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Numerical study of debris flows around bridge piers

Thai Thi Kim Chi

Roads and Bridges - Drogi i Mosty

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2022

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Vol. 21, no. 4

331--342

EN

Landslide is a natural hazard that has crucial direct impact on the socio-economic system. Among various types of landslides, debris flows are a major threat to transportation structures such as bridges in mountainous areas. Vulnerability analysis of bridges that are exposed to debris flows is an important part of risk assessment and management. In the presented study, the characteristics of debris flows around bridge piers are investigated numerically for different boundary conditions using ANSYS FLUENT software. The non-Newtonian power-law model was used to model the debris flow. Drag coefficient was also determined to quantify the vulnerability of bridge piers to debris flows with different velocities and Reynolds numbers.

PL

Osuwiska stanowią naturalne zagrożenie mające bezpośredni wpływ na środowisko, warunki społeczne i ekonomiczne. Spośród różnych typów osuwisk, spływy rumoszowe stanowią poważne zagrożenie dla konstrukcji drogowych, takich jak mosty w terenach górzystych. Analiza podatności mostów na uszkodzenia spowodowane spływem rumoszowym jest ważnym elementem oceny ryzyka i zarządzania nimi. W niniejszej pracy zbadano charakterystyki spływów rumoszowych w bezpośrednim sąsiedztwie filarów mostu, wykorzystując symulacje numeryczne, dla różnych warunków brzegowych, przy zastosowaniu oprogramowania ANSYS FLUENT. Do modelowania spływu rumoszowego użyto potęgowego modelu reologicznego cieczy nienewtonowskiej. W celu oceny ilościowej odporności filarów mostu na spływy rumoszowe charakteryzujące się różnymi prędkościami i liczbami Reynoldsa, w artykule wyznaczono także współczynnik oporu przepływu osuwiska rumoszowego.

2

Probabilistic assessment of the seismic vulnerability of a rammed earth construction: a case study

Jama Balil, Agliz Driss, Abderrahman Atmani, Derife Mina

Archives of Civil Engineering

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2022

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Vol. 68, nr 2

325--335

EN

Rammed earth significantly reduces intrinsic energy compared to concrete construction and has an environmental benefit throughout the life cycle of the building: phases of construction, operation, maintenance, renovation, and demolition. Several studies have recently been carried out to study this material. However, the seismic behavior of rammed earth constructions is still an important topic that needs to be studied in more detail. Through the analysis of non-linear behavior of the rammed earth construction for different wall thicknesses according to the Moroccan earthquake regulation RPS2011, we were able to assess the seismic performance under the corresponding conditions (loads, seismic zone). The results show that the walls studied can have good resistance in areas of seismicity ranging from “very low” to “moderate” and acceptable performance in areas of high seismicity. Furthermore, fragility analysis shows that rammed construction with a wall thickness equal to 50 centimeters exhibits better seismic performance and a low probability of damage, particularly in the case of moderate, severe, and complete damage states.

3

Estimation of local site efects and seismic vulnerability using geotechnical dataset at fyover site Agartala India

Bashir Khalid, Debnath Rajat, Saha Rajib

Acta Geophysica

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2022

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Vol. 70, no 3

1003--1036

EN

Considering future earthquakes, the vulnerability of Agartala city is following an increasing trend mainly due to the recent surge in population density and significant infrastructure developments. The recent moderate intensity earthquake at Tripura, namely the 2017 Dhalai Earthquake (Mw 5.7), with its epicentre being the adjoining district of Agartala, resulted in liquefaction cases, sand blows and lateral spreads, which may be an alarm for the geotechnical engineering fraternity. The present study attempts to evaluate local soil sites’ effect in the form of developing site-specific ground motions using stochastic point-source program SMSIM based on past scenario earthquakes in this region and performing one-dimensional nonlinear ground response analysis (1D GRA) of a recently constructed flyover site of 2.3 km length at Agartala city. Further, the seismic vulnerability of the flyover structure incorporating the local site effect is also assessed herein. The results obtained are explained in terms of surface acceleration time history, the ratio of shear stress to effective vertical stress with depth, acceleration response spectrum, Fourier amplitude ratio with frequency, etc. 1D GRA presented contrasting results with higher values of acceleration in areas with stiffer soils due to attenuation of the seismic waves. In general, the amplification ratio (Af ) evaluated from the present study indicated that the central portion of the flyover yielded high values and a high fundamental frequency value of 6.0 Hz, which might be detrimental for low-lying buildings. The generated synthetic motions of scenario earthquakes will be helpful for researchers and designers for earthquake resistant assessment or design of geotechnical structures in north-eastern India or similar sites in the absence of site-specific data. Finally, this study sheds important observations on seismic design guidelines of the structure located in this region, which may revamp the existing codal procedures.

4

Modelling the ranking of lithuanian railways level crossing by safety level

Bureika G., Komaiško M., Jastremskas V.

Transport Problems

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2017

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T. 12, z. spec.

