Alejandro Josa

Environmental analysis of rainwater harvesting infrastructures in diffuse and compact urban models of Mediterranean climate

PurposeAt present, many urban areas in Mediterranean climates are coping with water scarcity, facing a growing water demand and a limited conventional water supply. Urban design and planning has so far largely neglected the benefits of rainwater harvesting (RWH) in the context of a sustainable management of this resource. Therefore, the purpose of this study was to identify the most environmentally friendly strategy for rainwater utilization in Mediterranean urban environments of different densities.Materials and methodsThe RWH systems modeled integrate the necessary infrastructures for harvesting and using rainwater in newly constructed residential areas. Eight scenarios were defined in terms of diffuse (D) and compact (C) urban models and the tank locations ((1) underground tank, (2) below-roof tank, (3) distributed-over-roof tank, and (4) block tank). The structural and hydraulic sizing of the catchment, storage, and distribution subsystems was taken into account using an average Mediterranean rainfall, the area of the harvesting surfaces, and a constant water demand for laundry. The quantification of environmental impacts was performed through a life cycle assessment, using CML 2001 Baseline method. The necessary materials and processes were considered in each scenario according to the lifecycle stages (i.e., materials, construction, transportation, use, and deconstruction) and subsystems.Results and discussionThe environmental characterization indicated that the best scenario in both urban models is the distributed-over-roof tank (D3, C3), which provided a reduction in impacts compared to the worst scenario of up to 73% in diffuse models and even higher in compact ones, 92% in the most dramatic case. The lower impacts are related to the better distribution of tank weight on the building, reducing the reinforcement requirements, and enabling energy savings. The storage subsystem and the materials stage contributed most significantly to the impacts in both urban models. In the compact density model, the underground-tank scenario (C1) presented the largest impacts in most categories due to its higher energy consumption. Additionally, more favorable environmental results were observed in compact densities than in diffuse ones for the Global Warming Potential category along with higher water efficiencies.ConclusionsThe implementation of one particular RWH scenario over another is not irrelevant in drought-stress environments. Selecting the most favorable scenario in the development of newly constructed residential areas provides significant savings in CO2 emissions in comparison with retrofit strategies. Therefore, urban planning should consider the design of RWH infrastructures using environmental criteria in addition to economic, social, and technological factors, adjusting the design to the potential uses for which the rainwater is intended.Recommendations and perspectivesAdditional research is needed to quantify the energy savings associated with the insulation caused by using the tank distributed over the roof. The integration of the economic and social aspects of these infrastructures in the analysis, from a life cycle approach, is necessary for targeting the planning and design of more sustainable cities in an integrated way.

Fatigue behavior of polymer-modified porous concretes

Abstract Highly permeable materials provide drainage and noise-absorption properties that are useful in pavement top layers. In such porous concretes, the voids reduce the mechanical integrity, which may have to be compensated for with the incorporation of nonconventional components, such as polymers. A basic property needed for the design of pavements is the fatigue behavior of the material, which has not been studied thoroughly for polymer-modified porous concretes. This paper presents experimental results of fatigue tests in compression in terms of Wohler curves for four porous concretes (two of them with polymer). It is seen that the polymer-modified porous concretes exhibit better fatigue behavior than those without polymer. However, the improvement decreases for low values of the stress level, S , and appears to be negligible for the case of traffic loads in main roads or highways (number of load cycles, N > 10 6 ). Additionally, the deformation and internal temperature evolutions have been monitored, and it is concluded that their trends are similar to those of conventional concrete, with temperature increases significantly higher than in conventional concretes.

Sustainability Assessment of Concrete Structures within the Spanish Structural Concrete Code

Since 2008, the Spanish Structural Concrete Code (EHE in Spanish) has generally focused on respecting the environment; as a result, it has become a support tool for designing sustainable concrete structures. The Ministry of Public Works took charge of the initiative and a wide range of professionals and researchers, encompassing various points of view in this sector, carried it through. It is a pioneering initiative, opening up an avenue for the future of sustainable structural design. The purpose of this paper is to summarize the procedure used in drafting the sustainability appendix for the EHE and to present the EHE model for assessing the sustainability of concrete structures. Although the project has had its problems, the model that it produced is very thorough. It includes practically all the main criteria, taking into account the current state of the art and the fact that this was the first time a sustainability assessment technique has been included in a structural code.

