Sustainability based-approach to determine the concrete type and reinforcement configuration of TBM tunnels linings. Case study: Extension line to Barcelona Airport T1

Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20 years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.Peer ReviewedPostprint (author's final draft

Influence of the type of fiber on the structural response and design of FRC slabs

Most codes for the design of fiber reinforced concrete (FRC) structures are based on the experience achieved throughout the years with steel fibers. Recent codes include the possibility of applying the same considerations for FRC structures with plastic fiber. However, the consequences of assuming identical design considerations regardless of the type of fiber is scarcely known in terms of the structural behavior of full-scale elements. The main goal of this paper is to assess the influence of the type of fiber on the performance of full-scale concrete slabs, emphasizing on the consequences of using a common design approach. For that, a comparative experimental study was conducted in order to expose differences regarding the crack pattern and load-deflection behavior. Then, finite element simulations were performed using the constitutive equations from the Model Code 2010. The results indicate distinct levels of overestimation of the structural behavior measured experimentally, confirming that specific design considerations are required depending on the type of fiber used. Based on the findings, correction factors are proposed for the design of FRC slabs with each fiber.Peer ReviewedPostprint (author's final draft

Diseño y análisis de secciones de hormigón estructural frente solicitaciones normales

En esta comunicación se presenta una experiencia piloto en la enseñanza de la materia Hormigón Estructural de la titulación de Ingenieros de Caminos, Canales y Puertos de la UPC, la cual puede ser fácilmente extendida a otros ámbitos de conocimiento, territoriales y profesionales. Dicha experiencia consiste en una biblioteca de ayudas numéricas (programas) a las que el alumno puede tener acceso para simplificar la parte más tediosa de las operaciones matemáticas. Esta biblioteca, consta de numerosos programas, que responden a acciones simples y directas (no se trata de programas complejos). Estos programas están enlazados de forma tal que la entrada de datos de uno de ellos puede ser la salida de la acción anterior, pudiéndose llegar a responder a problemas complejos, por agregación de problemas simplesPeer Reviewe

Ampliación de Unidad Comunitaria Especializada de Salud Familiar de San Miguel (UCSFE San Miguel)

Realizar una propuesta de ampliación y remodelación de la UCSFE del municipio de San Miguel, brindándoles una opción que beneficie a su mejor desarrollo y solventando todas las necesidades espaciales y funcionales que la institución posee actualmente. La metodología se dividirá en cinco etapas que son: Fase I: Planteamiento Del Problema; Fase II: Marco Referencial; Fase III: Diagnóstico; Fase IV: Pronóstico. Al culminar el desarrollo y proceso de investigación del trabajo de graduación se concluye lo siguiente: El anteproyecto de ampliación de la Unidad Comunitaria Especializada de Salud Familiar, San Miguel, se desarrolló con el fin de proponer una solución a las necesidades espaciales con las cuales cuentas actualmente. Y finalmente la unidad comunitaria brindara los espacios necesarios en base a las normas, leyes y códigos establecidos, desarrollando así un mejor ambiente laboral y cubriendo las necesidades de los usuario

Formation and characterization of model cell membranes and their interaction with Magnetic Nanoparticles

In this final master project model cell membranes of a mixture of 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol were transferred onto mica substrates by Langmuir-Blodgett technique (LB) to mimic a real cell membrane. The high quality and chemical structure of the monolayers formed were confirmed by means of Atomic Force Microscopy (AFM) imaging and Contact Angle measurements. A study of the stability of the monolayer in liquid media considering the amphiphilic nature of the compounds was carried out, observing as the monolayer re-assembled into bilayer. This behaviour was explained by means of Force Spectroscopy (FS) studies with a noticeable increase in the breakthrough force values. Furthermore, the deposition of MNPs onto monolayer was carried out by LB in a successful way obtaining a well-covered distribution of MNPs with the final purpose of study the membrane response when it is exposed to alternating magnetic fields (Hyperthermia)

