► Retrofit of high-speed railway bridges of short/medium span with viscoelastic dampers. ► Attention is focused on mitigating resonant flexural vibrations. ► Viscoelastic behavior model based on ...fractional derivatives. ► A dimensioning procedure of the proposed retrofitting system is presented. ► The results show that the dynamic response of the bridge can be significantly reduced.
This paper presents a study on the energy-absorbing capacities of viscoelastic dampers (VEDs) for reducing the resonant vibrations of simply supported high-speed railway bridges of short to medium span. The proposed solution is based on retrofitting the bridge with a set of discrete VEDs connected to the slab and to an auxiliary structure, placed underneath the bridge deck and resting on the abutments. In this investigation attention is focused on mitigating flexural vibrations; therefore, both the bridge and the auxiliary structure are modelled as simply supported beams with Bernoulli–Euler (B–E) behavior, whereas a discrete fractional derivative model simulates the behavior of the damping material. Firstly, a parametric study of this planar model is carried out, which has led to a dimensioning procedure of the dissipative system. The technical feasibility of this particular retrofit design is numerically evaluated by applying it to a numerical model of a simply supported railway bridge with inadmissible vertical accelerations. Numerical results show that the dynamic response of the structure can be significantly reduced in resonance with the proposed damping system.
Lightweight reinforced thermoplastic (LWRT) is a newly developed porous material. The low density, high rigidity, design flexibility and sound absorption of LWRT facilitate its application in the ...automotive industry. Fibers are bonded with a matrix and air is imported by deconsolidation, which is not only economical but also environmentally friendly. In this work, film stacking and non-woven methods were employed as the impregnation techniques to manufacture LWRT. The molded thickness and surface density of LWRT were varied to study their influences on the structures and mechanical properties. Different lengths of fibers in LWRT were selected and 7 % PP-g-MAH was added to the matrix and compared with unmodified matrix. The mechanical properties decreased with the increase in molded thickness and the decrease in surface density. With higher fiber length, the strength and stiffness increased, while the toughness exhibited a maximum value at 80 mm fiber length. The strength and stiffness of LWRT were also enhanced when 7 % PP-g-MAH was added.
The thermal deformation, which is called “deconsolidation” or “springback,” is often observed when the randomly oriented short carbon fiber reinforced thermoplastics are heated. In the present study, ...the deconsolidation effect of two kinds of randomly oriented short carbon fiber reinforced thermoplastics was studied experimentally and theoretically. The deconsolidation ratios were measured as the thickness ratio of the deformed randomly oriented short carbon fiber reinforced thermoplastics in the experiments. The results indicated that the deconsolidation of the randomly oriented short carbon fiber reinforced thermoplastics is caused by the release of the molding elastic deformation of fibers. Structural and molding factors that can affect the deconsolidation ratio were defined and empirical fitting functions were established. The deconsolidation ratios calculated by the functions were compared with the experimental results and the agreement was found to be satisfactory. At last, the fiber volume fraction effect and molding pressure effect on the deconsolidation ratio were investigated using the equations.
This article provides a new explanation for the current democratic crisis by focusing on the growing opposition of citizens to political elites. Modern democracies are basically representative ...democracies in the sense that citizens are represented by a governing political elite. We argue that democracies are in crisis because this political elite cannot possess the knowledge necessary to manage the complexity of the social order and implement rational choices. They fail in dealing with knowledge and thus cast doubt among citizens on the very legitimacy of democracy. This produces generalized distrust toward elites, who were thought to be able to deal with social complexity. As a result, democracy is considered to be responsible for societal problems while they actually stem from elites' overestimation of their ability to deal with societal complexity.
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A summary of the article will be made in French for readers of the PHEBE site (LE POInt, https://www.lepoint.fr/phebe/) and on the counterpoint site (https://www.contrepoints.org/)
La crisis democrática y el problema del conocimiento
Este artículo proporciona una nueva explicación para la actual crisis democrática al centrarse en la creciente oposición de los ciudadanos a las élites políticas. Las democracias modernas son básicamente democracias representativas en el sentido de que los ciudadanos están representados por una elite política gobernante. Este artículo argumenta que las democracias están en crisis porque esta élite política no puede poseer el conocimiento necesario para gestionar la complejidad del orden social e implementar elecciones racionales. No logran tratar el conocimiento y, por lo tanto, ponen en duda a los ciudadanos sobre la legitimidad de la democracia. Esto produce una desconfianza generalizada hacia las élites, que se creía capaces de lidiar con la complejidad social. Como resultado, se considera que la democracia es responsable de los problemas sociales, mientras que en realidad provienen de la sobreestimación de las élites de su capacidad para lidiar con la complejidad social.
