Sensitivity of the hygrothermal behaviour of homogeneous masonry constructions: from Sobol indices to decision trees

Historic masonry constructions are difficult to mimic in hygrothermal models. Next to the usual uncertainties on the input of hygrothermal models as the outdoor/indoor climate also the properties of the wall themselves are often highly uncertain due to the natural origin of the aggregates and the various, manual production processes used through time. Therefore, this paper presents a probabilistic analysis that indicates the sensitivity of several damage criteria which are often encountered in practice such as mould growth at the interior surface, frost damage, and potential decay of wooden beam heads. The analysis is based on 1D simulations, including realistic variations on climate parameters as wall properties. With Kriging based surrogate modelling the output of the probabilistic simulations is translated into sensitivity indices, Total Sobol indices. These indices summarize the dependency of the damage criteria for each of the input parameters including multi order effects. The Total Sobol indices indicate a generally high dependency of each of the damage criteria on the rain intensity, the trend of the moisture retention/liquid conductivity curve and the absorption coefficient. Based on the probabilistic output binary flowcharts are generated to indicate for which combinations of input parameters high risks are to be expected. These binary flowcharts can be adopted by e.g. engineering firms to define whether, a more detailed assessment is required, and which input are necessary. This indicates when basic in situ assessments of the hygrothermal properties of the facade can suffice.

Download Full-text

Sensitivity analysis of the hygrothermal behaviour of homogeneous masonry constructions: Interior insulation, rainwater infiltration and hydrophobic treatment

Journal of Building Physics ◽

10.1177/17442591211009937 ◽

2021 ◽

Vol 44 (6) ◽

pp. 510-538

Author(s):

Klaas Calle ◽

Nathan Van Den Bossche

Keyword(s):

Infiltration Rate ◽

Frost Damage ◽

Water Infiltration ◽

Sensitivity Analyses ◽

Mould Growth ◽

Damage Potential ◽

Interior Surface ◽

High Dependency ◽

The Impact ◽

Damage Criteria

Historical masonry constructions are difficult to mimic in hygrothermal models. The material properties of the walls are often highly uncertain due to the natural origin of the aggregates and the various, manual production processes used through time. Therefore, sensitivity analyses based on probabilistic simulations are powerful tools to indicate the risks on damage in masonry constructions. Damage criteria for relevant pathologies such as frost damage, potential decay of wooden beam heads and mould growth at the interior surface are used. The assessment methods (Scatter plots, Classification trees and Sobol indices) are based on 1D Heat, Air and Moisture simulations, including realistic variations on climate parameters and wall properties. These methodologies are applied to probabilistic simulations in which a potential damage risk is expected in historic masonries. The application of interior insulation, the use of hydrophobic treatments, and the impact of potential water infiltrations through cracks are discussed. In most of these situations a high dependency of each of the damage criteria on the rain intensity, the trend of the moisture retention/liquid conductivity curve and the absorption coefficient is evident, but also additional insights are found. For example, the thermal impact of interior insulation is negligible compared to its reduction of the first phase drying potential towards the interior. For hydrophobic treatments, the risk for damage typically decreases, but in combination with a rain water infiltration rate above approximately 5% of the wind driven rain the risk on mould growth at the interior surface significantly increases.

Download Full-text

Derivative-based generalized sensitivity indices and Sobol’ indices

Mathematics and Computers in Simulation ◽

10.1016/j.matcom.2019.10.017 ◽

2020 ◽

Vol 170 ◽

pp. 236-256

Author(s):

Matieyendou Lamboni

Keyword(s):

Sobol Indices ◽

Sensitivity Indices ◽

Generalized Sensitivity

Download Full-text

How to perform global sensitivity analysis of a catchment-scale, distributed pesticide transfer model? Application to the PESHMELBA model

10.5194/gmd-2021-425 ◽

2021 ◽

Author(s):

Emilie Rouzies ◽

Claire Lauvernet ◽

Bruno Sudret ◽

Arthur Vidard

Keyword(s):

