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Tesis doctoral: Evaluaci贸n multicriterio de la sostenibilidad social para el desarrollo de proyectos de infraestructuras

El pasado viernes 27 de octubre del 2017 tuvo lugar la defensa de la tesis doctoral de Leonardo A. Sierra Varela titulada “Evaluaci贸n multicriterio de la sostenibilidad social para el desarrollo de proyectos de infraestructuras”, dirigida por Eugenio Pellicer y V铆ctor Yepes.聽La tesis recibi贸 la calificaci贸n de 鈥淪obresaliente Cum Laude鈥 por unanimidad, con menci贸n internacional. Presentamos a continuaci贸n un peque帽o resumen de la misma.

Resumen:

Hoy en d铆a existe un consenso por el cual las consideraciones econ贸micas, ambientales y sociales en el desarrollo de los pa铆ses constituyen dimensiones necesarias para alcanzar la sostenibilidad. En el 谩mbito de la construcci贸n se han impulsado agendas que promueven el desarrollo sostenible considerando el ciclo de vida de los proyectos. Sin embargo, se reconoce que la limitaci贸n fundamental de la sostenibilidad es que tiende a centrarse en las consideraciones biof铆sicas y econ贸micas del entorno construido; sin prestar la suficiente atenci贸n a los aspectos sociales. La no consideraci贸n temprana de los aspectos sociales afecta al desarrollo de la infraestructura en la sociedad a corto y largo plazo. Dado que los impactos sobre la sociedad son multidimensionales, una representaci贸n que eval煤e los aspectos sociales tambi茅n debe serlo. La valoraci贸n de los aspectos sociales y la calidad de vida superan los aspectos cuantitativos. En efecto, los resultados de una evaluaci贸n son igual de trascedentes que la legitimidad participativa de su proceso. En este sentido los m茅todos de toma de decisiones multicriterio constituyen una alternativa que representa de un modo 贸ptimo la evaluaci贸n multidimensional y participativa de los aspectos sociales. Con todo, la sostenibilidad social en la evaluaci贸n de infraestructuras no ha sido adecuadamente tratada hasta este momento.

A la vista de estos antecedentes, la dimensi贸n social en la evaluaci贸n de las infraestructuras requiere una revisi贸n y nuevos enfoques en la toma de decisi贸n en las fases tempranas del desarrollo del proyecto. Todo ello conduce a plantear el objetivo general de la investigaci贸n de la siguiente forma: Evaluar la sostenibilidad social de las infraestructuras integr谩ndola en la toma de decisiones. Este objetivo general se desglosa en diferentes objetivos espec铆ficos que buscan explorar las 谩reas de mejora en el tratamiento de la sostenibilidad social. A partir de este punto, se proponen metodolog铆as para estimar la contribuci贸n a la sostenibilidad social a trav茅s de la evaluaci贸n multicriterio de infraestructuras.

El alcance de la investigaci贸n se concentra en la evaluaci贸n de infraestructuras de ingenier铆a civil en las etapas de formulaci贸n, factibilidad y planificaci贸n; y la consideraci贸n de m煤ltiples aspectos sociales. El documento presentado se compone por seis art铆culos complementarios (tres de ellos ya publicados y otros tres en proceso de revisi贸n en revistas cient铆ficas). En general para el desarrollo de los objetivos de la investigaci贸n los estudios utilizan diferentes t茅cnicas: panel de expertos Delphi, el Proceso Anal铆tico Jer谩rquico (AHP), la teor铆a de la utilidad, sistemas estoc谩sticos, m茅todos multiobjetivo y las t茅cnicas de razonamiento Bayesiano.

La investigaci贸n se ha aplicado a distintos contextos internacionales. La contextualizaci贸n de los criterios sociales en el ciclo de vida se implement贸 en infraestructuras chilenas. Se aplic贸 un m茅todo de aprendizaje activo de la聽 sostenibilidad en un curso de posgrado en Espa帽a con estudiantes internacionales. Por su parte, se implementaron dos m茅todos de estimaci贸n de la contribuci贸n social, a corto y largo plazo, en infraestructuras viarias en El Salvador.

