• Proceedings of the Korean Geotechical Society Conference
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• 1993.03a
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• pp.41-48
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• 1993

The 2nd phase of Seoul Subway, Lines 5,6,7 and 8, is in progress. To reduce the surface traffic congestion during construction the greater part of the system has been engineered by bored tunnelling. The current tunnelling methodology is based on the New Austrian Tunnelling Method. Serveral collapses have been reported to date. Most of the collapses took place in the area forwed with soft ground. The modes and causes of the collapses were progressive failures in the unsupported surface and sliding failures due to the unfavourable joint direction. The major causes turned out to be the weakness of ground and the sudden influx of ground water from the surface. Some measures to prevent the failures are also presented. To ensure the safe tunnelling ghrough the soft ground the unsupported excavation area has to be minimized and closed as early as possible. Additional support measures such as supporting core, sealing shotcrete, forepoling, spread footing, face rock bolting and grouting should be employed as well depend on ground conditions.

• Structural Engineering and Mechanics
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• v.3 no.6
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• pp.529-539
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• 1995

The rigid-plastic yield-line analysis of isotropically reinforced concrete slabs acting in conjunction with torsionally weak supporting beams is developed as the lower-bound form of a linear programming formulation. The analysis is extended to consider geometric variation of chosen yield-line patterns by the technique of sequential linear programming. A strategy is followed of using a fine potential yield-line mesh to identify possible collapse modes, followed by analysis using a coarser, simplified mesh to refine the investigation and for use in conjunction with geometric optimization of the yield-line system. The method is shown to be effective for the analysis of three slabs of varying complexity. The modes detected by the fine and simplified analyses are not always similar but close agreement in load factors has been consistently obtained.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.115-124
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• 1993

A structural system reliability analysis is studied for the safety assessment of midship section. Probabilistically dominant collapse modes are generated by Element Replacement Method and Incrimental Load Method. In order to avoid generating the same modes repeatedly, it is branched at final plastic hinge. Using first and second order bound methods, system failure probability of midship section is computed and compared with deterministic load factor method to show the usefulness of the proposed method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.103-111
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• 2002

The objective of this study is to collect and classify bridge failures that occurred in domestic from 1974 through 2001 and to draw the engineering informations by analyzing the principal causes and the trends of the bridge failures. Total 45 failures of bridge were obtained and analyzed based on the factors such as time of failures, modes of failures, classification of materials of failed elements, types of failed elements, distribution of failure cases with respect to the highway grades. The critical problems of bridge failures are associated with the construction deficiencies, external causes, maintenance deficiencies, and design deficiencies. Since the study of failures in bridges would enhance the design and construction of safe bridges in the future, it would be needed to create data bases at the national level and to alter the related codes with identifying potential deficiencies from past failures data.

• Steel and Composite Structures
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• v.17 no.2
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• pp.159-172
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• 2014

A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.11-17
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• 1997

Simple and efficient way of nonlinear analysis considering elasto-plastic large deformation is introduced to calculate the strength of ring-stiffened cylinears subject to combined load of axial compression and lateral pressure. Parametric study gives various collapse modes according to the combination ratio of axial compression and lateral pressure, interaction between axial compression and lateral pressure and imperfection sensitivity of ultimate strength.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.6
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• pp.711-729
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• 2018

This paper reports on the experimental investigations on the failure modes of ring-stiffened cylinder models subjected to external hydrostatic pressure. Nine models were welded from general structural steel. The shells were initially formed by cold-rolling, and flat-bar ring frames were welded to the shell. The hydrostatic pressure tests were conducted by using water as the medium in pressure chambers. The details of the preparation and main test were briefly explained. The investigation identified the consequence of the structural failure modes, including: shell yielding, local shell buckling between ring stiffeners, overall buckling of the shell together with the stiffeners, and interactive buckling mode combining local and overall buckling. In addition, the ultimate strengths were predicted by using existing design codes. Non-linear numerical computations were also conducted by employing the actual imperfection coordinates. Finally, accuracy and reliability of the predictions of design formulae and numerical were substantiated with the test results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.218-227
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• 2014

In this paper, it performed to the elastic-plastic large deflection series analysis using the experimental model and predicted a failure mode and ultimate strength. The collapse mode of numerical analysis model is formed a plastic hinge on loaded flange and consistent with the collapse mode of experimental model. Also, The yield line is formed in the web could observed that have occurred the crippling collapse mode and the ultimate loads of the experimental model and numerical analysis model have maintained linearly Means 1.07, Standard deviation 0.04, Coefficient of variation(COV) 0.04 and the result of ultimate loads have appeared approximately 8% error rate. it was found that very satisfied to the experimental results and the applied rules. if it is considered to be maintain a reasonable safety level, it is possible to predict the failure modes of aluminium alloy plate girders and ultimate loads.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.569-583
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• 2018

The purpose of this study is to identify the collapse characteristics by analyzing various factors causing collapse based on field survey and existing data on rock slopes occurring in the construction of roads and industrial complexes in Gyeongsangnam - do area. In the case of the slope where the slope has been directly surveyed, the analysis of the collapse characteristics can be used for the prediction and prevention of slope failure through the continuous collection of the slope data, database construction, management and analysis. The evaluation items used in the collapse characteristics of slope were selected among the items that can be regarded as objective evaluation items among the overlapping factors by comparing the evaluation items frequently used for the evaluation of the existing slope stability among various factors. The type of destruction of the rock slope depends on the type of carcass of the bedrock, such as planar fracture, wedge fracture, onho fracture, and conduction fracture, which are different from each other. And the slope stability analysis should be performed accordingly.

• Steel and Composite Structures
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• v.39 no.4
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• pp.383-399
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• 2021

In the study, three 1:3-scale unequal span steel-concrete composite substructures with top-seat angle and double web angle connection were designed and identified as specimens GTSDWA-0.6, GTSDWA-1.0, and GTSDWA-1.4. Pseudo-static tests and refined numerical model analysis were conducted to examine the anti-progressive collapse performance of a semi-rigid steel-concrete composite substructure. The results indicated that the failure modes of the three specimens revealed that the fracture occurred in the root of the long leg of the top/seat angle in tension at the connection. With increases in the span ratio of the left and right composite beams, the bearing capacities of the composite substructures decreased, and the corresponding displacement increased. With respect to GTSDWA-0.6 and GTSDWA-1.4, the resistance due to the short composite beam corresponded to 62% and 60%, respectively, and the total resistance provided by the short composite beam exceeded that of the long composite beam. With respect to GTSDWA-1.0, the resistance due to the left and right composite beams was similar. All three specimens underwent the flexure mechanism and flexure-axial mixed mechanism stages. They resisted the external load mainly via the flexure mechanism. Moreover, the addition of stiffeners on both sides of the top and seat angles is advantageous in terms of improving the collapse resistance and ductility of unequal span composite substructures.