Punching Shear Behavior of UHPC Flat Slabs

At the Institute of Structural Engineering of the Faculty of Civil Engineering, Kassel University, series tests of slab-column connection were carried out, subjected to concentrated punching load. The effects of steel fiber content, concrete compressive strength, tension reinforcement ratio, size effect, and yield stress of tension reinforcement were studied by testing a total of six UHPC slabs and one normal strength concrete slab. Based on experimental results; all the tested slabs failed in punching shear as a type of failure, except the UHPC slab without steel fiber which failed due to splitting of concrete cover. The post ultimate load-deformation behavior of UHPC slabs subjected to punching load shows harmonic behavior of three stages; first, drop of load-deflection curve after reaching maximum load, second, resistance of both steel fibers and tension reinforcement, and third, pure tension reinforcement resistance. The first shear crack of UHPC slabs starts to open at a load higher than that of normal strength concrete slabs. Typically, the diameter of the punching cone for UHPC slabs on the tension surface is larger than that of NSC slabs and the location of critical shear crack is far away from the face of the column. The angle of punching cone for NSC slabs is larger than that of UHPC slabs. For UHPC slabs, the critical perimeter is proposed and located at 2.5d from the face of the column. The final shape of the punching cone is completed after the tension reinforcement starts to yield and the column stub starts to penetrate through the slab. A numerical model using Finite Element Analysis (FEA) for UHPC slabs is presented. Also some variables effect on punching shear is demonstrated by a parametric study. A design equation for UHPC slabs under punching load is presented and shown to be applicable for a wide range of parametric variations; in the ranges between 40 mm to 300 mm in slab thickness, 0.1 % to 2.9 % in tension reinforcement ratio, 150 MPa to 250 MPa in compressive strength of concrete and 0.1 % to 2 % steel fiber content. The proposed design equation of UHPC slabs is modified to include HSC and NSC slabs without steel fiber, and it is checked with the test results from earlier researches.

Asociación entre degeneración macular relacionada con la edad y la hipertensión arterial Bogotá 2014

Estudio Casos y Controles 1:1 que busca la relación entre la DMRE e HTA. Se estudian otras variables. Muestra de 400 pacientes, edad promedio 66,9 años +/-9,2 años. HTA y DM OR 2,315 y OR 4,626. Oclusión vascular OR 13,549 (IC 95% 3,023-60,724).

Plan de Negocio Avanzalogistic

Avanzalogistic corresponde a una plataforma multilateral que hace parte de las nuevas tecnologías de información y servicios, por lo cual se considera como una nueva opción para la ciudad de Bogotá, enfocada en dar solución al transporte de mercancía para las pequeñas y medianas empresas de un sector de la ciudad. Teniendo como diferenciación, la asistencia y atención personalizada para este tipo de clientes, donde por medio de la configuración de carga en tiempo real y con la facilidad virtual, podrán recibir el mejor servicio, en el menor tiempo posible y con los mejores precios del mercado. Considerando las necesidades de confiabilidad, seguridad, rapidez y buena atención que exige nuestro segmento objetivo, Avanzalogistic propone un servicio con calidad integral, donde por medio del desempeño enfocado al cliente y el cubrimiento de las necesidades del mismo será potencialmente reconocido como una de las mejores opciones del mercado para las empresas que soliciten transportar su carga de manera rápida y segura, disminuyendo el tiempo de respuesta de 24 horas (tiempo actual de respuesta de la competencia) a instantáneamente (tiempo por Avanzalogistic). Teniendo en cuenta lo anterior, en el proyecto se decide realizar una inversión inicial de $ 135 627 200 pesos colombianos, alcanzando su punto de equilibrio a partir del mes seis del primer año y teniendo un periodo de recuperación representado a partir del segundo año. Avanzalogistic es un proyecto que presenta una rentabilidad del 68,51%, justificada por la baja inversión y los bajos costos de operación, teniendo como principal ventaja la tercerización de los vehículos, además de la gran oportunidad de tener un mercado potencial lo suficientemente amplio que evidencia un ingreso que justifica la utilidad en cada servicio prestado. Siendo así un proyecto no solo viable, sino también con posibilidad de crecimiento y atractivo para invertir.

Just like you.

A la caída de la tarde, Little Mouse se dirige con su mamá a casa y de camino por el bosque encuentra a otros animales cuidando de sus crías y piensa lo importante que deben ser estos bebes para sus madres. Cuando llegan, Little Mouse le pregunta,inquieto a su madre '¿qué puedes hacer por mí?'. La respuesta es muy tranquilizadora para él.