A partir de los resultados de la investigaci贸n se han propuesto m茅todos para tratar la dimensi贸n social en la evaluaci贸n multicriterio de infraestructuras civiles e integrarla en el proceso de toma de decisi贸n. Las propuestas han surgido a partir de una exploraci贸n de las necesidades de mejora de los m茅todos multicriterio para evaluar la sostenibilidad social. De esta forma se proponen tratamientos integrados para fortalecer la dimensi贸n social en el proceso de evaluaci贸n de la sostenibilidad. Espec铆ficamente se proponen sistemas de participaci贸n multidisciplinar y multisectorial integrados; se considera la contribuci贸n no compensatoria de las infraestructuras a la mejora social a corto y largo plazo; se promueve la equidad intergeneracional de las oportunidades de mejora social; se trata la incertidumbre interna de los m茅todos propuestos; y, finalmente, se mejora la interacci贸n con el contexto y la promoci贸n del aprendizaje social en los procesos de evaluaci贸n. Esta investigaci贸n aporta las herramientas que respaldan a los organismos p煤blicos encargados de la planificaci贸n territorial y de la priorizaci贸n de infraestructuras para apoyar los procesos de toma de decisi贸n.

Los resultados de los m茅todos propuestos presentan las siguientes limitaciones: el desempe帽o se ajusta al conjunto de alternativas de infraestructuras evaluadas; considera el impacto de primer orden de la infraestructura sobre los criterios sociales; y la independencia de los indicadores que interact煤an sobre un mismo criterio. Las futuras investigaciones podr铆an simplificar los tratamientos propuestos a trav茅s de la adaptaci贸n a contextos y tipos espec铆ficos de infraestructuras, integrados con la evaluaci贸n de las dimensiones econ贸micas y ambientales de la sostenibilidad.


Referencias:

SIERRA, L.A.; YEPES, V.; PELLICER, E. (2017).聽Assessing the social sustainability contribution of an infrastructure project under conditions of uncertainty.Environmental Impact Assessment Review, 67:61-72.聽DOI:10.1016/j.eiar.2017.08.003聽(link)

SIERRA, L.A.; PELLICER, E.; YEPES, V. (2017).聽Method for estimating the social sustainability of infrastructure projects.Environmental Impact Assessment Review, 65:41-53. DOI: 10.1016/j.eiar.2017.02.004

SIERRA, L.A.; PELLICER, E.; YEPES, V. (2016).聽Social sustainability in the life cycle of Chilean public infrastructure.Journal of Construction Engineering and Management ASCE, 142(5):聽 05015020.聽DOI:聽10.1061/(ASCE)CO.1943-7862.0001099.

PELLICER, E.; SIERRA, L.A.; YEPES, V. (2016).聽Appraisal of infrastructure sustainability by graduate students using an active-learning method.Journal of Cleaner Production,聽113:884-896. DOI:10.1016/j.jclepro.2015.11.010

31 octubre, 2017
 
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Life-cycle assessment: A comparison between two optimal post-tensioned concrete box-girder road bridges

Acaban de publicarnos un art铆culo en la revista del JCR (Q2) Sustainability que compara dos puentes postesados 贸ptimos de secci贸n en caj贸n atendiendo a su ciclo de vida. Creemos que la metodolog铆a empleada puede ser de inter茅s para casos de estructuras de hormig贸n similares a las presentadas. El art铆culo forma parte del proyecto de investigaci贸n BRIDLIFE聽“Puentes pretensados de alta eficiencia social y medioambiental bajo presupuestos restrictivos“.

Os paso a continuaci贸n el resumen y el art铆culo propiamente dicho, pues est谩 publicado en abierto.

