Simplified Methodologies Research Articles

Assessing the distribution of forest ecosystem services in a highly populated Mediterranean region

Forest ecosystems provide a wide range of goods and services to society and host high levels of biodiversity. Nevertheless, forest ecosystem services (ES) are often quantified and assessed using simplified methodologies (e.g., proxy methods based exclusively on Land Use Land Cover maps) that introduce substantial uncertainty in the analysis by ignoring, for instance, the species composition and spatial configuration of the ecosystems studied. In this work we defined and calculated a set of 12 indicators of several ES for the forests of the highly populated region of Catalonia (North-eastern Iberian Peninsula). The indicators combined different sources of information such as forest surveys, ecological model predictions and official statistics, but also included additional land cover information. All ES indicators were aggregated at the municipality level to compare their values and distribution patterns. We assessed spatial trade-offs and synergies among ES, as well as their relationships with a set of socioeconomic, climatic and biodiversity variables using correlation analyses and mixed-effects models. The results suggest a clustering of provisioning and regulating ES in mountainous zones towards the North of the study area. These two types of services showed a high degree of spatial similarity and presented high positive correlations. In contrast, cultural ES showed a more scattered pattern, which included lower elevation areas in the South of the study region. Climatic conditions were the main determinants of the spatial variability in the supply of the different ES, with most indicators being positively associated with precipitation and negatively associated with temperature. In addition, biodiversity (particularly woody species richness) showed positive relations with most of these ES, while socioeconomic variables (such as population density and the percentage employment in agriculture) showed negative associations with most of them. The combination of information from different data sources (including primary data) allowed for a detailed analysis of forest ES, likely removing some of the problems derived from approaches based only on proxy methods. In addition, the use of municipalities as study unit makes results directly relevant to management and planning strategies operating at this scale (e.g., forest management and planning).

Experimental lateral-torsional buckling behaviour of web tapered I-section steel beams

Tapered steel members are often chosen instead of prismatic due to a better cross-section utilization along the member, which makes them an interesting and more economical alternative. Although EN1993-1-1 offers several methodologies for the stability verification of steel members and frames, it does not provide a clear guidance for the stability design of such members.Recently, the research group has provided simplified stability verification methodologies for tapered columns and beams. The developed methodologies are based on analytical derivations which were validated with advanced numerical simulations.In order to improve the accuracy of the proposed procedures, full-scale experimental tests on tapered columns, beams and beam-column were carried out. The experiments are used to calibrate a numerical model, incorporating all relevant parameters, such as: geometrical imperfections (local and global) and material imperfections (residual stresses). In this paper, firstly a global overview of the experimental programme on web-tapered steel members is given. The key results from each experiment are summarized; they are further used for the calibration of an advanced numerical model.

Depositional environment effects on observed liquefaction performance in silt swamps during the Canterbury earthquake sequence

Stratified silty soils deposited in back-swamp settings are shown through regional CPT-based analyses to have mitigating effects on the manifestation of liquefaction in Christchurch. Liquefaction triggering within these deposits is inadequately captured by simplified liquefaction assessment methodologies. Differing near-surface geology and depositional environments indicated in historical documents explain in part the limitations of current liquefaction evaluation procedures in southwest Christchurch. The historical swamp areas are shown through a regional CPT study to contain stratified silt/sand deposits or thick silt layers. Consideration of depositional environment distinguishes between liquefaction performances that are not able to be differentiated through the CPT-based liquefaction triggering assessment alone. CPT resolution is shown to be insufficient to capture the thin layering at these stratified sites, and the simplified liquefaction assessment methods do not take into account the effects of the stratification on pore water pressure movement within a soil profile. Instead, continuous sampling and careful logging of high-quality samples provide important insights on stratification at these silty soil swamp sites and in discerning differences in stratigraphy resulting from differences in depositional environment.

