• Computers and Concrete
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• 제22권3호
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• pp.291-303
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• 2018

As the concept of "sponge city" is proposed, the pervious concrete for permeable pavement has been widely used in pavement construction. This paper aims at investigating the dynamic behavior and energy evolution of pervious concrete under impact loading. The dynamic compression and split tests are performed on pervious concrete by using split Hopkinson pressure bar equipment. The failure criterion on the basis of incubation time concept is used to analyze the dynamic failure. It is demonstrated that the pervious concrete is of a strain rate sensitive material. Under high strain rate loading, the dynamic strength increases while the time to failure approximately decreases linearly as the strain rate increases. The predicted dynamic compressive and split tensile strengths based on the failure criterion are in accordance with the experimental results. The total damage energy is found to increase with the increasing of strain rate, which means that more energy is needed to produce irreversible damage as loading rate increases. The fractal dimensions are observed increases with the increasing of impact loading rate.

• Journal of Construction Engineering and Project Management
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• 제6권4호
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• pp.24-34
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• 2016

Disputes seem to be synonymous with large-scale construction projects in Ethiopia. The purpose of this study is to determine the factors responsible for impacting the performance of Ethiopian public construction projects. To this end, 35 success and failure attributes responsible for impacting the performance of the projects were identified and presented to Ethiopian construction professionals in the form of a structured questionnaire, and responses were collected. The factor analysis conducted on the success and failure attributes influencing no-dispute performance separately resulted in six success factors and five failure factors. Further analysis using stepwise multiple regression indicates that owner competence and interaction among project participants have a positive impact on no-dispute performance. However, conflict among project participants has a negative impact on the no-dispute performance of Ethiopian public construction projects. Although Ethiopia-specific, the results reflect construction management problems common to both developed and developing countries. The findings are expected to help researchers and practitioners gain a better understanding of critical success and failure factors and to help them take proactive measures to avoid disputes in public construction projects.

• 한국정밀공학회지
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• 제14권7호
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• pp.116-125
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• 1997

An investigation was performed to study the impact damage in CFRP laminated composites subjected to impact loading. A finite element model has been developed for predicting the impact damage in laminated composite plates resulting from the ballistic impact. The finite element model was based on the higher-order shear deformation theory and was used to predict the initial intraply matrix cracking and the shape and size of interface delamination in laminated composites. Numerical simulation was performed and then the initiation of the matrix cracking and the shape and size of impacted induced delamination were predicted, and te results were compared with those of impact experiments with the same dimension and stacking sequences. A linear relationship holds between impact velocity and length and width of delamination. As impact velocity is increased, the increase of delamination length is highger than the increase of delamination width.

• 한국산학기술학회논문지
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• 제22권6호
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• pp.283-290
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• 2021

본 연구에서는 매입채무가 기업규모에 따라 기업실패에 미치는 영향에 차이가 있는지를 생존분석을 통해 분석하였다. 이를 위해 1999년부터 2019년까지 한국거래소 유가증권시장과 코스닥시장에 상장된 총 41,781개(연도-기업) 기업을 분석하였다. 매입채무의 대용변수로는 단기부채지표인 매입채무비율을 사용하였다. 분석기간을 전체기간과 금융위기 전, 후로 나누어 분석하였다. 실증분석결과 첫째, 전체기간에서 매입채무의 증가는 중소기업의 기업의 실패 가능성을 높이는 요인이라는 것을 확인하였다. 하지만 대기업에서 매입채무비율과 기업실패 가능성간의 유의적인 영향관계를 확인하지 못하였다. 둘째, 1999년~2007년과 2009년~2019년의 하위기간으로 나누어 분석한 결과에 의하면 중소기업에서는 매입채무 증가가 기업실패 가능성을 증가시키는 요인으로 작용되는 것으로 나타났다. 하지만 대기업의 경우 금융위기 이후의 기간인 2009년~2019년에서 매입채무의 증가는 기업의 실패 가능성을 줄이는 것으로 나타났다. 이것은 매입채무의 증가가 부채의 증가로 인한 기업리스크의 확대로 연결되기 보다는 활발한 영업활동의 전개나 무이자부채의 적극적인 활용으로 인식되어 기업의 재무적 곤경 리스크를 완화시켜 기업의 실패 가능성을 감소시키는 것으로 이해되었다. 이러한 분석결과에서 매입채무가 기업실패에 미치는 영향은 기업의 규모에 따라 차이가 발생할 수 있다는 것을 알 수 있었다.

• Industrial Engineering and Management Systems
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• 제16권1호
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• pp.52-63
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• 2017

The inventory level of concurrent spare parts (CSP) has a significant impact on the availability of a weapon system. A failure rate function might be of particular importance in deciding the CSP inventory level. We developed a CSP optimization model which provides a compromise between purchase costs and shortage costs on the basis of the Weibull and the exponential failure rate functions, assuming that a failure occurs according to the (non-) homogeneous Poisson process. Computational experiments using the data obtained from the Korean Navy identified that, throughout the initial provisioning period, the optimization model using the exponential failure rate tended to overestimate the optimal CSP level, leading to higher purchase costs than the one using the Weibull failure rate. A Pareto optimality was conducted to find an optimal combination of these two failure rate functions as input parameters to the model, and this provides a practical solution for logistics managers.

