• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.45-52
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• 2014

The tunnel construction is increasing in order to secure a good driving performance of the car and train. A cases of tunnel collapse and the tunnel excessive displacement are increasing with the increase in tunnel construction. In terms of empirical construction methods using the strength characteristics of soil, it is important for tunnel construction to analyze causes of collapse and displacement. In the paper, it was analyzed the causes of collapse and excessive displacement of tunnel in the fractured ground condition. The results of analysis is that the increase of rainfall and lasting increase of displacement and large scale fractured ground are interconnected.

• Computers and Concrete
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• v.33 no.5
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• pp.545-557
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• 2024

A real-case incident occurred where a 9-meter-high segment of a pre-fabricated concrete separation wall unexpectedly collapsed. This collapse was triggered by improperly depositing excavated soil against the wall's back, a condition for which the wall segments were not designed to withstand lateral earth pressure, leading to a flexural failure. The event's analysis, integrating technical data and observational insights, revealed that internal forces at the time of failure significantly exceeded the wall's capacity per standard design. The Lattice Discrete Particle Model (LDPM) further replicates the collapse mechanism. Our approach involved defining various parameter sets to replicate the concrete's mechanical response, consistent with the tested compressive strength. Subsequent stages included calibrating these parameters across different scales and conducting full-scale simulations. These simulations carried out with various parameter sets, were thoroughly analyzed to identify the most representative failure mechanism. We developed an equation from this analysis that quickly correlates the parameters to the wall's load-carry capacity, aligned with the simulation. Additionally, our study examined the wall's post-peak behavior, extending up to the point of collapse. This aspect of the analysis was essential for preventing failure, providing crucial time for intervention, and potentially averting a disaster. However, the reinforced concrete residual state is far from being fully understood. While it's impractical for engineers to depend on the residual state of structural elements during the design phase, comprehending this state is essential for effective response and mitigation strategies after initial failure occurs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.28-39
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• 2013

The most common housing type in Korea is low-rise buildings with unreinforced masonry walls (UMWs) that have been known as a vulnerable seismic-force-resisting system (SFRS) due to the lack of ductility capacities compared to high lateral stiffness of an UMW. However, there are still a little experimental investigation on the shear strength and stiffness of UMWs and on the seismic performance of buildings using UMWs as a SFRS. In Korea, the shear strength and stiffness of UMWs have been evaluated with the equations suggested in FEMA 356 which can not reflect the structural and material characteristics, and workmanship of domestic UMW construction. First of all, this study demonstrates the differences in shear strength and stiffness of UMWs obtained from between FEMA 356 and test results. The influence of these differences on the seismic performance of UMW buildings is then discussed with incremental dynamic analyses results of a prototype UMW building that were selected by the site survey of more than 200 UMW buildings and existing test results of UMWs. The seismic performance assessment of the prototype UMW building are analyzed based on collapse margin ratios and beta values repesenting uncertainty of seismic capacity. Analysis results show that the seismic performance of the UMW building estimated using the equations in FEMA 356 underestimates both a collapse margin ratio and a beta value compared to that estimated by test results. Whatever the estimation is carried out two cases, the seismic performance of the prototype building does not meet the criteria prescribed in a current Korean seismic code and about 90% collapse probability presents for more than 30-year-old UMW buildings under earthquakes with 2400 return years.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.699-710
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• 2020

Pitting corrosion commonly shaped in hull structure due to marine corrosive environment seriously causes the deterioration of structural performance. This paper deals with the ultimate strength behaviors of stiffened ship panels damaged by the pits subjected to uniaxial compression. A series of no-linear finite element analyses are carried out for three stiffened panels using ABAQUS software. Influences of the investigated typical parameters of pit degree (DOP), depth, location and distribution on the ultimate strength strength are discussed in detail. It is found that the ultimate strength is significantly reduced with increasing the DOP and pit depth and severely affected by the distribution. In addition, the pits including their distributions on the web have a slight effect on the ultimate strength. Compared with regular distribution, random one on the panel result in a change of collapse mode. Finally, an empirical formula as a function of corrosion volume loss is proposed for predicting the ultimate strength of stiffened panel.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.67-74
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• 2010

The cases of collapse of greenhouses in rural areas have been increasing due to the unexpected heavy snow load. Studies on how to prevent the collapse of greenhouses are rare, however, and the damages are repeated annually. This studysuggests two reinforcing methods: the use of ahigh-strength tapered module, and the addition of a pre-tension tie. The high-strength tapered section is installed where the bending moment is maximum. The design of a plastic greenhouse is controlled by its strength rather than its deflection. The shape of a greenhouse resembles that of an arch system, but its actual structural behavior is the frame behavior, because it is non-continually composed of a curved element (a beam) and vertical elements (columns). This system is too weak and slender to resist a vertical load, because an external load is resisted by the moment rather than by axial force. In this study, a new method, the installation of a temporary tie at the junction of the arch and the column only during snow accumulation, is proposed. The tie changes the action of the greenhouse frame to an arch action. The arch action is more effective when the pre-tension force is applied in the tie, which results in a very strong temporary structural system during snowfall. As a result of using this high-strength tapered section, the combined strength ratio of what? decreased from 10% to 30%. In the case of the additional reinforcement with a tie, it was reduced by half.

