• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.53-62
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• 2018

Follofwing the accelerating speed-up of trains and rising demand for large-volume transfer capacity, not only in Korea, but also around the world, track structures for trains have been improving consistently. Precast concrete slab track (PST), a concrete structure track, was developed as a system that can fulfil new safety and economic requirements for railroad traffic. The purpose of this study is to provide the information required for the development and design of the system in the future, by analyzing the behavior of each structural member of the PST system. The stress distribution result for different combinations of appropriate loads according to the KRL-2012 train load and KRC code was analyzed by conducting a three-dimensional finite element analysis, while the result for different thicknesses of the grouting layer is also presented. Among the structural members, the largest stress took place on the grouting layer. The stress changed sensitively following the thickness and the combination of loads. When compared with a case of applying only a vertical KRL-2012 load, the stress increased by 3.3 times and 14.1 times on a concrete panel and HSB, respectively, from the starting load and temperature load. When the thickness of the grouting layer increased from 20 mm to 80 mm, the stress generated on the concrete panel decreased by 4%, while the stress increased by 24% on the grouting layer. As for the cracking condition, tension cracking was caused locally on the grouting layer. Such a result indicates that more attention should be paid to the flexure and tension behavior from horizontal loads rather than from vertical loads when developing PST systems. In addition, the safety of each structural member must be ensured by maintaining the thickness of the grouting layer at 40 mm or more.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.125-132
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• 2019

Because the water exposed to shock waves caused by an underwater explosion cannot withstand the appreciable tension induced by the change in both pressure and velocity, the surrounding water is cavitated. This cavitating water changes the transferring circumstance of the shock loading. Three phenomena contribute to hull-plate damage; initial shock loading and its interaction with the hull plate, local cavitation, and local cavitation closure then shock reloading. Because the main concern of this paper is local cavitation due to a near-field underwater explosion, the water surface and the waves reflected from the sea bottom were not considered. A set of governing equations for the structure and the fluid were derived. A simple one-dimensional infinite plate problem was considered to verify this uncoupled solution approach compared with the analytic solution, which is well known in this area of interest. The uncoupled solution approach herein would be useful for obtaining a relatively high level of accuracy despite its simplicity and high computational efficiency compared to the conventional coupled method. This paper will help improve the understanding of fluid-structure interaction phenomena and provide a schematic explanation of the practical problem.

• Journal of the Korean Geotechnical Society
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• v.24 no.7
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• pp.25-36
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• 2008

The plane strain test can reproduce the real field condition and failure behavior precisely over other laboratory shear tests. Accordingly, this test has been utilized to investigate the shearing behaviors associated with overall failure behavior and local deformation of soils. However, most plane strain tests have been carried out with restrained end plates due to difficulties in manufacturing the equipment and also performing it. This restraint induces different results with real field because of shear stress on end plates. In this study, plane strain tests with/without bottom plate restraint were performed on Jumunjin-sand. The measurement of overall and local deformation was accomplished by digital image correlation technique as well as external LVDT. By applying digital image correlation method using two consecutive images captured through the transparent wall, local deformation behavior of various parts inside the specimen was estimated. And the formation and development of shear band caused by the restrained effect of end plate and the deformation mechanism of sand under plane strain condition were examined.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.251-258
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• 2011

Steel pipe piles have been used as various deep foundation materials for a long time. Recent increase in steel material cost has made engineers reluctant in using it even with its good quality and ease of construction. Therefore when constructing with steel pipe pile, the decision to reuse the excessive pile length that is cut off from the designed pile head elevation after pile driving can be cost saving. This has caused many constructors to reuse the pile leftovers with new piles, but the absence of quantitative structural capacity behaviors of steel pipe pile after pile driving or appropriate countermeasures and standards in reusing steel pipe pile has resulted in wrong applications, pile structural integrity problems, inappropriate limitation of reusable pile length, etc. The structural performance analysis between a new pile and a pile that has undergone working state and ultimate state stress level during pile driving was performed in this research by means of comparing the results between the dynamic pile load test, tensile load test, charpy energy test and fatigue test for high strength steel of $440N/mm^2$ yield strength. Test results show that under working load conditions the yield strength variation is less than 2% and for ultimate load conditions the variation is less than 5% for maximum total blow count of 3000. The results have been statistically analyzed to check the sensitivity of each factors involved. From the test results, reusability of steel pipe pile lies not in the main pipe yield strength deviation but in the reduction of absorb energy, strength changes and quality control at the welded section, shape deformation and local buckling during pile driving.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.9-20
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• 2019

