• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.129-138
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• 1996

Localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region with softening behavior and it governs ultimate load of concrete. In this Paper, concrete under strain localization was modeled with localization region and non-localization region and lc~calization behavior was formulated based on averaging concept of heterogeneous material. By using the formulation, the localization phenomena of concrete under uniaxial loadings were well predicted. The analytical results show that size of localization region of concrete under uniaxial compression is three times of maximum aggregate size and the size effect of concrete is well predicted. The use of tension-softening curve obtained from direct tension test is suitable for well prediction of localization of concrete under uniaxial tension.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.7-13
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• 2002

The behaviors of the reinforced concrete membrane elements are expected by Navier's three principles of the mechanics of materials. The adopted cyclic stress-strain curves of concrete consist of seven different unloading and loading stages in the compressive zone and six other stages in the tensile zone. The curves took into account the softening of concrete that was influenced by the tensile strain in the perpendicular direction of cracks. The stress-strain relationships for steel bar embedded in concrete subjected to reversed cyclic forces considered the tension stiffening effect and Baushinger effect. The predicted results of the analysis based on Navier's principles were in good agreement with the observed shear stress-strain relationships as well as transverse and longitudinal strains.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.43-58
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• 2018

In this study, the load-transfer behavior along the shaft of the prebored and precast piles was investigated by pile loading tests. Special attention was given to quantifying the skin frictions developed between the pile-soil interfaces of the 14 instrumented test piles. Based on this detailed field tests, the load - settlement curves and axial load distributions of piles were obtained and the load-transfer curves (t-z curves) for the test piles were proposed. As such, it is found that the test results show two different load transfer behaviors; ductile and brittle behavior curves. The corresponding t-z curves are proposed based on the hyperbolic- and sawtooth-shape, respectively. By validating the accuracy of the proposed curves, it is also found that the prediction results based on the proposed load-transfer curve are in good agreement with the general trends observed by the field loading tests.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.301-310
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• 2001

Gypsum blocks with sixteen flaws have been prepared and tested in uniaxial compression. Results from these experiments are compared with observations from the same material with two and three flaws. The results indicate that the cracking pattern observed in specimens wish multiple flaws is analogous to the pattern obtained in specimens with two and three flaws such as initiation and propagation of wing, and secondary cracks and coalescence. Wing cracks initiate at an angle with the flaw and propagate in a stable manner towards the direction of maximum compression. Secondary cracks initiate and propagate in a stable manner. As the load is increased, secondary cracks may propagate in an unstable manner and produce coalescence. Two types of secondary cracks are observed: quasi-coplanar, and oblique secondary cracks. Coalescence is produced by the linkage of two flaws: wing and/or secondary cracks. From the sixteen flaws test, four types of coalescence are observed. Observed types of coalescence and initiation stress of wing and secondary crackle depend on flaw geometries, such as spacing, continuity, flaw inclination angle, ligament angle, and steppings.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.177-177
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• 2011

현재 대부분 사용되는 지하매설물용 뒤채움재는 다짐공법을 많이 사용하고 있으며, 실제로 이러한 방법은 부적절한 다짐으로 인해 침하 및 내구성 저하로 인해 파손을 초래하는 경우가 많다. 이러한 문제를 해결 할 수 있는 하나의 대안으로 유동성 뒤채움재를 이용할 수 있다. 유동성 뒤채움재는 초기 유동성, 시간에 따른 자기 강도 발현 무다짐공법 적용 등 많은 장점을 가지고 있다. 본 연구에서는 현장발생토사, 정수장슬러지 및 폐타이어분말 등 재활용 재료를 이용한 유동성 뒤채움재의 기본물성을 평가하였다. 각각의 재활용재료에 대한 입도 및 비중을 평가하였고, 최적배합설계를 결정하였으며, 모형 시험과 유한요소 해석을 위한 기본 물성값을 위해 일축압축시험, 삼축압축시험, 공진주시험 등을 수행하였다. 최적배합설계를 산정하는 과정에서 수행한 실험중 대표적인 시험으로 자가수평능력 및 자기다짐등에 필요한 유동성을 판단하는 Flow시험(ASTM D 6133) 결과 기준으로 정한 20cm이상의 값을 얻을 수 있었으며 일축압축강도의 경우 시공 후 유지 보수가 용이한 강도인 $3.0kg/cm^2{\sim}5.6kg/cm^2$이하로 설계하였으며 28일재령 일축압축강도 결과 $3.15{\sim}3.74kg/cm^2$라는 유지보수에 적당한 결과값을 나타내었다. 이 배합이 현장에서 사용이 가능하다는 것으로 판단하고 현장모형시험과 유한요소해석를 통하여 현장에서 사용하였을 때 관의 변형과 관에 작용하는 하중변화를 확인하고 현장모형시험과 유한요소해석 간의 상관관계를 규명하였다. 현장 모형 시험은 현장과 비슷하게 제작된 모형을 이용하였으며 최대한 현장과 비슷한 조건에서 뒤채움재를 타설과정 중과 타설이 완료된 상태에서 7일 양생 후 하중재하와 같이 두가지 경우에서 수직 수평토압, 관의 수직 수평변위, 관의 종단변형을 측정하였다. 유한요소해석 프로그램은 Midas GTS를 이용하여 실시하였으며 관의 변형률, 유효응력을 측정하여 규명하였다.

