Nonlocal Damage Formulation for a Flexibility-Based Frame Element

2009 ◽  
Vol 135 (10) ◽  
pp. 1213-1221 ◽  
Author(s):  
Hamid R. Valipour ◽  
Stephen J. Foster
2020 ◽  
Vol 5 ◽  
Author(s):  
Marta N. Lukacovic

This study analyzes securitized discourses and counter narratives that surround the COVID-19 pandemic. Controversial cases of security related political communication, salient media enunciations, and social media reframing are explored through the theoretical lenses of securitization and cascading activation of framing in the contexts of Slovakia, Russia, and the United States. The first research question explores whether and how the frame element of moral evaluation factors into the conversations on the securitization of the pandemic. The analysis tracks the framing process through elite, media, and public levels of communication. The second research question focused on fairly controversial actors— “rogue actors” —such as individuals linked to far-leaning political factions or militias. The proliferation of digital media provides various actors with opportunities to join publicly visible conversations. The analysis demonstrates that the widely differing national contexts offer different trends and degrees in securitization of the pandemic during spring and summer of 2020. The studied rogue actors usually have something to say about the pandemic, and frequently make some reframing attempts based on idiosyncratic evaluations of how normatively appropriate is their government's “war” on COVID-19. In Slovakia, the rogue elite actors at first failed to have an impact but eventually managed to partially contest the dominant frame. Powerful Russian media influencers enjoy some conspiracy theories but prudently avoid direct challenges to the government's frame, and so far only marginal rogue actors openly advance dissenting frames. The polarized political and media environment in the US has shown to create a particularly fertile ground for rogue grassroots movements that utilize online platforms and social media, at times going as far as encouragement of violent acts to oppose the government and its pandemic response policy.


2009 ◽  
Vol 36 (5) ◽  
pp. 813-825
Author(s):  
G. Akhras ◽  
W. Li

Many government departments have hundreds of buildings located in active seismic regions. Most of these buildings were built decades ago according to old design codes, and could be vulnerable to strong or even moderate earthquakes. To evaluate the seismic performance of concrete moment frames or moment frames with shear walls in these buildings, the static, vibration and modal response spectrum analyses are carried out according to the 2005 National building code of Canda NBCC. The analysis uses 2-D finite element models consisting of frame elements and inplane elements. The frame element has a built-in rigid linear segment at each end for modeling the portion within the beam–column joint, whereas the inplane element may have openings for modeling doors and windows in shear walls. The stiffness of both elements is adjusted to include effects of shear deformation in beams and bending deformation in wall piers. The results are further adjusted to incorporate effects of torsion and accidental torsion. Then, CSA-A23.3-04 is followed for detailed evaluation on safety in limit states, “strong column – weak beam” concept and shear strength requirements. Based on this approach, a new computer program is developed to perform this evaluation with minimum input data. Important issues in each step are discussed in detail. Examples are presented, and results are compared with available existing data.


Author(s):  
Zhang Xianmin ◽  
Liu Jike

Abstract Control of dynamic vibration is critical to the operational success of many flexible mechanism systems. This paper addresses the problem of vibration control of such mechanisms through passive damping, using constrained layer damping treatment technique. A new type of shape function for three layer frame element containing a viscoelastic layer is developed. The equations of motion of the damped flexible mechanism are derived. Modal loss factors of this kind mechanisms are predicated from undamped normal mode by means of the modal strain energy method. Comparisons between the results obtained by this paper and the results obtained by exact solution of the governing equations for a well known sandwich beam demonstrate that the method presented in this paper is correct and reliable. Application of this method in predication of modal damping ratios for damped mechanisms is discussed. It is believed that the method of this paper hold the greatest potential for optimal design of damped flexible mechanism systems.


2014 ◽  
Vol 7 (5) ◽  
pp. 879-904 ◽  
Author(s):  
E. Parente Jr ◽  
G. V. Nogueira ◽  
M. Meireles Neto ◽  
L. S. Moreira

The analysis of reinforced concrete structures until failure requires the consideration of geometric and material nonlinearities. However, nonlinear analysis is much more complex and costly than linear analysis. In order to obtain a computationally efficient approach to nonlinear analysis of reinforced concrete structures, this work presents the formulation of a nonlinear plane frame element. Geometric nonlinearity is considered using the co-rotational approach and material nonlinearity is included using appropriate constitutive relations for concrete and steel. The integration of stress resultants and tangent constitutive matrix is carried out by the automatic subdivision of the cross-section and the application of the Gauss quadrature in each subdivision. The formulation and computational implementation are validated using experimental results available in the literature. Excellent results were obtained.


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