FRD - Investigación - Ciencia y Tecnología
Permanent URI for this communityhttp://48.217.138.120/handle/20.500.12272/1225
Browse
6 results
Search Results
Item Natural vibrations of anisotropic plates with several internal line hinges(Sprimger Link, 2013-05-29) Grossi, Ricardo; Raffo, JavierThis paper deals with the free transverse vibration of anisotropic plates with several arbitrarily located internal line hinges and piecewise smooth boundaries, elastically restrained against rotation and translation. The equations of motion and the associated boundary and transition conditions are derived using Hamilton’s principle in a rigorous framework. A new analytical manipulation based on a condensed notation is used to compact the corresponding analytical expressions. A combination of the Ritz method and the Lagrange multipliers method with polynomials as coordinate functions is used to obtain tables of the nondimensional frequencies and the corresponding mode shapes, for rectangular plates with different boundary conditions and restraint conditions in the internal line hinges. The cases not previously treated of two- and three line hinges are particularly analyzed.Item A Note on the Influence of Intermediate Restraints and Hinges in Frequencies and Mode Shapes of Beams(2014) Raffo, Javier; Grossi, RicardoThis note deals with the free transverse vibration of a beam with two arbitrarily located internal hinges, four intermediate elastic restraints, and ends elastically restrained against rotation and translation. The method of separation of variables is used for the determination of the exact frequencies and mode shapes. New results are presented for different boundary conditions and restraint conditions in the internal hinges. The mathematical model is also used to study the influence on the frequencies and mode shapes of varying intermediate supports that are located at the nodal points of higher modes. A detailed numerical study on the effects of the locations of intermediate translational restraints and their stiffness on the natural frequencies and mode shapes is performed for different boundary conditions. The effect of the presence of the internal hinges is alsoanalysed. Graphsandtablesofthenon-dimensionalfrequenciesandthecorrespondingmodeshapesaregiven in order to illustrate the behaviour of frequency parameters and the presence of mode shape switching.Item Variational approach of Timoshenko beams with internal elastic restraints(2013) Raffo, Javier; Grossi, RicardoAn exact approach for free transverse vibrations of a Timoshenko beam with ends elastically restrained against rotation and translation and arbitrarily located internal restraints is presented. The calculus of variations is used to obtain the equations of motion, the boundary conditions and the transitions conditions which correspond to the described mechanical system. The derived differential equations are solved individually for each segment of the beam with the corresponding boundary and transitions conditions. The derived mathematical formulation generates as particular cases, and several mathematical models are used to simulate the presence of cracks. Some cases available in the literature and the presence of some errors are discussed. New results are presented for different end conditions and restraint conditions in the intermediate elastic constraints with their corresponding modal shapes.Item On application of theory of distributions to static and dynamic analysis of cracked beams(2016) Grossi, Ricardo; Raffo, JavierThis paper presents a rigorous study on the static and dynamic behavior of beams affected by cracks. The theory of distributions developed by Laurent Schwartz is adopted as it is particularly suitable for the treatment of discontinuities in functions for the deflection and derivatives of the beam. Thus, this paper presents a contribution towards the understanding and application of the theory of distributions to the static and dynamic behavior of structural elements affected by cracks. A simple, computationally efficient and accurate algorithm is developed for the problems of concern. Numerical results are presented for beams with two cracks. The algorithms developed for beams with discontinuities are obtained in a rigorous framework for static and vibration problems.Item Vibraciones de una viga de eje curvo con una rótula elástica intermedia y condiciones de extremo elásticas(Asociación Argentina de Mecánica Computacional, 2018-11-09) Raffo, Javier; Calambás, Andrés SaavedraEn este trabajo se analiza el problema de vibraciones libres de una viga curva en el plano de dos tramos de longitud arbitraria, diferentes propiedades, con una rótula intermedia afectada por restricciones elásticas traslacionales y rotacionales, ubicada arbitrariamente. Ambos extremos de la viga también se encuentran restringidos elásticamente contra rotación y traslación. Mediante una aplicación rigurosa del principio de Hamilton, se obtienen: las ecuaciones diferenciales, las condiciones de contorno y las condiciones de transición que corresponden al problema del comportamiento estático y dinámico del sistema mecánico en estudio. Se determina una solución analítica mediante la aplicación del método variacional de Ritz. Para obtener indicadores sobre los resultados obtenidos con la metodología propuesta, se realizan comparaciones de estos, con ciertos casos particulares que figuran en la literatura. Se presentan además resultados nuevos que consisten en: frecuencias naturales y formas modales de vibración para una viga curva con diferentes características.Item Estudio Paramétrico de una modelo de reactor nuclear de potencia con interacción sueloestructura(2018-11-09) Raffo, Javier; Guennam, AhmadSe presenta un estudio paramétrico del modelo de elementos finitos de un problema de análisis estructural dinámico del edificio de un reactor nuclear con interacción suelo-estructura para analizar el efecto sobre el espectro de aceleraciones resultante en diferentes puntos de la estructura. El modelo incluye al suelo donde se encuentra emplazada la estructura junto con todas sus propiedades mecánicas como amortiguamiento, velocidades de propagación de ondas, densidades, amortiguamientos, distribución de capas. A la vez, el modelo incluye al edificio del reactor con parte del mismo embebida en el suelo. Se destaca que este modelo resuelve la dinámica del sistema sueloestructura como un único modelo mediante el mallado del suelo, la estructura y la generación de una función de transferencia. Como excitación del sistema se introduce un sismo tipo utilizado en centrales nucleares el cual consiste en un espectro de aceleraciones en las tres direcciones coordenadas. El estudio analiza el efecto del cambio de los resultados ante la variación de las diferentes propiedades del suelo.