Impact Response and Structural Optimization of CSCS Sandwich Shells Under Vehicle Impact

Chen Yan,Yonghui Wang,Ximei Zhai 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

In this study, curved steel-concrete-steel (CSCS) shells were employed as protective walls to resist vehicle impact, owing to its high resistance, small deformation and damage found in the former studies. LS-DYNA was employed to numerically study the behaviors of CSCS shells under vehicle impact. Impact force, displacement and internal energy of CSCS shell, displacement of supports and damage contours of concrete were obtained from the FE simulations and discussed in detail. The influences of concrete thickness, steel plate thickness, rise height and impact velocity on the impact response of CSCS shell were also numerically investigated. The results showed that the initial kinetic energy was mainly dissipated through the plastic deformation of the vehicle, and the failure mode was dominated by local deformation. Global deformation only occurred when the CSCS shell was subjected to a high-velocity vehicle impact (i.e., 120 km/h). The comparison between CSCS shell and flat SCS panel subjected to the same vehicle impact showed that the CSCS shell had better performance in terms of higher resistance, smaller deformation and damage level. In order to propose a guideline for designing CSCS shell against vehicle impact, the response surface models for determining displacements of CSCS shell and support were established. Multi-objective optimization method was utilized to obtain the Pareto solution sets between displacement ratio of CSCS shell and vertex displacement of support, as well as between displacement ratio and mass of CSCS shell, which provided the suggestions for the design and application of CSCS shell in protective engineering.

A novel strategy for response and force reconstruction under impact excitation

Jie Liu,Bing Li 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

Force and response amplitude are vital to mechanical product life-time. However, these data are always difficult, even impossible, to measure directly. Therefore, we propose a reconstruction strategy based on the subspace identification (SI) algorithm and fast iterative shrinkage-thresholding (FIST) algorithm to reconstruct impact-force and response at desired location. For the reconstruction strategy, reconstruction equations are built by a state-space model, and SI algorithm is utilized to estimate coefficient matrices of the state-space model to form transfer matrices. And then, considering ill-condition of transfer matrix and sparsity of impact-force, FIST algorithm is employed to solve sparse regularization model by minimizing the l 1 -norm. Numerical and experimental studies indicate that the proposed reconstruction strategy can be used to accurately reconstruct force and response under impact excitation, and compared with typical l 2 -norm regularization methods, FIST algorithm is more efficient and accurate in both single-time impact and consecutive impact cases.

Transient energy flow in ship plate and shell structures under low velocity impact

Liu, Z.S.,Swaddiwudhipong, S.,Lu, C.,Hua, J. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.4

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

Effect of High Hardness Armor Plate Sequences on Ballistic Impact Response

박찬영(Chanyoung Park),조종두(Chongdu Cho) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.6

In this study, a numerical analysis on the impact response of HHA (High Hardness Armor Plate) sequences under a 7.62 mm projectile impact was performed to obtain the fundamental design data for a combat-vehicle platform. Recently, the ballistic-protection levels for combat vehicles have increased, and ballistic-protection designs should now be able to deflect multi-hit projectiles. To study the ballistic-impact characteristics, armor-plate sequences of one or two layers with a gap of 0 mm to 2 mm between the front and rear plate were defined under the same weight and thickness. For the certification of the reliability of the numerical model, ballistic tests and an analysis of the single plate under the 7.62 mm projectile impact were performed and analyzed. On the basis of a valid numerical model, a numerical analysis was performed and analyzed. Lastly, it was proved that the performances of the two-layer sequence with the 2 mm gap regarding the impact-response acceleration, deflection efficiency, and penetration depth are the highest.

