scholarly journals Structural Response and Stochastic Impact Modeling

2018 ◽  
Vol 183 ◽  
pp. 01050
Author(s):  
Renata Troian ◽  
Manel Dallali ◽  
Didier Lemosse ◽  
Leila Khalij

The problem of the vulnerability of structures facing explosions came to the front line of the scientific scene in the last decades. Uncertainty of the environmental conditions and material properties have to be taken into account. The corresponding numerical models are very complex and depend on numerous parameters. Consequently, such models are cursed with issues which limit their use for real applications. Most of the existing approaches are based on a deterministic point of view, and are not able to represent the extreme sensitivity of a model towards uncertain parameters. That is why the uncertainty analysis is needed. The proposed research is devoted to the analysis of a structural behavior under an uncertain impact loading. Elasto-plastic Bernoulli beam model is used as structural model for the case simplicity, while the different formulation for impact itself are studied to simulate the wide range of possible types of impact. Model sensitivity is studied first. The influence of input parameters on structural behavior, that are the impact force, duration and position, as well as beam material are then considered. The obtained insights can provide the guidelines for modeling the structure under the explosive loading taking into account the uncertainties.

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7658
Author(s):  
Marcin Kozłowski ◽  
Kinga Zemła ◽  
Magda Kosmal ◽  
Ołeksij Kopyłow

Due to the high cost of experiments commonly performed to verify the resistance of glass elements to impact loads, numerical models are used as an alternative to physical testing. In these, accurate material parameters are crucial for a realistic prediction of the behaviour of glass panels subjected to impact loads. This applies in particular to the glass’s strength, which is strictly dependent on the strain rate. The article reports the results of an extensive experimental campaign, in which 185 simply supported toughened glass samples were subjected to hard-body impacts. The study covers a wide range of glass thicknesses (from 5 to 15 mm), and it aims to determine a critical drop height causing fracture of the glass. Moreover, a 3D numerical model of the experimental set-up was developed to reproduce the experiments numerically and retrospectively to determine the peak stress in glass that developed during the impact. Based on the results of numerical simulations, a load duration factor of 1.40 for toughened glass for impact loads is proposed. In addition, the paper includes a case study to demonstrate the use of the modelling methodology and results of the work on a practical example of an internal glass partition wall.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Allan Webster ◽  
Sangeeta Khorana ◽  
Francesco Pastore

PurposeThe choice of Southern Europe is partly based on the observation that the sample includes a number of countries whose economies faced more severe difficulties than elsewhere in Europe. Economically they were less able to absorb the economic shock posed by COVID-19. It is also partly based on the characteristics of the pandemic. A number of countries in the sample were amongst the earliest in Europe to be hit by the pandemic and a several were harder hit in terms of both morbidity and mortality.Design/methodology/approachThis study uses evidence from World Bank enterprise surveys of a sample of firms from six countries in Southern Europe. It examines the early evidence of the effects of COVID-19 on labour markets. The economic consequences potentially cover a wide range of issues. The focus of this study is on firm level evidence of the effect on labour. The evidence and the analysis are provided at a time when the pandemic is still in progress. The authors use both traditional regression analysis and IPWRA to assess the joint effect of loans versus government support on, firstly, the change in sales revenues and, secondly, the number of weeks that the firm would expect to survive with no sales revenues.FindingsThe study suggests that, despite efforts to support firms and hoard labour, there is a prospect of a significant number of firm closures with a consequent loss of employment. Temporary firm closures also represent a substantial loss of labour weeks. These are partly related to a significant number of workers subject to furloughs. The empirical findings suggest that COVID-19 cases and deaths have directly affected firm sales but government containment measures, particularly closures, have more strongly affected firms. Losses of sales were unsurprisingly related to losses of employment. Remote working has contributed to sustaining employment but online business has not affected most sectors.Research limitations/implicationsThe future progress of COVID-19 and government containment measures is uncertain, and the full economic consequences will probably continue to emerge after the end of the pandemic. The full extent of the impact on labour will probably not be the first of these. There are obvious advantages in seeking to learn lessons from the early stages of the pandemic but there are also obvious constraints. The full economic consequences will take longer to emerge than the pandemic itself and the full consequences for employment will take longer to be evident than many other economic effects.Practical implicationsBoth temporary closures and furloughs impose costs that will be borne by firms, workers and government. The effects of COVID-19 on firms differ across sectors. Adverse effects tend to be higher in hospitality, non-essential retail and travel. That many firms lack the capacity to survive further temporary closures of a similar duration to those in the earlier stages emphasises that the support provided in the near future is of critical importance to control employment losses through permanent firm closures. A long-term perspective suggests neither permanent closure nor laying off workers may be the best response to a temporary crisis in demand. A stakeholder model of the firm would often suggest that it is not an optimal for the point of view of workers or the wider economy either. Both imply a preference for labour hoarding.Social implicationsThe most affected are sectors with a high proportion of female workers and, in consequence, most of the countries in the sample exhibit an early decline of the already lower than average share of women in employment.Originality/valueThe data used have been recently released and this is the first analysis using the data to look at the consequence on firms employment decisions during the Pandemic. The case of Southern Europe is much understudied, though one of the most dramatic as to the consequences of the pandemic. From a methodological point of view, the authors use not only traditional regression analysis, but also the matching approach to identify the effect of different policy options on labour demand by firms.


