The objective of this paper is to evaluate the influence of sulfate exposure on the pore network development of several Portland cement matrices. MIP, XRD and SEM analysis were performed at different ages in samples exposed to sulfates after 2 days of casting. Results suggest that patterns of precipitation of the expansive products are linked to the degree of refinement of the pore network. During early stages of exposure, large pores concentrate a higher proportion of the expansive product formed. At later stages, precipitation evolves towards finer pore sizes.
Fatigue is associated with the deterioration caused by applying repeated loads, and is affected by temperature or aging. Generally, time sweep tests are used to simulate fatigue, in order to obtain the fatigue laws. However, this requires too much time, often preventing its use. A method to estimate the fatigue laws from a strain sweep test is presented. The test was performed on a semi-dense mixture with different types of binder (unconditioned or aged) tested at different temperatures. This test is able to estimate fatigue laws more quickly, allowing the effect of different factors on the mixtures' fatigue life to be studied.
This paper studies the cross-sectional behaviour of austenitic, ferritic and duplex stainless steel hollow sections subjected to several loading conditions and presents a full slenderness range DSM approach for the prediction of cross-sectional strengths. Pure compression, pure bending moment and combined uniaxial bending and compression loading resistances are predicted using the same strength curve, which is based on experimental data gathered from the literature and ultimate strengths generated through parametric studies. The proposed approach is applicable to slender and stocky cross-sections leading to an accurate full slenderness range DSM design approach since the resistance reduction due to local buckling and the effect of strain hardening are taken into account, as is the effect of partial yielding of the cross-section in bending. A new method based on the actual stress distribution of the cross-section is also presented for combined loading conditions, where the cross-sectional behaviour is directly tackled through the same strength curve, providing more accurate results than the methods considering the uncoupled problem. Finally, a statistical analysis is presented to demonstrate the reliability of the proposed DSM approach.
In contrast to terrestrial environment, the harsh lunar environment conditions include lower gravity acceleration, ultra-high vacuum and high (low) temperature in the daytime (night-time). This paper focuses on the effects of those mentioned features on soil cutting tests, a simplified excavation test, to reduce the risk of lunar excavation missions. Soil behavior and blade performance were analyzed under different environmental conditions. The results show that: (1) the cutting resistance and the energy consumption increase linearly with the gravity. The bending moment has a bigger increasing rate in low gravity fields due to a decreasing moment arm; (2) the cutting resistance, energy consumption and bending moment increase significantly because of the raised soil strength on the lunar environment, especially in low gravity fields. Under the lunar environment, the proportions of cutting resistance, bending moment and energy consumption due to the effect of the van der Waals forces are significant. Thus, they should be taken into consideration when planning excavations on the Moon. Therefore, considering that the maximum frictional force between the excavator and the lunar surface is proportional to the gravity acceleration, the same excavator that works efficiently on the Earth may not be able to work properly on the Moon.
The Campo de Cartagena (Eastern Spain) is one of Europe’s driest areas with a mean precipitation of around 300 mm. One of the main challengesin the region is to secure a reliable water supply in both quantity and quality terms, to provide a water supply and agricultural irrigation, while water desalination has become an extensively applied solution, and one of the most sustainable solutions to the water scarcity problem. As water availability is lacking and groundwater quality is poor, the agricultural sector in Campo de Cartagena has developed small private brackish groundwater desalination plants (15-20 m3/h) through already existing agricultural wells. Costs and benefits (C-B) for citrus cultivation (1 ha) in three such plants have been assessed. The results indicate that for the studied cases, current agricultural management is feasible and costs outweigh benefits, with a positive NPV and a cost/benefit ratio higher than 1. The internal rate of return is also positive and higher than 11%. The results evidence practical and theoretical implications as to how to increase water resources in areas where water is scarce by closing the loop, ensuring farmers’ profitability and encouraging private sector investments.
La presente invención se refiere, en estructuras flotantes de soporte de turbinas eólicas, a la materialización mediante una lámina de hormigón pretensado de la zona de transición entre la torre, de menor diámetro, y el flotador de hormigón de mayor diámetro, tanto si la torre es metálica como de hormigón. Dicha lámina de revolución presenta una geometría óptima para la correcta transmisión de esfuerzos entre ambas partes, torre y flotador, con un espesor reducido y sin necesidad de elementos de rigidización y refuerzo exteriores a sus superficies que aumentarían el peso y el coste de la estructura.
Montero-Chacón, F.; Zaghi, S.; Rossi, R.; García-Pérez, E.; Heras, I.; Martinez, X.; Oller, S.; Doblaré, M. Finite elements in analysis and design Vol. 127, p. 31-43 DOI: 10.1016/j.finel.2016.12.006 Data de publicació: 2017-05 Article en revista
Solar selective coatings can be multi-layered materials that optimize the solar absorption while reducing thermal radiation losses, granting the material long-term stability. These layers are deposited on structural materials (e.g., stainless steel, Inconel) in order to enhance the optical and thermal properties of the heat transfer system. However, interesting questions regarding their mechanical stability arise when operating at high temperatures. In this work, a full thermo-mechanical multiscale methodology is presented, covering the nano-, micro-, and macroscopic scales. In such methodology, fundamental material properties are determined by means of molecular dynamics simulations that are consequently implemented at the microstructural level by means of finite element analyses. On the other hand, the macroscale problem is solved while taking into account the effect of the microstructure via thermo-mechanical homogenization on a representative volume element (RVE). The methodology presented herein has been successfully implemented in a reference problem in concentrating solar power plants, namely the characterization of a carbon-based nanocomposite and the obtained results are in agreement with the expected theoretical values, demonstrating that it is now possible to apply successfully the concepts behind Integrated Computational Materials Engineering to design new coatings for complex realistic thermo-mechanical applications.
The paper presents a constitutive model for argillaceous rocks, developed within the framework of elastoplasticity, that includes a number of features that are relevant for a satisfactory description of their hydromechanical behaviour: anisotropy of strength and stiffness, behaviour nonlinearity and occurrence of plastic strains prior to peak strength, significant softening after peak, time-dependent creep deformations and permeability increase due to damage. Both saturated and unsaturated conditions are envisaged. The constitutive model is then applied to the simulation of triaxial and creep tests on Callovo-Oxfordian (COx) claystone. Although the main objective has been the simulation of the COx claystone behaviour, the model can be readily used for other argillaceous materials. The constitutive model developed is then applied, via a suitable coupled hydromechanical formulation, to the analysis of the excavation of a drift in the Meuse/Haute-Marne Underground Research Laboratory. The pattern of observed pore water pressures and displacements, as well as the shape and extent of the damaged zone, are generally satisfactorily reproduced. The relevance and importance of rock anisotropy and of the development of a damaged zone around the excavations are clearly demonstrated.
