• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.1
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• pp.106-116
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• 1989

This study aims at scrutinizing the long4errn consolidation characteristics of peats sampled at three different regions of Chonbuk province. The standard consolidation test and the single load consolidation test were performed about these samples and especially in case of the latter the loading period was 350 days. The main condusions analyzed are as follows. 1. Void ratio showed much greater values than that of the general clay and was decresed greatly according to the increase of the load. 2. In case of the relationship between the sefflement and the long-term settlement time the rate of settlement increment became great according to the increase of the load step and the long4erm settlement became linely proportional to the logarithm of time alter 10 minutes. 3. The linear correlation was showed between the long4erm settlement time and the void ratio and therefore equations by regression analysis were derived in order to estimate the long-term settlement The slope of straight lines increased according th the increase of the load step and secondary consolidation coefficients ranged from 0.04-0.27. 4. The secondary consolidation coeffcient became linealy proportional to the compression index and the ratio of Ca to CC was 0.072. 5. The period required in ending the primary consolidation was about 10 minutes and alter that the secondary consolidation coefficient appeared to have constant value. Therefore the secondary consolidation coefficient was judged to be used as a significant factor in estimating the long4erm settlement. 6. In case of the single load consolidation test the secondary consolidation coefficient showed the tendancy increasing according to the increase of the consolidation pressure.

• Wind and Structures
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• v.6 no.5
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• pp.403-418
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• 2003

This paper presents an extensive analysis of the short term, unsteady wind loading on a low-rise building. The building is located in a rural environment and only the specific situation of wind flow orthogonal to the long face of the structure is considered. The data is analysed using conventional analysis and less traditional methods such as conditional sampling and wavelet analysis. The nature of the flow field over the building is found to be highly unsteady and complex. Fluctuating pressures on the windward wall are shown to a large extent to be caused by the fluctuations in the upstream flow, whereas extreme pressures on the roof are as a result of high intensity small scale flow structures. On the roof of the building a significant amount of energy is shown to exist at frequencies above 1 Hz.

• The Journal of Advanced Prosthodontics
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• v.14 no.3
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• pp.133-142
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• 2022

PURPOSE. A large number of studies have suggested the practicability and predictability of immediate implant function, but few studies have reported marginal bone level changes during sequential loading periods. The purpose of this study was to evaluate the marginal bone remodeling of immediately loaded self-tapping implants both at each time point and during each loading period between two time points. MATERIALS AND METHODS. The patients included in this retrospective study were treated with immediately loaded NobelSpeedy Replace implants between August 2008 and July 2009. Differences in the marginal bone level (MBL) at each time point and the marginal bone level change (ΔMBL) between two time points were analyzed with Bonferroni correction (P < .05). RESULTS. Overall, 24 patients (mean age, 47.3 ± 12.8 years) with 42 immediately loaded implants and a median follow-up of 6.5 years (IQR, 67.8 months) were included. The cumulative survival rate after 10 - 12 years was 95.2%. Continuous but slow marginal bone loss was observed during long-term follow-up. MBL at both 7.5 years and 11 years was significantly lower than that at loading, 6 months, 2 years and 4 years (P < .05). No bone loss difference was found in any period before 4 years of follow up (P > .05). The loading period of 4 years to 7.5 years showed the largest ΔMBL compared to those of other time periods (P < .05). CONCLUSION. Slight bone loss occurred continuously, and more radical changes of marginal bone can be observed during the period of 4-7.5 years. Thus, long-term effective follow-up of immediately loaded implants is needed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.343-350
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• 2017

The RC flat plate system has benefits such as a short construction time, an improvement of workability and a floor height reduction. In the case of long span slab, cracking damages and large deflections tend to occur due to the low flexural stiffness of flat plates. Specially, over-loading by self-weight of slab during construction increases short and long-term deflections. These problems may be solved by the use of void slab that has benefits of the reduced self-weight. In this study, to analyze an effect of self-weight reduction of void slab on slab deflections, the parametric study is performed. Including variable conditions such as a concrete strength, a slab construction cycle, the number of shored floors, a compressive reinforcement ratio and a tensile reinforcement ratio, slab construction loads and deflections are calculated by considering the construction stages, concrete cracking, and long-term effects. The short-term deflections during construction and the long-term deflections after construction of both of normal and void slabs are compared and the effects of void slab on the reduction of slab deflections are analyzed.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.531-552
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• 2016

The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.65-76
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• 2011

This paper presents the results of a numerical investigation on the long-term behavior of geosynthetic reinforced soil abutment. The investigation was carried out aiming at identifying the governing mechanisms of the long-term deformation of geosynthetic-reinforced soil abutment subjected to sustained loads during service life. A numerical modeling strategy was first established using the Singh-Mitchell creep model and the power law model, respectively, for the backfill and the geosyntehtic reinforcement. A parametric study on the creep properties of the backfill and the geosynthetic reinforcement was then conducted. The results indicated that a geosynthetic reinforced soil structure backfilled with marginal soil may exhibit substantial long-term deformation due to the creep effects caused by both the backfill soil and the geosynthetic reinforcement, the magnitude of which depends largely on the creep properties. This paper highlights the importance of considering the creep effect on load supporting geosynthetic reinforced soil structures when the long-term serviceability requirement is of prime importance.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.31-38
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• 2012

In this present study, the long-term consolidation tests were performed using the remolded Kwang-Yang port clayey soil to clarify the effect of stress history and over-consolidation ratio (OCR) on the long-term consolidation characteristics of the soft clayey soil. For the over-consolidated state clayey soils, in case OCR exceeds 1.5, there are no great differences of secondary consolidation settlement and final settlement even if OCR increases from 2.0 to 3.0. Therefore, it has been understood that the value of OCR applied on the field site to reduce the secondary consolidation settlement and the final settlement is about 1.5. In addition, in order to investigate the relationship between the pre-loading period and the characteristics of long-term consolidation behavior obtained from the test results using the remolded Kwang-Yang port clayey soils, the influence on long-term consolidation behavior was not large though the pre-load was unloaded with the consolidation degree 70~80% exceeded.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.1029-1034
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• 2002

Object of this paper are numerical and experimental evaluation of Korean Standard Train Loading(L-loading scheme) with respect to UIC's and real train loading, quantitative formulation of the real train types in South Korea. These objects are require to changing environment of train operation, for example, high density traffic and gradual train speed increase. For the reasonable repair, reinforcement and rehabilitation of existing railway infrastructures, statistical analysis of the loading effect during the long term experiment in conventional lines have to conduct. Statistical quantitative formulation of the loading case need to consistency numerical evaluation of the railway safety. Hereafter, those results will be core technical data for the economy enhancement of international line construction. Further, these results are using to make track maintenance criterions for transcontinental, speed up railway and revision of standard train leading diagram.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.101-116
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• 2008

The use of reinforced earth walls id permanent structures is getting its popularity. Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exists concerns over long-term residual deformations when subjected to repeated and/or cyclic loads, during their service period. In this investigation, the effects of pre-loading in reducing long term residual deformation of reinforced soil structures under sustained and/or repeated loading environment are investigated using a series of reduced-scale model tests. A model pier and a back-to-back (BTB) reinforced soil structures were constructed and tested under various loading and backfilling conditions. The results indicate that the pre-loading technique can be an effective means of controlling residual deformations of reinforced soils under various loading conditions.