11--22

EN

The article describes the assessment of safety of Lithuanian Railways level crossing. The statistical analysis of the railway accidents in Lithuania and abroad in recent years has shown that about 30% of all transport accidents in railway occur at railway level crossings. The safety assessment of the country's crossings is carried out considering the following technical criteria: the category of crossing, visibility, the intensity of the movement of trains and road vehicle, the width of the railway crossing, and the maximum speed of trains. Applying the binary model of logistic regression, the probability of accidents at the 337 railway crossings of the country was calculated. Depending on the degree of risk or the probability of accident, the country's railway crossings are ranked. The most dangerous crossings of four regions in the country were identified. Finally, the main conclusions and recommendations are presented.

5

Protector control: Extension to a class of nonlinear distributed systems

Qaraai Y., Bernoussi A. S.

International Journal of Applied Mathematics and Computer Science

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2010

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Vol. 20, no 3

427-443

EN

We present an extension of the protector control scheme introduced for the linear case in a previous work to a class of nonlinear systems. The systems considered are assumed to have a finite propagation velocity while the initial state is subject to a spreading disturbance. We characterize such a control first by using the remediability approach to the resulting nonlinear delay system, and then by coupling families of transformations and the delay approach. To illustrate this work, we provide a simulation example.

6

A quantitative analysis of risk from natural hazard

Howell D.G., Yurkovich E.S., Manning C.D.

Technika Poszukiwań Geologicznych

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2003

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R. 42, nr 3

35-40

EN

Exponential population growth, unprecedented urban development and increasing severity and occurrence of natural disasters; these are the legacies of the Twentieth Century. Globalizing world economies, the concentration of urban populations and infrastructure, and increased vulnerability to natural hazards are the reality for the Twenty-first Century. Understanding risk to these increasingly connected populations and their sustaining infrastructure requires an expanded regional analysis to adequately gage the scope and impact of natural hazards on the global community. To better understand disaster risk in the Twenty-first Century, we calculate the impact that significant natural hazards: earthquake, flood, tropical storm, tsunami and volcanic eruption, have had on people and infrastructure in the past, factored by an assessment of their vulnerability. Quantified models considering elements of population and infrastructure reflect differently the repercussions of natural hazards: loss of life and disruption of economic activity. Population and infrastructure are distributed heterogeneously across the Pacific Rim region; therefore, two contrasting portraits of risk emerge: human populations are most at risk in developing countries while high-valued infrastructure is most at risk in developed countries. The addition of another component in the measurement of risk is proposed, a measure of interconnectivity, the dynamic linkages of people, information and commodities in a globalized socio-economic system. Globalization has, and will, increase this interconnectivity, adding to the spatial reach of local disasters, presenting a legitimate need for the analysis of its reverberating effects.

PL

Znaczący wzrost populacji, bezprecedensowa urbanizacja i wzmożone występowanie klęsk żywiołowych oraz ich dotkliwych skutków - oto spuścizna dwudziestego wieku. Globalizacja światowej gospodarki, koncentracja populacji i infrastruktury miejskiej oraz podatność na zagrożenia naturalne są rzeczywistością dwudziestego pierwszego wieku. Zrozumienie ryzyka, jakie niesie za sobą powstawanie coraz większych skupisk ludności i związanej z nimi infrastruktury wymaga rozległych badań regionalnych, które przyniosłyby odpowiedź na pytanie, jaki jest zakres i wpływ naturalnych zagrożeń na społeczność globalną. Aby lepiej zrozumieć ryzyko klęsk żywiołowych w dwudziestym pierwszym wieku, oceniono wpływ, jaki na ludzi i infrastrukturę wywierały w przeszłości najbardziej znaczące zagrożenia naturalne, do których zaliczono: trzęsienie ziemi, powódź, sztorm tropikalny, tsunami i erupcję wulkanu. W ocenie tej uwzględniono podatność na uszkodzenia populacji ludzkiej i infrastruktury. Modele ilościowe, uwzględniające czynniki dotyczące populacji i infrastruktury, odmiennie odzwierciedlają następstwa zagrożeń naturalnych: utratę życia i przerwanie aktywności gospodarczej. W regionie Pacyfiku ludność i infrastruktura rozmieszczone są nierównomiernie, w związku z czym wyłaniają się dwa kontrastujące obrazy ryzyka: populacje ludności są najbardziej narażone na ryzyko w krajach rozwijających się, podczas gdy infrastruktura o wysokiej wartości bardziej jest narażona na takie ryzyko w krajach rozwiniętych. Proponuje się dodanie kolejnego elementu służącego do oceny omawianego ryzyka, jakim jest badanie wzajemnych powiązań, w tym dynamicznych powiązań międzyludzkich oraz dostępu do informacji i towarów w ogólnoświatowym systemie społeczno-ekonomicznym. Globalizacja powoduje i będzie powodować wzrost tych wzajemnych powiązań, co będzie skutkować zwiększeniem przestrzennego zakresu lokalnych klęsk żywiołowych i dobitnie wykaże konieczność analizowania powodowanych przez nie skutków.