EMPIRICAL METHODS FOR ESTIMATING REFERENCE SURFACE NET RADIATION FROM SOLAR RADIATION

In agrometeorology, reference surface consists of those traditional grass cover on weather stations. Net radiation (Rn) of this surface is an important information that has many applicability, but its measurement is rare due to the high cost of the sensor and the complexity involved on the measurement. Therefore, estimate Rn from another variable is desirable, as from solar radiation (Rs); however, standard methods used are complex, making interesting the use of simplified methodologies. Considering these aspects, the present study aimed to set two empirical methods to estimate Rn from Rs for Dourados region, located in the Mato Grosso do Sul State, Brazil. One method was set with a scientific purpose (Gauss Method) and it comprised a mathematical modeling. The other one was set with a practical purpose (Practical Method) and comprised the determination of fixed monthly conversion factors. It was used daily Rs data of a 12-years database. With these, there were estimated Rn values by the standard method recommended by FAO. Gauss Method was set using Table Curve 2D 5.01 software. Modeling consisted in defining the values of the equation parameters. On Practical Method we developed monthly coefficients of the ratio Rn/Rs. In order to validate both methods it was measured Rs and Rn during two years using high precision sensors. In addition, Rn values were estimated by both methods and then compared with those measured. Both estimating methods showed satisfactory results, with low error and low advantage for the Gauss Method.

Análisis modal y dinámico de una pasarela peatonal en servicio

Civil engineering constructions like pedestrian footbridges are structures increasingly slender, ambitious and complex in which the dynamic effects caused by the loads to which they are subjected (pedestrians) may induce service problems and / or significant or repetitive amplifications of the efforts and deformations. This fact together with the current social demands related to the perception and comfort raise the need to integrate the analysis and computer-aided design in the evaluation of the vibrations generated by the loads this type of structures supports. In the specific case of finite element commercial programs, their use has not proliferated as much as in other engineering fields due to the existence of simplified methodologies in numerous national and international guidelines and regulations and the difficulty of making realistic models in the case of complex structures. However, the knowledge generated by the analysis of this type of numerical models would be especially useful in the earlier phases of the design of similar structures, so much initial as of the necessary modifications to solve existing dynamic problems, since it is in these stages when the best solution could be applied from both a technical and an economic point of view. This article describes the process of generation and updating of the mechanical finite element model (FEM) of a footbridge in service and the simulation of two types of load: an excitation generated by a shaker and a pedestrian load, contrasting the results generated by the numerical model with those obtained experimentally.

Flexural, Compressive Arch, and Catenary Mechanisms in Pseudostatic Progressive Collapse Analysis

Progressive collapse has drawn significant attention from researchers because of its potential to inflict severe damage and casualty. Much research has focused on simulation techniques for collapse, but comparatively little has examined the interactions among the three main mechanisms of flexural, compressive arching, and catenary actions by way of simplified methodologies. This paper introduces a theoretical method to calculate the collapse resistance of reinforced concrete frame structures in static progressive collapse analysis. The lumped-damaged plasticity method was used to simulate flexural analysis, and compressive arch and catenary actions were calculated using geometry analogies assuming rigid body rotation after initiation of plastic hinging. The method was validated by comparing the simulation results with experimental data, wherein reinforced concrete beam-column assemblies subjected to column removal were tested pseudostatically. The flexural and arching actions were well predicted by the proposed methodology, though the assumed failure mechanism at the end of the simulated catenary action was conservative compared to the experimental results. Overall, the developed method integrating flexural, compressive arch, and catenary actions during collapse was found to be a reliable tool for quick estimation of collapse resistance in static progressive collapse resistance.

Seismic vulnerability assessment of stone masonry façade walls: Calibration using fragility-based results and observed damage

This paper is focused on the calibration of a simplified seismic vulnerability index method for masonry façade walls, through an innovative two-step calibration process based on two complementary approaches. The first one is based on a set of fragility curves constructed from out-of-plane damage limit states obtained from experimental data, which are used to calibrate the weights associated to the parameters of the vulnerability index method that rule the out-of-plane response of the masonry façade walls. The second approach, subsequently used to calibrate the weights of the remaining vulnerability parameters, is based on post-earthquake damage data collected after the seismic event that struck the Azores Archipelago in July 1998. The results obtained from such calibration are then presented and critically discussed taking into account not only the calibration itself, but also their reliability from the methodological point of view. Finally, the addition of three new evaluation parameters is further proposed and analysed. This two-step calibration process represents a valuable contribution for the current state-of-art of the simplified seismic vulnerability assessment methodologies which, up to the present, have been developed and calibrated only on the basis of empirical data.

