Lecturas 01.05.2014

What If We Never Run Out of Oil? By Charles Mann.

For a long time, companies collected oil and discarded the methane that burbled up with it, often by burning the gas in a cinematic flare atop special derricks, or even simply dumping it into the atmosphere. People did use natural gas for energy—gaslights have existed since the days of Jane Austen—but transporting it was costly. Unlike liquid oil, which could be poured into containers and carried on a railroad network that had already been built and paid for by somebody else, gaseous methane had to be pumped through sealed tubes to its destination, which required energy firms and utilities to lay thousands upon thousands of miles of pipeline. Not until the Second World War and war-production advances in welding did this effort gather speed. (Methane can be cooled into a liquid and transported in pressurized tanks that are loaded and unloaded in special facilities, but this is also expensive.) Oil from wells in Texas is readily dispatched via tanker to Europe or Asia, but even today, natural gas from the same wells is often effectively limited to use in the United States.

If People Could Immigrate Anywhere, Would Poverty Be Eliminated? Some economists are pushing for "open borders". By Shaun Raviv.

"Open borders will become a reality when the public stops believing that immigrants are a threat," sociologist Fabio Rojas recently wrote, comparing the open borders movement to the gay rights movement. "Even if a pro-immigration referendum fails to pass, it will still serve the function of forcing the issue onto the public stage. These actions won't ­­change the minds of those strongly committed to anti-immigration policy. Instead, they will make immigration seem 'normal' to a later generation of people."

La primera autopista de Kenia: Nairobi-Thika, por Eugenio Rodríguez.

Las inversiones en infraestructuras en el continente africano siguen creciendo aun ritmo constante, y uno de los ejemplos más recientes lo tenemos con la nueva autopista de 8 carriles de 50 kilómetros que une Nairobi y Thika, inaugurada en noviembre de 2012. El proyecto vial de un presupuesto de 280 millones de euros, se espera que ofrezca un fuerte impulso en la economía de la zona del África Oriental, siendo la primera autopista de su tipo construida en Kenia, que ayudará al país en el cumplimiento de su objetivo de alcanzar la condición de país de ingresos medios en 2030.

Un limbo para Caracas, por Raúl Rivero.

Los expertos coinciden en que la única forma de salir de la crisis general que padece la nación es mediante la unidad de todas las fuerzas y de los diversos sectores de la sociedad más dividida hoy que nunca en dos mitades perfectamente identificables después de los resultados de las elecciones. Pero Maduro mantiene el tono que aprendió de Chávez y de sus jefes cubanos que es el de manejarse con sus adversarios como una pandilla en un bar del puerto.

Chart of the day: In 2012, the US had the most energy efficient economy in history. By Mark J. Perry.

energy

The EIA released new energy data this week showing that the U.S. had the most energy-efficient economy in history last year, based on the amount of energy consumed to produce each real dollar of Gross Domestic Product (GDP). In 2012, it required only 6,990 BTUs of energy (petroleum, natural gas, nuclear and renewables) to produce each real dollar of GDP, an all-time record low. Even though the US produced 2.2% more real output last year compared to 2011, the total energy consumed in 2012 was actually 2.45% lower than the previous year, which led to a 4.6% reduction in the total energy consumed to produce each dollar of GDP in 2012.

Nueva Propuesta Diseño Pórticos Uniones Semirígidas Acero

2006.
José Manuel Cabrero.
Universidad de Navarra.
Enlace para descarga.

Resumen:

El empleo de uniones semirrígidas es una de las novedades incorporadas en el Eurocódigo 3. Las ventajas obtenidas con su utilización, principalmente mayor economía y redundancia estructural, han sido ya extensamente documentadas. Pero este tipo de uniones no se emplean en la práctica habitual. Uno de los motivos principales es que no existen métodos de diseño, modelos ni herramientas adecuados. En esta tesis se presenta un método de diseño apropiado para las uniones semirrígidas. El método propuesto permite no sólo optimizar los perfiles estructurales, sino también la unión, de modo que se ajuste a los valores teóricos óptimos. Se aportan métodos de prediseño para uniones de chapa de testa extendida. La tesis presenta también el comportamiento semirrígido de uniones tridimensionales. Para ello se desarrolló un programa experimental en la Universidad de Navarra, España. Los ensayos realizados proporcionan un primer acercamiento al comportamiento de estas uniones cuando se aplica carga en ambos ejes (carga tridimensional). Se ha desarrollado y verificado un nuevo componente para placas sujetas lateralmente sometidas a flexión (aplica en la tesis al alma del pilar y a la chapa adicional a flexión). El componente se ha aplicado satisfactoriamente al análisis de uniones en el eje menor. Además, se han desarrollado modelos elásticos completos para el análisis de uniones tridimensionales en los ejes mayor y menor. La formulación propuesta incluye los efectos de rigidización adicional de cada componente debidos a la carga en ambos ejes.

Summary:

The use of semi-rigid joints is among the novelties incorporated in Eurocode 3. The benefits of semi-rigid joints are extensively documented, but they are not really used much in practice. There is a lack of appropriate design methods, models and tools. In this thesis a design method suitable for semi-rigid joints is introduced. The proposed method allows to optimize not only the size of the structural profiles, but also the joint design to match the optimal theoretical values. Pre-design methods for semi-rigid extended end-plate joints are also provided to easily check the feasibility and suitability of a particular connection design. The thesis has also introduced the semi-rigid behaviour of three-dimensional joints. An experimental investigation of statically loaded extended end-plate connections in both major and minor column axis was undertaken at the University of Navarra, Spain. The aim was to provide insight into the behaviour of these joints when loading is applied to both axes (three-dimensional loading). A new component for laterally supported plates in bending (applied to the column web and the additional plate in bending) is presented and applied to minor axis joints. Also, complete elastic models for both major- and minor-axis three-dimensional joints are developed. The proposed formulation takes into account the stiffening effects of each component caused by the loads applied to both axes.


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