Tests and finite element analysis on the local buckling of 420 MPa steel equal angle columns under axial compression

G. Shi,Z. Liu,H.Y. Ban,Y. Zhang,Y.J. Shi,Y.Q. Wang 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.1

Local buckling can be ignored for hot-rolled ordinary strength steel equal angle compression members, because the width-to-thickness ratios of the leg don’t exceed the limit value. With the development of steel structures, Q420 high strength steel angles with the nominal yield strength of 420 MPa have begun to be widely used in China. Because of the high strength, the limit value of the width-to-thickness ratio becomes smaller than that of ordinary steel strength, which causes that the width-to-thickness ratios of some hot-rolled steel angle sections exceed the limit value. Consequently, local buckling must be considered for 420 MPa steel equal angles under axial compression. The existing research on the local buckling of high strength steel members under axial compression is briefly summarized, and it shows that there is lack of study on the local buckling of high strength steel equal angles under axial compression. Aiming at the local buckling of high strength steel angles, this paper conducts an axial compression experiment of 420MPa high strength steel equal angles, including 15 stub columns. The test results are compared with the corresponding design methods in ANSI/AISC 360-05 and Eurocode 3. Then a finite element model is developed to analyze the local buckling behavior of high strength steel equal angles under axial compression, and validated by the test results. Followingthe validation, a finite element parametric study is conducted to study the influences of a range of parameters, and the analysis results are compared with the design strengths by ANSI/AISC 360-05 and Eurocode 3.

Compression Properties of Weft Knitted Fabrics Consisting of Shrinkable and Non-Shrinkable Acrylic Fibers

Bakhtiari M.,Najar S. Shaikhzadeh,Etrati S. M.,Toosi Z. Khorram The Korean Fiber Society 2006 Fibers and polymers Vol.7 No.3

High-bulk worsted yams with different shrinkable and non-shrinkable acrylic fibers blend ratios are produced and then single jersey weft knitted fabrics with three different structures and loop lengths are constructed. The physical properties of produced yams and compression properties of produced fabrics at eight pressure values (50, 100, 200, 500, 1000, 1500 and $2000 g/cm^2$) were measured using a conventional fabric thickness tester. Then, weft-knitted fabric compression behavior was analyzed using a two parameters model. It is found that at 40 % shrinkable fibre blending ratio the maximum yam bulk, shrinkage, abrasion resistance and minimum yarn strength are obtained. It is also shown that high-bulk acrylic yarn has the highest elongation at 20 % shrinkable fibre blend ratio. The statistical regression analysis revealed that the compression behavior of acrylic weft-knitted fabrics is highly closed to two parameter model proposed for woven fabrics. It is also shown that for weft-knitted structure, there is an incompressible layer (V') which resists against high compression load. Acrylic weft-knitted fabrics with knit-tuck structure exhibit higher compression rigidity and lower softness than the plain and knit-miss structures. In addition, at 20 % shrinkable fibre blend ratio, the high-bulk acrylic weft-knitted fabrics are highly compressible.

Using GA - BP Coupling Algorithm to Predict the High-performance Concrete Mechanical Property

Libing Jin,Jie Duan,Tai Fan,Pengfei Jiao,Tianyun Dong,Qiang Wu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