Picolo, R.; Pialarissi Cavalaro, S.H.; Monte, R.; de Figueiredo, A.D. Cement & concrete composites Vol. 79, p. 117-132 DOI: 10.1016/j.cemconcomp.2017.02.002 Data de publicació: 2017-05 Article en revista
Cement and accelerator compatibility is critical for achieving proper mechanical performance in sprayed matrices. Few studies in the literature focus on establishing relationships between accelerated chemical reactions and the resulting mechanical properties of these matrices. The objective of this study is to evaluate the correlation between the chemical processes occurring in accelerated matrices and their mechanical strength development from a quantitative standpoint, elucidating the main mechanisms governing their performance. Hydration kinetics were analyzed by XRD and isothermal calorimetry, while mechanical properties were evaluated by needle and pin penetration resistance and compressive strength of extracted cores. Results showed the influence of the accelerated hydration and the evolution of phase composition on the development of mechanical properties of the matrices. Based on an extensive statistical analysis, multivariate linear regressions were established between the mechanical strength of sprayed mortars and the main chemical parameters influencing its development at early and late ages.
Sole, M.; Cucina, M.; Folch, M.; Tapias, J.; Gigliotti, G.; Marianna Garfi'; Ferrer, I. Science of the total environment Vol. 586, p. 1-9 DOI: 10.1016/j.scitotenv.2017.02.006 Data de publicació: 2017-05 Article en revista
Microalgae anaerobic digestion produces biogas along with a digestate that may be reused in agriculture. However, the properties of this digestate for agricultural reuse have yet to be determined. The aim of this study was to characterise digestates from different microalgae anaerobic digestion processes (i.e. digestion of untreated microalgae, thermally pretreated microalgae and thermally pretreated microalgae in co-digestion with primary sludge). The main parameters evaluated were organic matter, macronutrients and heavy metals content, hygenisation, potential phytotoxicity and organic matter stabilisation. According to the results, all microalgae digestates presented suitable organic matter and macronutrients, especially organic and ammonium nitrogen, for agricultural soils amendment. However, the thermally pretreated microalgae digestate was the least stabilised digestate in comparison with untreated microalgae and co-digestion digestates. In vivo bioassays demonstrated that the digestates did not show residual phytotoxicity when properly diluted, being the co-digestion digestate the one which presented less phytotoxicity. Heavy metals contents resulted far below the threshold established by the European legislation on sludge spreading. Moreover, low presence of E. coli was observed in all digestates. Therefore, agricultural reuse of thermally pretreated microalgae and primary sludge co-digestate through irrigation emerges a suitable strategy to recycle nutrients from wastewater.
Perez, F.; Botella, R.; López-Montero, T.; Miro, R.; Martinez, A. International journal of fatigue num. 98, p. 111-120 DOI: 10.1016/j.ijfatigue.2017.01.026 Data de publicació: 2017-05 Article en revista
This paper compares the results obtained in two types of cyclic tension-compression tests, a time sweep test, constant strain amplitude, and a strain sweep test, increasing strain amplitude every 5000 cycles, called EBADE (standing for the Spanish words for strain sweep test). This comparison has shown that the rapid loss of stiffness during the initial part of cyclic testing is recoverable in bituminous materials. It has been found that reversible phenomena dominate in asphalt binders, while in mixtures are as important as damage. A damage equation has been proposed to describe the evolution of the material distress during the phase II in time sweep tests. In addition, a new methodology to estimate the fatigue law of bituminous mixtures is proposed.
The testing of mode III and mixed mode failure is every so often encountered in the dedicated literature of mechanical characterization of brittle and quasi-brittle materials. In this work, the application of the mixed strain displacement e-ue-u finite element formulation to three examples involving skew notched beams is presented. The use of this FE technology is effective in problems involving localization of strains in softening materials.
The objectives of the paper are: (i) to test the mixed formulation in mode III and mixed mode failure and (ii) to present an enhancement in terms of computational time given by the kinematic compatibility between irreducible displacement-based and the mixed strain-displacement elements.
Three tests of skew-notched beams are presented: firstly, a three point bending test of a PolyMethyl MethaAcrylate beam; secondly, a torsion test of a plain concrete prismatic beam with square base; finally, a torsion test of a cylindrical beam made of plain concrete as well. To describe the mechanical behavior of the material in the inelastic range, Rankine and Drucker-Prager failure criteria are used in both plasticity and isotropic continuum damage formats.
The proposed mixed formulation is capable of yielding results close to the experimental ones in terms of fracture surface, peak load and global loss of carrying capability. In addition, the symmetric secant formulation and the compatibility condition between the standard irreducible method and the strain-displacement one is exploited, resulting in a significant speedup of the computational procedure.
The Discrete Element Method (DEM) was found to be an effective numerical method for the calculation of engineering problems involving granular materials. However, the representation of irregular particles using the DEM is a very challenging issue, leading to different geometrical approaches. This document presents a new insight in the application of one of those simplifications known as rolling friction, which avoids excessive rotation when irregular shaped materials are simulated as spheric particles. This new approach, called the Bounded Rolling Friction model, was applied to reproduce a ballast resistance test.
A meaningful contribution to the evaluation of heterogeneous public investments is described in this article. The proposed methodology provides a step towards sustainable urban planning in which decisions are taken according to clear, consistent and transparent criteria assisted by the MIVES multi-criteria analysis framework. The MIVES methodology combines multi-criteria decision making (MCDM) and multi-attribute utility theory (MAUT), incorporating the value function (VF) concept and assigning weights through the analytic hierarchy process (AHP). First, a homogenization coefficient is calculated to develop the Prioritization Index for Heterogeneous Urban Investments (PIHUI), so that non-homogenous alternatives may be comparable. This coefficient measures the need of society to invest in each public project through the consideration of its contribution to the regional balance, the scope of its investment, the evaluation of the current situation and the values of the city. Then, the MIVES multi-criteria framework is used to evaluate the degree to which each investment would contribute to sustainable development. Different economic, environmental and social aspects were considered through a decision framework, constructed with the three aforementioned requirements, five criteria and eight indicators. The case study conducted for the Ecology, Urban Planning and Mobility Area of Barcelona municipal council is presented in this article, showing how this method performs accurate, consistent, and repeatable evaluations.