• Advances in concrete construction
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• 제12권5호
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• pp.391-398
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• 2021

This paper presents an experimental study exploring impact resistant properties of Kagome truss reinforced composite panels. Three types of panels with different materials and reinforcements, i.e., ultra-high-performance mortar, steel fiber, and Kagome truss, were designed and manufactured. High-velocity projectile impact tests were performed to investigate the impact response of panels with dimensions of 200 mm×200 mm×40 mm. The projectile used in the testing was a steel slug with a hemispherical front; the impact energy was 1 557 J. Test results showed that the Kagome truss reinforcement was effective at improving the impact resistance of panels in terms of failure patterns, damaged area, and mass loss. Synergy effects of a combination of Kagome truss and fiber reinforcements for the improvement of impact resistance capacity of ultra-high-performance mortar were also observed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.645-648
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• 2008

교량 신축이음장치의 파손 유형을 보면, 그 원인이 주로 후타재와 관련된 부재에서 많이 발생하는것을 알 수 있다. 중차량 통과에 따른 충격과 진동하중으로 인해서 후타재의 파손이 심하게 일어나고, 신축이음장치를 후타재에 고정하기 위해서 사용하는 앵커에서 풀림 현상이 많이 발생하고 있다. 후타재의 파손은 모든 신축이음장치에서 발생하는 현상으로 기존의 후타재로는 신축이음장치의 종류와 관계없이 차량의 충격하중을 충분히 흡수할 수 없으므로, 차량이 교량의 신축이음장치를 통과 할 때에 가해지는 충격하중으로부터 하자 발생원인을 제거하기 위해서는 충격하중을 흡수 할 수 있는 새로운 후타재의 개발이 절실하게 필요한 상황이다. 따라서 본 연구에서는 에폭시변성 폴리우레탄 바인더와 필러(filler), 골재를 사용하여 우수한 성능을 갖는 고내충격성 모르타르를 개발하는데 목적을 두었다.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.73-80
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• 2014

A concrete cask is an option for spent nuclear fuel interim storage. A concrete cask usually consists of a metallic canister which confines the spent nuclear fuel assemblies and a concrete overpack. When the overpack undergoes a missile impact, which might be caused by a tornado or an aircraft crash, it should sustain an acceptable level of structural integrity so that its radiation shielding capability and the retrievability of the canister are maintained. A missile impact against a concrete overpack produces two damage modes, local damage and global damage. In conventional approaches [1], those two damage modes are decoupled and evaluated separately. The local damage of concrete is usually evaluated by empirical formulas, while the global damage is evaluated by finite element analysis. However, this decoupled approach may lead to a very conservative estimation of both damages. In this research, finite element analysis with material failure models and element erosion is applied to the evaluation of local and global damage of concrete overpacks under high speed missile impacts. Two types of concrete overpacks with different configurations are considered. The numerical simulation results are compared with test results, and it is shown that the finite element analysis predicts both local and global damage qualitatively well, but the quantitative accuracy of the results are highly dependent on the fine-tuning of material and failure parameters.

• 자동차안전학회지
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• 제13권3호
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• pp.60-68
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• 2021

Invisible passenger airbag door system of hard panel types must be designed with a weakened area such that the side airbag will deploy through the instrument panel as like intended manner, with no flying debris at any required operating temperature. At the same time, there must be no cracking or sharp edges in the head impact test. If the advanced airbag with the big difference between high and low deployment pressure ranges are applied to hard panel types of invisible passenger airbag (IPAB) door system, it becomes more difficult to optimize the tearseam strength for satisfying deployment and head impact performance simultaneously. It was introduced the 'Operating Window' idea from quality engineering to design the hard panel types of IPAB door system applied to the advanced airbag for optimal deployment and head impact performance. Zigzab airbag folding and 'n' type PAB mounting bracket were selected.

• 한국정밀공학회지
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• 제12권11호
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• pp.98-109
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• 1995

An investigation was performed to study the inner damage of laminated composite plates subjected to out-of-plane load. During the investigation, inpact velocity and equivalent static load relationship was derived. Reddy's higher-order shear deformation theory(HSDT) and Hashin's failure criteria were used to determine inner stresses and damaged area. And impact testing was carried out on laminated composite plates by air gun type impact testing machine. The CFRP specimens were composed of [ .+-. 45 .deg. ]$_{4}$and [ .+-. 45 .deg. /0 .deg. /90 .deg. ]$_{2}$ stacking sequences with 0.75$^{t}$ * 26$^{w}$ * 100$^{l}$ (mm) dimension. After impact testing. As a result, a relationship holds between damaged area and impact energy, and a matrix cracking was caused by the interlaminar shear stress in the middle ply and was caused by the inplane transverse stress in the bottom ply.