• 국제강구조저널
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• 제18권4호
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• pp.1177-1190
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• 2018

This study presents an analytical framework for estimating the thermo-mechanical behavior of a composite beam exposed to fire. The framework involves: a fire simulation from which the evolution of temperature on the structure surface is obtained; data transfer by an interface model, whereby the surface temperature is assigned to the finite element model of the structure for thermo-mechanical analysis; and nonlinear thermo-mechanical analysis for predicting the structural response under high temperatures. We use a plastic-damage model for calculating the response of concrete slabs, and propose a method to determine the stiffness degradation parameter of the plastic-damage model by a nonlinear regression of concrete cylinder test data. To validate simulation results, structural fire experiments have been performed on a real-scale steel-concrete composite beam using the fire load prescribed by ASTM E119 standard fire curve. The calculated evolution of deflection at the center of the beam shows good agreement with experimental results. The local test results as well as the effective plastic strain distribution and section rotation of the composite beam at elevated temperatures are also investigated.

• Computers and Concrete
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• 제26권6호
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• pp.515-531
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• 2020

Due to the construction difficulties of steel reinforced concrete (SRC), a new composite structure of steel and steel fiber reinforced concrete (SSFRC) is proposed for solving construction problems of SRC. This paper aims to investigate the bond properties and composition of interfacial bond stress between steel and steel fiber reinforced concrete. Considering the design parameters of section type, steel fiber ratio, interface embedded length and concrete cover thickness, a total of 36 specimens were fabricated. The bond properties of specimens were studied, and three different methods of calculating interfacial bond stress were analyzed. The results show: relative slip first occurs at the free end; Bearing capacity of specimens increases with the increase of interface embedded length. While the larger interface embedded length is, the smaller the average bond strength is. The average bond strength increases with the increase of concrete cover thickness and steel fiber ratio. And calculation method 3 proposed in this paper can not only reasonably explain the hardening stage after the loading end curve yielding, but also can be applied to steel reinforced high-strength concrete (SRHC) and steel reinforced recycled coarse aggregate concrete (SRRAC).

• Steel and Composite Structures
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• 제41권6호
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• pp.861-871
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• 2021

This study aims at investigating the hysteretic performance of a novel composite wall panel fabricated by infilling aerated concrete blocks into a novel light-steel frame used for low-rise residential buildings. The novel light-steel frame is consisted of two thin-wall rectangular hollow section columns and a truss-beam assembled using patented U-shape connectors. Two bare light-steel frames and two composite wall panels have been tested to failure under horizontal cyclic loading. Hysteretic curves, lateral resistance and stiffness of four specimens have been investigated and analyzed. Based on the testing results, it is found that the masonry infill can significantly increase the lateral resistance and stiffness of the novel light-steel frame, about 2.3~3 and 21.2~31.5 times, respectively. Failure mode of the light-steel frame is local yielding of the column. For the composite wall panel, firstly, masonry infill is crushed, subsequently, local yielding may occur at the column if loading continues. Hysteretic curve of the composite wall panel obtained is not plump, implying a poor energy dissipation capacity. However, the light-steel frame of the composite wall panel can dissipate more energy after the masonry infill is crushed. Therefore, the composite wall panel has a much higher energy dissipation capacity compared to the bare light-steel frame.

• Steel and Composite Structures
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• 제41권5호
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• pp.731-746
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• 2021

The purpose of this paper is to investigate the axial bearing capacity and residual properties of steel reinforced recycled aggregate concrete (SRC) column after elevated temperature. A total of 48 SRC columns were designed for the static loading test after elevated temperature. The variables include replacement ratios, designed temperature, target duration, thicknesses of cover concrete, steel ratios and stirrup spacing. From this test, the mass loss ratio and stress load-deformation curve were obtained, and the influence of various parameters on residual bearing capacity were analyzed. ABAQUS was used to calculate the temperature field of specimens, and then got temperature damage distribution on the cross-section concrete. It was shown that increasing of the elevated temperatures leaded to the change of concrete color from smoky-gray to grayish brown and results in reducing the bearing capacity of SRC columns. The axial damage and mechanism of SRC columns were similar to those of reinforced natural aggregate concrete columns at the same temperatures. Finally, the calculation method of axial compressive residual bearing capacity of SRC columns recycled concrete columns after high temperature was reported based on the test results and finite element analysis.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1775-1782
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• 2023