Pelissari, C.; Guivernau, M.; Viñas , M.; Silva de Souza, S.; Garcia, J.; Sezerino, P.; Avila, C. Science of the total environment Vol. 584-585, p. 642-650 DOI: 10.1016/j.scitotenv.2017.01.091 Data de publicació: 2017-04 Article en revista
The dynamics of the active microbial populations involved in nitrogen transformation in a vertical subsurface flow constructed wetland (VF) treating urban wastewater was assessed. The wetland (1.5 m2) operated under average loads of 130 g COD m- 2 d- 1 and 17 g TN m- 2 d- 1 in Period I, and 80 g COD m- 2 d- 1 and 19 g TN m- 2 d- 1 in Period II. The hydraulic loading rate (HLR) was 375 mm d- 1 and C/N ratio was 2 in both periods. Samples for microbial characterization were collected from the filter medium (top and bottom layers) of the wetland, water influent and effluent at the end of Periods I (Jun–Oct) and II (Nov–Jan). The combination of qPCR and high-throughput sequencing (NGS, MiSeq) assessment at DNA and RNA level of 16S rRNA genes and nitrogen-based functional genes (amoA and nosZ-clade I) revealed that nitrification was associated both with ammonia-oxidizing bacteria (AOB) (Nitrosospira) and ammonia-oxidizing archaea (AOA) (Nitrososphaeraceae), and nitrite-oxidizing bacteria (NOB) such as Nitrobacter. Considering the active abundance (based in amoA transcripts), the AOA population revealed to be more stable than AOB in both periods and depths of the wetland, being less affected by the organic loading rate (OLR). Although denitrifying bacteria (nosZ copies and transcripts) were actively detected in all depths, the denitrification process was low (removal of 2 g TN m- 2 d- 1 for both periods) concomitant with NOx-N accumulation in the effluent. Overall, AOA, AOB and denitrifying bacteria (nosZ) were observed to be more active in bottom than in top layer at lower OLR (Period II). A proper design of OLR and HLR seems to be crucial to control the activity of microbial biofilms in VF wetlands on the basis of oxygen, organic-carbon and NOx-N forms, to improve their capacity for total nitrogen removal.
In this work we prove that weak solutions constructed by a variational multiscale method are suitable in the sense of Scheffer. In order to prove this result, we consider a subgrid model that enforces orthogonality between subgrid and finite element components. Further, the subgrid component must be tracked in time. Since this type of schemes introduce pressure stabilization, we have proved the result for equal-order velocity and pressure finite element spaces that do not satisfy a discrete inf-sup condition.
This paper presents the results of an experimental program carried out in the laboratory to evaluate the shear strength of aerial lime mortar brickwork. Masonry triplets and walls were tested after one year from their construction by adopting two different testing methods. The first approach consisted in the shear tests of masonry triplets, whereas the second technique was based on core drilling from walls of 90 mm diameter cylindrical specimens to be subjected to Brazilian tests with varying inclination of the diametric mortar joint. The first method is more adequate to characterize new masonry, whilst the second one is a suitable MDT procedure for the analysis of existing structures. The experimental results from standard and non-standard tests were properly investigated in order to obtain the shear failure envelope of the bond interface and mortar joint. The comparisons between the different tests and their interpretative theories show the possibilities of the novel non-standard testing method for the evaluation of the shear strength of structures of the built cultural heritage.
Lloberas-Valls, O.; Cafiero, M.; Cante, J.C.; Ferrer, A.; Oliver, J. Computational mechanics (Online) Vol. 59, num. 4, p. 579-610 DOI: 10.1007/s00466-016-1361-4 Data de publicació: 2017-04 Article en revista
The Domain Interface Method (DIM) is extended in this contribution for the case of mixed fields as encountered in multiphysics problems. The essence of the non-conforming domain decomposition technique consists in a discretization of a fictitious zero-thickness interface as in the original methodology and continuity of the solution fields across the domains is satisfied by incorporating the corresponding Lagrange Multipliers. The multifield DIM inherits the advantages of its irreducible version in the sense that the connections between non-matching meshes, with possible geometrically non-conforming interfaces, is accounted by the automatic Delaunay interface discretization without considering master and slave surfaces or intermediate surface projections as done in many established techniques, e.g. mortar methods. The multifield enhancement identifies the Lagrange multiplier field and incorporates its contribution in the weak variational form accounting for the corresponding consistent stabilization term based on a Nitsche method. This type of constraint enforcement circumvents the appearance of instabilities when the Ladyzhenskaya–Babuška–Brezzi (LBB) condition is not fulfilled by the chosen discretization. The domain decomposition framework is assessed in a large deformation setting for mixed displacement/pressure formulations and coupled thermomechanical problems. The continuity of the mixed field is studied in well selected benchmark problems for both mixed formulations and the objectivity of the response is compared to reference monolithic solutions. Results suggest that the presented strategy shows sufficient potential to be a valuable tool in situations where the evolving physics at particular domains require the use of different spatial discretizations or field interpolations.
The paper presents an integrated approach aimed at assessing the seismic safety of Mallorca cathedral. This cathedral is an extraordinary historical construction dating back to the middle-ages. The experimental modal parameters of the cathedral were identified using Ambient Vibration Testing (AVT). The cathedral numerical model was updated using the identified modal parameters. This updated model was then used to study the seismic response of the cathedral using non-linear static (pushover) analysis. A sensitively analysis was carried out to reveal the dependency of the seismic capacity on the input materials properties. To assess the seismic performance and the safety of the cathedral, the N2 method was employed. It was found that the cathedral is safe when subjected to the earthquakes expected in Mallorca Island.
The aim of this study was to assess the environmental impact of microbial fuel cells (MFCs) implemented in constructed wetlands (CWs). To this aim a life cycle assessment (LCA) was carried out comparing three scenarios: 1) a conventional CW system (without MFC implementation); 2) a CW system coupled with a gravel-based anode MFC, and 3) a CW system coupled with a graphite-based anode MFC. All systems served a population equivalent of 1500 p.e. They were designed to meet the same effluent quality. Since MFCs implemented in CWs improve treatment efficiency, the CWs coupled with MFCs had lower specific area requirement compared to the conventional CW system. The functional unit was 1 m3 of wastewater. The LCA was performed with the software SimaPro® 8, using the CML-IA baseline method. The three scenarios considered showed similar environmental performance in all the categories considered, with the exception of Abiotic Depletion Potential. In this impact category, the potential environmental impact of the CW system coupled with a gravel-based anode MFC was around 2 times higher than that generated by the conventional CW system and the CW system coupled with a graphite-based anode MFC. It was attributed to the large amount of less environmentally friendly materials (e.g. metals, graphite) for MFCs implementation, especially in the case of gravel-based anode MFCs. Therefore, the CW system coupled with graphite-based anode MFC appeared as the most environmentally friendly solution which can replace conventional CWs reducing system footprint by up to 20%. An economic assessment showed that this system was around 1.5 times more expensive than the conventional CW system.
