 표점 거리 규정을 비교 분석하고, 철근 인장시험을 통하여 규격의 엄격성을 평가하였다. 그 결과, 국내 철근 규격인 KS D 3504가 가장 엄격한 것으로 평가되었다. 이 엄격성 비교 결과를 바탕으로 KS D 3504의 일반용 철근 규격의 최소 연신율 규정을 수정할 것을 제안하였으며, 내진용 철근 규격을 제안하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제19권1호
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• pp.81-89
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• 2015

본 연구에서는 철근콘크리트구조에서 전단벽체를 대상으로 설계단계에서부터 Set-Based Design과 계층화분석기법을 통하여 선정된 최적배근그룹을 적용한 S-BIM기반 자동철근배근시스템 제안을 목적으로 한다. 복합적인 기준에 대한 쌍대비교 분석을 통해 최적 철근배근그룹을 선정하고 BIM 소프트웨어 벤더 (Vendor)에서 제공하는 Open API를 이용하여 구조설계 알고리즘을 통한 부재의 생성 및 철근배근이 자동으로 수행될 수 있도록 하였다. 결과적으로 가중치가 가장 높은 ALT1 (0.142)의 최적철근배근그룹이 선정되었고, 이를 TS상에 생성하였다.