Water Quality ◽

Sensitivity Analysis ◽

Global Sensitivity Analysis ◽

Transfer Model ◽

Valuable Insight ◽

Catchment Scale ◽

Sobol Indices ◽

Global Sensitivity ◽

Sensitivity Indices ◽

The Impact

Abstract. Pesticide transfers in agricultural catchments are responsible for diffuse but major risks to water quality. Spatialized pesticide transfer models are useful tools to assess the impact of the structure of the landscape on water quality. Before considering using these tools in operational contexts, quantifying their uncertainties is a preliminary necessary step. In this study, we explored how global sensitivity analysis can be applied to the recent PESHMELBA pesticide transfer model to quantify uncertainties on transfer simulations. We set up a virtual catchment based on a real one and we compared different approaches for sensitivity analysis that could handle the specificities of the model: high number of input parameters, limited size of sample due to computational cost and spatialized output. We compared Sobol' indices obtained from Polynomial Chaos Expansion, HSIC dependence measures and feature importance measures obtained from Random Forest surrogate model. Results showed the consistency of the different methods and they highlighted the relevance of Sobol' indices to capture interactions between parameters. Sensitivity indices were first computed for each landscape element (site sensitivity indices). Second, we proposed to aggregate them at the hillslope and the catchment scale in order to get a summary of the model sensitivity and a valuable insight into the model hydrodynamical behaviour. The methodology proposed in this paper may be extended to other modular and distributed hydrological models as there has been a growing interest in these methods in recent years.

Download Full-text

Sensitivity analysis of surface runoff parameters for hydrological modeling of periurban ungauged basin

10.5194/egusphere-egu21-13249 ◽

2021 ◽

Author(s):

Irene Di Cicco ◽

Carlo Giudicianni ◽

Armando Di Nardo ◽

Roberto Greco

Keyword(s):

Land Use ◽

Sensitivity Analysis ◽

Water Resources ◽

Surface Runoff ◽

Model Structure ◽

Hydrological Models ◽

Ungauged Basins ◽

Model Simplification ◽

Sensitivity Indices ◽

Input Parameters

Rapid human-induced changes, such as climate change, population growth and rapid urbanization, are putting enormous stress on water resources. An accurate estimate of available water resources is a prerequisite for sustainable water resources planning and management. For gauged basins, historical records of hydrological observations are available, but for ungauged basins, the assessment of water availability is a challenging task. Therefore, the major focus of studies in ungauged basins is the development of appropriate tools that can accurately quantify hydrologic responses under various land use and climatic conditions. The reduction of the number of unknown parameters to be estimated is a key aspect in the development of hydrological models for ungauged basins.This work is part of these issues and proposes an approach to reduce the complexity of hydrological models that include substantial uncertainties about the input data, initial and boundary conditions, model structure and parameters, owing to lack of data (i.e. for ungauged basins) and poor knowledge of hydrological response mechanisms. The case study of a basin of the District of Licola, located in the territory of the municipality of Giugliano, a city near Naples (southern Italy) is analyzed. Originally devoted to agriculture and grazing, it has been affected in the last decades by intense urbanization, which caused an increase in the impermeability of the soil cover. The increase in residential, commercial and production buildings has changed the functioning of the drainage network canals, compared to the original conditions, causing an increase in the frequency of flooding in the area. The semi-distributed hydrological model SWMM is adopted, which allows the subdivision of the basin in sub-basins according to land use and soil data.Sensitivity Analysis (SA) is an effective approach to model simplification, providing an assessment of how much each input / parameter contributes to the output uncertainty. In general, SA is an essential part of model development, reducing uncertainties that have negative effects on the accuracy and reliability of simulated results. Specifically, in this study the SA is carried out with a method based on the decomposition of the variance of the peak flow and runoff volume, to quantitatively evaluate the contributions of single uncertain inputs/parameters that characterize the surface runoff with respect to different rainfall events, for both pervious and impervious areas. To this aim, the Fourier Amplitude Sensitivity Test (FAST) is implemented. This method allows quantifying not only the &#8220;main effect&#8221; of variance, but also provides the Total Sensitivity Indices (TSI), defined as the sum of all the sensitivity indices for each parameter (including the effects of the interaction with other uncertain parameters).The research objectives aims at: (i) increased understanding of the relationships between input and output variables in a complex hydrological system; (ii) reduction of model uncertainty, through the identification of input parameters mostly contributing to output variability and should therefore be the focus of sensitivity analysis; (iii) model simplification, fixing&#160; the values of input parameters that have little effect on the output, and identifying and removing redundant parts of the model structure.