Primary science equipment.

La ciencia en la escuela primaria resulta cada vez más solicitada, por ello los maestros deben aprender a elegir entre una gama de equipos cada vez más sofisticados. El objetivo es ayudar a los docentes en su tarea de garantizar que los niños accedan a un equipamiento científico adecuado,y que las escuelas desarrollen una política progresista en el suministro, uso y cuidado de estos aparatos.

Primary science and literacy.

La ciencia y el conocimiento del lenguaje, oral y escrito, es decir, la lectura y la escritura están indisolublemente ligados. La sociedad actual, muy desarrollada, necesita personas científicamente alfabetizadas. Además, la asociación entre ciencia y alfabetización es recíproca: la ciencia ofrece contextos para el uso y desarrollo de las aptitudes de lectura, escritura y comprensión, mientras que la alfabetización contribuye al acceso individual al apasionante y difícil mundo científico.

Primary science and numeracy.

Del mismo modo, que en el corazón de la ciencia esta la matemática, la enseñanza de la ciencia se basa en la comprensión de las matemáticas por los niños, como base sobre la cual desarrollar su capacidad científica en la enseñanza primaria. Por ello, se marcan unas líneas de actuación a cumplir: importancia de la aritmética en la ciencia, desarrollo de habilidades numéricas en actividades familiares, estrategias de apoyo a la aritmética. Este texto sirve de apoyo al plan de estudios de Gales, Irlanda del Norte y Escocia, y además, tiene en cuenta el National Numeracy Strategy for England.

Child-initiated learning : hundreds of ideas for independent learning in the early years.

El aprendizaje independiente y las actividades promovidas por los niños son los principios de la estimulación temprana. Por ello, se aportan muchas ideas que ayudan a desarrollar un entorno donde se celebre este aprendizaje independiente y donde los niños asuman la responsabilidad de planificar y organizar sus propias actividades.

La escritura de la historia en Ecuador tiene cuerpo de mujer: a propósito de Baldomera de Alfredo Pareja Diezcanseco (Del Fabulador)

"El lenguaje despojado del realismo le sirve al autor, un sobreviviente al igual que su personaje, para pensar una representación de los hechos cuando los gusanos hayan destruído la materialidad de los cuerpos y sus testimonios." En Baldomera, los referentes locales adquieren universalidad en las cuestiones de género: la historia de esta heroína fracasada puede ser leída como la del país, inscrita en el cuerpo de una mujer pobre, fea y negra, que termina sus días en una cárcel. Aunque es fuerte y resiste (sobrevive sin armas la matanza de noviembre de 1922), en los enfrentamientos con la ley -con la violencia racional de sus armas-, ella pierde, esto agrega un elemento más a las tensiones entre la pequeñez y lo grande, presentes en toda la novela. Un poco como el mismo autor, sobreviviente del Grupo de Guayaquil, cuando testifica sobre el trabajo literario de los Cinco como un Puño, intelectuales modernos con voz crítica ante las realidades sociales y las contradicciones de los años treinta.

Design, testing, and simulation of fibre composite leaf springs for heavy axle loads

This paper summarizes the design, manufacturing, testing, and finite element analysis (FEA) of glass-fibre-reinforced polyester leaf springs for rail freight vehicles. FEA predictions of load-deflection curves under static loading are presented, together with comparisons with test results. Bending stress distribution at typical load conditions is plotted for the springs. The springs have been mounted on a real wagon and drop tests at tare and full load have been carried out on a purpose-built shaker rig. The transient response of the springs from tests and FEA is presented and discussed.

Evolution of the eye-end design of a composite leaf spring for heavy axle loads

This paper presents the design evolution process of a composite leaf spring for freight rail applications. Three designs of eye-end attachment for composite leaf springs are described. The material used is glass fibre reinforced polyester. Static testing and finite element analysis have been carried out to obtain the characteristics of the spring. Load-deflection curves and strain measurement as a function of load for the three designs tested have been plotted for comparison with FEA predicted values. The main concern associated with the first design is the delamination failure at the interface of the fibres that have passed around the eye and the spring body, even though the design can withstand 150 kN static proof load and one million cycles fatigue load. FEA results confirmed that there is a high interlaminar shear stress concentration in that region. The second design feature is an additional transverse bandage around the region prone to delamination. Delamination was contained but not completely prevented. The third design overcomes the problem by ending the fibres at the end of the eye section.

