• 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 Korean Society of Environmental Restoration Technology
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• v.7 no.6
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• pp.19-28
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• 2004

Segmental Retaining Wall(SRW) has been variously applying in Civil and Architecture construction. Recently, the application of environmental element in all type's structures came to essential requirement, and the construction cases of retaining wall using reinforced soil and block are more increased than the past. But, this trend more widely was spread environmental element as landscape work for the backside of reinforced retaining wall as well as block itself. New environmental block, Greenstone Block, developed to apply of this tendency. The retaining wall system using Greenstone can be environmental constructing at both block itself and backside of retaining wall. The material tests, the axial compressive strength test of block and bending test of fiber-pipe, exercised to design and construction of vertical SRW, which were satisfied NCMA standard. Through this procedure, Rewall (ver 1.0) was developed, which can be automation design of SRW including internal stability, external stability and local stability. And these can be considered setback of retaining wall, as well the examples of vertical retaining wall using block presented to satisfying the follows; strength of reinforced geotextile, height of retaining wall, surcharge, types of backfill and groundwater level etc. Many problems investigated on after or before of construction were due to local failure, insufficiency of bearing capacity and groundwater level. Especially, the local failure was many occurred to during compaction or after construction, and the cases of SRW construction is similar to the results of model test on vertical SRW.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.37-43
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• 2007

This paper discusses the failure mode of reinforced concrete beams strengthened with composite materials based on six experimental set-ups to determine the FRP-to-concrete bond strength. Interfacial bond behavior between concrete and CFRP plates was discussed. Shear test were performed with different concrete compressive strengths (21 MPa and 28 MPa) and different bonding length (100 mm, 150 mm, 200 mm, and 250 mm). Shear test results indicate that the effective bond length (the bond length beyond which the ultimate load does not increase) was estimated as $196{\sim}204\;mm$ through linear regression analysis. Failure mode of specimens occurred due to debonding between concrete and CFRP plates. Maximum bond stress is calculated as about $3.0{\sim}3.3\;MPa$ from the relationships between bond stress and slip. Finally, the interfacial bond-slip model between CFRP plates and concrete, which is governed debonding failure, has been estimated from shear tests. Average bond stress was about $1.86{\sim}2.04\;MPa$, the volume of slip between CFRP plate and concrete was about $1.45{\sim}1.72\;mm$, and the fracture energy was found to be about $1.35{\sim}1.71\;N/mm$.

• Structural Engineering and Mechanics
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• v.37 no.1
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• pp.39-59
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• 2011

Results of an experimental investigation on the behavior and ultimate shear capacity of 27 reinforced concrete Transfer (deep) beams are summarized. The main variables were percent longitudinal(tension) steel (0.28 to 0.60%), percent horizontal web steel (0.60 to 2.40%), percent vertical steel (0.50to 2.25%), percent orthogonal web steel, shear span-to-depth ratio (1.10 to 3.20) and cube concrete compressive strength (32 MPa to 48 MPa).The span of the beam has been kept constant at 1000 mm with100 mm overhang on either side of the supports. The result of this study shows that the load transfer capacity of transfer (deep) beam with distributed longitudinal reinforcement is increased significantly. Also, the vertical shear reinforcement is more effective than the horizontal reinforcement in increasing the shear capacity as well as to transform the brittle mode of failure in to the ductile mode of failure. It has been observed that the orthogonal web reinforcement is highly influencing parameter to generate the shear capacity of transfer beams as well as its failure modes. Moreover, the results from the experiments have been processed suitably and presented an analytical model for design of transfer beams in high-rise buildings for estimating the shear capacity of beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.331-340
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• 2011

The application of newly developed fiber-sheet and steel-plate composite plate (FSP) as a means of improving strength and ductility capacity of concrete cylinders under axial compression load through confinement is investigated experimentally in this study. An experimental investigation involves axial load tests of two types of FSP strengthening material, two anchoring methods, and three concrete strengths. The FSP-confined cylinder tests showed that FSP provided a substantial gain in compressive strength and deformability. The performance of FRP-confined cylinders was influenced by type of the FSP strengthening material, the anchoring method, and concrete compressive strength. The FSP failure strains obtained from FSP-confined cylinder tests were higher than those from FRP-confined cylinder tests. The magnitude of FSP failure strain was related to the FSP composite effectiveness. The effects of FSP confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, radial, and volumetric strains. From the observations obtained in this investigation, it is believed that FSP is one of the best solutions for the confinement of concrete compressive members.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.323-334
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• 2003