Avila, C.; Pelissari, C.; Sezerino, P.; Sgroi, M.; Roccaro, P.; Garcia, J. Science of the total environment Vol. 584-585, p. 414-425 DOI: 10.1016/j.scitotenv.2017.01.024 Data de publicació: 2017-04 Article en revista
The effect of effluent recirculation on the removal of total nitrogen (TN) and eight pharmaceuticals and personal care products (PPCPs) was evaluated during 9 months in an experimental hybrid constructed wetland (CW) system applied in the treatment of urban wastewater. An Imhoff tank was followed by three stages of CWs (two 1.5-m2 vertical subsurface flow (VF) beds alternating feed-rest cycles, a 2-m2 horizontal (HF) and a 2-m2 free water surface (FWS) wetland in series). A fraction of the final effluent was recycled back to the Imhoff tank with a recirculation rate of 50% (hydraulic loading rate = 0.37 m d- 1). The system's performance varied throughout the study. In Period I (summer) consistently high load removal efficiencies of TN (89 ± 5%) and a removal rate of 6.6 ± 1.4 g TN m- 2 d- 1 were exhibited. In Period II (fall), the poor performance of the FWS during the senescence of macrophytes caused a large increase in organic matter, solids and nutrient concentrations, drastically deteriorating water quality. The determination of PPCPs was conducted during this period. Recalcitrant compounds, namely sulfamethoxazole, carbamazapine, TCEP and sucralose were negligibly removed in all CWs. However, noteworthy was the ˜ 30% removal of sucralose in the VF wetland. Caffeine (80%) and fluoxetine (27%) showed similar elimination rates in both VF and HF units, whereas trimethoprim and DEET were significantly better removed in the VF than in the HF. The concentration of the four latter compounds showed a severe increase in the FWS, indicating possible desorption from the sediment/biomass during adverse conditions. Harvesting of the aboveground biomass in this unit returned the system's performance back to normality (Period III), achieving 77 ± 7% TN removal despite the winter season, proving effluent recirculation as an effective strategy for TN removal in hybrid CW systems when stringent restrictions are in place.
Constructed wetlands are currently recognized as an effective environmental biotechnology for wastewater treatment, but the influence of their design parameters on internal functioning and contaminant removal efficiency is still under discussion. In this work, the effect of aspect ratio and water depth on bacteria communities as well as treatment efficiency of horizontal subsurface flow constructed wetlands (HSSF) under the Mediterranean climate was evaluated, using a mathematical model. For this purpose, experimental results from four pilot-scale wetlands of equal surface area but different aspect ratios and water depth were used. The HSSF system was fed with municipal wastewater. The experimental data were simulated using the BIO_PORE model, developed in the COMSOL Multiphysics™ platform. Simulations with the BIO_PORE model fitted well to the experimental results, showing a higher removal efficiency for the shallower HSSF for COD (93.7% removal efficiency) and ammonia nitrogen (73.8%). The aspect ratio had a weak relationship with the bacteria distribution and the removal efficiency. In contrast, the water depth was a factor. The results of the present study confirm a previous hypothesis in which depth has an important impact on the biochemical reactions causing contaminants transformation and degradation.
Casas, G.; Mukherjee, D.; Celigueta, M.A.; Zohdi, T.; Oñate, E. Computational particle mechanics Vol. 4, num. 2, p. 181-198 DOI: 10.1007/s40571-015-0089-9 Data de publicació: 2017-04 Article en revista
A modular discrete element framework is presented for large-scale simulations of industrial grain-handling systems. Our framework enables us to simulate a markedly larger number of particles than previous studies, thereby allowing for efficient and more realistic process simulations. This is achieved by partitioning the particle dynamics into distinct regimes based on their contact interactions, and integrating them using different time-steps, while exchanging phase-space data between them. The framework is illustrated using numerical experiments based on fertilizer spreader applications. The model predictions show very good qualitative and quantitative agreement with available experimental data. Valuable insights are developed regarding the role of lift vs drag forces on the particle trajectories in-flight, and on the role of geometric discretization errors for surface meshing in governing the emergent behavior of a system of particles.
Aliguer, I.; Carol, I.; Sture, S. International journal for numerical and analytical methods in geomechanics Vol. 41, num. 6, p. 918-939 DOI: 10.1002/nag.2654 Data de publicació: 2017-04 Article en revista
The paper proposes a stress-driven integration strategy for Perzyna-type viscoplastic constitutive models, which leads also to a convenient algorithm for viscoplastic relaxation schemes. A generalized trapezoidal rule for the strain increment, combined with a linearized form of the yield function and flow rules, leads to a plasticity-like compliance operator that can be explicitly inverted to give an algorithmic tangent stiffness tensor also denoted as the m-AGC tangent operator. This operator is combined with the stress-prescribed integration scheme, to obtain a natural error indicator that can be used as a convergence criterion of the intra-step iterations (in physical viscoplasticity), or to a variable time-step size in viscoplastic relaxation schemes based on a single linear calculation per time step. The proposed schemes have been implemented for an existing zero-thickness interface constitutive model. Some numerical application examples are presented to illustrate the advantages of the new schemes proposed.
This paper deals with the Middle Triassic-to-earliest Jurassic evaporite sedimentation in the epicontinental, eastern Iberian platform. This deposition occurred under extensional regime during the westwards migration of the Neotethys Ocean at the start of the Pangea break-up. Although attention is focused on the evaporitic episodes recorded in the Epicontinental (Germanic) Triassic of the platform, the evaporite units in the carbonatic Alpine Triassic are also considered. In the Epicontinental Triassic, up to six evaporitic episodes, which alternated with three carbonatic episodes and a siliciclastic one, occurred between the Anisian and the Lower Hettangian. The evaporitic episodes may be divided into two groups. The stratigraphic units of the older group have similar characteristics in salinity and facies, and were formed in chloride-rich, evaporitic mudflats. In the younger group, the salinity and depositional features display considerable differences and the environments evolved from evaporitic mudflats to extensive salterns. The different evolutive trends in the evaporites of the two groups suggest major re-structuration of the platform after the sedimentation of the siliciclastic units of the middle Keuper (Carnian Humide Episode). Progressive marine influence in the assemblage of the six evaporitic episodes is deduced from the changing nature of the evaporites and their host sediment. All the evaporite units accumulated as transgressive and highstand systems tracts. The close relationship between evaporite units and thick accumulation suggests that the structural control played a major role in the sedimentation. In the Alpine Triassic, the presence of evaporites interbedded in the allochthonous carbonate units is documented. Lateral correlation of the evaporite units of the Epicontinental and the Alpine types of Triassic allows us to reconstruct the facies continuum across the original Iberian platform. Such a west-to-east transect illustrates the palaeogeography, structural evolution, and major depositional controls in the platform during the period under study. The deduced evaporitic pattern could be applied to other Triassic platforms which acted as epeiric seaways for the westward advance of the Neotethys.
