• Advances in concrete construction
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• v.10 no.4
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• pp.289-299
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• 2020

A reliability analysis of the axial compressive load bearing capacity of postfire reinforced concrete (RC) columns strengthened with carbon fiber reinforced polymer (CFRP) sheets was presented. A 3D finite element (FE) model was built for heat transfer analysis using software ABAQUS. Based on the temperature distribution obtained from the FE analysis, the residual axial compressive load bearing capacity of RC columns was worked out using the section method. Formulas for calculating the residual axial compressive load bearing capacity of the columns after fire exposure and the axial compressive load bearing capacity of postfire columns retrofitted with CFRP sheets were developed. Then the Monte Carlo method was used to analyze the reliability of the axial compressive load bearing capacity of the RC columns retrofitted with CFRP sheets using a code developed in MATLAB. The effects of fire exposure time, load ratio, number of CFRP layers, concrete cover thickness, and longitudinal reinforcement ratio on the reliability of the axial compressive load bearing capacity of the columns after fire were investigated. The results show that within 60 minutes of fire exposure time, the reliability index of the RC columns after retrofitting with two layers of CFRPs can meet the requirements of Chinese code GB 50068 (GB 2001) for safety level II. This method is effective and accurate for the reliability analysis of the axial load bearing capacity of postfire reinforced concrete columns retrofitted with CFRP.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.447-454
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• 1999

The compressive capacity and the soil plugging resistance of single open-ended pipe pile were completely decreased in the previous study on the behavior of shorter single pile during simulated seaquake induced by the vertical component of earthquake. But the capacity of single open-ended pipe pile with greater penetration and the capacity of piles group with shorter penetration were expected to be stable after seaquake motion. In this study, first, 2-piles or 4-piles are driven into the calibration chamber included in saturated fine medium sand with several simulated penetrations, and the compressive load test for each piles group was performed. Then, about 95 % compressive load of the ultimate capacity was applied on the pile head during the simulated seaquake motion. Finally, In confirm the reduction of pile capacity during the simulated seaquake motion, the compressive load test for each single pile or piles group after seaquake motion was performed. During the simulated seaquake, the compressive capacity of open-ended pipe piles with greater penetration ( 〉about 27 m) was not degraded even in deep sea deeper than 220 m and soil plug within open-ended pipe pile installed in deep sea was stable after seaquake motion. Also, in the case of 2-piles or 4-pile groups, the compressive capacity after seaquake motion was not degraded at all regardless of pile penetration depth beneath seabed, sea water depth and seaquake frequency.

• Steel and Composite Structures
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• v.35 no.3
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• pp.415-437
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• 2020

Circular concrete filled steel tube (CFST) columns have an advantage over all other sections when they are used in compression members. This paper proposes a new approach for deriving a new empirical equation to predict the axial compressive capacity of circular CFST columns using the Artificial Neural Network (ANN). The developed ANN model uses 5 input parameters that include the diameter of circular steel tube, the length of the column, the thickness of steel tube, the steel yield strength and the compressive strength of concrete. The only output parameter is the axial compressive capacity. Training and testing the developed ANN model was carried out using 219 available sets of data collected from the experimental results in the literature. An empirical equation is then proposed as an important result of this study, which is practically used to predict the axial compressive capacity of a circular CFST column. To evaluate the performance of the developed ANN model and the proposed equation, the predicted results are compared with those of the empirical equations stated in the current design codes and other models. It is shown that the proposed equation can predict the axial compressive capacity of circular CFST columns more accurately than other methods. This is confirmed by the high accuracy of a large number of existing test results. Finally, the parametric study result is analyzed for the proposed ANN equation to consider the effect of the input parameters on axial compressive strength.

• Journal of the Korea Furniture Society
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• v.21 no.4
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• pp.273-283
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• 2010

Structural larger timber have some weak points as like much longer drying time at lower MC(15%), a considerable check developing and the difficulty for the chemicals injection, so it is necessary to develop lighter structural size member for using the new Hanok, heavy timber construction, living necessaries, furniture and industrial goods. The developed skin timber can be a good raw material for those uses. Skin timber is a hollowed timber which be bored out of its considerable cross-sectional area. The intention of this study was the evaluation of compressive capacity of skin timber. Specially, skin timbers which have more than 200mm in sizes were used to analyze the compressive capacity. From the results of this study, the following conclusions have been made: 1. Though considerable inner parts were bored out, both pine skin timber and larch skin timber showed a good compressive capacity to that of non-bored solid timber. 2. According to ASTM, pine skin timber showed various failure types, but Splitting type, Brooming and end rolling type were main failure types for the larch skin timber. 3. Pine skin timber didn't show the significance between cylindrical shape and rectangular shape, but larch skin timber showed the significance between two shapes. Therefore, for the larch skin timber, cylindrical shape and rectangular shape should be used as a column uses and beam uses respectively. 4. Pine skin timber and larch skin timber didn't show the significance on the compressive capacity. There is not much difference of compressive capacity between them, so it can be possible to select on the user convenience.

