• Journal of the Korean Geotechnical Society
• /
• v.15 no.3
• /
• pp.113-129
• /
• 1999

In this study, a total of 12 types of sequential model tests were conducted at the laboratory for small scale anchored walls. The sequential behavior for flexible wall embedded in sand was investigated by varying degrees of relative density of Joomoonjin sand and flexibility number of model wall. The model tests were carried out in a 1000mm width, 1500mm length, and 1000mm high steel box. Load cells, pressure cells, displacement transducer and dial gauges were used to measure the anchor forces, lateral wall deflections, lateral earth pressures and vertical displacements of ground surface, respectively. Limited model tests were performed to examine the parameters for soil-wall interaction model and the formulation of analytical method was revised in order to predict the behavior of anchored wall in sand. Based on the model tests and proposed analytical method, model simulations were performed and the predictions by the present approach were compared with measurements by the model tests and predictions by other commercial programs. It is shown that the prediction by the present approach simulates qualitatively well the general trend observed for model test.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.2
• /
• pp.87-96
• /
• 2004

Application of the soil nailing method is continuously extending in maintaining stable excavations and slopes. However, ground anchor support system occasionally may not be used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing) is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, laboratory model tests are carried out to investigate the failure mechanism and behavior characteristics of the PSN system. Various results of model tests are also analyzed to provide a fundamental basis for the efficient design.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.5
• /
• pp.2125-2133
• /
• 2013

Recently, an interest on joint behavior between adjacent concrete slab tracks has increasing due to large application of such track system. Dowel bars are widely used to improve load transfer capacity across the joints. Dowel bars reduce the deflections and stresses by transferring the load between the slabs. This study proposes the lumped shear spring model to efficiently model dowel joints of adjacent slabs. This model includes bearing stiffness between dowel bar and concrete as well as dowel gap. Strength of the proposed spring model is evaluated based on Concrete Capacity Design method under the assumption of shear failure mode in the joints. Experiments are also performed up to failure to evaluate the accuracy of the proposed model. It has been observed that the proposed model is able to predict initial nonlinearity due to dowel gap, and capture material nonlinearity of the test slabs. Thus, it is recommended that the proposed model can be effectively applied to the dowel joints of concrete slab track.

• Safety and Health at Work
• /
• v.9 no.1
• /
• pp.42-52
• /
• 2018

Background: Maintenance operations on-board ships are highly demanding. Maintenance operations are intensive activities requiring high man-machine interactions in challenging and evolving conditions. The evolving conditions are weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress. For example, extreme weather condition affects seafarers' performance, increasing the chances of error, and, consequently, can cause injuries or fatalities to personnel. An effective human error probability model is required to better manage maintenance on-board ships. The developed model would assist in developing and maintaining effective risk management protocols. Thus, the objective of this study is to develop a human error probability model considering various internal and external factors affecting seafarers' performance. Methods: The human error probability model is developed using probability theory applied to Bayesian network. The model is tested using the data received through the developed questionnaire survey of >200 experienced seafarers with >5 years of experience. The model developed in this study is used to find out the reliability of human performance on particular maintenance activities. Results: The developed methodology is tested on the maintenance of marine engine's cooling water pump for engine department and anchor windlass for deck department. In the considered case studies, human error probabilities are estimated in various scenarios and the results are compared between the scenarios and the different seafarer categories. The results of the case studies for both departments are also compared. Conclusion: The developed model is effective in assessing human error probabilities. These probabilities would get dynamically updated as and when new information is available on changes in either internal (i.e., training, experience, and fatigue) or external (i.e., environmental and operational conditions such as weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress) factors.

• IEIE Transactions on Smart Processing and Computing
• /
• v.6 no.2
• /
• pp.93-101
• /
• 2017

This paper proposes an algorithm for adaptive loop filter (ALF) complexity reduction in the decoding process. In the original ALF algorithm, filtering for I frames is performed in the frame unit, and thus, all of the pixels in a frame are filtered if the current frame is an I frame. The proposed algorithm is designed on top of the local gradient calculation. On both the encoder side and the decoder side, homogeneous areas are checked and skipped in the filtering process, and the filter coefficient calculation is only performed in the inhomogeneous areas. The proposed algorithm is implemented in Joint Exploration Model (JEM) version 3.0 future video coding reference software. The proposed algorithm is applied for frame-level filtering and intra configuration. Compared with the JEM 3.0 anchor, the proposed algorithm has 0.31%, 0.76% and 0.73% bit rate loss for luma (Y) and chroma (U and V), respectively, with about an 8% decrease in decoding time.

• Proceedings of the KSPS conference
• /
• 2002.11a
• /
• pp.123-126
• /
• 2002

In this paper, we describe our LVCSR system for Korean broadcast news transcription. The main focus is to find the most proper morpheme-based lexical model for Korean broadcast news recognition to deal with the inflectional flexibilities in Korean. There are trade-offs between lexicon size and lexical coverage, and between the length of lexical unit and WER. In our system, we analyzed the training corpus to obtain a small 24k-morpheme-based lexicon with 98.8％ coverage. Then, the lexicon is optimized by combining morphemes using statistics of training corpus under monosyllable constraint or maximum length constraint. In experiments, our system reduced the number of monosyllable morphemes from 52％ to 29％ of the lexicon and obtained 13.24％ WER for anchor and 24.97％ for reporter.

• Geotechnical Engineering
• /
• v.14 no.3
• /
• pp.63-72
• /
• 1998

Laboratory model test results for ultimate uplift capacity of horizontal circular anchors embedded in soft clay overlain by dense sand are presented. The effect of the critical embedment ratio on the thickness of the clay layer was evalyated. An approximate preocedure for estimating the net ultimate capacity is presented.

• Journal of Mechanical Science and Technology
• /
• v.19 no.3
• /
• pp.826-835
• /
• 2005

Exposed-type steel column bases are used widely in low-rise building construction. Numerous researchers have examined methods to identify their stiffness and strength, but those studies have heretofore been restricted to in-plane behaviors. This paper presents an experimental investigation of inelastic behaviors of square hollow section (SHS) steel column bases under biaxial bending. Two types of failure modes are considered : anchor bolt yielding and base plate yielding. Different pinching effects and interaction surfaces for biaxial bending are observed for these two modes during bi-directional quasi-static cyclic loading tests. Differences are elucidated using limit analyses based on a simple analytical model.

• Geomechanics and Engineering
• /
• v.11 no.4
• /
• pp.587-605
• /
• 2016

This study aimed to develop upper and lower bounds to predict the tunnel support pressure under the pile tip during the circular tunnel excavation. Most previous studies on the upper and lower bound methods were carried out for the single ground structures, e.g., retaining wall, foundation, ground anchor and tunnel, in the homogeneous ground conditions, since the pile-soil-tunnel interaction problem is very complicated and sophisticated to solve using those bound methods. Therefore, in the lower bound approach two appropriate stress fields were proposed for single pile and tunnel respectively, and then they were superimposed. In addition, based on the superimposition several failure mechanisms were proposed for the upper bound solution. Finally, these upper bound mechanisms were examined by shear strain data from the laboratory model test and numerical analysis using finite element method.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1433-1438
• /
• 1994

Laboratory model test results for uplift capacity of a circular plate anchors embedded in saturated clayey soils have been presented. Clayey soils used in this study are kaolinite and montmorillonite. Suction effects on the ultimate uplift capacity of plate anchors with respect to various embedment depths of anchor have been considered.