• Steel and Composite Structures
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• 제32권4호
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• pp.497-507
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• 2019

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.

• Steel and Composite Structures
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• 제43권3호
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• pp.375-388
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• 2022

Nibellen structural system is a novel resilient bracing system based on the application of Bellville disks and Nitinol rods. The cyclic behavior of Nibellen assembly was obtained, and the design equations were developed based on the available literature. Seismic performance of the system was then studied analytically. Two groups of buildings with different lateral force resisting systems were designed and studied: one group with the Nibellen system, and the other with the special concentrically braced frame system. Each building group consisted of 5-, 10-, and 15-story buildings. The Design-Base-Event (DBE) and Maximum Considered Event (MCE) were considered as the seismic hazard, and a suite of seven ground motions were scaled accordingly for response history analyses. Finally, the resiliency of the buildings was studied by obtaining the functionality curve of the buildings before and after the seismic event. The construction cost of the 5-story building with Nibellen bracing system increased but the post-earthquake cost decreased significantly. The application of Nibellen system in the 10- and 15-story buildings reduced both the construction and repair costs, considerably. Resiliency of all the buildings was improved when Nibellen system was used as the lateral force resisting system.

• 한국구조물진단유지관리공학회 논문집
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• 제10권6호
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• pp.183-190
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• 2006

본 연구는 철근콘크리트 보에 대해 선가력 후 보강재료별로 보강 효과를 파악하기 위하여 휨 실험한 결과, 다음과 같은 결론을 얻었다. 실험결과, CB 보강 실험체가 콘크리트 내부에 매입되어 일체 거동함으로써 휨내력 향상 및 연성능력 면에서 가장 우수한 것으로 나타났으며, 섬유계 보강재인 CFS와 GFS 보강 실험체 또한 우수한 내력을 가지는 것으로 나타났다. GSP 보강실험체의 경우 다른 보강 실험체에 비해 보강재 자체의 내력은 큰데 반해 콘크리트와 부착성이 떨어져 상대적으로 낮은 보강효과를 보였으며 실제 구조체에서는 콘크리트와 부착성이 개선 되어 보다 큰 보강효과를 발휘할 것으로 사료된다.

• 한국건축시공학회지
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• 제9권6호
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• pp.161-168
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• 2009

건축공사에서 지하공사는 주공정으로 전체공기와 공사비에서 큰 부분을 차지하고 있으며, 특히 도심지의 경우 해마다 규모가 증가하고 있다. 현재 현장에서 시공하는 지하옹벽은 많은 기능 인력이 필요하고, 공사기간 측면에서도 불리한 유로폼+솔져시스템에 의하여 공사가 진행되고 있다. 따라서 본 연구에서는 토목공사 현장에서 일부 사용되고 있는 무지주 거푸집을 기초로하여 건축공사에 적용 가능한 무지주 거푸집을 개발하였다. 또한 거푸집의 크기를 가정하여 건축공사 현장에서 가장 많이 사용되는 유로폼+솔져시스템과 경제성 측면에서 비교.분석하였다. 연구 결과, 합성 무지주 거푸집은 유로폼+솔져시스템에 비해 공사비가 약 9%높게 나타났으며, 비합성 무지주 거푸집은 약 9%낮게 나타났다. 하지만 합성 무지주 거푸집의 경우 구조체공사에서 콘크리트와 철근의 물량이 현저히 감소하여, 기존옹벽 시공가격 보다 약 35% 경제적 원가절감 효과를 볼 수 있다.

• Steel and Composite Structures
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• 제26권6호
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• pp.745-757
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• 2018

The inclusion of a ductile steel bracing as means of repairing an earthquake-damaged bridge bent is evaluated and experimentally assessed for the purposes of restoring the damaged bent's strength and stiffness and further improving the energy dissipation capacity. The study is focused on substandard reinforced concrete multi-column bridge bents constructed in the 1950 to mid-1970 in the United States. These types of bents have numerous deficiencies making them susceptible to seismic damage. Large-scale experiments were used on a two-column reinforced concrete bent to impose considerable damage of the bent through increasing amplitude cyclic deformations. The damaged bent was then repaired by installing a ductile fuse steel brace in the form of a buckling-restrained brace in a diagonal configuration between the columns and using post-tensioned rods to strengthen the cap beam. The brace was secured to the bent using steel gusset plate brackets and post-installed adhesive anchors. The repaired bent was then subjected to increasing amplitude cyclic deformations to reassess the bent performance. A subassemblage test of a nominally identical steel brace was also conducted in an effort to quantify and isolate the ductile fuse behavior. The experimental data from these large-scale experiments were analyzed in terms of the hysteretic response, observed damage, internal member loads, as well as the overall stiffness and energy dissipation characteristics. The results of this study demonstrated the effectiveness of utilizing ductile steel bracing for restoring the bent and preventing further damage to the columns and cap beams while also improving the stiffness and energy dissipation characteristics.