• Journal of Aerospace System Engineering
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• v.4 no.3
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• pp.1-5
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• 2010

Understanding the crushing behaviour of aluminum honeycombs under dynamic loading is useful for crash simulations of vehicles and for design of impacting energy absorbers. In the study of honeycomb crushing under quasi-static, dynamic loading, the most important parameter is crush strength. Crush strength is indicated to energy absorption characteristic of aluminum honeycomb. In this study, Using Finite Element Analysis carried out crush strength of hexagonal aluminum honeycomb then the results was compared with Quasi-static test. Consequently, Crush strength is different in quasi-static loading and dynamic loading about 16%.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.55-61
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• 2009

Recently, highway tunnel construction has rapidly been increased due to the limited ground usage and geographical characteristic in Korea, i.e. Korea consists of 70% mountains. In this paper, it was analyzed tunnel collapse patterns in the weathered rockmass. Recent tunnel collapse pattern is quite different from that of past ten years. Tunnels in past years have been collapsed at shallow valley area because of shear strength decrease after heavy rain. Tunnels, which have been constructed recently, were collapsed at even the deeper ground position after primary support. Also in the case that proper reinforcement was not applied, it caused excessive crack at shotcrete and local collapse near tunnel face. In this paper, it was analysed the cause of the recent tunnel collapses and proper reinforcement for the collapsed tunnels.

• International Journal of High-Rise Buildings
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• v.4 no.3
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• pp.171-180
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• 2015

A shaking table test was conducted at the E-Defense shaking table facility to investigate the damage and collapse behavior of a steel high-rise building under exceedingly large ground motions. The specimen is a one-third scale 18-story steel moment frame designed and constructed according to design specifications and practices used in the 1980s and 1990s. The shaking table tests used a long-duration, long-period ground motion simulated for a sequential Tokai, Nankai, and Nankai earthquake scenario. The building specimen was subjected to a series of progressively increasing scaled motions until it completely collapsed. The damage to the steel frame began through the yielding of beams along lower stories and column bases of the first story. After several excitations by increasing scaled motions, cracks initiated at the welded moment connections and fractures in the beam flanges spread to the lower stories. As the shear strength of each story decreased, the drifts of lower stories increased and the frame finally collapsed and settled on the supporting frame. From the test, a typical progression of collapse for a tall steel moment frame was obtained, and the hysteretic behavior of steel structural members including deterioration due to local buckling and fracture were observed. The results provide important information for further understanding and an accurate numerical simulation of collapse behavior.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.421-433
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• 2020

Masonry infills are normally considered as non-structural elements in design practice, therefore, the interaction between the bounding frame and the strength contribution of masonry infills is commonly ignored in the seismic analysis work of the RC frames. However, a number of typical RC frames with irregular distributed masonry infills have suffered from undesirable weak-story failure in major earthquakes, which indicates that ignoring the influence of masonry infills may cause great seismic collapse risk of RC frames. This paper presented the investigation on the risk of seismic collapse of RC frames with irregularly distributed masonry infills through a large number of nonlinear time history analyses (NTHAs). Based on the results of NTHAs, seismic fragility curves were developed for RC frames with various distribution patterns of masonry infills. It was found that the existence of masonry infills generally reduces the collapse risk of the RC frames under both frequent happened and very strong earthquakes, however, the severe irregular distribution of masonry infills, such as open ground story scenario, results in great risk of forming a weak story failure. The strong-column weak-beam (SCWB) ratio has been widely adopted in major seismic design codes to control the potential of weak story failures, where a SCWB ratio value about 1.2 is generally accepted as the lower limit. In this study, the effect of SCWB ratio on inter-story drift distribution was also parametrically investigated. It showed that improving the SCWB ratio of the RC frames with irregularly distributed masonry infills can reduce inter-story drift concentration index under earthquakes, therefore, prevent weak story failures. To achieve the same drift concentration index limit of the bare RC frame with SCWB ratio of about 1.2, which is specified in ACI318-14, the SCWB ratio of masonry-infilled RC frames should be no less than 1.5. For the open ground story scenario, this value can be as high as 1.8.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1249-1250
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• 2013