Author(s):  
Tizian Bucher ◽  
Min Zhang ◽  
Chang Jun Chen ◽  
Ravi Verma ◽  
Wayne Li ◽  
...  

Sandwich panels with metal foam cores have a tremendous potential in various industrial applications due to their outstanding strength-to-weight ratio, stiffness, and shock absorption capacity. A recent study paved the road toward a more economical implementation of sandwich panels, by showing that the material can be successfully bent up to large angles using laser forming. The study also developed a fundamental understanding of the underlying bending mechanisms and established accurate numerical models. In this study, these efforts were carried further, and the impact of the foam core structure, the facesheet and foam core compositions, and the adhesion method on the bending efficiency and the bending limit was investigated. These factors were studied individually and collectively by comparing two fundamentally different sandwich panel types. Thermally induced stresses at the facesheet/core interface were thoroughly considered. Numerical modeling was carried out under different levels of geometric accuracy to complement bending experiments under a wide range of process conditions. Interactions between panel properties and process conditions were demonstrated and discussed.


2021 ◽  
Author(s):  
Saad Saad ◽  
Rashid Bashir ◽  
Stavroula Pantazopoulou

<p>The purpose of this study is to investigate the impact of climate change on the thermal and structural response of concrete box girders. An advanced finite element platform was used to model a concrete box girder and analyze the additional thermal stresses that result from climate change. Meteorological data for future climate scenarios in Toronto, Canada was used as input in a thermal model to simulate the temperature distribution within the bridge deck. The temperature distribution was then used as input in a structural model of the bridge, to determine the resulting thermal stresses. The results show increases in tensile and compressive stresses as well as increased bridge movements. This study highlights the importance of explicitly considering climate change to achieve more robust bridge codes, particularly when it comes to thermal effects.</p>


Author(s):  
Marion Erdelen-Peppler ◽  
Christoph Kalwa ◽  
Jens Schröder

Toughness testing of the heat affected zone (HAZ) of longitudinal welds is increasingly often required in pipeline standards and specifications. This includes simple tests such as the Charpy impact test that was designed to serve as quality test as well as enhanced methods including crack tip opening displacement (CTOD) tests that are necessary to conduct an engineering critical assessment (ECA). If occasional low toughness values are observed, the question turns towards assessing the impact of such numbers and how representative they are of the behavior of a pipe in service. The significance of low toughness values measured in laboratory testing can be judged on basis of ring expansion and hydraulic burst tests. The current study summarises an extensive test series to quantify the toughness of submerged arc welds (SAW) obtained by different test methods. The tested pipes cover a wide range of material including medium strength X70 up to high strength X100. Their welds are characterized in terms of fracture toughness properties with single edge notch tension (SENT) and single edge notch bending (SENB) tests. Different constraint levels are obtained within each series by introducing notches of standard depth as well as shallow notches. Structural behavior is characterized with burst tests as well as ring expansion tests containing notches in the longitudinal weld. The experimental results are assessed within dedicated finite element studies. The assessment is conducted for pipes serving as pressure containment, thus having circumferential stress resulting from internal pressure. Based on the results achieved the conclusion can be drawn that the standard route including high constraint CTOD leads to overly conservative results concerning the integrity of longitudinal welds. A better representation of structural behavior is observed in ring expansion tests.