• Nuclear Engineering and Technology
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• 제50권2호
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• pp.223-228
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• 2018

AREVA NP (Courbevoie, Paris, France) is actively developing several enhanced accident-tolerant fuels cladding concepts ranging from near-term evolutionary (Cr-coated zirconium alloy cladding) to long-term revolutionary (SiC/SiC composite cladding) solutions, relying on its worldwide teams and partnerships, with programs and irradiations planned both in Europe and the United States. The most advanced and mature solution is a dense, adherent chromium coating on zirconium alloy cladding, which was initially developed along with the CEA and EDF in the French joint nuclear R&D program. The evaluation of the out-of-pile behavior of the Cr-coated cladding showed excellent results, suggesting enhanced reliability, enhanced operational flexibility, and improved economics in normal operating conditions. For example, because chromium is harder than zirconium, the Cr coating provides the cladding with a significantly improved wear resistance. Furthermore, Cr-coated samples exhibit extremely low corrosion kinetics in autoclave and prevents accelerated corrosion in harsh environments such as in water with 70 ppm Li leading to improved operational flexibility. Finally, AREVA NP has fabricated a physical vapor deposition prototype machine to coat full-length cladding tubes. This machine will be used for the manufacturing of full-length lead test rods in commercial reactors by 2019.

• Computers and Concrete
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• 제23권1호
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• pp.61-68
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• 2019

This paper presents a computational rational model to predict the ultimate and optimized load capacity of reinforced concrete (RC) beams strengthened by a combination of longitudinal and transverse fiber reinforced polymer (FRP) composite plates/sheets (flexure and shear strengthening system). Several experimental and analytical studies on the confinement effect and failure mechanisms of fiber reinforced polymer (FRP) wrapped columns have been conducted over recent years. Although typical axial members are large-scale square/rectangular reinforced concrete (RC) columns in practice, the majority of such studies have concentrated on the behavior of small-scale circular concrete specimens. A high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. In this paper, the mechanism of mechanical interaction of smooth and lugged FRP rods with concrete is presented. A general modeling and application of various elements are demonstrated. The contact parameters are defined and the procedures of calculation and evaluation of contact parameters are introduced. The method of calibration of the calculated parameters is presented. Finally, the numerical results are obtained for different bond parameters which show a good agreement with experimental results reported in literature.

• Restorative Dentistry and Endodontics
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• 제34권2호
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• pp.145-153
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• 2009

본 연구에서는 측정장치의 compliance유무가 복합레진의 중합수축응력 측정에 미치는 영향을 알아보았다. 변위센서, cantilever load cell과 부궤환 (negative feedback) 시스템을 적용하여 compliance를 허용하는 것과 허용하지 않는 두 가지 모드로 중합수축응력의 측정이 가능한 stress-strain analyzer를 제작하였다. 한 종의 flowable (Filtek Flow: FF) 복합레진과 두 종의 universal hybrid (Z100: Z1 and Z250: Z2) 복합레진이 사용되었다. Load cell의 끝과 base plate에 고정된 직경 3.0 mm의 금속 막대에 silane을 처리하였다. 1.0 mm의 거리로 고정한 두 개의 금속 막대 사이 에 복합레진을 적용한 후 광중합을 하였다. 복합레진의 수직 중합수축률과 중합수축응력을 10 분 동안 기록하였고 인장탄성계수도 구하였다. 통계처리는 일원분산분석과 paired t-test를 시행하였고 95% 유의수준에서 Tukey's test로 사후 검정하였다. 측정된 중합수축 응력은 재료와 compliance의 유무에 따라 큰 차이를 보였다. Compliance를 허용한 모드에서 중합수축응력은 FF: 3.11 (0.13)이 가장 컸으며 Z1: 2.91 (0.10), Z2: 1.94 (0.09) Mpa의 순서였다. 측정장치의 compliance를 허용하지 않은 경우에는 Z1 17.08 (0.89)이 가장 컸고 FF: 10.11 (0.29), Z2: 9.46 (1.63) MPa의 순이었다. 또한 Z1, Z2, FF의 인장탄성계수는 각각 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa 이었다. 중합수축응력은 compliance mode에서는 복합레진의 수직 중합수축률이 주요 영향 요인이었으며, compliance를 배제한 모드에서는 탄성계수의 효과가 지배적이었다.