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• Dynamic buckling of shell-like structures under pressures due to an explosion

  M. Ameijeiras, L. Godoy

  RIDNAIC (2018). Vol. 18, (2), 4

  
  

  Abstract

  The nonlinear dynamic response and buckling of a simple, two degree of freedom system is investigated in this work under an impulsive load that simulates a nearby detonation-like explosion. The system includes force and moment springs in much the same way as membrane and bending effects develop in shell structures. The static response is first obtained to evaluate bifurcation states and nonlinear equilibrium paths including geometric imperfections. The dynamic problem is modeled using Lagrange equation of motion. The nonlinear dynamic response under impulsive load is next computed for the perfect configuration under increasing load levels. The presence of quasi-bifurcations is detected using stability coefficients based on second order derivatives of the total potential energy. For a given load level, it is found that one stability coefficient vanishes at the first maximum in the displacement versus time trajectory, at which the system passes through a state of zero velocity. This occurs for the same displacement configuration as in the static buckling mode. The results show that quasi-bifurcation loads thus obtained are independent of the amplitude of the geometric imperfection considered but display high sensitivity to changes in the membrane to bending stiffness ratio.

  Abstract
  The nonlinear dynamic response and buckling of a simple, two degree of freedom system is investigated in this work under an impulsive load that simulates a nearby detonation-like [...]

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• On load interaction in the non linear buckling analysis of cylindrical shells

  L. Godoy, S. Idelsohn, E. Barbero

  Advances in Engineering Software and Workstations (1991). Vol. 13 (1), pp. 46-50

  
  

  Abstract

  The elastic stability of shells or shell-like structures under two independent load parameters is considered. One of the loads is associated to a limit point form of buckling, whereas the second is a bifurcation. A simple one degree of freedom mechanical system is first investigated, for which an analytical solution is possible. Next, a cylindrical shell under the combined action of axial load and localised lateral pressure is studied via a non linear, two-dimensional, finite element discretization. It is shown that both problems display the same general behaviour, with a stability boundary in the load space which is convex towards the region of stability. The results show the need of performing a full non-linear analysis to evaluate the stability boundary for the class of interaction problems considered.

  Abstract
  The elastic stability of shells or shell-like structures under two independent load parameters is considered. One of the loads is associated to a limit point form of buckling, [...]

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• Assessment of elastic lateral displacements of walls with multiple openings considering an equivalent opening and the slab stiffness

  A. Tena Colunga, A. Paredes

  RIDNAIC (2017). Vol. 17, (2), 6

  
  

  Abstract

  Approximations obtained with the equivalent frame method and Beck-Coull method to assess elastic lateral displacement profiles of walls with multiple openings per story are compared to results obtained with the finite element method using reasonably fine meshes. Multistory walls were studied, considering symmetric and asymmetric distribution of two openings per story with respect to a vertical axis. The contribution of slabs in the lateral stiffness was considered through an equivalent flange as recommended in the masonry guidelines of Mexican codes. Different stiffnesses are considered for the walls and the slabs. An updated proposal to define an equivalent opening from multiple openings per story is evaluated. From the obtained results it is confirmed that approximations obtained with the studied methods is improved: a) as multiple openings are more regular and symmetric and, b) as the number of stories of the wall increases in the Beck-Coull method. The contribution of the stiffness of the slab has an important impact for walls with typical door openings, but it is less important for walls with only typical window openings, particularly if multiple window openings are symmetrically disposed.

  Abstract
  Approximations obtained with the equivalent frame method and Beck-Coull method to assess elastic lateral displacement profiles of walls with multiple openings per story are [...]

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• Numerical symulation of the paddlefish rostrum

  F. Acosta, G. Rus

  RIDNAIC (2017). Vol. 17, (2), 5

  
  

  Abstract

  The main purpose of the rostrum of a Paddlefish is to provide hydrodynamic stability during feeding process in addition to detect the food using receptors that are randomly distributed in the rostrum. The rostrum is formed in the exterior by the tissue that is covering the cartilage that surrounds the bones forming interlocking star shaped bones. The objective of this work is to evaluate the mechanical behavior of four finite element models varying the type of formulation as follows: linear-reduced integration, linear-full integration, quadratic-reduced integration, and quadratic-full integration. In addition the load transfer mechanisms of the rostrum bone structure were observed. The base material used in the study was steel with elastic-plastic behavior as a homogeneous material before applying materials properties that represents the behavior of bones, cartilages and tissues. From the study is found that quadratic formulation resulted in lower structural stiffness as seen by higher displacements and stresses than using linearly formulated elements.

  Abstract
  The main purpose of the rostrum of a Paddlefish is to provide hydrodynamic stability during feeding process in addition to detect the food using receptors that are randomly [...]

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• Una nueva etapa de la Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil

  L. Godoy, L. Suarez

  RIDNAIC (2017). Vol. 17, (2)

  
  

  Abstract
  Editorial 2017: Una nueva etapa de la Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil

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