Soriguera, F.; Martínez, I.; Sala, M.; Menéndez, M. Transportation research. Part C, emerging technologies Vol. 77, p. 257-274 DOI: 10.1016/j.trc.2017.01.024 Data de publicació: 2017-04 Article en revista
Recent years have seen a renewed interest in Variable Speed Limit (VSL) strategies. New opportunities for VSL as a freeway metering mechanism or a homogenization scheme to reduce speed differences and lane changing maneuvers are being explored. This paper examines both the macroscopic and microscopic effects of different speed limits on a traffic stream, especially when adopting low speed limits. To that end, data from a VSL experiment carried out on a freeway in Spain are used. Data include vehicle counts, speeds and occupancy per lane, as well as lane changing rates for three days, each with a different fixed speed limit (80 km/h, 60 km/h, and 40km/h). Results reveal some of the mechanisms through which VSL affects traffic performance, specifically the flow and speed distribution across lanes, as well as the ensuing lane changing maneuvers. It is confirmed that the lower the speed limit, the higher the occupancy to achieve a given flow. This result has been observed even for relatively high flows and low speed limits. For instance, a stable flow of 1942 veh/h/lane has been measured with the 40 km/h speed limit in force. The corresponding occupancy was 33%, doubling the typical occupancy for this flow in the absence of speed limits. This means that VSL strategies aiming to restrict the mainline flow on a freeway by using low speed limits will need to be applied carefully, avoiding conditions as the ones presented here, where speed limits have a reduced ability to limit flows. On the other hand, VSL strategies trying to get the most from the increased vehicle storage capacity of freeways under low speed limits might be rather promising. Additionally, results show that lower speed limits increase the speed differences across lanes for moderate demands. This, in turn, also increases the lane changing rate. This means that VSL strategies aiming to homogenize traffic and reduce lane changing activity might not be successful when adopting such low speed limits. In contrast, lower speed limits widen the range of flows under uniform lane flow distributions, so that, even for moderate to low demands, the under-utilization of any lane is avoided. These findings are useful for the development of better traffic models that are able to emulate these effects. Moreover, they are crucial for the implementation and assessment of VSL strategies and other traffic control algorithms.
The purpose of this paper is to determine the Recreational Carrying Capacity of three estuarine beaches (Colares, Marudá and Murubira) on the Amazon coast of Brazil, based on the combined assessment of natural conditions and visitor facilities. In the final analysis, the carrying capacity of Colares beach was estimated to be 1089 visitors per day, and that of Murubira beach, 238 visitors per day. At Marudá beach, however, the inadequate quality of the water resulted in an RCC of zero, indicating that the beach should not be visited for recreational use. The results of this study may provide a valuable diagnostic tool for the development of future state and municipal coastal management programs. We believe that the procedures adopted in this study are applicable to other estuarine beaches on the Amazon coast, as well as in other estuarine beaches elsewhere with similar natural characteristics.
Currently, the AISC code provides guidance for the calculation of the ultimate strength of unstiffened plate girder webs subjected to concentric edge loads. Specifications consider three categories: local web yielding, web crippling, and sideway web buckling. Based on previous studies, the presence of longitudinal stiffeners in the web has not been considered in the calculation procedures. Longitudinal stiffeners in steel plate girders are primarily used to increase bending and shear strength. In the last two decades, a number of projects regarding the positive effect of longitudinal stiffening on the strength of plate girder webs to concentrated load have been conducted around the world. The results have shown that this type of stiffening enhances ultimate strength for web crippling depending on the position of the stiffener that modifies the slenderness of the directly loaded panel; and flexural and torsional rigidities of the stiffener. This paper presents a methodology for the consideration of longitudinal stiffening on the ultimate strength of plate girders webs subjected to concentrated loads. The methodology is based on the plastic collapse mechanism observed experimentally, in which plastic hinges are formed in the loaded flange and yield lines result in the portion of the web limited by the loaded flange and stiffener. Then, a closed-form solution accounting for the influence of the stiffener is developed following the current expression available in the AISC specifications. Theoretical predictions are compared with available test results, showing that the predicted ultimate loads are in good agreement with experimental results.
Embedded boundary methods are very attractive, because eliminate the need to define body-fitted meshes. In particular, at large scales, the meshing step is a bottleneck of the simulation pipeline, since mesh generators do not usually scale properly. In some other situations, like in additive manufacturing simulations, the geometry evolves in time, and the use of boddy-fitted meshes is not suitable. On the contrary, algorithms to create adaptive cartesian meshes are highly scalable. However, using embedded boundary methods, one can destroy the condition number of the linear systems to be solved, since cut elements can have close to zero support. As a result, these techniques require direct linear solvers, since standard preconditioned iterative solvers are not robust and scalable. In this work, we take as a starting point a balancing domain decomposition by constraints (BDDC) preconditioner. Next, we consider a recent physics-based version of the method that is robust with respect to high variations of the materials. Finally, we show to how to make these preconditioners robust also for embedded boundary methods for coercive PDEs, by a proper modification of the inter-subdomain constraints.
Angrill, S.; Segura, L.; Petit-Boix, A.; Rieradevall, J.; Gabarrell, X.; Josa, A. International journal of life cycle assessment Vol. 22, num. 3, p. 398-409 DOI: 10.1007/s11367-016-1174-x Data de publicació: 2017-03 Article en revista
Purpose: The rapid urbanization and the constant expansion of urban areas during the last decades have locally led to increasing water shortage. Rainwater harvesting (RWH) systems have the potential to be an important contributor to urban water self-sufficiency. The goal of this study was to select an environmentally optimal RWH strategy in newly constructed residential buildings linked to rainwater demand for laundry under Mediterranean climatic conditions, without accounting for water from the mains.
Methods: Different strategies were environmentally assessed for the design and use of RWH infrastructures in residential apartment blocks in Mediterranean climates. The harvested rainwater was used for laundry in all strategies. These strategies accounted for (i) tank location (i.e., tank distributed over the roof and underground tank), (ii) building height considering the number of stories (i.e., 6, 9, 12, and 15), and (iii) distribution strategy (i.e., shared laundry, supply to the nearest apartments, and distribution throughout the building). The RWH systems consisted of the catchment, storage, and distribution stages, and the structural and hydraulic calculations were based on Mediterranean conditions. The quantification of the environmental performance of each strategy (e.g., CO2eq. emissions) was performed in accordance with the life cycle assessment methodology.
Results and discussion: According to the environmental assessment, the tank location and distribution strategy chosen were the most important variables in the optimization of RWH systems. Roof tank strategies present fewer impacts than their underground tank equivalents because they enhance energy and material savings, and their reinforcement requirements can be accounted for within the safety factors of the building structure without the tank. Among roof tanks and depending on the height, a distribution strategy that concentrates demand in a laundry room was the preferable option, resulting in reductions from 25 to 54 % in most of the selected impact categories compared to distribution throughout the building.