For performance-based design using nonlinear static analysis, it is required to predict the inelastic behavior of structural members accurately. In the present study, a nonlinear numerical analysis was peformed to develop the method describing the moment-curvature relationship of structural wall with boundary confinement. Through the numerical analysis, variations of behavioral characteristics and failure mechanism with the arrangement of vertical reinforcement and the length of boundary confinement were studied. According to the analysis, the maximum moment-carrying capacity of structural walls with adequately confined boundary elements is developed at the moment the unconfined concrete reaches the ultimate compressive strain. Walls with flexural re-bars concentrated on the boundaries fails in a brittle manner. As vortical re-bars in the web increases, the brittle failure is prevented and a ductile failure occurs. Based on the findings, moment-curvature curves for walls with a variety of re-bar arrangement were developed. According to the proposed relationships, deformability of the structural walls wth boundary confinement increases as the compressive strength of the confined concrete increases compared to the applied compressive force.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.169-175
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• 1993

Possibility of fatigue failure in punching shear of reinforced concrete decks of highway bridges is analytically investigated by applying Matsui et al.'s experimental finding to models of 2-meter span decks designed in compliance with previous and current codes. Decks made of concrete of compressive strength of 240㎏/㎠ showed longer fatigue life than decks made of 210㎏/㎠ concrete at the same Md/U rations ; higher Md/U ratio resulted in linger fatigue life but its effect is insignificant in decks having effective depths of 14 and 15cm. Decks designed to higher load factors as specified by current codes showed longer fatigue life than decks designed to lower load factors specified by previous codes ; yet fatigue failure appeared to occur in both decks within their normal life span, thus indicating need for redefining the minimum deck thickness.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.471-474
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• 2005

Reliability-based durability model was developed to consider the uncertainty of analysis variables in durability model for harbor concrete structures. The durability analysis program based on Finite Element Method (FEM) was modified adopting the reliability concept to estimate the probability of durability failure. Water-cement ratio in the durability analysis is the most important factor influencing chloride diffusion coefficient, evaporable water, etc. The probability distribution of water-cement ratio was calculated converting standard deviations of compressive strength in Concrete Standard Code to those of water-cement ratio. Based on the Monte Carlo Simulation, the probabilities of penetration depth and durability failure were calculated.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.181-195
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• 2022

Roughness and joint inclination angle are the important factors that affect the strength and deformation characteristics of jointed rock mass. In this paper, 3D printer has been employed to make molds firstly, and casting the jointed specimens with different joint roughness coefficient (JRC), and different joint inclination angle (α). Conventional triaxial compression tests were carried out on the jointed specimens, and the influence of JRC on the strength and deformation parameters was analyzed. At the same time, acoustic emission (AE) testing system has been adopted to reveal the AE characteristic of the jointed specimens in the process of triaxial compression. Finally, the morphological of the joint surface was observed by digital three-dimensional video microscopy system, and the relationship between the peak strength and JRC under different confining pressures has been discussed. The results indicate that the existence of joint results in a significant reduction in the strength of the joint specimen, JRC also has great influence on the morphology, quantity and spatial distribution characteristics of cracks. With the increase of JRC, the triaxial compressive strength increase, and the specimen will change from brittle failure to ductile failure.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.2
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• pp.112-119
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• 1991

Some experiments were carried out to investigate the effects of freezing and thawing on the strength and strain characteristics of alluvial silty clay under the different temperatures, loading and moisture conditions. The results were as follows; 1. The soil used was proved to be consisted of silty clay with honey-combed structure, and showed higher dilatancy, frost activity and lower stability in natural state. 2. Soil treated with freezing and thawing cycles showed lower compressive strength compared with the non treated, The strength decreased with incement of freezing and thawing cycles. It's shapes of stress-strain curves were flat and did not formulate a peak while the peak strength of higher moisture content soil decreased with the increment of moisture content. It's decrement ratio was most distinctly shown at the first one cycle of freezing and thawing. 3. The cohesion decreased due to freezing and thawing cycles but internal frcition angle was not changed. 4. The liquid limit decreased with increment of freezing and thawing cycles, and became almost constant after three cycles of freezing and thawing. 5. The strength under simple loading at failure mode was appeared to be higher compared with the cyclic loading after freezing and thawing but initial moisture content effect was not observed. 6. Ice lense was not observed within 50% of ice content ratio but observed over 100%. The higher the ice content ratio, the higher the peak strength. As a matter of fact, it seems that an optimum ice content ratio exists for plastic mode and the least compressive strength.