As a cementitious composite, concrete’s property depends on the matrix generated from cement hydration and the dispersed phases such as aggregates. Compression strength is an important mechanics performance index of concrete quality, especially the High-performance Concrete (HPC). However, owing to the expensive cost of test and the existence of high-dimensional nonlinear mapping between compression strength and basic materials, it is uneasiness to precisely forecast the compression strength value of HPC by general formula method. In this research, a novel machine learning system, Genetic Algorithm and BP Neural Network (GA-BPNN) coupling algorithm, is offered to predict the compression strength of HPC. GA-BPNN coupling algorithm model used 181 groups of HPC mixture data to determine 8 factors affecting its compression strength (i.e., Water, Portland Cement, Water-binder Ratio, Fine Aggregate Ratio, Air-entraining Agent, Fly Ash, Silica Fume, and Superplasticizer) as the input variables of the model, while compression strength was set as the output variable. In addition, 166 sets of training set data were segmented into training, validation and test set again, and BP neural network (BPNN) was compared with GA-BPNN to verify the generalizationcapacity of the model in this research. By forecasting the compression strength of 15 test sets, the average relative error is only 0.902%. Finally, the sensitivity of input variables of GA-BPNN model was analyzed by using Gray Relational analysis (GRA) method. Six models were established to research the impact of sensitivity and quantity of input variables on model performance by ignoring individual input variable. The research is shown that GA-BPNN model not only has the powerful nonlinear mapping ability of BPNN, but also has the global search optimization ability of GA, and showed stronger robustness and prediction potential in the assessment of compression strength value of HPC. The sensitivity analysis shows that, to compression strength of HPC, Cement, Water and Water-binder ratio has a sensitivity score of 0.8166, 0.70122, 0.66772, respectively while Fly Ash has the lowest sensitivity.

고성능감수제의 종류와 첨가량에 따른 모르타르의 유동특성 및 강도특성에 관한 기초적 연구

박혜선,이상수,송하영 대한건축학회지회연합회 2008 대한건축학회지회연합회 학술발표대회논문집 Vol.2008 No.1

High effectiveness of concrete need to improve work-capacity, through concrete capacity improvement. The quality characteristics of concrete using high-range water reducer in domestic market are evaluated in order to put to practical use of high performance concrete with high mobility, high strength and high durability. This study discusses the fluidity and strength properties of cement mortar mixed according to the addition ratio and type of high-range water reducer. The purpose of study is a fundamental study on performance comparison and effect of high-range water reducer. As a result, The fluidity augment in the addition ratio of high-range water reducer. one of the most fluidity is poly carboxylic acid high-range water reducer. Air content considered that the later addition is bigger than the first addition. Compressive strength analyzed one of the most naphthalene sulphonate of type and 0.5% of addition rate. Also, strength increase in the time. Tensile strength and flexural strength does not undergo a big influence in the addition and type is not.

TiC-Mo 공정복합재료의 고온 변형특성

신순기,Shin, Soon-Gi 한국재료학회 2013 한국재료학회지 Vol.23 No.10

The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperatures ranging from room temperature to 2053 K and at strain rates ranging from $3.9{\times}10^{-5}s^{-1}$ to $4.9{\times}10^{-3}s^{-1}$. It was found that this material shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that the material is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength is observed. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a high temperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature- and yield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed high-temperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of the deformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concluded that the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plastic deformation of the Mo phase.

냉시동시 압축착화 조건의 상관관계에 관한 수소 HCCI 기관의 실험적 연구

이광주,이종구,안병호,이종태 한국수소및신에너지학회 2012 한국수소 및 신에너지학회논문집 Vol.23 No.6

It was found that the pure hydrogen-air pre-mixture was self-ignited at a high compression ratio without any assisting method in room temperature, thus refuting the preconception that compression ignition of hydrogen engine was impossible. Therefore, in order to analyze the correlation of compression ignition condition at cold start with hydrogen HCCI engine clearly, the possibility of compression igniting compression ratio is investigated with the change of equivalence ratio and engine speed, experimentally. As the results, it is confirmed that the possibility of compression-igniting compression ratio at cold start was decreased by increasing equivalence ratio due to decreasing auto-ignition temperature. In addition, it is grasped that the possibility of compression-igniting compression ratio at cold start is decreased around 14.9% by increasing engine speed at same supply energy.