Conclusions: These results may set new urban planning standards for the design and construction of buildings from the perspective of sustainable water management. In this sense, a behavioral change regarding demand should be promoted in compact, dense urban settlements.
In this work a kinematics for laminated beams enriched with a refined formulation ZigZag (RZT), originally presented by Tessler et al. in 2007, introduced in a hierarchical one dimensional type “p” finite element is presented. The finite element employs Lagrange polynomials for the approximation of the degrees of freedom of the ends (nodes) and orthogonal Gram-Schmidt polynomials to the internal degrees of freedoms. This finite element allows a very low discretization, is free of shear locking and behaves very well when the analysis of laminated composites with accurate determination of local stresses and strains at laminar level is necessary.
This element has been validated in the analysis of laminated beams with various sequences of symmetric and asymmetric stacking, studying in each case its accuracy and stability.
Angrill, S.; Petit-Boix, A.; Morales, T.; Josa, A.; Rieradevall, J.; Gabarrell, X. Journal of environmental management Vol. 189, p. 14-21 DOI: 10.1016/j.jenvman.2016.12.027 Data de publicació: 2017-03 Article en revista
Rainwater harvesting might help to achieve self-sufficiency, but it must comply with health standards. We studied the runoff quantity and quality harvested from seven urban surfaces in a university campus in Barcelona according to their use (pedestrian or motorized mobility) and materials (concrete, asphalt and slabs). An experimental rainwater harvesting system was used to collect the runoff resulting from a set of rainfall events. We estimated the runoff coefficient and initial abstraction of each surface and analyzed the physicochemical and microbiological properties, and hydrocarbon and metal content of the samples. Rainfall intensity, surface material and state of conservation were essential parameters. Because of low rainfall intensity and surface degradation, the runoff coefficient was variable, with a minimum of 0.41. Concrete had the best quality, whereas weathering and particulate matter deposition led to worse quality in asphalt areas. Physicochemical runoff quality was outstanding when compared to superficial and underground water. Microorganisms were identified in the samples (>1 CFU/100 mL) and treatment is required to meet human consumption standards. Motorized traffic mostly affects the presence of metals such as zinc (31.7 µg/L). In the future, sustainable mobility patterns might result in improved rainwater quality standards.
Fatigue cracking of bituminous mixtures is closely related to the loss of ductility produced by the stiffening of the bituminous binder. The main two factors that cause the asphalt binder to lose its ductility are aging and exposure to low temperatures. However, most of the tests designed to evaluate the fatigue behavior of bituminous mixtures are very time consuming, and make unpractical those studies that try to evaluate the influence of many variables. In this research project a strain sweep test was used to analyze the influence of aging, test temperature and bituminous binder type on the fatigue behavior of a continuously graded mixture. As expected, the mixture with SBS polymer modified binder retained more ductility at low temperatures, while the mixture with crumb rubber modified binder had the highest stiffness modulus. All mixtures exhibited the worst fatigue behavior at low temperatures and aging was equivalent to testing an unaged mixture at a lower temperature. The main result of this paper was the implementation of a new methodology to estimate the fatigue law of the material using a strain sweep test, which allowed this fatigue analysis to be carried out in nearly 10 times less testing time than that required by the procedure described in the EN 12697-24 standard.
Ryzhakov, P.; Marti, J.; Idelsohn, S.R.; Oñate, E. Computer methods in applied mechanics and engineering Vol. 315, p. 1080-1097 DOI: 10.1016/j.cma.2016.12.003 Data de publicació: 2017-03 Article en revista
We propose here a displacement-based updated Lagrangian fluid model developed to facilitate a monolithic coupling with a wide range of structural elements described in terms of displacements. The novelty of the model consists in the use of the explicit streamline integration for predicting the end-of-step configuration of the fluid domain. It is shown that this prediction considerably alleviates the time step size restrictions faced by the former Lagrangian models due to the possibility of an element inversion within one time step. The method is validated and compared with conventional approaches using three numerical examples. Time step size and corresponding Courant numbers leading to optimal behavior in terms of computational efficiency are identified.
This paper presents advanced computer simulation of rock cutting process typical for excavation works in civil engineering. Theoretical formulation of the hybrid discrete/finite element model has been presented. The discrete and finite element methods have been used in different subdomains of a rock sample according to expected material behaviour, the part which is fractured and damaged during cutting is discretized with the discrete elements while the other part is treated as a continuous body and it is modelled using the finite element method. In this way, an optimum model is created, enabling a proper representation of the physical phenomena during cutting and efficient numerical computation. The model has been applied to simulation of the laboratory test of rock cutting with a single TBM (tunnel boring machine) disc cutter. The micromechanical parameters have been determined using the dimensionless relationships between micro- and macroscopic parameters. A number of numerical simulations of the LCM test in the unrelieved and relieved cutting modes have been performed. Numerical results have been compared with available data from in-situ measurements in a real TBM as well as with the theoretical predictions showing quite a good agreement. The numerical model has provided a new insight into the cutting mechanism enabling us to investigate the stress and pressure distribution at the tool–rock interaction. Sensitivity analysis of rock cutting performed for different parameters including disc geometry, cutting velocity, disc penetration and spacing has shown that the presented numerical model is a suitable tool for the design and optimization of rock cutting process.
Scenario-based risk assessment for rockfalls, requires assumptions for different scenarios of magnitude (volume). The magnitude of such instabilities is related to the properties of the jointed rock mass, with the characteristics of the existing unfavourably dipping joint sets playing a major role. The critical factors for the determination of the maximum credible rockfall volume in a study site, the Forat Negre in Andorra, are investigated. The results from two previous analyses for the rockfall size distribution at this site are discussed. The first analysis provides the observed size distribution of the rockfall scars, and it is an empirical evidence of past rockfalls. The second one, calculates the kinematically detachable rock masses, indicating hypothetical rockfalls that might occur in the future. The later gives a maximum rockfall volume, which is one order of magnitude higher, because the persistence of the basal planes is overestimated. The tension cracks and lateral planes interrupt systematically the basal planes, exerting a control over their persistence, and restricting the formation of extensive planes and large rockfall failures. Nonetheless, the formation of basal planes across more than one spacings of tension cracks is possible and small step-path failures have been observed too. Concluding, the key factor for the determination of the maximum credible volume at the study-site is the maximum realistic length of the basal planes, penetrating into the rock mass, their spacing, and, if applied, the contribution of the rock bridges to the overall rock mass resistance.