 

 

Abstract:

The goal of sustainability involves a consensus among economic, environmental and social factors. Due to climate change, environmental concerns have increased in society. The construction sector is among the most active high environmental impact sectors. This paper proposes new features to consider a more detailed life-cycle assessment (LCA) of reinforced or pre-stressed concrete structures. Besides, this study carries out a comparison between two optimal post-tensioned concrete box-girder road bridges with different maintenance scenarios. ReCiPe method is used to carry out the life-cycle assessment. The midpoint approach shows a complete environmental profile with 18 impact categories. In practice, all the impact categories make their highest contribution in the manufacturing and use and maintenance stages. Afterwards, these two stages are analyzed to identify the process which makes the greatest contribution. In addition, the contribution of CO2fixation is taken into account, reducing the environmental impact in the use and maintenance and end of life stages. The endpoint approach shows more interpretable results, enabling an easier comparison between different stages and solutions. The results show the importance of considering the whole life-cycle, since a better design reduces the global environmental impact despite a higher environmental impact in the manufacturing stage.

Keywords:

sustainability;聽environmental impact;聽life-cycle assessment;聽construction LCA;聽bridge LCA;聽ReCiPe;sustainable construction

Reference:

PENAD脡S-PL脌, V.; MART脥, J.V.; GARC脥A-SEGURA, T.;聽 YEPES, V. (2017).聽Life-cycle assessment: A comparison between two optimal post-tensioned concrete box-girder road bridges.Sustainability, 9(10):1864. doi:10.3390/su9101864聽(link)

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20 octubre, 2017
 
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Environmental impact shares of a reinforced concrete earth-retaining wall with buttresses

http://blog.360gradosenconcreto.com/tipos-muros-contencion-prefabricados-concreto/

Abstract: Structural engineers focus on the reduction of carbon emissions in reinforced concrete structures, while other impacts affecting ecosystems and human health become secondary or are left behind. The featured life cycle assessment shows the impacts corresponding to each construction stage of an earth-retaining wall with buttresses. In this study the contribution ratio of each input flow is analyzed. Accordingly, concrete, landfill, machinery, formwork, steel, and transport are considered. Results show that despite the concrete almost always accounts for the largest contribution to each impact, the impact shares of steel present noticeable sensitivity to the steel-manufacturing route. The parameter of study is the recycling rate, usually 75% reached in Spain. Noticeable variation is found when the recycling content increases. The relationship between the impacts of each material with the amount of material used discloses research interest.

 

Keywords: Life cycle assessment, Functional unit, Steel recycling rate, Concrete ratio, Photochemical oxidation, Ozone depletion, Global warming.

Reference:

MOLINA-MORENO, F.; MART脥, J.V.; YEPES, V.; CIROTH, A. (2017).聽Environmental impact shares of a reinforced concrete earth-retaining wall with buttresses.The Ninth International Structural Engineering and Construction Conference, Resilient Structures and Sustainable Construction ISEC-9, Valencia, Spain July 24-July 29.

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17 julio, 2017
 
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Carbon embodied optimization for buttressed earth-retaining walls: implications for low-carbon conceptual designs

Nos acaban de publicar en la revista de Elsevier del primer decil, Journal of Cleaner Production, un art铆culo donde se estudia el dise帽o de los muros de contrafuertes optimizados para reducir sus emisiones de CO2. Este art铆culo forma parte de nuestra l铆nea de investigaci贸n BRIDLIFE en la que se pretenden optimizar estructuras atendiendo no s贸lo a su coste, sino al impacto ambiental que generan a lo largo de su ciclo de vida. El art铆culo lo pod茅is descargar GRATUITAMENTE hasta el 27 de agosto de 2017 en el siguiente enlace:

https://authors.elsevier.com/a/1VLOP3QCo9NDzg

Abstract:

This paper shows the differences between the design of a reinforced concrete structure considering two objectives to minimize; economic cost and CO2 emissions. Both objectives depend on the amount of two high carbon intensive materials: cement in the concrete and steel; therefore, these objectives are related. As the balance between steel and cement per m3 of concrete depends on several factors such as the type of structure, this study focuses on buttressed earth-retaining walls. Another factor that determines the balance between steel and concrete is the height of the wall. Thus, the methodology considers a parametric study for optimal designs of buttressed earth-retaining walls, where one of the parameters is the wall height. One of the objectives is to show the variation in cost when CO2 is minimized, respectful of minimizing the economic cost. The findings show that wall elements under bending-compressive strains (i.e. the stem of the buttressed retaining wall) perform differently depending on the target function. On one hand, the study reveals an upward trend of steel per unit volume of concrete in emission-optimized earth-retaining buttressed walls, compared to the cost-optimized. On the other hand, it is checked that unlike the cost-optimized walls, emission-optimized walls opt for a higher concrete class than the minimum class available. These findings indicate that emission-optimized walls penalize not only concrete volume, but also the cement content, to the extent that a higher concrete class outperforms in reduced emissions. Additionally, the paper outlines how and to what extent the design of this typology varies for the two analyzed objectives in terms of geometry and amount of materials. Some relevant differences influencing the geometry of design strategies are found.

Keywords:

Cargon emission; CO2; earth-retaining wall; reinforced concrete; Harmony search; Threshold accepting

Reference:

MOLINA-MORENO, F.; MART脥, J.V.; YEPES, V. (2017).聽Carbon embodied optimization for buttressed earth-retaining walls: implications for low-carbon conceptual designs.Journal of Cleaner Production, 164:872-884.

13 julio, 2017
 
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Lifetime reliability-based optimization of post-tensioned box-girder bridges

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23 mayo, 2017
 
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Multi-objective design of post-tensioned concrete road bridges using artificial neural networks

Nos acaban de publicar en l铆nea en la revista Structural and Multidisciplinary Optimization聽(revista indexada en JCR en el primer cuartil) un trabajo de investigaci贸n en el que utilizamos las redes neuronales artificiales junto para el dise帽o multiobjetivo de puentes postesados de carreteras. Os paso a continuaci贸n el resumen y el enlace al art铆culo por si os resulta de inter茅s. El enlace del art铆culo es el siguiente:聽http://link.springer.com/article/10.1007%2Fs00158-017-1653-0

Referencia:

Garc铆a-Segura, T.; Yepes, V.; Frangopol, D.M. (2017). Multi-objective design of post-tensioned concrete road bridges using artificial neural networks. Structural and Multidisciplinary Optimization,聽doi:10.1007/s00158-017-1653-0

Abstract:

In order to minimize the total expected cost, bridges have to be designed for safety and durability. This paper considers the cost, the safety, and the corrosion initiation time to design post-tensioned concrete box-girder road bridges. The deck is modeled by finite elements based on problem variables such as the cross-section geometry, the concrete grade, and the reinforcing and post-tensioning steel. An integrated multi-objective harmony search with artificial neural networks (ANNs) is proposed to reduce the high computing time required for the finite-element analysis and the increment in conflicting objectives. ANNs are trained through the results of previous bridge performance evaluations. Then, ANNs are used to evaluate the constraints and provide a direction towards the Pareto front. Finally, exact methods actualize and improve the Pareto set. The results show that the harmony search parameters should be progressively changed in a diversification-intensification strategy. This methodology provides trade-off solutions that are the cheapest ones for the safety and durability levels considered. Therefore, it is possible to choose an alternative that can be easily adjusted to each need.

Keywords:

Multi-objective harmony search;聽Artificial neural networks;聽Post-tensioned concrete bridges;聽Durability;聽Safety.

Method for estimating the social sustainability of infrastructure projects

Niigata soil liquefaction. Wikipedia

La evaluaci贸n de la sostenibilidad social de los proyectos no es un tema sencillo ni inmediato. Si bien los impactos medioambientales se han estudiado en el 谩mbito cient铆fico con cierta profundidad, los impactos sociales de las infraestructuras se han investigado mucho menos. Es m谩s, en numerosas ocasiones dichos impactos se han minusvalorado. Pues bien, nos acaban de publicar un art铆culo en la revista Environmental Impact Assessment Review (revista indexada en el JCR, primer cuartil de impacto) en el cual proponemos una metodolog铆a que permite afrontar este reto.