Towards the sustainability in the design of wind towers

Wind farms are both a renewable energy production alternative and a profitable economic enterprise. At the same time these groups of wind towers can be a social-friendly solution if they solve challenging demands from the society such as integration in landscape, aesthetics, low noise nuisances… This paper presents part of a complete research project that was carried out between 2009 and 2015. First this article presents a new wind tower proposal that has been designed to reduce these social impacts as well as satisfying environmental aspects, economic requirements and boundary conditions such as height, turbine power, soil conditions. This proposal is composed of precast concrete modules joined with high-resistance steel bars that define a post-tension structure. These components define an attractive and transparent tripod that is transversally reinforced with steel profiles. This system holds the Spanish patent “Support structure to wind turbines, number ES 2 319 709 B8” and aims to build 100-120m high towers. At this height there is better wind quality and large turbines of 3 MW can be installed. Second, a sustainability assessment of this new hybrid wind tower has been carried out in order to evaluate its social, environmental and economic impacts compared to other solutions. Steel lattice structures, steel tubular systems, in situ concrete towers and precast concrete structures are the alternatives for wind farms that have been considered. MIVES, a MCDM methodology based on the value function concepts has been used to do this assessment, which has relied upon seminars of experts. This sustainability assessment enabled the identification of the aspects with the lowest sustainability index. These are the maintenance and deconstruction costs and for occupational hazards. Now these weak points can be corrected in the process of bringing the patented technology to market.Postprint (published version

Dynamics of the QCD String with Light and Heavy Quarks

The generalization of the effective action [1] of the quark--antiquark system in the confining vacuum is performed for the case of arbitrary quark masses. The interaction of quarks is described by the averaged Wilson loop for which we use the minimal area law asymptotics. The system is quantized by the path integral method and the quantum Hamiltonian is obtained. It contains not only quark degrees of freedom but also the string energy density. As well as in the equal masses case [1] two dynamical regimes are found [2]: for large orbital excitations ($l \gg 1$) the system is represented as rotating string, which leads to asymptotically linear Regge trajectories, while at small $l$ one obtains a potential-like relativistic or nonrelativistic regime. In the limiting cases of light-light and heavy-light mesons a unified description is developed [2]. For the Regge trajectories one obtains nearly straight-line patterns with the slope very close to $1/2 \pi \sigma$ and $1/ \pi\sigma$ correspondingly. The upper bound on the light quark(s) masses which doesn't change considerably this property of the trajectories is also found.Comment: 31 pages, preprint ITEP 62-9

Sustainability evaluation of the concrete structures

Sustainability is a new and settled concept in advanced societies, even though the term is sometimes inappropriately used, which may represents a threat. For this reason it is suitable to supply methods of measuring sustainability. Given that the sustainability concept involves distinct requirements and criteria, it seems reasonable to use multi-criteria methods in the decision making process. This work shows a brief review of such methods applied to concrete structures. The MIVES method is applied in this work for assessing the sustainability of the concrete structures. Three examples are proposed to show the capacity of the method. One of them is based on the general application of the Spanish Structural Code for Concrete Structures (EHE-08), and the other two assess the sustainability of reinforced concrete columns by adopting distinct type of concrete and building procedures.Postprint (published version

Dovelas de hormigón (concreto) reforzado con fibras para el soporte de túneles y pozos verticales

El empleo del hormigón reforzado con fibras (HRF) para dovelas de anillos de revestimiento de túneles es ya una práctica habitual a nivel nacional e internacional. En este sentido, las ventajas técnicas a las que conduce su uso (control del ancho de fisura, tenacidad frente a impacto y cargas concentradas, entre otras) son también conocidas. Asimismo, a nivel económico su uso puede ser atractivo si se hace un análisis integral considerando el proceso de producción y mantenimiento de la dovela, y no sólo la comparación del coste (costo) de la fibra y el de la armadura. Aún existe inercia al empleo del HRF como alternativa al refuerzo clásico; pues su contribución estructural raramente se ha considerado. Por una parte, debido a que hasta el año 2008 no aprobó la EHE – 08, cuyo anexo 14 aborda aspectos de diseño y control de HRF; y, por otra, a la falta de criterios para considerar aspectos como la orientación y distribución de las fibras.Peer ReviewedPostprint (published version

Design procedure and experimental study on fibre reinforced concrete segmental rings for vertical shafts

Structural fibres are used to replace partially or totally the passive reinforcement in precast concrete segments for tunnel linings constructed with TBM, showing several advantages. Fibre reinforced concrete (FRC) could also be applied with similar benefits to vertical shafts. However, to the author's knowledge, this material has not been used in such application yet. The Model Code 2010 gathers an approach for the design of FRC structural elements. This approach should be adapted according to the structural needs of precast segment, for which the transient load stages are often the most critical and specific ductility requirements should be established. The objective of this paper is twofold: propose a general analytical formulation to assess the minimum mechanical requirements that FRC must fulfil in case of partial or complete substitution of the steel rebars and confirm that it is possible to replace the rebars by using fibres in vertical shaft linings. First, the general analytical formulation is proposed. Then, the segments of the Montcada vertical shaft (Barcelona) are redesigned considering the total substitution of the traditional reinforcement by fibres. Finally, two full-scale tests of the FRC precast segments were performed to verify the suitability of the analytical formulation proposed.Peer ReviewedPostprint (author's final draft