Several reactor physics commissioning experiments were conducted to obtain the neutronic parameters at the beginning of the G.A. Siwabessy Multi-purpose Reactor (RSG-GAS) operation. These parameters are essential for the reactor to safety operate. Leveraging the experimental data, this study evaluated the calculated core reactivity, control rod reactivity worth, integral control rod reactivity curve, and fuel reactivity. Calculations were carried out with Serpent 2 code using the latest neutron cross-section data ENDF/B-VIII.0. The criticality calculations were carried out for the RSG-GAS first core up to the third core configuration, which has been done experimentally during these commissioning periods. The excess reactivity for the second and third cores showed a difference of 510.97 pcm and 253.23 pcm to the experiment data. The calculated integral reactivity of the control rod has an error of less than 1.0% compared to the experimental data. The calculated fuel reactivity value is consistent with the measured data, with a maximum error of 2.12%. Therefore, it can be concluded that the RSG-GAS reactor core model is in good agreement to reproduce excess reactivity, control rod worth, and fuel element reactivity.

• Structural Engineering and Mechanics
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• 제87권4호
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• pp.375-389
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• 2023

In many fiber concrete beams with Carbon Fiber Reinforced Polymer (CFRP), debonding occurs between the carbon sheets and the concrete due to the low strength of the bonding resin. A total of 42 fiber concrete beams with a cross-section of 10×10 cm with a span length of 50 cm are fabricated and retrofitted with CFRP and subjected to a 4-point bending test. Graphene Oxide (GO) at 1, 2, and 3 wt% of the resin is used to improve the mechanical properties of the bonding resins, and the effect of length, width, and the number of layers of CFRP and resin material are investigated. The crack pattern, failure mode, and stress-strain curve are analyzed and compared in each case. The results showed that adding GO to polyamine resin could improve the bonding between the resin and the fiber concrete beam. Furthermore, the optimum amount of nanomaterials is equal to 2% by the weight of the resin. Using 2% nanomaterials showed that by increasing the length, width, and number of layers, the bearing and stiffness of fiber concrete beams increased significantly.

• Earthquakes and Structures
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• 제25권2호
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• pp.113-123
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• 2023

A novel type of buckling restrained brace with built-up angle steel was developed. The core segment was formed by welding angle steel, and the middle section was reduced by cutting technology to solve the problem that the end of BRB was easy to buckle. The experimental program has been undertaken to study the performance of BRBs with different unbonded materials (silica gel, kraft paper) and different filler materials (ordinary concrete, full light-weight concrete). Four specimens were designed and fabricated for low cycle reciprocating load tests to simulate horizontal seismic action. The failure mode, hysteretic curves, tension-compression unbalance coefficient and other mechanical parameters were compared and analyzed. The finite element software ABAQUS was used to conduct numerical simulation, and the simulation results were compared with the experimental phenomena. The test results indicated that the hysteretic curve of each specimen was plump. Sustaining cumulative strains of each specimen was greater than the minimum value of 200 required by the code, which indicated the ductility of BRB was relatively good. The energy dissipation coefficient of the specimen with silica gel as unbonded material was about 13% higher than that with kraft paper. The experimental results were in good agreement with the simulation results.

• Earthquakes and Structures
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• 제25권5호
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• pp.343-358
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• 2023

The superelastic viscous damper (SVD) is a hybrid passive control device comprising a viscoelastic damper and shape memory alloy (SMA) cables connected in series. The SVD is an innovative damper through which a large amount of seismic energy can dissipate. The current study assessed the seismic collapse induced by steel moment-resisting frames (SMRFs) equipped with SVDs and compared them with the performance of special MRFs and buckling restrained brace frames (BRBFs). For this purpose, nonlinear dynamic and incremental dynamic analysis (IDA) were conducted in OpenSees software. Both 5- and 9-story special MRFs, BRBFs, and MRFs equipped with the SVDs were examined. The results indicated that the annual exceedance rate for maximum residual drifts of 0.2% and 0.5% for the BRBFs and MRFs with SVDs, respectively, were considerably less than for SMRFs with reduced-beam section (RBS) connections and that the seismic performances of these structures were enhanced with the use of the BRB and SVD. The probability of collapse due to residual drift in the SVD, BRB, and RBS frames in the 9-story structure was 1.45, 1.75, and 1.05 times greater than for the 5-story frame.

