Static analyses of elastic plates with voids

Simplified analysis of circular plates including voids

En la actualidad, una de las variables de mayor relevancia en el proyecto de puentes de ferrocarril de alta velocidad es la aceleracion vertical del tablero, cuyo valor maximo se ve limitado por la normativa vigente y constituye uno de los Estados Limites de Servicio (ELS) libado a la seguridad del trafico. En especial, los puentes isostaticos de luces medias-cortas y situados en lineras de ferrocarril convencionales son los mas susceptibles de experimentar vibraciones inadmisibles, causadas por la aparicion de fenomenos de resonancia ante el progresivo aumento de la velocidad de circulacion de los trenes. El problema de vibraciones excesivas ha llevado a que se tome la decision de sustituir algunos tableros de puentes antiguos para mejorar su comportamiento dinamico ante los nuevos requerimientos de trafico. Esta decision debe tomarse sobre la base de un calculo riguroso y acorde a la normatiiva. El modelo numerico a utilizar es, por tanto, un factor clave que queda a eleccion del calculista del puente. Tradicionalmente se han empleado modelos de viga simplemente apoyada para el calculo dinamico de los tableros isostaticos, una aproximacion ventajosa en terminos de costes computaciones aunque podra no ser suficiente para los puentes de via doble, debido a la contribucion de las formas modales tridimensionales. Otra practica frecuente en la modelizacion de estos tableros es la de despreciar el efecto de los apoyos elasticos (neoprenos) situados en los estribos, una tendencia que se ha extendido a los modelos de eparrillado y de placa ortortropa. En el marco de esta Tesis Doctoral se analiza la influencia de estas practicas habituales de modelizacion en la verificacion del ELS de la aceleracion vertical, a traves del estudio del comportamiento dinamico de un conjunto de puentes isostaticos de diferentes tipologias y relaciones anchura/luz. Los tableros seleccionados se han modelizado empleando modelos numericos de elementos finitos espaciales, basados en la aproximac

Comportamiento dinámico de puentes de ferrocarril para tráfico de alta velocidad y reacondicionamiento mediante disipadores viscoelásticos pasivos

In order to study the basic mechanical property of cast-in-place stiffening-ribbed-hollow-pipe reinforced concrete girderless floor, and similarities and differences of the structural performance compared with traditional floor, we carried out the destructive stage loading test on the short-term load test of floor model with four clamped edges supported in large scale, and conducted the long-term static load test. Also, the thesis conducted finite element analysis in virtue of ANSYS software for solid slab floor, stiffening-ribbed-hollow-pipe floor and tubular floor. The experiment indicates that the developing process of cracks, distribution and failure mode in stiffening-ribbed-hollow-pipe floor are similar to that of solid girderless floor, and that this kind of floor has higher bearing capacity and better plastic deformation capacity. The finite element analysis manifests that, compared with solid slab floor, the deadweight of stiffening-ribbed-hollow-pipe floor de- creases on greater level while deformation increases little, and that compared with tubular floor, this floor has higher rigidity. So stiffening-ribbed-hollow-pipe reinforced concrete girderless floor is particularly suitable for long-span and large-bay building structure.

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Experimental Study on Mechanical Property of Stiffening-ribbed-hollowpipe Reinforced Concrete Girderless Floor with Four Clamped Edges Supported

Novel locally resonant and widely scalable seismic metamaterials for broadband mitigation of disturbances in the very low frequency range of 0–33 Hz

Finite element procedures for determining the plate bending stiffnesses of a circular voided slab are presented and the results are compared with those obtained from tests on model elastic voided plates. Preliminary investigations showed that a simplified plane-strain formulation, rather than a more complex general plane-strain formulation, could be used to determine the transverse flexural stiffness. Torsional stiffnesses were obtained from an analysis using the Prandtl stress-function formulation of the torsion problems. Tests were carried out on four epoxy-resin model plates having different void sizes. Good agreement was obtained between the finite element and experimental results. For design purposes, charts are presented which enable a designer of a concrete voided slab, having a Poisson's ratio of 0.2, to determine the values of the plate bending stiffnesses required for a thin plate analysis of such a slab. It is also shown that simple calculations based upon replacing a circular void with an equivalent square void are often adequate for design purposes.

L. A. Clark

Papers

Circular Voided Concrete Slab Stiffnesses