Numerical Analysis of an Instrumented Steel-Reinforced Soil Wall

AbstractThe paper describes the results and lessons learned using a FEM model to simulate quantitative performance features of the Minnow Creek steel-strip reinforced soil wall structure located in the United States. The Minnow Creek Wall structure was constructed and instrumented in 1999. It is a unique case study because of the comprehensive measurements that were taken to record a wide range of wall performance features. Two different constitutive models for the soil were used (a linear-elastic Mohr-Coulomb model and hardening soil model with a Mohr-Coulomb failure criterion), and numerical outcomes were compared with physical measurements. The numerical results were shown to be sensitive to boundary conditions assumed at the toe of the wall. The generally encouraging agreement between physical and numerically predicted results gives confidence that commercial FEM software packages can be useful for the analysis and design of these types of structures, provided that care is taken in the selection of in...

Vertical-Facing Loads in Steel-Reinforced Soil Walls

The paper investigates the influence of backfill soil, foundation soil, and horizontal joint vertical compressibility on the magnitude of vertical loads developed in steel-reinforced soil concrete panel retaining walls at the end of construction. Measurements of toe loads recorded from instrumented field walls are reviewed and demonstrate that vertical toe loads can be much larger than the self-weight of the facing. In extreme cases, these loads can result in panel-to-panel contact leading to concrete spalling at the front of the wall. Vertical loads in excess of panel self-weight have been ascribed to relative movement between the backfill soil and the panels that can develop panel-soil interface shear and downdrag loads at the connections between the panels and the steel-reinforcement elements. A two-dimensional finite-element model is developed to systematically investigate the influence of backfill soil, foundation soil, bearing pad stiffness, and panel-soil interaction on vertical loads in the panel facing. The results show that an appropriately selected number and type of compressible bearing pads can be effective in reducing vertical compression loads in these structures and at the same time ensure an acceptable vertical gap between concrete panels. The parametric analyses have been restricted to a single wall height (16.7 m) and embedment depth of 1.5 m, matching a well-documented field case. However, the observations reported in the paper are applicable to other similar structures. The general numerical approach can be used by engineers to optimize the design of the bearing pads for similar steel-reinforced soil wall structures using available commercial finite-element model packages together with simple constitutive models.

Numerical study of the influence of foundation compressibility and reinforcement stiffness on the behavior of reinforced soil walls

Abstract Most geosynthetic and metallic reinforced soil walls are designed assuming that the wall foundation is rigid and/or does not influence the magnitude and distribution of reinforcement loads under operational conditions. This assumption may not apply to walls constructed over compliant (compressible) foundations. This paper describes the results of a series of numerical simulations that were carried out on idealized 3·6, 6, and 9 m-high modular block walls seated on foundations having four different compressibility values. The walls were constructed with two reinforcement materials having very different stiffness values but the same tensile strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at end of construction.

Life cycle assessment of granite application in sidewalks

PurposeSidewalks are important built areas for promoting environmental sustainability in cities since they support walking as a zero emission form of transportation contributing to protect the environment and the health of individuals. However, sidewalk management is typically focused on assessing their suitability for users without applying any environmental criteria on the infrastructure design. The paper aims to quantify the environmental impact that sidewalks can contribute to the urban space if no environmental criteria are applied in sidewalk design.MethodsThis study focuses on the environmental assessment of a very common sidewalk system found in cities to support pedestrian and light motorized traffic for over 45 years. The constructive solution consists of granite slabs (top layer) fixed on a mortar layer (3-cm thick) that is settled on a base of concrete (15-cm thick). The life cycle methodology was employed to conduct the environmental assessment of the system. The results are compared with the environmental outcomes of a sidewalk system that has the same function but is paved with concrete slabs to identify the environmentally optimal sidewalk design. The impact assessment method was CML Baseline 2001, and the inventory data were compiled from manufacturers associations, local authorities, and literature review.Results and discussionConstruction materials have the highest environmental impact (48–87%) in the sidewalk life cycle, where the granite top layer is the first contributor, although the amount of granite in the sidewalk system represents the 30% of the total weight of the construction materials used. A granite sidewalk has from 25% to 140% higher impact than a concrete one. The energy required to produce slabs is the key factor that characterizes the environmental impact of granite. Electricity and diesel consumption in stone cutting and moving represent over the 70% of the environmental burden of granite. The transportation of granite slabs is also relevant to the environmental impact. The use of imported granite could account for up to 76–177% of the total environmental impact of the sidewalk life cycle.ConclusionsAlthough granite is a natural material, using granite slabs as flooring material is not an environmentally suitable alternative over using concrete ones for paving sidewalks. The results have shown that if no environmental criteria are applied during sidewalk design and management, urban planners may be unconsciously contributing to an important environmental burden on the built environment. The ecodesign is a strategic opportunity to promote environmentally suitable urban infrastructures that contribute to promote urban sustainability in cities.RecommendationsEnergy efficiency techniques, water management, and well-considered transportation management should be developed and implemented in the granite industry to minimize the environmental impact of using it for paving. Additionally, further research is needed to quantify the environmental performance of other construction materials used in sidewalk construction in order to identify the best environmental alternatives and design improvements by optimizing the use of materials to the sidewalks functions.