Elsevier permite descargar de forma gratuita este art铆culo hasta el 14 de junio de 2017 accediendo al siguiente enlace:聽https://authors.elsevier.com/a/1UxW7iZ5spJDe

Referencia:

SIERRA, L.A.; PELLICER, E.; YEPES, V. (2017). Method for estimating the social sustainability of infrastructure projects.聽Environmental Impact Assessment Review, 65:41-53.聽https://doi.org/10.1016/j.eiar.2017.02.004

Highlights:

  • Method to select suitable infrastructure projects from the social sustainability point of view
  • Emphasizes social interactions of the infrastructure in the short and long term
  • Distinguishes the social sustainability of infrastructure projects in different locations
  • Efficiency of a social contribution in terms of early social benefits and a long-term distribution
  • Supports early decision-making of public agencies regarding infrastructure projects

 

Abstract:

Nowadays, sustainability assessments tend to focus on the biophysical and economic considerations of the built environment. Social facets are generally underestimated when investment in infrastructure projects is appraised. This paper proposes a method to estimate the contribution of infrastructure projects to social sustainability. This method takes into account the interactions of an infrastructure with its environment in terms of the potential for short and long-term social improvement. The method is structured in five stages: (1) social improvement criteria and goals to be taken into account are identified and weighed; (2) an exploratory study is conducted to determine transfer functions; (3) each criterion is homogenized through value functions; (4) the short and long-term social improvement indices are established; and finally, (5) social improvement indices are contrasted to identify the socially selected alternatives and to assign an order of priority. The method was implemented in six alternatives for road infrastructure improvement. The results of the analysis show that the method can distinguish the contribution to social sustainability of different infrastructure projects and location contexts, according to early benefits and potential long-term equitable improvement. This method can be applied prior to the implementation of a project and can complement environmental and economic sustainability assessments.

Keywords:

  • Social contribution;
  • Social improvement;
  • Infrastructure;
  • Method;
  • Social sustainability

 

 

Design optimization of precast-prestressed concrete road bridges with steel fiber-reinforcement by a hybrid evolutionary algorithm

http://www.tierra-armada.com/

http://www.tierra-armada.com/

Recientemente hemos publicado un art铆culo donde hemos empleado un algoritmo evolutivo h铆brido para optimizar tanto el coste como las emisiones de聽CO2 de puentes en viga artesa, con la particularidad de usar hormigones con fibras de acero. Se trata de un problema combinatorio complejo, con 41 variables de dise帽o, que se aplic贸 a un puente de 30 m de luz y una anchura de calzada de 12 m. Os dejo a continuaci贸n el art铆culo completo.

Abstract:聽

In this paper, the influence of steel fiber-reinforcement when designing precast-prestressed concrete (PPC) road bridges with a double U-shape cross-section is studied through heuristic optimization. A hybrid evolutionary algorithm (EA) combining a genetic algorithm (GA) with variable-depth neighborhood search (VDNS) is formulated to minimize the economic cost and CO2 emissions, while imposing constraints on all the relevant limit states. The case study proposed is a 30-m span-length with a deck width of 12 m. The problem involved 41 discrete design variables. The algorithm requires the initial calibration. Moreover, the heuristic is run nine times so as to obtain statistical information about the minimum, average and deviation of the results. The evolution of the objective function during the optimization procedure is highlighted. Findings show that heuristic optimization is a forthcoming option for the design of real-life prestressed structures. This paper provides useful knowledge that could offer a better understanding of the steel fiber-reinforcement in U-beam road bridges.

Keywords: hybrid evolutionary algorithm, precast-prestressed concrete, steel fiber-reinforcement, U-shape cross-section.

