• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.74-83
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• 2001

After the concept of fracture mechanics was applied to fatigue crack propagation by Paris. Paris' law is widely used to predict fatigue crack growth behavior. Since Elber proposed the effective stress intensity factor(SIF) and showed a good agreement with experimental results using the proposed SIF, emphasis in crack propagation studies has been placed on measuring the effective stress range ratio. This paper proposes a numerical model to simulate the crack closure and propagation behaviour under various loading spectrum. The validity of the proposed model is checked by comparing with the Toyosada numerical solutions on the crack propagation behaviour. Important insights developed are summarized.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.479-487
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• 2023

Recently, the destructive power of typhoons is continuously increasing owing to global warming. In a situation where the installation of floating wind turbines is increasing worldwide, concerns about the huge loss and collapse of floating offshore wind turbines owing to strong typhoons are deepening. A new type of disconnectable mooring system must be developed for the safe operation of floating offshore wind turbines. A new submersible mooring pulley considered in this study is devised to more easily attach or detach the floating of shore wind turbine with mooring lines compared with other disconnectable mooring apparatuses. To investigate the structural safety of the initial design of submersible mooring pulley that can be applied to an 8MW-class floating type offshore wind turbine, scale-down structural models were developed using a 3-D printer and structural tests were performed on the models. For the structural tests of the scale-down models, tensile specimens of acrylonitrile butadiene styrene material that was used in the 3-D printing were prepared, and the material properties were evaluated by conducting the tensile tests. The finite element analysis (FEA) of submersible mooring pulley was performed by applying the material properties obtained from the tensile tests and the same load and boundary conditions as in the scale-down model structural tests. Through the FEA, the structural weak parts on the submersible mooring pulley were reviewed. The structural model tests were conducted considering the main load conditions of submersible mooring pulley, and the FEA and test results were compared for the locations that exceeded the maximum tensile stress of the material. The results of the FEA and structural model tests indicated that the connection structure of the body and the wheel was weak in operating conditions and that of the body and the chain stopper was weak in mooring conditions. The results of this study enabled to experimentally verify the structural safety of the initial design of submersible mooring pulley. The study results can be usefully used to improve the structural strength of submersible mooring pulley in a detailed design stage.

• Journal of the Korean GEO-environmental Society
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• v.16 no.2
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• pp.53-58
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• 2015

The Pre-loading method has been widely used for the soft ground stabilization but long construction times and the transport of large quantities of fill material are required. To shorten the construction periods, the vertical drain method is generally applied simultaneously. But the high costs of the fill materials along with environmental damages remain as the main difficulties to apply this method. Therefore, a complimentary way to reduce both the height of the embankment and the consolidation time is needed. In this study, the electro-osmosis method, which is able to shorten the consolidation time and minimize the damage of the environment, was performed with a model test. The results show that as the voltage increases the consolidation settlements, consolidation drainage and shear strength also increase while the water content decreases.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.7-14
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• 2011

The numerical analyses were performed to investigate the curling behavior of the post-tensioned prestressed concrete approach slab (PTAS) under environmental loads. A technique to include properly the boundary conditions of one end of PTAS that was connected to the bridge abutment using hinges was proposed for the numerical model. The applicability of a simplified model not having hunches was also investigated. By using the developed models, the curling behavior of PTAS was analyzed when the foundation settlement occurred. The analysis results showed that the maximum tensile stress obtained from the simplified model involving a simplified hinge connection was very closed to that obtained from a rigorous model. When the slab curled up, the maximum tensile stress occurred in the model including no foundation settlement, but when the slab curled down, the maximum stress occurred in the model including partial settlement of the foundation. Therefore, the design of PTAS should be performed considering those maximum tensile stresses.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.471-480
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• 2015

The building structure is planned to maximize the use of space in recent. It was developed of a hybrid OCB (Optimized Composite Beam) for trying to take advantage of the maximize space. The OCB is composed of the steel h-beam section reinforced by open strands in negative moment zone and the psc concrete section in positive zone. Flexural behaviors of typical architectural bybrid OCB section was investigated. The 15 m OCB specimen was tested under three point static loading system. Following results are obtained from the tests; 1) The OCB with 15 m span develop initial flexural crackings under the 171% of full service loading. 2) Overall deflections of OCB under the service loads are less than those of the allowable limit in KCI Code provision. 3) The crack patterns, failure mode and ultimate load capacity of test specimen and F.E. model in this paper and they are compared to each other. The OCB is verified of structural reliability from the experimental results.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.285-294
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• 2002

