• Journal of Construction Engineering and Project Management
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• 제7권4호
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• pp.13-19
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• 2017

This study is based on the use and performance of bamboo reinforcements in construction of low-cost structures. This study investigated the physical and mechanical properties of bamboo reinforcements. Bamboo reinforced concrete beam specimens were tested with different reinforcement ratios and observed the load capacity, deflection and failure patterns. It was observed that, flexural strength of bamboo reinforced column is sufficient higher than plain cement concrete and comparable to steel reinforced concrete beams. Bamboo reinforced concrete columns with different reinforcement ratio also tested and observed the ultimate compressive strength and failure pattern. It found, all columns failed in a similar pattern due to crushing of concrete. According to cost analysis, bamboo reinforced beams and columns with moderate reinforcement ratio showed the best strength-cost ratio among plain cement concrete and steel reinforced concrete.

• Steel and Composite Structures
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• 제24권3호
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• pp.323-337
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• 2017

This paper presents the results of a comprehensive experimental investigation on the compressive behaviour of steel tube-confined concrete (STCC) stub columns with active and passive confinement. To create active confinement in STCC columns, an innovative technique is used in which steel tube is laterally pre-tensioned while the concrete core is simultaneously pre-compressed by applying pressure on fresh concrete. A total of 135 STCC specimens with active and passive confinement are tested under axial compression load and their compressive strength, ultimate strain capacity, axial and lateral stress-strain curves and failure mode are evaluated. The test variables include concrete compressive strength, outer diameter to wall thickness ratio of steel tube and prestressing level. It is shown that applying active confinement on STCC specimens can considerably improve their mechanical properties. However, applying higher prestressing levels and keeping the applied pressure for a long time do not considerably affect the mechanical properties of actively confined specimens. Based on the results of this study, new empirical equations are proposed to estimate the axial strength and ultimate strain capacity of STCC stub columns with active and passive confinement.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.709-722
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• 2014

Ultra-High Performance Concrete (UHPC) is an innovative new material that, in comparison to conventional concretes, has high compressive strength and excellent ductility properties achieved through the addition of randomly dispersed short fibers to the concrete mix. This study presents the results of an experimental investigation on the behavior of axially loaded UHPC short circular columns wrapped with Carbon-FRP (CFRP), Glass-FRP (GFRP), and Aramid-FRP (AFRP) sheets. Six plain and 36 different types of FRP-wrapped UHPC columns with a diameter of 100 mm and a length of 200 mm were tested under monotonic axial compression. To predict the ultimate strength of the FRP-wrapped UHPC columns, a simple confinement model is presented and compared with four selected confinement models from the literature that have been developed for low and normal strength concrete columns. The results show that the FRP sheets can significantly enhance the ultimate strength and strain capacity of the UHPC columns. The average greatest increase in the ultimate strength and strain for the CFRP- and GFRP-wrapped UHPC columns was 48% and 128%, respectively, compared to that of their unconfined counterparts. All the selected confinement models overestimated the ultimate strength of the FRP-wrapped UHPC columns.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.73-74
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• 2020

Predicting the compressive strength of concrete is important for shortening construction time and reducing construction costs. In this study, the coefficients required for maturity method and compressive strength prediction equation were calculated by measuring the cement hydration reaction rate, concrete setting time and ultimate strength. The experiment was conducted in an isothermal environment of 10℃, 20℃ and 30℃ using a normal Portland cement, and the experiment was conducted with a total of 9 levels of W/C (40%, 50%, 60%) of 3 levels for each temperature. As a result of comparing the predicted strength and the measured strength for each blend, only an error of less than 5% was found for all blending and curing periods.

• 콘크리트학회지
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• 제11권2호
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• pp.197-208
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• 1999

고강도 콘크리트는 기둥부재에서 그 사용효과가 극대화될 것이 예상되지만, 아직 고강도 콘크리트를 사용한 기둥의 연성특성과 최대강도효과에 대한 구체적인 자료가 부족한 실정이다. 띠근 보강된 콘크리트 기둥은 삼축압축상태가 되며, 고강도 콘크리트의 연성을 증가시키므로 이에 대한 많은 연구가 필요하다. 본 연구에서는 축하중을 받는 띠근보강 고강도 콘크리트 기둥부재의 횡보강효과에 의한 극한강도와 변형율 특성에 대하여 정성적 평가와 정량적 평가를 수행하는 것을 목적으로, 삼축압축상태하의 콘크리트 파괴이론과 기존의 실험결과들을 활용한 통계적기법을 이용하였다. 그 결과 콘크리트 강도, 띠근의 항복강도 및 간격비, 체적비 등을 변수로 고려하는 띠근의 횡보강응력 산정식, 최대압축강도 추정식 그리고 변형율 특성식을 제안하였다. 또한 제안된 식들은 실험결과를 적절히 예측하고 있음을 확인하였다.