This book was born with the vocation of being a tool for the training of engineers in continuum mechanics. In fact, it is the fruit of the experience in teaching this discipline during many years at the Civil Engineering School of the Technical University of Catalonia (UPC/BarcelonaTech), both in undergraduate degrees (Civil Engineering and Geological Engineering) and postgraduate degrees (Master and PhD courses). Unlike other introductory texts to the mechanics of continuous media, the work presented here is specifically aimed at engineering students. We try to maintain a proper balance between the rigor of the mathematical formulation used and the clarity of the physical principles addressed, although always putting the former at the service of the latter. In this sense, the essential vector and tensor operations use simultaneously the indicial notation (more useful for rigorous mathematical proof) and the compact notation (which allows for a better understanding of the physics of the problem). However, as the text progresses, there is a clear trend towards compact notation in an attempt to focus the reader’s attention on the physical component of continuum mechanics. The text content is intentionally divided into two specific parts, which are presented sequentially. The first part (Chapters 1-5) introduces fundamental and descriptive aspects common to all continuous media (motion, deformation, stress and conservation-balance equations). In the second (Chapters 6 to 11), specific families of the continuous medium are studied, such as solids and fluids, in an approach that starts with the corresponding constitutive equation and ends with the classical formulations of solid mechanics (elastic-linear and elasto-plastic) and fluid mechanics (laminar regime). Finally, a brief incursion into the variational principles (principle of virtual work and minimization of potential energy) is attempted, to provide the initial ingredients needed to solve continuum mechanics problems using numerical methods. This structure allows the use of this text for teaching purposes both in a single course of about 100 teaching hours or as two different courses: the first based on the first five chapters dedicated to the introduction of the fundamentals of continuum mechanics and, the second specifically dedicated to solid and fluid mechanics. The theoretical part in every chapter is followed by a number of solved problems and proposed exercises so as to help the reader in the understanding and consolidation of those theoretical aspects.
This paper reviews the simplified procedure proposed by Ghosn and Sivakumar to model the maximum expected traffic load effect on highway bridges and illustrates the methodology using a set of Weigh-In-Motion (WIM) data collected on one site in the U.S.A. The paper compares different approaches for implementing the procedure and explores the effects of limitations in the site-specific data on the projected maximum live load effect for different bridge service lives. A sensitivity analysis is carried out to study changes in the final results due to variations in the parameters that define the characteristics of the WIM data and those used in the calculation of the maximum load effect. The procedure is also implemented on a set of WIM data collected in Slovenia to study the maximum load effect on existing Slovenian highway bridges and how the projected results compare to the values obtained using advanced simulation algorithms and those specified in the Eurocode of actions.
Numerical simulations have been widely applied, for the determination of the resistance of steel structural elements, when experimental analysis are not possible (due to cost or size limitations) or when parametric studies with high number of variables are needed. However, the numerical models must be properly validated with experimental tests in order to deliver reliable studies. With the purpose of studying the behaviour of stainless steel plate girders in fire situation, a total of 34 experimental tests from the literature have been numerically modelled. The tested girders had different configurations: rigid and non-rigid end posts, 2 and 4 panels, and transversal and longitudinal stiffeners were considered. Comparative analyses between those experimental and numerical results have been done. Good approximations to the experimental results at normal temperatures have been achieved with differences on average lower than 5%. Afterwards, the developed numerical model has been used to perform a sensitivity analysis on the influence of the initial geometric imperfections at both normal and elevated temperatures, considering different values for its maximum amplitudes, concluding that 10% of the web thickness is an appropriate value for the maximum amplitude of the geometric imperfections when modelling experimental tests. The effect of the residual stresses has also been analysed, being obtained differences lower than 2%. Finally, comparisons between the numerical results and the Eurocode 3 design procedures have been performed considering different uniform elevated temperatures.
Petracca, M.; Pela, L.; Rossi, R.; Oller, S.; Camata, G.; Spacone, E. Computer methods in applied mechanics and engineering Vol. 315, p. 273-301 DOI: 10.1016/j.cma.2016.10.046 Data de publicació: 2017-03 Article en revista
This work presents a multiscale method based on computational homogenization for the analysis of general heterogeneous thick shell structures, with special focus on periodic brick-masonry walls. The proposed method is designed for the analysis of shells whose micro-structure is heterogeneous in the in-plane directions, but initially homogeneous in the shell-thickness direction, a structural topology that can be found in single-leaf brick masonry walls. Under this assumption, this work proposes an efficient homogenization scheme where both the macro-scale and the micro-scale are described by the same shell theory. The proposed method is then applied to the analysis of out-of-plane loaded brick-masonry walls, and compared to experimental and micro-modeling results.
This paper describes the capabilities of a novel technique to investigate crack formation and propagation in drying soils. The technique is a relatively simple, non-destructive indirect technique using a ground-penetrating-radar (GPR) system to detect cracks that form and propagate inside a soil specimen during desiccation. Although GPR devices have been used for multiple applications, their use in soils for the detection of small desiccation cracks has not been demonstrated yet. The experiment and the methodology used to test the accuracy of a small compact commercial GPR device for crack identification are described. The main objective was to identify what type of signals and what crack width and separation between them can be detected using the GPR device. The results indicate that cracks of 1 or 2mm wide can be detected depending on its position and shape, whereas sub-millimeter cracks are undetectable with the currently existing devices in the market. Regardless of this limitation, the GPR method can be useful to find time-related bounds of when the cracks appear, to point at their location and sometimes at the separation between two of them. Detection of cracks with origin at the bottom or within the specimen was accomplished with this system. Distances of 5 cm or more between cracks can be detected and measured, as well, with accuracy.
Cateura, J.; Sospedra, J.; González-Marco, D.; Sanchez-Arcilla, A. HydroSenSoft - Simposio Internacional de Sensores y Software Hidro-Ambiental con Exposición p. 37-38 Data de presentació: 2017-03-01 Presentació treball a congrés
The pressure on coastal seas keeps on increasing (navigation, fisheries, tourism, etc.) and this requires robust observations with adequate coverage. The deployment of wind turbines in shallow waters offers a good example demanding high resolution data in the air column, from the free surface to a height of order 200m. The corresponding structural assessment (loads for fixed towers and loads/motions for floating structures) needs also waves/current/sea level data in the upper part of the water column.
To address this challenge a prototype buoy, equipped to measure airflow with a LIDAR and water flow with an acoustic Doppler profiler, has been developed and is here presented. The paper shows the conceptual design and performance of this new buoy as a platform for efficient multi-variable observations. The operation of the buoy is based on batteries and solar cells. The resulting observations have been calibrated with data from an instrumented coastal pier during a pilot deployment off the Badalona coast and a meteo mast off the Dutch coast, covering a number of representative met-ocean events.
