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- 저자 : 양근혁(Yang, Keun-Hyeok) (검색결과 492 건)
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콘크리트 CO<sub>2</sub> 저감을 고려한 혼화재 및 단위 결합재 양의 설계
양근혁,문재흠,Yang, Keun-Hyeok,Moon, Jae-Heum 한국콘크리트학회 2012 콘크리트학회논문집 Vol.24 No.5
The present study assessed the $CO_2$ emissions of concrete according to the type and replacement ratio of supplementary cementitious materials (SCM) and concrete compressive strength using a comprehensive database including 2464 cement concrete specimens and 776 cement concrete mixes with different SCMs. The system studied in $CO_2$ assessment of concrete based on Korean lifecycle inventory was from cradle to pre-construction, which includes consistent materials, transportation and production phases. As the performance efficiency indicators, binder and $CO_2$ intensities were analyzed, and simple equations to evaluate the amount of $CO_2$ emission of concrete were then formulated as a function of concrete compressive strength and the replacement ratio of each SCM. Hence, the proposed equations are expected to be practical and useful as a guideline to determine the type and replacement ratio of SCM and unit content of binder in concrete mix design that can satisfy the target compressive strength and $CO_2$ reduction percentage relative to cement concrete. 이 연구에서는 2464개의 시멘트 콘크리트 배합과 776개의 혼화재가 치환된 혼합 시멘트 콘크리트 배합을 포함하는 실험 데이터베이스를 이용하여 콘크리트 압축강도 및 혼화재 치환율에 따른 콘크리트 $CO_2$ 배출량을 평가하였다. 국내 생애주기 데이터 목록에 기반한 콘크리트 $CO_2$ 평가에서 고려된 시스템은 요람에서 현장 콘크리트 타설 전까지로서 구성재료, 운반 및 생산단계를 포함하고 있다. 콘크리트의 성능 효율성 지표로서 결합재 지수와 $CO_2$ 지수가 분석되었으며, 콘크리트 $CO_2$ 배출량을 평가하기 위한 단순 식이 각 혼화재의 치환비 및 콘크리트 압축강도의 함수로서 제시되었다. 따라서 이 제안된 모델은 목표 압축강도 및 목표 시멘트 콘크리트 대비 $CO_2$ 배출 저감율을 만족하는 콘크리트 배합설계를 위하여 단위 결합재 양 및 혼화재 종류와 치환비를 결정하는 데 가이드 라인으로서 유용하게 이용될 수 있을 것으로 기대된다.
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양근혁,유성원,이현호,김상철,Yang, Keun-Hyeok,Yoo, Sung-Won,Lee, Hyun-Ho,Kim, Sang-Chel 한국건설순환자원학회 2013 한국건설순환자원학회 논문집 Vol.1 No.2
본 연구에서는 공동주택의 난방시스템을 위한 단열재로서 지속가능한 알카리활성 기포콘크리트 배합설계를 제시하기 위한 5배합을 실험하였다. 알카리활성 결합재를 위해 73.5%의 고로슬래그와 15%의 고로슬래그가 5%의 수산화칼슘과 6.5%의 규산나트륨에 의해 활성화되었다. 주요 실험변수인 단위 결합재양은 $325kg/m^3$에서 $425kg/m^3$까지 $25kg/m^3$ 단위로 증가하였다. 실험결과 AA 기포콘크리트는 단위 결합재양이 $375kg/m^3$일 때 KS F 4039에서 제시하는 최소 강도조건 및 경제성을 만족시켰다. 또한 보통포틀랜드시멘트 기포콘크리트 대비 알카리활성 기포콘크리트의 환경영향 저감율은 광화학산화물의 경우 99%, 지구온난화의 경우 87~89%, 자원고갈의 경우 78~82%, 그리고 산성화와 인간독성의 경우 70~75% 수준으로서 매우 높았다. The present study tested 5 concrete mixes to develop reliable mixing proportions for the sustainable alkali-activated(AA) foamed concrete as a thermal insulation material for the floor heating system of buildings. The AA binder used was composed of 73.5% ground granulated blast-furnace slag, 15% fly ash, 5% calcium hydroxide, and 6.5% sodium silicate. As a main variable, the unit binder content varied from $325kg/m^3$ to $425kg/m^3$ at a space of $25kg/m^3$. The test results revealed that AA foamed concrete has considerable potential for practical applications when the unit binder content is close to $375kg/m^3$, which achieves the minimum quality requirements specified in KS F 4039 and ensures economic efficiency. In addition, lifecycle assessment demonstrated the reduction in the environmental impact profiles of all specimens relative to typical ordinary portland cement foamed concrete as follows: 99% for photochemical oxidation potential, 87~89% for global warming potential, 78~82% for abiotic depletion, and 70~75% for both acidification potential and human toxicity.