Simplified Finite Element Models to Study the Wet Collapse of Straight and Curved Flexible Pipes

When the external sheath of flexible pipes experiences damage, seawater floods the annulus. Then, the external pressure is applied directly on the internal polymeric layer, and the load is transferred to the interlocked carcass, the innermost layer. In this situation, the so-called wet collapse failure of the interlocked carcass can occur. Simplified methodologies to address such a scenario, using restricted three-dimensional (3D) finite element models, are presented in this work. They are compared with full 3D models, studying both straight and curved flexible pipes scenarios. The curvature of the flexible pipe is shown to be important for wet collapse pressure predictions.

05.10: Numerical model for the buckling behaviour of tapered steel members based on experimental tests

ABSTRACTTapered steel members can provide optimum cross‐section utilization along the member length, which makes them an interesting alternative to prismatic members due to the economy of this solution. However, EN1993‐1‐1[1] does not provide a clear guidance for the stability design of such members. Recently, the authors have provided simplified stability verification methodologies for tapered columns and beams [2, 3]. The developed methodologies are based on analytical derivations which were validated with advanced numerical simulations.In order to improve the accuracy of the proposed procedures and extend them to members of Class 4 and beam‐columns, an experimental study on tapered columns, beams and beam‐column was carried out. The experiments are used to calibrate a numerical model, incorporating all relevant parameters, such as: geometrical imperfections (local and global) and material imperfections (residual stresses). Unfortunately, the available data on measurements of the material and geometrical imperfections is often found incomplete, even less information is available regarding tapered members. In this paper, firstly a global overview of the experimental programme carried out on web‐tapered steel member is given. The key results from each experiment are summarized; they are further used for the calibration of an advanced numerical model. Finally, an assessment to the magnitude of the adopted geometrical and material imperfections to the member resistance is carried out.

Evolution of viscoelastic behaviour of a curing LY5052 epoxy resin in the rubbery state

In this work, we investigate the relationship between the rubbery modulus and the degree of cure for partially to fully cured LY5052 epoxy resin. In particular, this paper experimentally tests an existing model formulated for shear modulus by redefining for in the tensile storage modulus. Experiments to characterize viscoelastic behaviour were performed in a dynamic mechanical and thermal analysis (DMTA) instrument in the frequency domain. Master curves are then created from DMTA using general time–temperature–cure superposition. The master curves are then normalized using the model so that the master curve does not depend on the properties in the rubbery region. This results in a unique master curve that describes the viscoelastic behaviour of the LY5052 epoxy resin for the given conditions. Once the relationship between the rubbery modulus and the degree of cure has been established, the amount of experimental characterization can be reduced. This could lead to the development of simplified experimental methodologies and simplified models to characterize the viscoelasticity of low molecular weight resins like the LY5052 epoxy resin system.

Seismic safety evaluation of reinforced concrete masonry infilled frames using macro modelling approach

Many reinforced concrete buildings have been built with masonry infill walls for architectural needs without considering their mechanical contribution. However, ignoring the structural influence of infills may lead to significant inaccuracies in the prediction of the actual seismic capabilities of the structure. Aiming at providing numerical tools suitable for engineering practice, simplified methodologies for predicting the nonlinear seismic behaviour of infilled frame structures (IFS) have been proposed, mostly considering the contribution of the infill as an equivalent diagonal strut element. In this paper, an alternative plane macro-element approach for the seismic assessment of IFS is proposed, validated and applied to a benchmark prototype building. The model validation is focused on recent experimental and numerical results that investigate the influence of non-structural infills, also in the presence of different openings layouts. As a benchmark investigation, a multi-storey plane frame prototype, for which the results of pseudo-dynamic tests are available, is investigated and compared to the results obtained by using a commonly adopted single-strut model. The merits and drawbacks of the considered numerical approaches are highlighted.