• Composites Research
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• v.26 no.1
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• pp.66-71
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• 2013

As a fundamental structural element of construction, a pile is constructed to transfer loads from superstructure to foundation. In general, since the pile foundation is constructed in the ground or ground under water, it is difficult to protect from the damages due to moisture and/or salt which create corrosive environment and it is even more difficult to estimate its durability. In this study, in order to enhance the durability and constructibility of the pile foundation, FRP-concrete hybrid composite pile (HCFFT) is suggested. Moreover, equation for the prediction of load carrying capacity of HCFFT circular members under compression is suggested and discussed based on the results of analytical and experimental investigations. In addition, we also conducted the finite element simulation for the structural behavior of new HCFFT composite pile and the result is compared with those of experimental and analytical studies. In addition, the axial loading capacity of new HCFFT composite pile is compared with those of existing PHC pile and hollow circular steel pipe pile, and it was found that the new HCFFT composite pile has advantages over conventional PHC and steel pipe piles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.411-419
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• 2006

In this study, a new approach employing 3-dimensional strut-tie models for analysis and design of 3-dimensional structural concrete with disturbed regions that are not properly occupied by current design codes is proposed. In addition, a computer graphics program for the practical application of the approach is developed. The approach adopts a grid strut-tie model to exclude the subjectivity in the selection of strut-tie model and evaluates the effective strength of concrete strut by considering the 3-dimensional failure criteria of concrete and the deviation angles between the struts and compressive principal stress trajectories. To verify the appropriateness of the approach, nine pile caps tested to failure are analyzed and a bridge pier is designed. The analysis and design results are compared with those obtained by several different methods.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.165-170
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• 2008

This study discusses the inelastic behavior of single-layer latticed dome, composed of tubular truss member and newly proposed joint sections, through loading test on the scale-down structure. The loading test was performed under displacement control conditions, using loading transfer system for the same value of point loads on all joints. Maximum applied load was nearly 1.6 times of the design load, and inelastic buckling occured beyond compressive yeilding in some members. The displacement of structure was maimtained upto the limit of oil jack. The behavior of latticed dome from the loading test was analyzed on the view of structural design practice.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.357-360
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• 2008

This study was performed to estimate the workability and the static behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Static test was executed for 20m railway bridge girder specimen and evaluated whether pure bending moment was introduced or not, and the behaviors after cracking, and at the ultimate load. Test results showed that a bicon girder had the enough safety in the introduction of pure moment, the serviceability, and the ultimate behavior.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.223-231
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• 2007

Considering wind speed uncertainty, reliability analysis of the LNG unloading arm at Tongyoung Production Site was performed. Extreme distribution of wind speed was estimated from the data collected at the weather center and wind load was calculated using wind velocities and coefficients of wind pressure. The unloading arm was modeled with plate and solid elements. Contact elements were used to describe the interface between base of structure andground. Response surface for maximum effective stress was found for reliability analysis and then reliability functions was defined and used to determine exceeding probability of allowable and yield stresses. In addition, sensitivity analysis was also performed to estimate the effect of possible material deterioration in the future.