Embankment Piles, which is subjected to damage due to lateral movement of soft ground, can be classified into pile slab, cap beam pile, and isolated cap pile according to the installation pattern of pile cap. In the cap beam pile and the isolated cap pile method, the soil arch is developed by the different stiffness between pile and soil, and most embankment loads are transferred into embankment piles through soil arch. In these two methods, the difference of soil arch is that the soil arch of the cap beam pile method develops like the arch from of tunnel between cap beams and the soil arch of the isolated cap pile method develops like dome between isolated caps. Therefore, theoretical analysis methods on soil arching effect of the cap beam pile and the isolated cap pile method were respectively proposed according to their own arch form considering the limiting equilibrium of stresses in a crown of soil arch. And a series of model tests were performed both to investigate the load transfer by soil arching in fills above embankment piles and to verify the reliability of the theoretical analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.61-68
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• 1988

This study is intended to propose an approach to reliability-based safety evaluation as well as LRFR(Load and Resisitance Factor Rating) type capacity classification of military or civilian bridges based on the limit state models which are delived by incorporating all the uncertainties of resistance and load random variables including deterioration, and are used in a practical AFOSM (Advanced First Order Second Moment) method. The proposed methods for the assement of safety and load carrying capacity are applied for the evaluation of rating and classifications of several practical bridges against the crossing of military vehicles. Based on the observation of the numerical results, it can be concluded that the current NATO classification method which is based on the traditionl allowable stress concept can not provide real load carrying capacity but results in nominal classification, and therefore the reliability-based safety evaluation and LRFR-classification method or the corresponding rational allowable stress method proposed in this paper may have to be introduced into the classification practice.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1947-1955
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• 2013

The purpose of this paper is to present an photoelasticity technique for measuring the displacement and stress distribution in particle assembly subjected to shallow foundation loading. Photoelastic measurement technique was employed to visualize the force transmission of a particle assembly. A model assembly bounded by a steel frame was built by stacking bi-dimensional circular particles made of polycarbonate elastomer. Each particle was coated by a thin photoelastic sheet so that the force transmission represented by bright light stripes can be visualized. In a contacted particle, both magnitude and orientation of principal stress difference can also be measured via the photoelasticity technique. The different distributions of the contact stresses at the initial loading and near the failure were quantitatively compared. The photoelastic patterns and displacement fields observed in the pre-failure state disappears immediately after the buckling of confined force chains.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.329-338
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• 1999

A systematic procedure to evaluate fatigue damages and to predict remaining fatigue lives is introduced for a steel railway bridge. Fatigue damages are evaluated by using the currently available fatigue damage theory. Fatigue lives with the condition of fatigue crack initiation are estimated by the probabilistic approach based on the reliability theory as well as the simplified procedure. A equivalent deterministic procedure is also suggested to assess the remaining fatigue life under various traffic conditions. Numerical simulations are used to assess dynamic stress histories with correction factors. Loading models are obtained from the passenger volume data. Train coincidences are also considered. Based on the results, the fatigue life is found to be underestimated by without considering the coincidence of trains on the bridge. The simplified method proposed in this study are found to yield approximately the same results as the systematic procedure.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.711-720
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• 2002

A 3-D numerical model, which could demonstrate the static and dynamic responses of a curved bridge more precisely with the moving vehicles, was developed The dynamic response induced by the centrifugal rolling motion of vehicle was identified according to the variations of the partial grade and the curvature of the slab. Dynamic characteristics of the curved bridge with the moving vehicle were analyzed under the condition of support types and two different support systems. Parametric studies were conducted to compare the efficiency of load distribution in the curved bridge. In general, while the vehicle was crossing the curved bridge, negative reaction occurred in the inside of the girder. The final result showed that the support system located outside the girder was more advantageous than other systems, and the characteristics of load distributions differed from the others in the various conditions of support systems.