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양근혁,심재일,송진규,이정한,Yang, Keun-Hyeok,Sim, Jea-Il,Song, Jin-Gyu,Lee, Jung-Han 대한건축학회 2011 대한건축학회논문집 Vol.27 No.1
The present study evaluated the various material properties of concrete brick-masonry using alkali-activated (AA) ground granulated blast-furnace slag (GGBS) binder in order to examine the limitation and significance of environmental-friendly cementless masonry. The reasonable mixing proportions for cementless bricks and masonry mortar using AA GGBS binder were determined from the laboratory and practical plant tests. The compressive strengths of brick and masonry mortar were measured for individual cementless materials. In addition, compressive strength, elastic modulus, diagonal shear strength and modulus of elasticity in shear of masonry prisms were recorded for cementless masonry wall. The measured properties of GGBS-based AA concrete brick-masonry were compared with those of ordinary portland cement (OPC) concrete brick-masonry and empirical equations proposed by different codes including UBC-97, EC 6, and KBC-2009 and existing researchers, wherever possible. The present study clearly showed that the developed GGBS-based AA concrete brick-masonry can be practically applicable as environmental-friendly masonry structures.
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콘크리트 시공줄눈 면에서 점착력 및 마찰계수의 변화를 고려한 전단내력 평가
양근혁,권혁진,박종범,Yang, Keun-Hyeok,Kwon, Hyuck-Jin,Park, Jong-Beom 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 논문집 Vol.21 No.6
This paper presents a mathematical model derived from the upper-bound theorem of concrete plasticity to rationally evaluate the shear friction strength of concrete interfaces with a construction joint. The upper limit of the shear friction strength was formulated from the limit state of concrete crushing failure on the strut-and-tie action along the construction joints to avoid overestimating the shear transfer capacity of a transverse reinforcement with a high clamping force. The present model approach proposed that the cohesion and coefficient of friction of concrete can be set to be $0.27(f_{ck})^{0.65}$ and 0.95, respectively, for rough construction joints and $0.11(f_{ck})^{0.65}$ and 0.64, respectively, for smooth ones, where $f_{ck}$ is the compressive strength of concrete. From the comparisons with 155 data compiled from the available literature, the proposed model gave lower values of standard deviation and coefficient of variation of the ratios between predictions and experiments than AASHTO and fib 2010 equations, indicating that the proposed model has consistent trends with test results, unlike the significant underestimation results of such code equations in evaluating the shear friction strength. 본 연구에서는 콘크리트 시공줄눈 면의 전단마찰 내력을 합리적으로 평가하기 위하여 콘크리트 소성론의 상계치 이론에 기반한 수학적 모델을 제시하였다. 전단면에서 횡보강근의 전단전달에 대한 과대평가를 피하기 위하여 시공줄눈 면에서의 하중전달에 대한 스트럿-타이 모델에서 콘크리트 할렬 및 압괴의 한계상태로부터 전단마찰 내력의 상한값을 유도하였다. 제시된 모델은 시공줄눈 면에서 콘크리트 점착력과 마찰계수를 거친 면의 경우 각각 $0.27(f_{ck})^{0.65}$와 0.95를, 부드러운 면의 경우 각각 $0.11(f_{ck})^{0.65}$와 0.64로 결정하였는데, 여기서 $f_{ck}$는 콘크리트 압축강도이다. 직접전단에 대한 기존 문헌으로부터 수집한 146 실험데이터와의 비교로부터, 제시된 모델은 AASHTO 및 fib 2010 식에 비해 예측 값과 실험 값들의 비의 표준편차 및 변동계수에 대해 더 낮은 값을 보였다. 특히 전단마찰 내력 평가에서 기준식들의 상당한 과소평가 경향과 달리 제시된 모델은 실험결과와 잘 예측하였다.
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고성능 콘크리트의 실용화를 위한 시공특성에 관한 실험적 연구
양근혁,이영호,Yang, Keun-Hyeok,Lee, Young-Ho 한국건축시공학회 2003 한국건축시공학회지 Vol.3 No.1
The special requirements of high-performance concrete(HPC) could be enhanced property over others such as compressive strength, durability, and construction practices. In order to satisfy these requirements a series of laboratory trial mixes and following mock-up test of reinforced concrete wall at field were performed in this study. The objective of this study was to quantitatively evaluate the workability, compressive strength, and the increased heat of hydration caused by the increase of the specific weight of cement according to various variables. Six example series designed about a minimum compressive strength of 500kgf/$\textrm{cm}^2$ at 28 days, and an approximately slump and slump flow of 25cm and 60cm respectively were tested. The selection process of the specific weight of water and the percentage of fly-ash transposition determined to be most suitable for the production of HPC is presented in the following paper.