Reference:

YEPES, V.; MART脥, J.V.; GARC脥A-SEGURA, T. (2017). Design optimization of precast-prestressed concrete road bridges with steel fiber-reinforcement by a hybrid evolutionary algorithm. International Journal of Computational Methods and Experimental Measurements, 5(2):179-189.

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3 enero, 2017
 
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Optimization of buttressed earth-retaining walls using hybrid harmony search algorithms

Para empezar este a帽o 2017, nada mejor que te comuniquen la publicaci贸n de un art铆culo de investigaci贸n el mismo d铆a 1. Se trata en este caso de la utilizaci贸n de algoritmos heur铆sticos h铆bridos para optimizar el coste de muros de contrafuertes. Se ha publicado en la revista Engineering Structures.

Como suele ser habitual en la editorial Elsevier, os pod茅is descargar GRATUITAMENTE el art铆culo hasta el 20 de febrero accediendo al siguiente enlace:

https://authors.elsevier.com/a/1UJQQW4G4Bl2d

Abstract:

This paper represents an economic optimization of buttressed earth-retaining walls. We explore the optimum solutions using a harmony search with an intensification stage through threshold accepting. The calibration of the resulting algorithm has been obtained as a result of several test runs for different parameters. A design parametric study was computed to walls in series from 4 to 16 m total height. The results showed different ratios of reinforcement per volume of concrete for three types of ground fill. Our main findings confirmed that the most sensitive variable for optimum walls is the wall-friction angle. The preference for wall-fill friction angles different to 0 in project design is confirmed. The type of fill is stated as the main key factor affecting the cost of optimum walls. The design parametric study shows that the soil foundation bearing capacity substantially affects costs, mainly in coarse granular fills (F1). In that sense, cost-optimum walls are less sensitive to the bearing capacity in mixed soils (F2) and fine soils of low plasticity (F3). Our results also showed that safety against sliding is a more influential factor for optimum buttressed walls than the overturning constraint. Finally, as for the results derived from the optimization procedure, a more suitable rule of thumb to dimension the footing thickness of the footing is proposed.

Keywords:

Structural design; Heuristics; Harmony search; Cost optimization; Concrete structures

Reference:

MOLINA-MORENO, F.; GARC脥A-SEGURA, T.; MART脥, J.V.; YEPES, V. (2017).聽Optimization of buttressed earth-retaining walls using hybrid harmony search algorithms. Engineering Structures, 134:205-216.聽http://dx.doi.org/10.1016/j.engstruct.2016.12.042

 

 

2 enero, 2017
 
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Heuristic design of a precast-prestressed concrete U-beam and post-tensioned cast-in-place concrete slab road bridges

Viaducto St. Cloud, Francia 鈥 2000. http://vslmex.com.mx/

En estos momentos es posible automatizar completamente el dise帽o 贸ptimo de puentes usando algoritmos heur铆sticos. A continuaci贸n os dejo, en abierto, un cap铆tulo de libro en el que se explica tanto la optimizaci贸n de un puente de vigas artesas prefabricado como otro construido “in situ” como losa de hormig贸n postesado. Se trata de un trabajo incluido dentro del proyecto de investigaci贸n BRIDLIFE. Este tipo de t茅cnicas acabar谩n imponi茅ndose en unos a帽os en los paquetes inform谩ticos de c谩lculo. Sin embargo, resulta muy importante resaltar que el proyectista es el que tiene la 煤ltima palabra en el dise帽o.

Referencia:

Mart铆, J.V.; Alcal谩, J.; Garc铆a-Segura, T.; Yepes, V. (2016).聽Heuristic design of a precast-prestressed concrete U-beam and post-tensioned cast-in-place concrete slab road bridges. In: Hern谩ndez, S.; Brebbia, C.A.; de Wilde, W.P. (eds.), High Performance and Optimum Design of Structures and Materials II. WIT Transactions on The Built Environment, Vol. 166. WIT Press, pp. 17-28. ISBN:聽978-1-78466-143-4.

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20 diciembre, 2016
 
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