The number of natural disasters in Korea, such as earthquakes, is increasing. As a result, there is growing need for temporary residences or shelters for disaster conditions. The aim of this study was to produce post-disaster refugees housing differentiated from existing shelters using lightweight composite panels. To accomplish this, the structural performance of lightweight composite panels was validated, and an in-plane shear strength test was conducted according to the ASTM E72 criteria among the performance test methods for panels. As a result of the experiment, the maximum load for each specimen under an in-plane shear load was determined. All the experiments ended with the tear of the panel's skin section. The initial stiffness of the specimens was consistent with that predicted by the calculations. On the other hand, local crushing and tearing, as well as the characteristics of the panel, resulted in a decrease in stiffness and final failure. Specimens with an opening showed a difference in stiffness and strength from the basic experiment. The maximum load and the effective area were found to be proportional. Through this process, the allowable shear stress of the specimens was calculated and the average allowable shear stress was determined. The average ultimate shear stress of the lightweight composite panels was found to be $0.047N/mm^2$, which provides a criterion of judgement that could be used to expect the allowable load of lightweight composite panels.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.13-23
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• 2010

In this study, centrifuge model tests with 50 g gravitational condition were performed to evaluate the bearing capacity of very soft ground, improved by spreading geotextile and sand on the surface of ground, for the heavy machinery to be able to access. For undrained shear strength of ground model, prepared with the clay sampled from the field, being in the range of 3.1~11.7 kPa, bearing capacity tests were performed with the model footing and the loading system built to simulate the heavy machinery on the ground model treated with geotextile and sand. Test results were compared with theoretically and numerically evaluated ones. Test results about load-settlement curves showed that the bearing capacity increases with the increase of the undrained shear strength of ground. Punching shear or local shear failure was also observed. For a relatively low undrained shear strength of ground, settlement behavior is found to be crucial to evaluating the trafficability of machinery whereas bearing capacity becomes a dominant factor with the increase of undrained shear strength of ground. The method for assessing the bearing capacity of the ground related to trafficability of machinery is presented by acquiring the regression relationship between the contact pressure of machinery and settlements using load-settlement curves with the change of the undrained shear strength. Furthermore, results of numerical analyses about load-settlement relation are in relatively good agreement with those of centrifuge model test.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.81-91
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• 2006

The corrugated web is a plate that was manufactured with a corrugated shape. It is widely used in bridges, buildings, and culverts. A girder with a corrugated web can be crippled by local, in-plane compressive loads. Due to its high out-of-plane strength, however, a stiffener is usually not needed in trapezoidally corrugated plates, and the corrugated profile of the web can change the boundary condition of the edge load. Some researchers have studied the strength of the partial-edge loading of the trapezoidally corrugated web, but they have not considered the profile of corrugation in their studies. This paper investigates the influence of the corrugate profile. A parametric study was conducted on the shape parameter using the finite-element method. In this parametric study, the relationship between the corrugated shape and the partial-edge strength was also investigated by dividing the partial-edge strength into the web capacity and the flange capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.69-77
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• 2017

By producing pre-engineered modular system in the factory, It is enable to expedite construction and can be distinguished from two types by the method resisting load. One is the open-sided modular system composed of beams and columns. The other is enclosed modular system composed of panels and studs. Of the modular systems, the open-sided modular system buildings the connection between modules are difficult due to closed member sections, and the overall strength is reduced as a result of local buckling. In this study, in order to solve these problems, a modular system with folded steel members filled with concrete are proposed. The capacity spectrum method presented in ATC 40 is used for seismic performance assessment of the proposed model structure and the structure with conventional steel members. The analysis results show that at the performance point of each model the number and rotation of plastic hinge formed in the proposed modular system are smaller than those in the conventional system. Based on this observation it is concluded that the proposed system with composite sections has superior seismic capacity compared with conventional system.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.134-139
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• 2002

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. However, effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study, we investigated failure modes of locally wall thinned pipes and AE signals by bending test. From test results, we could be divided four types of failure modes of ovalization, crack initiation after ovalization, local buckling and crack initiation after local buckling. And fracture behaviors such as elastic region, yielding range, plastic deformation range and crack progress could be evaluated by AE counts, accumulative counts and time-frequency analysis during bending test. It is expected to be basic data that can protect a risk according to local wall thinning of pipes, as a real time test of AE.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.32-39
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• 2006

An acoustic emission technique was applied to the structural strength test for the structural integrity evaluation of the nozzle assembly. These AE results were compared with data from the strain gages and displacement transducer. NDT using X-ray technique was performed to improve the test reliability before and after each test. In this structural integrity evaluation of the nozzle assembly, the internal crack initiation in the structure could not be precisely revealed by the strain and displacement results but the location and load level of the initiated crack could be precisely evaluated by using AE technique. From this test, it was proven that some new cracks can be generated in composite liner of nozzle assembly under the unexpected load due to interference between obturator and nozzle and these can be a cause of the unexpected abnormal failure.