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포스트텐션 경량콘크리트 일방향 슬래브의 휨 거동 및 비부착 긴장재의 응력
양근혁,문주현,변항용,오명호,Yang, Keun-Hyeok,Mun, Ju-Hyun,Byun, Hang-Yong,Oh, Myoung-Ho 대한건축학회 2011 대한건축학회논문집 Vol.27 No.6
Six post-tensioned lightweight concrete (LWC) one-way slabs were tested under a symmetrical one-point top loading system. According to tendon profile, the specimens were classified into two groups: S-group for slabs with straight tendons and V-groups for slabs with harped (counter-moment shaped) tendons. The span-to-tendon depth ratio($L/d_p$) varied to be 15, 35 and 55 in each group. The flexural cracking moment and ultimate moment of one-way slab tested and stress increase measured in unbonded tendons were compared with those of post-tensioned normal-weight concrete (NWC) beams compiled from the comprehensive database and predictions obtained from the design equations specified in the ACI 318-08 provision. Test results showed that the distribution and width of flexural cracks was significantly affected by the $L/d_p$, indicating that the larger the $L/d_p$, the smaller the crack width. On the other hand, tendon profile had a significant influence on deflection and flexural capacity of one-way slabs, showing a smaller deflection and a higher strength in slabs with harped tendons than in slabs with straight tendons. At the same value of reinforcing inde, the flexural cracking moment and ultimate moment of post-tensioned LWC one-way slabs were pretty comparable to those of post-tensioned NWC beams. In addition, flexural strengths and tendon stress increase of post-tensioned LWC one-way slabs could be conservatively predicted by the ACI 318-08 provision.
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IEEE 802.l1e 무선랜에서 MSI를 이용한 개선된 스케줄링 및 수락제어 알고리즘
양근혁,옥치영,이채우,Yang, Geun-Hyuk,Ok, Chi-Young,Lee, Chae-Woo 대한전자공학회 2007 電子工學會論文誌-TC (Telecommunications) Vol.44 No.10
무선랜에서 QoS를 지원하기 위해 제안된 IEEE 802.l1e의 HCCA (HCF Controlled Channel Access)는 폴링에 의한 채널 제어 방식이다. 즉 HCCA는 중앙 제어 방식이기 때문에 자원을 분배하기 위한 스케줄링 알고리즘이 필요하며 IEEE 802.11e 표준에는 Reference 스케줄러가 제시되어 있다. Reference 스케줄러븐 폴링 리스트에 있는 모든 스테이션들을 동일한 주기로 폴링하기 때문에 잦은 폴링으로 인해 오버헤드 면에서 비효율적이며, TXOP (Transmission Opportunity)의 활용률 면에서도 낮다. 본 논문에서는 이러한 단점을 극복하고자 스테이션들의 MSI (Maximum Service Interval)에 따라 폴링 주기를 단계별로 나누어서 스케줄링하기 위한 트래픽 스케줄링 및 수락 제어 (admission control) 알고리즘을 제안한다. 제안하는 알고리즘에서는 스테이션들이 자시의 MSI와 가능한 비슷한 주기로 폴링되기 때문에 Reference 스케줄러에 비해 폴링 오버헤드가 감소하게 되며, TXOP 활용률도 증가하게 된다. 시뮬레이션을 통한 Reference 스케줄러와의 성능 비교는 제안된 알고리즘이 전체적인 전송률 면에서 더 높은 성능을 보이고 더 많은 수의 스테이션이 서비스가 가능함을 보여준다. IEEE 802.lie is being proposed to improve QoS by IEEE 802.11 working group. HCCA (HCF Controlled Channel Access) a centralized polling based mechanism of IEEE 802.11e, needs a scheduling algorithm that decides on how the available radio resources are allocated to the polled STAs. In IEEE 802.l1e standard Reference Scheduler is presented. Reference Scheduler Polls all STAs in a polling list by the same interval that causes ineffectively frequent polling. It increases not only the overhead but it decreases the TXOP (Transmission Opportunity) utilization. In this paper, we propose the scheduling and admission control algorithm that poll stations depending on the MSI (Maximum Service Interval)o( stations to solve these shortcomings. In our proposed algorithm a station is polled by an interval close to its MSI, so polling overhead decrease and TXOP utilization increases than Reference Scheduler. Simulation results show that our algorithm outperforms Reference Scheduler. Our algorithm maintains higher aggregate throughput and services mere stations than Reference Scheduler.
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