Estimation of Floor Response Spectra Using the Uncoupled Modal Response History Analysis

In performance-based earthquake engineering, probabilistic seismic demand models are usually developed by using methods which need a large number of nonlinear dynamic analyses to be run. In order to reduce the numerical effort, simplified methodologies of analysis have been proposed. Objective of the present study is to use the uncoupled modal response history analysis for the estimation of acceleration floor spectra, engineering demand parameters commonly used for measuring seismic demand in acceleration-sensitive non-structural elements. The procedure is evaluated for a 6-story reinforced concrete frame case study, designed to be representative of an existing structure lacking in specific capacity design rules.

GoPros™ as an underwater photogrammetry tool for citizen science.

Citizen science can increase the scope of research in the marine environment; however, it suffers from necessitating specialized training and simplified methodologies that reduce research output. This paper presents a simplified, novel survey methodology for citizen scientists, which combines GoPro imagery and structure from motion to construct an ortho-corrected 3D model of habitats for analysis. Results using a coral reef habitat were compared to surveys conducted with traditional snorkelling methods for benthic cover, holothurian counts, and coral health. Results were comparable between the two methods, and structure from motion allows the results to be analysed off-site for any chosen visual analysis. The GoPro method outlined in this study is thus an effective tool for citizen science in the marine environment, especially for comparing changes in coral cover or volume over time.

Simplified methodology to evaluate the external sulfate attack in concrete structures

The external sulfate attack is a degradation process that causes expansion and cracking in concrete structures. Due to the absence of simplified methodologies to predict the potential damage, codes specify that sulfate resistant cement should be used whenever the surrounding sulfate concentration surpasses a predefined limit. This may lead to penalizing measures as the size of the element or the mechanical properties of the concrete used are not considered. In the present work, an alternative approach is proposed. A simplified chemo-mechanical methodology is deducted to assess the potential damage in concrete elements exposed to sulfate rich environments. Equations to estimate the penetration of sulfates are derived from a numerical model taking into account sulfate consumption, acceleration of the penetration induced by cracking and decrease in diffusivity caused by pore filling. Failure modes associated to this phenomenon are analyzed and a set of equations to assess the risk of failure are deducted. Finally, a parametric study with different geometries of elements and surrounding sulfate contents is performed. The results show that the criterion included in codes might be modified depending on the characteristics of the structure.

Reconciling material balances with laboratory test results: The case of the inorganic-to-organic ratio in black liquor

When evaluating the composition of black liquor using material balance techniques that estimate the organics from the wood and the inorganics from the cooking liquor, the solids content of the black liquor is determined to be roughly 1/3 inorganic matter and 2/3 organic matter. When actual laboratory testing using simplified ashing methodologies are performed, the results typically suggest that black liquor solids contain roughly 43%-49% organics and 51%-57% inorganics. We determined that the applied hydroxide and sulfide mineralize carbon and oxygen from the organic portion of the black liquor and convert it to carbonate and sulfate during the cooking and ashing process, thus increasing the apparent inorganic content of the black liquor. This becomes problematic when attempting to estimate total black liquor production using the organics removed during cooking and the inorganic content using results from the ashed black liquor sample. We used Microsoft Excel material balances to develop a conversion factor to correct the laboratory test results. Multiplying the percent ash in the laboratory test by 0.65 to 0.70 provided a more realistic estimate of the initial inorganics to be used along with organics removed in the digester to estimate black liquor production. This conversion factor was determined to be independent of pulp yield and white liquor charge in the digester. The initial white liquor composition, as reported by the ABC test, does have a slight effect on this value.

Integrating Simplified and Full Life Cycle Approaches in Decision Making for Building Energy Refurbishment: Benefits and Barriers

The life cycle assessment (LCA) method is a powerful tool that can serve to aid decision making regarding the environmental benefits of refurbishment projects. However, due to the relative complexity of LCA studies, simplified LCA methodologies are frequently used, focusing on just some of the building life cycle phases or a reduced number of indicators. The most common and widespread simplification is to only evaluate the differences a refurbishment project makes on the operational energy use of the building. This paper compares the results of applying full LCA, simplified LCA and operational energy use assessment in a refurbishment case study. Results show that simplified LCA methodologies including building use phase and product manufacturing phase can generally be sufficiently accurate to aid decision making for building energy refurbishment, as other building life cycle phases related to transport of products, on site construction, deconstruction or end of life represent a generally negligible part of the total life cycle impacts, both in terms of resource use or environmental impacts. Barriers and benefits of applying simplified LCA approaches to building energy refurbishment projects are subsequently discussed.