고온에 노출된 비정질 강섬유 보강 고강도 콘크리트의 역학적 특성

최경철,김규용,김홍섭,황의철,남정수 한국콘크리트학회 2020 콘크리트학회논문집 Vol.32 No.1

In this paper, stress-strain, compressive strength, elastic modulus and thermal expansion strain of amorphous steel fiber reinforced high strength concrete exposed to high temperatures of 100, 200, 300, 500 and 700 °C were investigated. The concrete used compressive strength 100 and 120 MPa high strength concrete, 0.0, 0.3 and 0.5 vol% amorphous steel fiber were mixed. As a result, the specimens containing amorphous steel fibers showed small peak strain and thermal expansion strain, and compressive strength and modulus of elasticity were measured relatively higher than 300 °C. Therefore, the cracks of concrete caused by the expansion of the aggregate and the shrinkage of the cement paste are controlled by the thermal expansion strain and the maximum strain due to the incorporation of the amorphous steel fiber, so that the strength and stiffness degradation phenomenon of the high-strength concrete could be improved.

초고강도 콘크리트(130MPa)에 대한 실험적 연구

조춘환 한국건설안전학회 2023 한국건설안전학회 논문집 Vol.6 No.1

High-rise, large-scale, and diversification of buildings are possible, and the reduction of concrete cross-sections reduces the weight of the structure, thereby increasing or decreasing the height of the floor, securing a large number of floors at the same height, securing a large effective space, and reducing the amount of materials, rebar, and concrete used for designating the foundation floor. In terms of site construction and quality, a low water binder ratio can reduce the occurrence of dry shrinkage and minimize bleeding on the concrete surface. It has the advantage of securing self-fulfilling properties by improving fluidity by using high-performance sensitizers, making it easier to construct the site, and shortening the mold removal period by expressing early strength of concrete. In particular, with the rapid development of concrete-related construction technology in recent years, the application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher is expanding in high-rise buildings. However, although high-rise buildings with more than 120 stories have recently been ordered or scheduled in Korea, the research results of developing ultra-high-strength concrete with more than 130 MPa class considering field applicability and testing and evaluating the actual applicability in the field are insufficient. In this study, in order to confirm the applicability of ultra-high-strength concrete in the field, a preliminary experiment for the member of a reduced simulation was conducted to find the optimal mixing ratio studied through various indoor basic experiments. After that, 130 MPa-class ultra-high-strength concrete was produced in a ready-mixed concrete factory in a mock member similar to the life size, and the flow characteristics, strength characteristics, and hydration heat of concrete were experimentally studied through on-site pump pressing. 건축물의 초고층화, 대형화, 다양화가 가능하고 콘크리트 단면의 축소로 구조물 자중이 경감되어 보와 슬래브 두께를 얇게 함으로 층 고를 증감하거나 같은 높이에서 많은 층수를 축조할 수 있고 넓은 유효공간이 확보되며, 기초 저면 지정에 사용된 자재 및 철근과 콘크 리트 양을 절감하는 효과를 기할 수 있다. 현장시공 및 품질측면에서는 낮은 물결합재비 배합으로 건조수축 발생 저감 효과와 콘크리트 표면의 블리딩 최소화 효과를 얻을 수 있으며, 고성능감수제 사용에 의한 유동성 증진으로 자체 충전성이 확보되어 현장시공이 용이해지 며, 콘크리트의 조기 강도 발현으로 거푸집 탈형 기간을 단축시킬 수 있는 장점이 있다. 특히 근래에 들어 콘크리트와 관련한 건축기술의 비약적인 발전에 따라 초고층 건축물에서는 설계기준강도 100MPa급 이상의 초고강도콘크리트의 적용이 확대되고 있다. 그러나 최근 국내 에서도 120층 이상의 초고층 건축물들이 발주 또는 발주 예정되어 있으나, 현장 적용성이 고려된 130MPa급 이상의 초고강도 콘크리트를 개발하여 현장에서 실제 적용 가능성 여부를 실험, 평가한 연구실적은 미흡하다. 본 연구에서는 초고강도콘크리트의 현장적용 가능성을 확인하기 위하여 여러 가지 방법의 실내기초 실험으로 연구되어진 최적의 배합비를 찾아서 축소모의부재 예비실험을 실시하였다. 그 후 실물크기와 유사한 모의부재에 130MPa급 초고강도콘크리트를 레미콘 공장에서 생산하여 현장 펌프압송 타설을 통해 콘크리트의 유동특 성, 강도특성, 수화열에 관하여 실험 연구하였다.