民主危机和知识问题
本文通过聚焦公民对政治精英的日益反对，为当前民主危机提供了新的解释。现代民主基本是代议型民主，即具备统治能力的政府精英代表公民。本文主张，民主正遭遇危机，因为政治精英不具备管理社会秩序复杂性、实施理性抉择所必需的知识。政治精英不具备相关知识，因此让公民质疑民主合法性。这导致对在此之前被认为能够应对社会复杂性的统治精英产生普遍的不信任。结果则是，民主被视为对社会问题负有责任，然而实际上这些社会问题源于统治精英高估其在应对社会复杂性上的能力。
The consumer culture created in post-Soviet Russian society has a negative impact on many aspects of sociocultural life of the individual and society as a whole. Consumer society is a set of ...relations with dominated symbolism of material objects being a life purpose, which causes consumers to purchase things, thus creating its high status position. Consumerism is the support of marks production included in every act of purchase and total semiotization of reality. The article examines such issues specific to Russian modernity as the weakening of social relations, individualism, political apathy, and refocusing of mass interest from serious political, economic and environmental topics to personal aspects. It is shown that these issues are directly related to the tendencies of consumer culture. Consumer culture suggests calls to an individual activity, but also to social inaction. Deconsolidation is a feature of voluntary marginalization typical of consumer society. When it becomes wide-scale, a paradoxical phenomenon should be observed as the “social exclusion of the majority”. An existing, permanent revolution of individualism expressed in the relevant changes of culture and value orientations eliminates political activity and displaces the political discourse of the mass consciousness. Insensitivity to issues concerning society, nation and the world is one of metaproblems and social meta-menaces typical of the era of consumption. The theories of consumption sociology and social philosophy are used as the theoretical and methodological basis for this research. Hypertrophy of consumption values in extreme cases leads society to a loss of its foundation, namely sociality.
The main message of this paper is that there are two periods of Europeanization and Democratization in the ECE political systems with a transitory grey zone in the 2000s. They can be termed as the ...periods of "permissive tolerance" and "increasing disappointment" seen from the side of the ECE populations, and the periods of "formalities" and "alienation" in Europeanization from the side of the ruling elites. This paper tries to describe these two periods of the political systems in general and the party systems in particular. The first party systems of the young ECE democracies have collapsed in the 2010s due to the failure of the catching up process in the last Quarter-Century that has been aggravated by the effects of the global crisis. This paper argues that the decline of democracy in ECE has been accompanied with the rise of the second party system. The critical elections in the 2010s have also meant the change in the party system towards the dominance of the populist parties. The new dominant parties of the last decade represent also some kind of the political reaction to the global crisis management, since they express the dissatisfaction of the large masses suffering from the long-term effects of global crisis in the 2010s. The populist parties in ECE have usually become the governing mainstream parties, and they have completed the state capture in the form of democracy capture leading to the deconsolidation of the ECE political systems. The new wave of populism in ECE that has produced the "populist eruption" in the region, therefore this situation necessitates the elaboration of the comprehensive conceptual framework of the ECE new political systems based on the duality of the external and internal Europeanization.
Thermoplastic composites offer the possibility of post processing by re-melting of the polymer, but this can lead to a loss of consolidation. The aim of this study is to investigate and quantify the ...mechanisms leading to deconsolidation. A model is introduced based on the first law of thermodynamics including the following mechanisms: decompaction of the fibre reinforcement network affected by the stored energy during compaction, void evolution due to the surface tension and the gas expansion, moisture in the polymer, and external pressure. These deconsolidation mechanisms are interdependent and have a significant effect on deconsolidation. The modeling approach predicts the deconsolidated state with good agreement to physical measurements.
We deepen our understanding of democratic
de
consolidation by understanding the legal-administrative responses to a security crisis. We expand prior “democratic breakdown” studies through a ...legal-administrative review of three countries which have experienced a security crisis: Peru, South Africa, and the United States. Using Freedom House and Polity IV scores, we discuss the initial crisis and the state’s legal-administrative responses. Different state responses offer a unique micro-political and administrative perspective on when, where, and why deconsolidation may or may not occur.
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