임팩에코 응답신호를 적용한 건설재료 비파괴 압축강도 산정

손무락(Moorak Son),김무준(Moojun Kim) 한국지반환경공학회 2017 한국지반환경공학회논문집 Vol.18 No.8

본 논문은 암석 및 콘크리트 등의 건설재료의 비파괴 압축강도를 산정하기 위하여 재료타격 시 발생하는 임팩에코 응답신호를 모두 측정하고 이를 누적한 전체 사운드 신호에너지의 이용성에 관해 파악하고 그 결과를 제시하는 것이다. 본 연구에서는 이를 위해서 타격장치를 고안하였고 이를 이용하여 재료를 회전 자유낙하에 의해 초기 타격토록 하고 이후 반발작용에 의한 반복타격이 소멸될 때까지 발생할 수 있도록 하였다. 본 연구에서는 서로 다른 강도를 가지도록 배합된 콘크리트 시편에 대하여 실험을 실시하고 임팩에코 응답신호를 측정하였다. 시편별 산정된 전체 사운드 신호에너지는 직접압축강도시험을 통한 시편별 압축강도와 상호 비교하였다. 비교결과, 임팩에코 응답신호를 통해 산정된 전체 사운드 신호에너지는 시편의 직접압축강도와 직접적인 관계가 있다는 것을 확인하였으며, 이를 통해 암석 및 콘크리트 등의 건설재료의 압축강도는 재료타격 시 발생하는 임팩에코 응답신호로부터 산정된 전체 사운드 신호에너지를 이용하여 비파괴적으로 산정할 수 있음을 알 수 있었다. This paper is to grasp the use of impact-echo response signal induced from impacting an object for the assessment of compressive strength of construction materials nondestructively and to propose the test results. For this study, an impact device was devised and used for impacting an object by an initial rotating free falling impact and following repetitive impacts from the rebound action which eventually disappears. Concrete test specimens which had been mixed for different strengths were tested and the impact echo response signal was measured for each test specimen. The total sound signal energy which is assessed from integrating the impact-echo response signal was compared with the directly measured compressive strength for each specimen. The comparison showed that the total sound signal energy has a direct relationship with the directly measured compressive strength and the results clearly indicated that the compressive strength of construction materials can be assessed nondestructively using total sound signal energy which is assessed from integrating the impact-echo response signal induced from impacting an object.

기후위기 대응을 위한 탄소중립·녹색성장 기본법에 따른 기후변화영향평가의 의의와 향후과제

한민지 ( Minji Han ) 한국환경법학회 2022 環境法 硏究 Vol.44 No.1

미국 열대 우림 행동 네트워크(Rainforest Action Network) 사무국장인 리베카 타버튼(Rebecca Tarbotton)은 “우리는 이 시대의 과제가 기후변화 그 이상이라는 점을 기억해야 하며, 더 높고 깊은 시야를 통해 이 문제를 바라볼 필요가 있다.”면서 “현재 우리가 논의하고 있는 것은 이 행성에서 살아가는 우리의 생활방식 그 일체를 바꾸는 것이다.”라고 강조하였다. 이를 통해 우리가 알 수 있는 바는, 기후변화 그 자체가 아니라 기후변화를 야기하거나 그로부터 초래되는 ‘영향’에 주목해야 한다는 점이다. 전 세계가 기후변화를 논의하고 기후변화 대응에 전력을 기울이는 이유가 바로 이 영향에 있기 때문이다. 기후변화에 대한 과학적 증거를 수집하는 이유 또한 인간의 행위양식에 기한 온도상승폭과 그에 따른 변화가 각각 다르기 때문에 온도 상승폭을 최대한 줄이고 그에 수반되는 영향을 최소화하기 위함이다. 기후변화 영향은 ‘기후변화에 미치는 영향’과 ‘기후변화로 인한 영향’으로 나누어 파악해 볼 수 있다. 전자에 있어 기후변화에 영향을 미치는 원인은 IPCC가 주지한 바와 같이 인간의 행위양식에 기한 인위적 배출임에 따라 해당 영향을 줄이는 방법은 무엇보다 온실가스 감축에 있다. 반면, 후자의 경우 지역, 산업, 생태계 등 여러 부문에서 그 영향이 나타날 수 있음에 따라 해당 사안에 대한 고려는 다양한 측면에서 파악되어야 한다. 여기서 한 가지 주의해야 할 점은 기후변화에 미치는 영향이든 기후변화로 인한 영향이든 기후변화는 국지적으로 나타나지 않기 때문에 거시적인 관점에서 이해되어야 한다는 것이다. 한편, 지난 ’22년 3월 25일 「기후위기 대응을 위한 탄소중립·녹색성장 기본법」(이하 탄소중립 기본법)이 발효되었다. 동법은 탄소중립을 사회전반에 내재화하기 위한 수단으로 기후변화영향평가를 규정하고 있다. 기후변화에 있어 ‘영향’에 대한 구체적인 고려가 있어야 그 대응방안 및 법이 정한 목적을 효과적으로 달성할 수 있다는 전제 하에 본 논문에서는 탄소중립기본법이 정하는 기후변화영향평가를 중심으로 향후 법제의 방향성을 논의해 본다. Rebecca Tarbotton, executive director of the U.S. Rainforest Action Network, said “We need to remember that the work of our time is bigger than climate change. We need to be setting our sights higher and deeper. What we’re really talking about, if we’re honest with ourselves, is transforming everything about the way we live on this planet.”This directly represents that we should focus on the ‘impacts’ that cause or result from climate change, not climate change itself, because those impacts are the reasons why the whole world is discussing climate change and focusing its efforts on responding to climate change. The objective of collecting scientific evidence on climate change is to reduce the temperature rise as much as possible and minimize the accompanying effects as the scale of impacts derived from temperature rise caused by human behavior can be changed according to the range of temperature rise. From this point of view, the impacts related to climate change can be divided into ‘impacts on climate change’ and ‘impacts caused by climate change’. In the former case, as the cause of climate change in relation to the increase in temperature is anthropogenic emissions as the IPCC noted, the reduction of greenhouse gas emission is the suitable option to reduce the impact. On the other hand, in the latter case, since the impact of climate change can appear in various sectors, such as regions, industries, and ecosystems, the impact should be considered from various aspects. One thing to note here is that as climate change does not appear locally, the impact should must be understood from a macroscopic perspective regardless of its type. Meanwhile, on March 25, 2022, the 「Framework Act on Green Growth, carbon neutrality for Response」 (hereinafter referred to as the Carbon Neutral Framework Act) came into effect. The Act stipulates climate change impact assessment as a tool to internalize carbon neutrality throughout society. Under the premise that the detailed consideration of ‘impact’ on climate change is required to effectively achieve the purpose set by the law and countermeasures, this paper discusses the direction of future legislation focusing on the climate change impact assessment settled by the Carbon Neutral Framework Act.