Esta tesis presenta un estudio de la reducción de modelos (MOR) para redes de transmisión y distribución de electricidad. El enfoque principal utilizado ha sido la dinámica transitoria y para la reducción de modelos se ha adoptado un punto de vista matemático. Las redes eléctricas son complejas y tienen un tamaño importante. Por lo tanto, el análisis y diseño de este tipo de redes mediante la simulación numérica, requiere la resolución de modelos no-lineales complejos. En el contexto del desarrollo de redes inteligentes, el objetivo es un análisis en tiempo real de sistemas complejos, por lo que son necesarios modelos rápidos, fiables y precisos. En el presente estudio se proponen diferentes métodos de reducción de modelos, tanto a priori como a posteriori, adecuados para modelos dinámicos de redes eléctricas. La dinámica transitoria de redes eléctricas, se describe mediante modelos dinámicos oscilatorios no-lineales. Esta no-linearidad del modelo necesita ser bien tratada para obtener el máximo beneficio de las técnicas de reducción de modelos. Métodos como la POD y la LATIN han sido inicialmente utilizados en esta problemática con diferentes grados de éxito. El método de TPWL, que combina la POD con múltiples aproximaciones lineales, ha resultado ser el mas adecuado para sistemas dinámicos oscilatorios.En el caso de las redes de transmisión eléctrica, se utiliza un modelo de parámetros distribuidos en el dominio de la frecuencia. Se propone reducir este modelo basándose en la PGD, donde los parámetros eléctricos de la red de transmisión son incluidos como coordenadas de la representación separada del modelo paramétrico. Este método es ampliado para representar la solución de modelos con parámetros dependientes de la frecuencia para las redes de transmisión eléctrica.Palabras claves Redes Inteligentes, Dinámicas Transitorias, Ecuaciones de MovimientoOscilatorio, Líneas de Transmisión, Reducción de Modelos, Descomposición OrtogonalPropia, Método de Incremento de Gran Tiempo, Método Lineal en TrayectoriaPiece-wise, Descomposición Generalizada Propia, Parámetros Dependientes de laFrecuencia
Paving the road to exascale will likely imply reformulating science problems and redesigning or reinventing their solution algorithms and software for exascale systems in order to face challenges such as energy consumption, resilience, and extreme concurrency. With the extreme concurrency challenge in mind, in this talk we will summarize our recent efforts towards fast sparse linear solver codes tailored for
the Finite Element approximation of elliptic PDEs (e.g., Laplacian or Linear Elasticity equations). At the kernel of these codes lies the so-called Balancing Domain Decomposition by Constraints (BDDC) preconditioner. In the first part of the talk, we will introduce this preconditioner and some of the salient properties that make it highly suitable for extreme scale solver design. Then, in the second part of
the talk, we will cover how we progressively took profit of these properties to end up with a fully-distributed, asynchronous, communicator-aware, recursive and interleveloverlapped MPI-parallel implementation of the Multilevel BDDC (MLBDDC) preconditioner. A comprehensive set of numerical experiments reveals remarkable weak scalability up to 458,752 IBM BG/Q cores and 1.8M MPI tasks (full JUQUEEN) for the 3/4-level BDDC preconditioner in the solution of 3D Laplacian and Linear Elasticity discrete problems with up to several dozens of billions of unknowns.
Esta Tesis se enfoca en el modelamiento numérico de la fractura y su propagación en materiales heterogéneos sujetos a degradación, mediante modelos multiescala jerárquicos basados en la técnica FE2, abordando a su vez la problemática del coste computacional excesivo mediante el desarrollo, la implementación y validación de un conjunto de herramientas computacionales basadas en técnicas de modelos reducidos.Para la modelización de problemas de fractura, se desarrolló, implementó y validó, un modelo multiescala de fallo con las siguientes características:- En la macroescala, se adaptaron los últimos avances de la Aproximación de Discontinuidades Fuertes del Continuo (CSDA), hasta el momento desarrollados para modelos monoescala. Se formula un nuevo elemento finito con alta capacidad de capturar y modelar localización de deformaciones en bandas que pueden interceptar al elemento finito en direcciones arbitrarias. Para evaluar la dirección de propagación de falla se utiliza la técnica del crack-path (oliver/2014).- En la microescala, en aras de usar mecanismos de fallo que sean simples de implementar y calcular, y de cara al posterior desarrollo de una formulación de modelos reducidos, se propone el uso de elementos cohesivos tipo banda, equipados con un modelo constitutivo de daño isótropo regularizado, capaz de representar la decohesión del material. Estos elementos cohesivos son distribuidos entre los diferentes componentes de la microestructura, y en sus fronteras.Se verificó la objetividad de los resultados del modelo con respecto al tamaño de la celda de fallo, y al tamaño del elemento finito de la macroestructura. De igual forma, también se verificó la consistencia del modelo multiescala por medio de la comparación de resultados obtenidos con el mismo, y soluciones obtenidas mediante Simulaciones Numéricas Directas (DNS).En cuanto a la reducción del coste computacional en los modelos multiescala jerárquicos del tipo FE2. Se propone reformular el problema de valores de contorno de la microescala, mediante el uso de dos técnicas sucesivas de reducción, definidas como Modelo de Orden Reducido MOR y Modelo de Orden Hiper-reducido (HROM ó HPROM), respectivamente.En primer lugar, para el Modelo de Orden Reducido, el problema de elementos finitos estándar (de alta fidelidad) de la microestructura, es proyectado y resuelto en un subespacio de menor dimensión mediante el método de la Descomposición Ortogonal Propia (POD). En segundo lugar, para el desarrollo del Modelo de Orden Hiper-reducido, dos técnicas han sido estudiadas y desarrolladas, a saber: los métodos de interpolación y los métodos de Cuadratura de Orden Reducido ROQ (An/2009). Las bases reducidas para la proyección de las variables primales, son calculadas por medio de la Descomposición en Valores Singulares SVD de snapshots captados de trayectorias de entrenamiento previamente definidas.Teniendo en cuenta el caracter discontinuo de las deformaciones en la microescala en problemas de fractura. Se propone la descomposición de la celda de fallo en dos partes, un dominio cohesivo que contiene la totalidad de bandas cohesivas, y un dominio regular compuesto por el dominio disjunto remanente de la microcelda. Cada uno de estos dominios tiene un tratamiento individual. El modelo de la microescala, es reformulado como un problema de punto de silla en el cual se busca minimizar el potencial de energía libre.Para la validar los modelos reducidos desarrollados en esta Tesis, se realizaron múltiples pruebas variando la cantidad de bases para ambas reducciones incrementando la cantidad de modos y puntos de integración. Se puede concluir que, para errores admisibles (inferiores al 5%), las aceleraciones del costo computacional involucrado respecto al tiempo requerido por el modelo de alta fidelidad (speed-up) son del orden de 110 veces. Lo que constituye aceleraciones considerablemente superiores a lo reportado por la literatura.