• The Korean Journal of Physiology
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• 제7권2호
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• pp.49-58
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• 1973

가토(家兎)의 외경동맥(外頸動脈)의 신장도(伸張度)를 알기 위(爲)하여 좌측(左側) 외경동맥(外經動脈)을 절단(切斷)하여 적출(摘出)하고 전혈질(全血質)과 횡절편(橫切片) 및 종절편(縱切片)을 작성(作成)한 후(後) 생리적식염수(生理的食鹽水) 중(中)에 둔 군(群)과 동일(同一)한 방법(方法)으로서 얻은 각(各) 혈질표본(血質標本)을 0.15 mM 및 0.30 mM의 ATP 용액중(溶液中)에 둔 군(群)에서 각각(各各) 15분(分), 45분(分) 및 75분(分)에서 길이 일장력곡선중(一張力曲線中) 탄성(彈性)의 한계(限界) 내(內)에서 Hooke의 법칙(法則)에 따르는 부위(部位)에서 Young 율(率)을 구(求)하여 서로 비교(比較)하였던 바 다음의 결과(結果)를 얻었다. 1) 가토(家兎) 외경동맥(外經動脈)의 전혈질(全血質)을 생리적식염수(生理的食鹽水)에 둔 군(群)에서는 그 Young 율(率)이 실험시간(實驗時間) 15분(分)에서는 $4.74{\times}10^7 dyne/cm^2$이었으나 45분(分) 및 75분(分)에서는 각각(各各) 4.62 및 $4.13{\times}10^7 dyne/cm^2$이었다. 한편 ATP 0.30mM의 농도(濃度)에서는 0.15mM의 농도(濃度)에 비(比)하여 낮은 Young 율(率)을 나타내었다. 2) 외경동맥(外經動脈)의 횡절편(橫切片)의 Young 율(率)은 생리적식염수중(生理的食鹽水中)에서는 15분(分), 45분(分) 및 75분(分)에서 각각(各各) 4.11, 3.75 및 $3.90{\times}10^7 dyne/cm^2$으로서 15분(分)이 가장 높고 그 후(後)는 큰 변화(變化)가 없는 경향(傾向)이었으나, ATP 첨가(添加)로서는 실험시간(實驗時間)에 따른 변화(變化)는 볼 수 없었다. ATP 첨가(添加)로서는 0.30mM의 농도(濃度)에서 0.15 mM의 농도(濃度)에 비(比)하여 Young 율(率)이 낮았다. 3) 외경동맥(外經動脈)의 종절편(縱切片)의 Young 율(率)은 생리적식염수(生理的食鹽水)에 둔 군(群)에서는 15분(分), 45분(分) 및 75분(分)에서 각각(各各) 2.12, 2.48 및 $2.46{\times}10^7 dyne/cm^2$으로서 실험초기(實驗初期)에 비(比)하여 후기(後期)에서 Young 율(率)이 약간(若干) 높은 경향(傾向)을 나타내었고, 이러한 경향(傾向)은 ATP의 첨가(添加)로서도 비슷하였다.

• 대한교통학회지
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• 제23권7호
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• pp.159-163
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• 2005

도로를 건설하는 궁극적인 목적은 운전자의 편의성을 고려해야 함에도 불구하고 지금까지의 도로선형설계시 도로 이용자인 운전자를 고려하지 않고 있는 실정이다. 운전자의 편의성은 시간적 측면에서 정시성 및 신속성을 고려하고 있지만, 더불어 부가적으로 고려되어야 할 요소로서 사고에 대한 안전성을 감안해야만 한다. 본 연구에서는 지방부 일반국도 4차선 단곡선부의 1차로를 대상으로 입체선형의 주행속도특성을 고려한 편경사 안전율을 산정하고자 한다. 첫째, 기하구조의 영향을 분석하기 위해 선행차에 의해 영향을 받지 않은 승용차의 주행속도를 조사하였다. 둘째, 종단선형의 영향과 평면선형의 영향을 조합하여 6개 구간, 즉 12개 지점에서 주행속도를 측정하여 주행속도 특성을 기초 통계 분석하였다. 섯째, 기초 통계 분석 결과를 바탕으로 최대편경사를 새로운 안전율(${\alpha}$)개념을 도입하여 주행속도를 고려한 편경사값을 산정하였다. 연구결과, 입체선형에서 승용차의 주행특성을 알 수 있었고, 이를 고려한 안전율을 제시할 수 있었다. 최대편경사를 산정함에 있어 본 연구의 결과인 3차원적 입체선형을 고려한 안전율을 적용한다면 도로설계시 운전자의 안전성을 향상시킬 수 있을 것으로 판단된다. 더불어, 본 연구의 범위를 확장하여 다양한 기하구조를 가진 도로구간에 대한 수집 분석한 후, 3차원적 입체선형을 고려한 모델이 개발되어야 할 것으로 판단된다.