Finite element aided design evolution of composite leaf spring

This paper shows the process of the virtual production development of the mechanical connection between the top leaf of a dual composite leaf spring system to a shackle using finite element methods. The commercial FEA package MSC/MARC has been used for the analysis. In the original design the joint was based on a closed eye-end. Full scale testing results showed that this configuration achieved the vertical proof load of 150 kN and 1 million cycles of fatigue load. However, a problem with delamination occurred at the interface between the fibres going around the eye and the main leaf body. To overcome this problem, a second design was tried using transverse bandages of woven glass fibre reinforced tape to wrap the section that is prone to delaminate. In this case, the maximum interlaminar shear stress was reduced by a certain amount but it was still higher than the material’s shear strength. Based on the fact that, even with delamination, the top leaf spring still sustained the maximum static and fatigue loads required, the third design was proposed with an open eye-end, eliminating altogether the interface where the maximum shear stress occurs. The maximum shear stress predicted by FEA is reduced significantly and a safety factor of around 2 has been obtained. Thus, a successful and safe design has been achieved.

A novel bogie design made of glass fibre reinforced plastic

This paper presents a completely new design of a bogie-frame made of glass fibre reinforced composites and its performance under various loading conditions predicted by finite element analysis. The bogie consists of two frames, with one placed on top of the other, and two axle ties connecting the axles. Each frame consists of two side arms and a transom between. The top frame is thinner and more compliant and has a higher curvature compared with the bottom frame. Variable vertical stiffness can be achieved before and after the contact between the two frames at the central section of the bogie to cope with different load levels. Finite element analysis played a very important role in the design of this structure. Stiffness and stress levels of the full scale bogie presented in this paper under various loading conditions have been predicted by using Marc provided by MSC Software. In order to verify the finite element analysis (FEA) models, a fifth scale prototype of the bogie has been made and tested under quasi-static loading conditions. Results of testing on the fifth scale bogie have been used to fine tune details like contact and friction in the fifth scale FEA models. These conditions were then applied to the full scale models. Finite element analysis results show that the stress levels in all directions are low compared with material strengths.

Influence of Post and Resin Cement on Stress Distribution of Maxillary Central Incisors Restored with Direct Resin Composite

The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm(2) was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 mu m). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.

Estudo da viabilidade do uso do pó de aciaria elétrica a arco na confecção de blocos de concreto para pavimentação

o Pó de Aciaria Elétrica (PAE) é um resíduo gerado em indústrias siderúrgicas que utilizam o Forno Elétrico a Arco (FEA) e a sucata como principal matéria-prima para a produção do aço. O PAE é composto por diferentes óxidos metálicos, entre eles o Zn, Cr, Pb e Cd. Devido às concentrações de Pb e Cdultrapassarem as pennitidas pela NBR 10004(1987), no ensaio de lixiviação, o PAE é classificado como resíduo perigoso Classe I. Este trabalho tem como objetivo o estudo da influência do PAEno desempenhomecânico e durabilidade de blocos de concreto para pavimentação. O programa experimental foi desenvolvido em duas etapas: a primeira. na qual foi fixada a relação água/cimento e a segunda, na qual foi fixado o índice de umidade, fator este relacionado com a capacidade de moldar os corpos-de-prova. Em ambas as etapas, o teor de adição do PAE empregado foi de 5%, 15% e 25% em relação à massa de cimento. Também foram moldados corpos-de-prova sem adição do resíduo (0%), utilizados como referência. Como ensaios complementares, foram detenninados o calor de hidratação, assim como a caracterização mineralógica e microestrutural de pastas de cimento com teores do PAE. Verificou-se que, nas duas etapas, os blocos contendo 15% de adição do PAE obtiveram melhor desempenho quanto à resistência à compressão axial. Para os ensaios de durabilidade, os blocos com o PAE mostraram-se com desempenho igual ou superior aos blocos que não o possuíam O PAE utilizado nos blocos de concreto, bem como em pastas de cimento, retardou os tempos de início e fim de pega. O cimento também pode agir como formador de uma matriz para encapsular os metais pesados contidos no pó de aciaria. Nos ensaios de caracterização ambiental, obselVou-seeste encapsulamento através da análise dos extratos lixiviados e solubilizados, onde as concentrações dos metais pesados, ao longo do tempo, diminuíram. Isto fez com que os blocos, contendo o resíduo em sua composição, fossem classificados neste trabalho como Classe II - não-inerte. Desta forma, a partir de um resíduo perigoso Classe L foi possível desenvolver, através do encapsulamento na matriz cimentante, um produto Classe 11.