LCM of Rainwater Harvesting Systems in Emerging Neighbourhoods in Colombia

Potential environmental impacts of water harvesting systems for rain to emerging neighbourhoods in Colombia were studied. Two tools were integrated into a simulation model (life cycle analysis and system dynamics). This was performed as an application case study in two urban areas of Colombia (Bogota and Pereira). We modelled a standard neighbourhood with 10 residential 5-storey buildings of 24 apartments. The results show that it is possible to avoid in every neighbourhood 150,729 kg CO2e and 44,857 kg CO2e, respectively.

Are we preventing flood damage eco-efficiently? An integrated method applied to post-disaster emergency actions

Flood damage results in economic and environmental losses in the society, but flood prevention also entails an initial investment in infrastructure. This study presents an integrated eco-efficiency approach for assessing flood prevention and avoided damage. We focused on ephemeral streams in the Maresme region (Catalonia, Spain), which is an urbanized area affected by damaging torrential events. Our goal was to determine the feasibility of post-disaster emergency actions implemented after a major event through an integrated hydrologic, environmental and economic approach. Life cycle assessment (LCA) and costing (LCC) were used to determine the eco-efficiency of these actions, and their net impact and payback were calculated by integrating avoided flood damage. Results showed that the actions effectively reduced damage generation when compared to the registered water flows and rainfall intensities. The eco-efficiency of the emergency actions resulted in 1.2kgCO2eq. per invested euro. When integrating the avoided damage into the initial investment, negative net impacts were obtained (e.g., -5.2E+05€ and -2.9E+04kgCO2eq. per event), which suggests that these interventions contributed with environmental and economic benefits to the society. The economic investment was recovered in two years, whereas the design could be improved to reduce their environmental footprint, which is recovered in 25years. Our method and results highlight the effects of integrating the environmental and economic consequences of decisions at an urban scale and might help the administration and insurance companies in the design of prevention plans and climate change adaptation.

Urban planning and agriculture. Methodology for assessing rooftop greenhouse potential of non-residential areas using airborne sensors

The integration of rooftop greenhouses (RTGs) in urban buildings is a practice that is becoming increasingly important in the world for their contribution to food security and sustainable development. However, the supply of tools and procedures to facilitate their implementation at the city scale is limited and laborious. This work aims to develop a specific and automated methodology for identifying the feasibility of implementation of rooftop greenhouses in non-residential urban areas, using airborne sensors. The use of Light Detection and Ranging (LIDAR) and Long Wave Infrared (LWIR) data and the Leica ALS50-II and TASI-600 sensors allow for the identification of some building roof parameters (area, slope, materials, and solar radiation) to determine the potential for constructing a RTG. This development represents an improvement in time and accuracy with respect to previous methodology, where all the relevant information must be acquired manually. The methodology has been applied and validated in a case study corresponding to a non-residential urban area in the industrial municipality of Rubí, Barcelona (Spain). Based on this practical application, an area of 36,312m2 out of a total area of 1,243,540m2 of roofs with ideal characteristics for the construction of RTGs was identified. This area can produce approximately 600tons of tomatoes per year, which represents the average yearly consumption for about 50% of Rubí total population. The use of this methodology also facilitates the decision making process in urban agriculture, allowing a quick identification of optimal surfaces for the future implementation of urban agriculture in housing. It also opens new avenues for the use of airborne technology in environmental topics in cities.