Buckling Modes of Cold-Formed Thin-Walled Steel Beams Under Different Impact Positions

Chang Wu,Junwei Duan,Renhong Wang,Ziheng Yang 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

This paper aims to study the buckling mode of cold-formed thin-walled channel steel beams under different impact positions. The impact test of the thin-walled channel steel beams was carried out using a drop hammer to obtain the acceleration of the measuring point and the buckling mode of the member. The experimental results and ANSYS/LS-DYNA numerical simulation results are compared and analyzed. The results show that the acceleration curve change trend obtained from the test is similar to numerical simulation. The difference between the acceleration obtained by numerical simulation and the maximum value obtained by test accounts for 5.86% of the simulated value. Therefore, the dynamic response results of cold-formed thin-walled channel steel beams under numerical simulation can be effectively verified by the test. Numerical simulation methods are used to analyze the dynamic response of two groups of members under impact at different positions and the corresponding buckling modes. The results show that the buckling of the members at 1/2, 1/3, and 1/4 of the flange of the impact member is similar to the O-I mode under the same conditions. The buckling mode is half-O mode when the midpoint of the intersection line between flange and web is impacted. The buckling mode is U-shaped when the midpoint of the intersection line between flange and the curling edge is impact.

선체구조의 탄성지지 효과를 고려한 LNG 운반선 방열구조의 슬로싱 충격응답 해석법에 관한 연구

노인식(In Sik Nho),기민석(Min-Seok Ki),김성찬(Sung-Chan Kim),이장현(Jang Hyun Lee),김용환(Yonghwan Kim) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.5

The sloshing pressure acting on a membrane-type LNG CCS is a typical irregular impact load, and the structural response of a tank system induced by sloshing also shows very complex behavior, including fluid structure interaction. Therefore, it is not easy to accurately estimate the sloshing impact pressures and resulting structural response. Moreover, a huge time consuming process to deal with the enormous pressure data obtained during a model tank test and the following structural analysis would be inevitable. To reduce the computation time for structural analysis, in this study, a rational structural modeling strategy was considered, and a simplified scheme to analyze the dynamic structural responses of an LNG CCS was introduced, which was based on the concept of the linear combination of the triangular response functions obtained by a transient response analysis of structures under unit triangular impact pressure. A structural analysis of a real Mark III membrane type insulation system under the sloshing impact pressure time histories obtained by model tests was performed using the various proposed structural models and simplified analysis scheme. The results were investigated in detail, including the elastic support effects of the hull structure.