Demand response modeling: A comparison between tools

Abstract The potential to reschedule part of the electricity demand in energy systems is seen as a significant opportunity to improve the efficiency of the systems, especially on remote and isolated systems. From the supply point of view, that flexibility might bring significant improvements to the generation dispatch, especially when in the presence of renewable resources; from the demand point of view, that flexibility could allow customers to benefit from reducing their energy bills. To study these types of implications, modeling tools have been introducing the possibility to include flexible loads on the optimization process, although some use very simplified methodologies to do it. This study compares how different modeling tools consider fixed and flexible loads in the dispatch optimization, analyzing their different strategies. Three different scenarios were simulated in HOMER, EnergyPLAN and an economic dispatch self-built model in Matlab, using as case study the Corvo Island, Portugal. The comparison results indicate that HOMER and EnergyPLAN still assume that flexible loads are a second priority load that are met in off-peak hours or in the presence of excess electricity from renewable sources, not taking directly into account the economic impact of such decision. On the other hand, the self-built model that is more flexible on the optimization approach is the more close to the actual operation and presents the best savings when using demand response strategies, albeit representing only a 0.3% decrease in the operation costs. We conclude that the modeling tools should evolve and refine their optimization strategies to capture the total benefits of using demand response to improve energy systems performance.

Self-ignition in stone wool insulation contaminated with fatty acid (fundamentals, case study, analysis methodology)

A combination of a residual film of flammable organic substance, air and porous structures like insulation material (e.g. stone wool) may result in a fire. The initiating self-heating process depends on the substance (reactivity, volatility), amount of accumulated liquid, volume and temperature. Specific information is given for application and extension of the Thomas criterion with a 2nd order reaction. The experimental part includes new experimental techniques to determine heat transfer and formal reaction kinetic data. The applied self-ignition temperature (SIT) simulation model relies on liquid film volume and not on liquid film surface reaction. As a further result of the studies detailed working procedure of three simplified methodologies for estimation of SITs in technical scale are presented. New techniques to determine parameters necessary for SIT prediction, especially in combination with Methodology III, have the power to reduce the costs for estimating the SIT up to 80%.

Seismic damage to pipelines in the framework of Na-Tech risk assessment

The structural integrity of pipelines undergone seismic waves is crucial for industrial installation and for the distributed transportation networks of gaseous and liquid fluids. However, it is nowadays proved that the definition of seismic vulnerability based on purely, structural-derived limit states or on return-to-service or even on the purely economic repair rate indications, is not sufficient for the holistic analysis of risks. On the other hand, detailed numerical studies based on full analyses (including fluid/soil/structure interaction) are too expensive for the aims of risk assessment and simplified methodologies are still needed.In this paper, a large database of earthquake-induced damage for steel and non-steel pipelines is presented. Each case was analyzed and collected from post-earthquake reconnaissance, seismic engineering reports and technical papers. The database may be adopted for the definition of specific vulnerability function (fragility curves), which are commonly implemented in multi-hazard analyses, and more in general for the assessment of Na-Tech risks (Natural events triggering Technological disasters).

Implications of integrating electricity supply dynamics into life cycle assessment: A case study of renewable distributed generation

Electricity supply is frequently cited as a significant hot spot in life cycle assessment (LCA) results. Despite its importance, however, LCA research continues to overuse simplified methodologies regarding electricity supply modeling. This work aims to demonstrate the usefulness of electricity trade analysis (proposed model) for integrating the short-term dynamics of electricity supply and refining LCA results. Distributed generation using renewable energy is applied as a case study to demonstrate how electricity trade analysis provides more refined estimates when environmental impact abatements are assessed compared with the conventional (simplified) approaches in LCA. Grid-connected photovoltaic panel (3 kWp mono- and poly-crystalline) and micro-wind turbine (1, 10 and 30 kW) environmental impact abatements are investigated by determining the displaced marginal electricity production on an hourly basis. The results indicate that environmental impact abatements calculated using the developed short-term time horizon approach can be significantly different (up to 200% difference) from those obtained using a simplified approach. Recommendations are provided to LCA practitioners to address this issue of differing results.