슬래그부산물을 자극제로 활용한 고활성 고로슬래그 미분말모르타르의 압축강도 발현 특성

이보경,김규용,구경모,신경수 한국건축시공학회 2014 한국건축시공학회지 Vol.14 No.1

건설산업에서는 탄산가스 저감을 위해 산업부산물을다량 활용하는 기술개발을 위한 연구가 이루어지고 있다. 산업부산물 중 특히 고로슬래그 미분말은 잠재수경성에기인하여 장기강도는 우수하나 초기강도가 낮기 때문에많은 양을 대체하는데 한계가 있다. 이에 본 연구에서는철강공정 중 용선예비처리 공정에서 발생하는 슬래그부산물을 활용하여 고활성 고로슬래그 미분말을 시험 제조후 고활성 고로슬래그 미분말의 모르타르 압축강도 강도발현 특성을 검토하였다. 또한, 고활성 고로슬래그 미분말 단독으로도 경화가 가능한 특징을 고려해서 2차 콘크리트 제품용 결합재로서 활용 가능성을 검토하고자 배합조건에 따른 콘크리트 제조 및 압축강도 발현특성을 검토하였다. 실험변수로써 슬래그부산물의 분말도, 치환율,양생조건 및 W/B를 설정하였다. 그 결과 슬래그부산물을자극제로 활용한 고활성 고로슬래그 미분말 모르타르의압축강도 향상을 확인하였으며 고활성 고로슬래그 미분말이 단독으로도 경화가 가능하기 때문에 양생 및 배합조건을 고려하면 고활성 고로슬래그 미분말을 콘크리트 2차제품용 결합재로서 활용 가능할 것으로 판단된다. Recently, many efforts related to the utilization of industrial by-products have been made to reduce carbon dioxide emissions in the construction industry. Of these various efforts, concrete incorporating ground granulated blast furnace slag (BFS) provides many advantages compared to conventional concrete, such as high long-term compressive strength, improved durability and economic benefits because of its latent hydraulic property, and low compressive strength at early curing age. This paper investigates the compressive strength of high-activated ground granulated blast furnace slag blended mortar with slag by-product S type(SBP-S). The results of the experiment revealed that incorporating high-activated ground granulated blast furnace slag would affect the compressive strength of mortar. Itwas found that increasing the Blaine fineness and replacement ratio of slag by-product S type shows highcompressive strength of mortar at early curing age because of its high SiO2 and CaO contents in the slag. It is confirmed that an increase of curing age does not affect the compressive strength of mortar made with slagby-product S type at a high curing temperature. Moreover, it is possible to develop and design concrete manufactured with high-activated ground granulated blast furnace slag as binder considering the acceleration curing conditions and mix proportions.

Compressive Properties of High-distance Warp-knitted Spacer Flexible Composite

Xiaohui Zhang,Yuanyuan Yu,Andrews Boakye,Pibo Ma 한국섬유공학회 2018 Fibers and polymers Vol.19 No.5

This paper mainly introduces a high-distance warp-knitted spacer flexible composite material which is a special material consisting of high-distance warp-knitted spacer fabric and some coating materials. It introduces the designing process as well as the preparation of high-distance warp-knitted flexible composite material. In order to comprehend the influence of internal pressure on the material, the mechanical properties under 100 %, 80 % and 60 % gas pressure have been explored. A compression test under these three kinds of gas pressure was carried out and the related force displacement diagram, the stress-strain curve and the energy strain curve which directly reflects the variation of the mechanical properties of the composites material under the different gas pressure were obtained and presented. A deep investigation and analysis was conducted into knowing the compressive properties of the material and how they are affected by the gas pressure. The experimental results obtained shows that the compressive properties of the high-distance warp-knitted space flexible material is dependent on the amount of gas inserted. Again the compressive strength of the material keeps growing stronger with an increase in the intensity of the gas pressure.