Variability of electricity load patterns and its effect on demand response: A critical peak pricing experiment on Korean commercial and industrial customers

Jang, D.,Eom, J.,Jae Park, M.,Jeung Rho, J. Elsevier Science Ltd 2016 Energy Policy Vol.88 No.-

To the extent that demand response represents an intentional electricity usage adjustment to price changes or incentive payments, consumers who exhibit more-variable load patterns on normal days may be capable of altering their loads more significantly in response to dynamic pricing plans. This study investigates the variation in the pre-enrollment load patterns of Korean commercial and industrial electricity customers and their impact on event-day loads during a critical peak pricing experiment in the winter of 2013. Contrary to conventional approaches to profiling electricity loads, this study proposes a new clustering technique based on variability indices that collectively represent the potential demand-response resource that these customers would supply. Our analysis reveals that variability in pre-enrollment load patterns does indeed have great predictive power for estimating their impact on demand-response loads. Customers in relatively low-variability clusters provided limited or no response, whereas customers in relatively high-variability clusters consistently presented large load impacts, accounting for most of the program-level peak reductions. This study suggests that dynamic pricing programs themselves may not offer adequate motivation for meaningful adjustments in load patterns, particularly for customers in low-variability clusters.

시간-주파수 영역 특성 응답을 이용한 매설 배관의 충격 손상 위치 표정에 대한 실험적 검증

이선호,박춘수,윤동진 한국비파괴검사학회 2023 한국비파괴검사학회지 Vol.43 No.4

Damage to buried pipelines resulting from third-party interference has garnered attention because it can lead to significant leaks owing to ruptures. Given that such incidents often occur suddenly owing to third-party actions, the importance of buried pipeline monitoring becomes paramount for prevention and early response. Acoustic emission localization have been recognized as an effective method for detecting damage sources in structures with restricted access. In this study, we propose a signal processing method based on the feature response in the time-frequency domain to apply acoustic emission localization in noisy environments. We compared the results of the feature response through simulation and experimentally verified its application on in-service buried pipelines. The pipeline is 564 m long and has a diameter of 1200 mm. By attaching vibration accelerometers to both ends, we confirmed the ability to detect impact damages. By observing the feature response, we derived the optimal frequency band without manual frequency analysis. Therefore, we could automatically enhance the signal-to-noise ratio under various noise conditions. Our study yielded an empirical impact damage detection in the in-service pipelines that was in good agreement with the impact location. 타공사에 의한 매설 배관 파손 사고는 파열로 인한 다량의 누출을 동반하여 사회적 문제로 주목받고 있다. 이러한 사고는 제 3 자에 의해 갑작스럽게 발생하는 관계로 예방과 조기 대응을 위해서는 매설 배관 모니터링 기술이 중요하다. 음향방출 위치 표정 기법은 접근이 제한되는 구조물을 대상으로 손상원 검출에 효과적인 방법으로 주목받아 왔다. 본 연구에서는 잡음 환경에서도 음향방출 위치 표정 기법을 적용하기위해 시간-주파수 영역의 특성 응답을 이용한 신호처리 기법을 제안한다. 시뮬레이션을 통한 특성 응답 결과를 비교하였으며, 이를 실제 운용중인 매설 배관에 적용하여 실험적으로 검증하였다. 대상 배관의 관경은1,200 mm이며, 길이 564 m에서 진동 가속도계를 부착하여 충격 손상의 검출이 가능함을 확인하였다. 특히, 특성 응답 관찰을 통해 인위적인 주파수 분석 없이 최적 주파수 대역을 도출하였다. 그 결과, 다양한 잡음조건에서 자동적으로 신호 대 잡음비 향상이 가능하였으며, 실제 충격 위치와 잘 일치함을 확인하였다.