• Geotechnical Engineering
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• v.5 no.4
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• pp.17-26
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• 1989

The creep ratio, which has been applied as a measure to prevent piping failure in designing embankments, has been originally proposed for the protection of masonry or concrete dam from piping along the boundary surface between the foundation soil and the bottom of the structure. In this study, it has been investigated whether this creep ratio could be applied for the earth embankment through the model test and we reevaluated the required creep ratio in the present design criteria. Based on this research, it was concluded that a piping failure would always occur within the embankment body and not through the boundary surface between the embankment and foundation. Therefore it could be said that the present design criteria are illogical to determine the design creep ratio according to less permeable soil no matter whether the soil forms embankment or foundation.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.43-51
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• 2014

A Large-diameter drilled shaft of deep water depth composite foundation supporting a high rise pylon of the test designed super long span bridge was designed by allowable stress design method and failure probability through reliability analysis to bearing capacity was estimated. The allowable stress design results for the bearing capacity of a drilled shaft were analyzed by reliability analysis and the probability of failure shows 0.12 % in case of CFEM, 0.0002 % in case of Korea Highway Corporation criterion, and 0.003 % in case of structure foundation design criterion. In the allowable stress design, the bearing capacity of a large-diameter drilled shaft was obtained by applying to safety factor 3 and reliability analysis for the results was done. If the failure probability suggested by AASHTO(2007) specification is set to 0.02 %, the socketed length of a drilled shaft shows an increase of 25 % in CFEM, decrease of 60 % in KHCC, and decrease of 89 % in SFDC.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.345-356
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• 2004

A plasticity model was developed to predict the behavioral characteristics of concrete in multiaxial compression. To extend the applicability of the proposed model to concrete in various stress states, a new approach for failure criteria was attempted. A stress was decomposed into one volumetric and two deviatoric components orthogonal to each other. Three failure criteria wire provided independently for each stress component. To satisfy the three failure criteria, the plasticity model using multiple failure criteria was Implemented. Each failure surface was defined by equivalent volumetric or deviatoric plastic strain. To present dilatancy due to compressive damage a non-associative flow nile was proposed. The proposed model was implemented to finite element analysis, and it was verified by comparisons with various existing test results. The comparisons show that the proposed model predicted well most of the experiments by using three independent failure criteria.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.655-664
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• 2007

The inherent characteristic of concrete tensile cracks, directional nonlocal crack damage, causes so-called rotating tensile crack damage and softening of compressive strength. In the present study, a plasticity model was developed to describe the behavior of reinforced concrete planar members In tension-compression. To describe the effect of directional nonlocal crack damage, the concept of microplane model was combined with the plasticity model. Unlike existing models, in the proposed model, softening of compressive strength as well as the tensile crack damage were defined by the directional nonlocal crack damage. Once a tensile cracking occurs, the microplanes of concrete are affected by the nonlocal crack damage. In the microplanes, microscopic tension and compression failure surfaces are calculated. By integrating the microscopic failure surfaces, the macroscopic failure surface is calculated. The proposed model was implemented to finite element analysis, and it was verified by comparisons with the results of existing shear panel tests.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.75-84
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• 2009

An analytical model for predicting the shear strength of prestressed concrete beams without shear reinforcement was developed, on the basis of the existing strain-based shear strength model. It was assumed that the compression zone of intact concrete in the cross-section primarily resisted the shear forces rather than the tension zone. The shear capacity of concrete was defined based on the material failure criteria of concrete. The shear capacity of the compression zone was evaluated along the inclined failure surface, considering the interaction with the compressive normal stress. Since the distribution of the normal stress varies with the flexural deformation of the beam, the shear capacity was defined as a function of the flexural deformation. The shear strength of a beam was determined at the intersection of the shear capacity curve and the shear demand curve. The result of the comparisons to existing test results showed that the proposed model accurately predicted the shear strength of the test specimens.

• International Journal of Highway Engineering
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• v.6 no.1 s.19
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• pp.37-45
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• 2004

The characteristics of concrete strength and fracture parameters of recycled aggregate concrete were investigated to apply to the concrete pavements. As the results, the early strength of recycled aggregate concrete showed to be lower than that of natural coarse aggregate concrete, whereas strength at 28 days showed to be similar. Young's modulus of recycled aggregate concrete was lower than that of natural coarse aggregate concrete due to the difference of aggregate strength. And recycled aggregate concrete contained with ground granulated blast furnace slag seemed to have an effect of strength increasing. The critical stress intensity factor of recycled aggregate concrete at the early age was increased, and converged to be similar, compared to natural aggregate concrete at later age. The reliability of two-parameter fracture model was identified by the good correlation between the theoretical value computed by P-CMOD relationship and experimental results for Young's modulus and tensile strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.206-215
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• 2017

An experimental program was carried out to investigate the mechanical properties of high-strength concrete. High-strength concrete with compressive strengths of 80 to 120 MPa was tested. Test results are presented regarding effect of water-binder ratio on compressive strength and compressive strength gain. In addition, the effect of curing methods on compressive strength, elastic modulus, splitting tensile strength, and modulus of rupture is investigated. Test results of elastic modulus, splitting tensile strength, and modulus of rupture are compared with predictions from the current design recommendations. Predictions of elastic modulus by using KCI recommendation has good agreement with test results. However, predictions of modulus of rupture by using KCI recommendation underestimate the test results. ACI 363R recommendations predict well test results of splitting tensile strength and modulus of rupture. ACI 363R recommendations for predicting splitting tensile strength and modulus of rupture can be used for high-strength concrete with compressive strengths up to 120 MPa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.72-81
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• 2014

This paper reports the test results of reinforced concrete exterior beam-column joints with high-strength concrete. The main parameters of eight specimens were joint failure modes, the compressive strength of concrete, and the head shapes of steel bars. All specimens were designed according to ACI 352R-02 design recommendations. Two types of failure modes were considered; J-failure and BJ-failure. The longitudinal steel bars were anchored by 90 degree standard hooks or headed reinforcement. Experimental results indicated that the current ACI design recommendation limited by the compressive strength of concrete somewhat underestimated the strength of beam-column joints with high-strength concrete. In the specimens showed joint shear failure, the strength of beam-column joints with headed bars was approximately 10 percent higher than that of joints with 90 degree standard hooks.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.25-34
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• 2011

In general, many instrumentations of slope rely on theory or experience because on-site accessibility and long term instrumentation are difficult to conduct the instrumentation of slopes. Also the prediction of disaster is very difficult. Therefore experimental research was conducted about an effective method to predict collapse of slope and on-site applicability in this study. The collapse of slope was able to be predicted by applying AE sensor which we call WEAD to the failure criteria. The parameters of AE generated during the collapse of slope were secured through bending shear test. Test construction was applied to the slope with a history and a possibility of collapse. As a result, it is shown that AE parameters do not exceed the failure criterion and is found to be stable slopes. As the real symptoms of collapse did not appear, AE was found to have excellent applicability.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.346-351
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• 2003

In this paper, an evaluation method of fracture toughness on interface cracks has been investigated under various mixed-mode conditions of the bonded scarf joints. Two types of the bonded scarf joints with an interface crack were prepared to analyze the stress intensity factors using boundary element method(BEM) and to perform the fracture toughness test. From the results of fracture toughness experiments and BEM analysis, an evaluation method of fracture toughness on interface cracks in the bonded components of dissimilar materials has been proposed and discussed.