• Structural Engineering and Mechanics
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• v.70 no.4
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• pp.499-511
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• 2019

In this study, the axial compressive behavior of novel quadruple C-channel built-up cold-formed steel columns with different slenderness ratio was investigated, using the experimental and numerical analysis. The axial compressive capacity and failure modes of the columns were obtained and analyzed. The finite element models considering the geometry, material and contact nonlinearity were developed to simulate and analyze the structural behavior of the columns further. There was a great correlation between the numerical analyses and test results, which indicated that the finite element model was reasonable and accurate. Then influence of, slenderness ratio, flange width-to-thickness ratio and screw spacing on the mechanical behavior of the columns were studied, respectively. The tests and numerical results show that due to small slenderness ratio, the failure modes of the specimens are generally local buckling and distortional buckling. The axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns decrease with the increase of maximum slenderness ratio. When the screw spacing is ranging from 150mm to 450mm, the axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns change little. The axial compressive capacity of quadruple C-channel built-up cold-formed steel columns increases with the decrease of flange width-thickness ratio. A modified effective length factor is proposed to quantify the axial compressive capacity of the quadruple C-channel built-up cold-formed steel columns with U-shaped track in the ends.

• Journal of the Korea Institute of Building Construction
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• v.5 no.2 s.16
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• pp.139-146
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• 2005

As a result of compressive strength, specimens having mixture rate of cockle shells of $15\%\;and\;20\%$ showed more increases of compressive strength than non-mixture specimens as age increases. Ductility capacity of specimens was higher in specimens mixing cockle shells than in specimens using general fine aggregates and specimen of $10\%$ of cockle shells was highest in ductility capacity. To sum up all experimental results, ductility capacity of specimen without shear reinforcement using mixture of cockle shell was higher than non-mixture specimen and it is considered that mixture of cockle shells up to $20\%$ as fine aggregate for concrete will be available. Continuous researches on durability, workability and economy of crushed cockle shells used for substitute fine aggregate of concrete will be needed.

• Journal of the Korean Wood Science and Technology
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• v.39 no.4
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• pp.333-343
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• 2011

The yellow poplar is an appropriate species for the age of low carbon green growth, because its absorption rates of ozone is greatly excellent, and also the absorption rates of carbon dioxide causing climate changes is very remarkable. The yellow poplar, which is a kind of rapid growth tree, shows a lack of performance as a structural member, however, it is suitable to use a variety of purposes like furniture materials, interior materials, plywood materials, and so on. In this study, the structural size skin-timbers were made by using the yellow poplar, and the compressive capacity was evaluated, also the numerical model was developed for the various uses. The rectangular shape skin-timber presented a good performance by showing 56.3% residual strength about the solid material. In case of the cylinder shape skin-timber showed a possibility to use diversely as a furniture material, as well as a structural uses, because almost 50% compressive capacity of material even though its residual area rates was 25%. Both rectangular shape and the cylinder shape represented that 'Brooming or end rolling' were the major failure mode, and partly splitting failure mode. The compressive capacity of the rectangular shape which residual area rates was large was higher than the cylinder shape, but it did not show statistical significance about the compressive capacity between them. Thus, it will be possible to use them mixed for a convenience of users. The result of the numerical analysis model was quite similar to actual test of the compressive capacity. Therefore, the yellow poplar can be utilized in the development of various uses by applying numerical analysis model about a variety of shapes and dimensions.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.45-54
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• 1999

It is known from the previous study on the behavior of sharter single pile during simulated seaquake induced by the vertical component of earthquake that the compressive capacity and the soil plugging resistance of single open-ended pipe pile were completely degraded. But, the capacity of single open-ended pipe pile with greater penetration and the capacity of piles group with shorter penetration were expected to be stable after seaquake motion. In this study, first single pile, 2-pile or 4-pile groups with several simulated penetrations were driven into the calibration chamber with saturated fine medium sand and the compressive load test for each installed pile or pile groups was performed. Then, about 95% compressive load of the ultimate capacity was applied on the pile head during the simulated seaquake motion. Finally, to confirm the reduction of pile capacity during the simulated seaquake motion, the compressive load test for each single pile or pile groups after seaquake motion was performed. During the simulated seaquake, compressive capacities of single open-ended pipe pile and piles group installed in shallow sea were not decreased. But, the stability of open-ended pile installed in deep sea was depended on the pile penetration depth. So, single open-ended pile with greater penetration of 27 m was stable, and 2-pile and 4-pile groups with penetration more than 13m were stable. But, 2-pile groups with penetration of 7m was failed, and the compressive capacity of 4-pile groups with penetration of 7m was degraded about 15%.

• Journal of Korean Association for Spatial Structures
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• v.17 no.3
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• pp.83-90
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• 2017

Preservation of wooden structure due to deterioration and corrosion is based on preservation of original form, and wooden member should not be arbitrarily replaced or damaged. Accordingly, preservation processing method with synthetic resins is embossed. But it has an adverse effect because there is no exact standard for the reinforcement ratio with the synthetic. This paper experimental study for reinforcement ratio of wooden compressive member with synthetic resins, Reinforced ratio on section area of compressive member and direction. As a result, synthetic resin reinforcement selected as experimental variables by proper ratio enhanced compressive capacity of reinforced wooden member, than new wooden member.

• Structural Engineering and Mechanics
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• v.40 no.2
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• pp.215-231
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• 2011

The axial compressive strength of unidirectional FRP is generally quite lower than its axial tensile strength. This fact decreases the advantages of FRP as main load bearing member in engineering structure. In order to restrain the lateral expansion and splitting of GFRP, and accordingly heighten its axial compressive bearing capacity, a project that to confine GFRP pole with surrounding CFRP sheet is suggested in the present study. The Experiment on the CFRP sheet confined GFRP poles showed that a combined structure of high bearing capacity was attained. Basing on the experiment research a theoretical iterative calculation approach is suggested to predict the ultimate axial compressive stress of the combined structure, and the predicted results agree well with the experimental results. Then the influences of geometrical parameters on the ultimate axial compressive stress of the combined structure are also analyzed basing on this approach.