2016 ◽  
Vol 74 (10) ◽  
pp. 2337-2348 ◽  
Author(s):  
Franz Tscheikner-Gratl ◽  
Peter Zeisl ◽  
Carolina Kinzel ◽  
Johannes Leimgruber ◽  
Thomas Ertl ◽  
...  

From a scientific point of view, it is unquestioned that numerical models for technical systems need to be calibrated. However, in sufficiently calibrated models are still used in engineering practice. Case studies in the scientific literature that deal with urban water management are mostly large cities, while little attention is paid to the differing boundary conditions of smaller municipalities. Consequently, the aim of this paper is to discuss the calibration of a hydrodynamic model of a small municipality (15,000 inhabitants). To represent the spatial distribution of precipitation, three distributed rain gauges were used for model calibration. To show the uncertainties imminent to the calibration process, 17 scenarios, differing in assumptions for calibration, were distinguished. To compare the impact of the different calibration scenarios on actual design values, design rainfall events were applied. The comparison of the model results using the different typical design storm events from all the surrounding data points showed substantial differences for the assessment of the sewers regarding urban flooding, emphasizing the necessity of uncertainty analysis for hydrodynamic models. Furthermore, model calibration is of the utmost importance, because uncalibrated models tend to overestimate flooding volume and therefore result in larger diameters and retention volumes.


2011 ◽  
Vol 8 (62) ◽  
pp. 1217-1232 ◽  
Author(s):  
Huajian Gao ◽  
Jin Qian ◽  
Bin Chen

Cell–matrix adhesion depends on the collective behaviours of clusters of receptor–ligand bonds called focal contacts between cell and extracellular matrix. While the behaviour of a single molecular bond is governed by statistical mechanics at the molecular scale, continuum mechanics should be valid at a larger scale. This paper presents an overview of a series of recent theoretical studies aimed at probing the basic mechanical principles of focal contacts in cell–matrix adhesion via stochastic–elastic models in which stochastic descriptions of molecular bonds and elastic descriptions of interfacial traction–separation are unified in a single modelling framework. The intention here is to illustrate these principles using simple analytical and numerical models. The aim of the discussions is to provide possible clues to the following questions: why does the size of focal adhesions (FAs) fall into a narrow range around the micrometre scale? How can cells sense and respond to substrates of varied stiffness via FAs? How do the magnitude and orientation of mechanical forces affect the binding dynamics of FAs? The effects of cluster size, cell–matrix elastic modulus, loading direction and cytoskeletal pretension on the lifetime of FA clusters have been investigated by theoretical arguments as well as Monte Carlo numerical simulations, with results showing that intermediate adhesion size, stiff substrate, cytoskeleton stiffening, low-angle pulling and moderate cytoskeletal pretension are factors that contribute to stable FAs. From a mechanistic point of view, these results provide possible explanations for a wide range of experimental observations and suggest multiple mechanisms by which cells can actively control adhesion and de-adhesion via cytoskeletal contractile machinery in response to mechanical properties of their surroundings.