• 터널과지하공간
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• 제7권2호
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• pp.130-135
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• 1997

When crystalline rocks are heated, thermal stress is induced by the differences in thermal expansion of the mineral composition and its orientation. In this study, high temperature uniaxial compressive tests were carried out for Iksan and Hwangdeung granites to study the deformation and failure behavior due to thermal loading. Compressive and tensile strength of Hwangdeung granite for 20$0^{\circ}C$ decreased to 80% and 82% of the room temperature strength, and those of Iksan granite decreased to 90% and 92% for 20$0^{\circ}C$, respectively. Elastic moduli of both granites were decreased sharply at the stress level of 80% of ultimate failure strength. Elastic moduli of both granites by variation of temperature at 50% of ultimate failure strength was decreased as almost linearly.

• Structural Engineering and Mechanics
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• 제18권6호
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• pp.769-790
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• 2004

The compressive behavior up to failure of short concrete members reinforced with fiber reinforced plastic (FRP) is investigated. Rectangular cross-sections are analysed by means of a simplified elastic model, able also to explain stress-concentration. The model allows one to evaluate the equivalent uniform confining pressure in ultimate conditions referred to the effective confined cross-section and to the effective stresses in FRP along the sides of section; consequently, it makes it possible to determine ultimate strain and the related bearing capacity of the confined member corresponding to FRP failure. The effect of local reinforcements constitute by single strips applied at corners before the continuous wrapping and the effect of round corners are also considered. Analytical results are compared to experimental values available in the literature.

• 해양환경안전학회지
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• 제27권3호
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• pp.447-456
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• 2021

Methods for predicting the ultimate/buckling strength of ship structures have been extensively improved in terms of design formulas and analytical solutions. In recent years, the design strategy of ships and offshore structures has tended to emphasize lighter builds and improve operational safety. Therefore, the corresponding geometrical changes in design necessitate the use of high-tensile steel and thin plates. However, the existing design formulas were mainly developed for thick plates and mild steels. Therefore, the calculation methods require appropriate modification for new designs beased on high-tensile steel and thin plates. In this study, a modified formula was developed to predict the ultimate strength of thin steel plates subjected to compressive and shear loads. Based on the numerical results, the effects of the yield stress, slenderness ratio, and loading condition on the buckling/ultimate strength of steel plates were examined, and a newly modified double-beta parameter formula was developed. The results were used to derive and modify existing closed-form expressions and empirical formulas to predict the ultimate strength of thin-walled steel structures.

• 대한조선학회논문집
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• 제41권6호
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• pp.48-55
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• 2004

Loads on offshore structures are largely transferred to the bracing members in the form of axial forces. The detrimental effects of imperfections on compressive strength are well recognized. Damage in the members of offshore structures would significantly affect the compressive behavior of the members. As a result, such damages may also affect the ability of the structure to withstand the functional and environmental loads. It is important to be able to assess the residual strength of damaged members quickly and accurately. This will help operators to make the decision whether the member has to be repaired or not. In this study, a series of calculation is performed to study the effects of different parameters on the behavior of such damaged members under axial load. And the results of analysis are compared with those of experiment.

• Advances in concrete construction
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• 제10권4호
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• pp.319-332
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• 2020

The impacts of reinforcing concrete matrix with steel fibers, polypropylene fibers and recycled plastic fibers using different volume fractions of 0.15%, 0.5%, 1.5% and 2.5% on the compressive and tensile characteristics are experimentally investigated in the current research. Also, flexural behavior of plain concrete (PC) beams, shear performance of reinforced concrete (RC) beams and compressive characteristics of both PC and RC columns reinforced with recycled plastic fibers were studied. The experimental results showed that the steel fibers improved the splitting tensile strength of concrete higher than both the polypropylene fibers and recycled plastic fibers. The end-hooked steel fibers had a positive effect on the compressive strength of concrete while, the polypropylene fibers, the recycled plastic fibers and the rounded steel fibers had a negative impact. Compressive strength of end-hooked steel fiber specimen with volume fraction of 2.5% exhibited the highest value among all tested samples of 32.48 MPa, 21.83% higher than the control specimen. The ultimate load, stiffness, ductility and failure patterns of PC and RC beams in addition to PC and RC columns strengthened with recycled plastic fibers enhanced remarkably compared to non-strengthened elements. The maximum ultimate load and stiffness of RC column reinforced with recycled plastic fibers with 1.5% volume fraction improved by 21 and 15%, respectively compared to non-reinforced RC column.