Webology ◽  
2021 ◽  
Vol 18 (Special Issue 04) ◽  
pp. 641-652
Author(s):  
Irina Gladilina ◽  
Svetlana Sergeeva ◽  
Nelli Kozhevnikova ◽  
Elizaveta Tokareva

The information eco-environment of the city, aimed at attracting investment, is designed to solve the problems of forming investment attractiveness, protection from unscrupulous investors, obtaining reliable information when justifying the implementation of investment projects, participation in them. Considering the dynamism of modern investment processes, the creation of an effective information eco-environment is an important component of the development of the investment process, especially from the point of view of ensuring effective interaction of its participants and attracting a wide range of investors to the investment activity process. Therefore, it is necessary to assess the impact of the information eco-environment on the processes of investment in the urban environment and increase the investment attractiveness of the city. However, the features of information support of the investment market specifically at the municipal level remain insufficiently studied. Based on the analysis of literary sources and an expert survey, this article examines the forms of information disclosure that are most effective from the point of view of investors; factors of investment attractiveness that should be paid attention to when forming an information eco-environment. Finally, this article suggests the identification of key areas of development of the urban information eco-environment, which can be transformed into the investment attractiveness of the city. The results showed that the systematic use of the information eco-environment of the city should create conditions for users to receive the necessary information promptly, which contributes to the activation of investment activity, increasing its efficiency.


2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Vincenzo Formisano ◽  
Andrea Moretta Tartaglione ◽  
Maria Fedele ◽  
Ylenia Cavacece

PurposeThe purpose of this paper is to analyse the quality of banking services provided in support of small- and medium-sized enterprises' (SMEs) internationalization from the customers' perspective.Design/methodology/approachCustomer satisfaction of 50 Italian SMEs with the banking services provided for international activities has been evaluated by adopting the Kano model's continuous and discrete analyses.FindingsResults show which banking services provided for business internationalization are necessary to satisfy customers' expectations, which services customers like having and dislike not having and which services are unexpected by customers creating a high increase in satisfaction when provided.Research limitations/implicationsThis work shows the value of the Kano model in evaluating the non-linear relationship between customer satisfaction and quality of banking services for the international activities of companies. The main limitation of this work is the limited geographical context of the investigation.Practical implicationsThis research suggests banks to transform their role in the relationship with SMEs from mere financiers to active partners committed to their growth abroad by offering a wide range of services not just financial, but also counselling and care professional, thus achieving mutual benefits.Originality/valuePrevious works on banking services and business internationalization are focussed on the transaction costs, information asymmetries and the impact of online banking. This work advances available knowledge by analysing the customer's point of view, evaluating the satisfaction of SMEs which, although more dependent on banks for their expansion abroad than large listed companies, are mostly ignored by literature.


Author(s):  
Min Sung Chun ◽  
Yong Suk Seo ◽  
Ito Hisasi ◽  
Wha Soo Kim ◽  
Byeong Jae Noh ◽  
...  

To verify the structural safety under impact load caused by sloshing of LNG is one of the main issues in the design of membrane type LNG cargo containment system of LNG carrier. In order to estimate structural response under sloshing impact load, many kinds of studies including experimental test and numerical simulation have been done by various research groups such as shipyards, oil companies, universities as well as classification societies. In spite of these efforts, many uncertainties still exist to predict the structural behavior of LNG insulation system under sloshing impact load. Therefore, it can be regarded as a challenge to investigate dynamic response of LNG cargo insulation system against sloshing load. In this paper, Cooperative research results obtained by SHI-HHI-PNU-Lloyd-ABS-DNV JDP focused on the impact damage or failure mode of membrane type LNG cargo insulation system are summarized. A systematic experimental research is carried out to find out failure mode of the insulation system under impact load and criteria which can be applied for the design of LNG carrier. A series of dry drop tests as well as static compressive tests are carried out. The structural behavior of the specimen under impact load is recorded using ultrahigh-speed camera and reaction force is measured using load cells which are installed under bottom of the test facility. By analyzing recorded video, deformation history of the specimen at impact moment is obtained. The numerical simulations are also carried out for the dry drop test for verification purpose, It is expected that the insights observed from the systematic experiments and numerical simulations for the structural response of the LNG cargo insulation system subjected to the impact load can be effectively used as design guide for evaluation of the integrity of structural components of LNG cargo hold system.


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