Download Full-text

Global Sensitivity Analysis of Large Reaction Mechanisms Using Fourier Amplitude Sensitivity Test

Journal of Chemistry ◽

10.1155/2018/5127393 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Shengqiang Lin ◽

Ming Xie ◽

Meng Wu ◽

Weixing Zhou

Keyword(s):

Sample Size ◽

Reaction Mechanisms ◽

Global Sensitivity Analysis ◽

Input Parameter ◽

Combustion Model ◽

Fast Method ◽

Fourier Amplitude ◽

Global Sensitivity ◽

Sensitivity Indices ◽

Input Parameters

Global sensitivity analysis (GSA) of large chemical reaction mechanisms remains a challenge since the model with uncertainties in the large number of input parameters provides large dimension of input parameter space and tends to be difficult to evaluate the effect of input parameters on model outputs. In this paper, a criterion for frequency selection to input parameter is proposed so that Fourier amplitude sensitivity test (FAST) method can evaluate the complex model with a low sample size. This developed FAST method can establish the relationship between the number of input parameters and sample size needed to measure sensitivity indices with high accuracy. The performance of this FAST method which can allow both the qualitative and quantitative analysis of complex systems is validated by a H2/air combustion model and a CH4/air combustion model. This FAST method is also compared with other GSA methods to illustrate the features of this FAST method. The results show that FAST method can evaluate the reaction systems with low sample size, and the sensitivity indices obtained from the FAST method can provide more important information which the variance-based GSA methods cannot obtain. FAST method can be a remarkably effective tool for the modelling and diagnosis of large chemical reaction.

Download Full-text

Global sensitivity analysis for the Rothermel model based on high-dimensional model representation

Canadian Journal of Forest Research ◽

10.1139/cjfr-2015-0148 ◽

2015 ◽

Vol 45 (11) ◽

pp. 1474-1479 ◽

Cited By ~ 7

Author(s):

Yaning Liu ◽

M. Yousuff Hussaini ◽

Giray Ökten

Keyword(s):

Sensitivity Analysis ◽

Global Sensitivity Analysis ◽

High Dimensional ◽

High Dimensional Model Representation ◽

Dimensional Model ◽

Global Sensitivity ◽

Sensitivity Indices ◽

Fuel Model ◽

Input Parameters ◽

Fuel Models

Rothermel’s wildland surface fire spread model is widely used in North America. The model outputs depend on a number of input parameters, which can be broadly categorized as fuel model, fuel moisture, terrain, and wind parameters. Due to the inevitable presence of uncertainty in the input parameters, knowing the sensitivity of the model output to a given input parameter can be very useful for understanding and controlling the sources of parametric uncertainty. Instead of obtaining the local sensitivity indices, we perform a global sensitivity analysis that considers the synchronous changes of parameters in their respective ranges. The global sensitivity indices corresponding to different parameter groups are computed by constructing the truncated ANOVA – high dimensional model representation for the model outputs with a polynomial expansion approach. We apply global sensitivity analysis to six standard fuel models, namely short grass, tall grass, chaparral, hardwood litter, timber, and light logging slash. Our sensitivity results show similarities, as well as differences, between fuel models. For example, the sensitivities of the input parameters, i.e., fuel depth, low heat content, and wind, are large in all fuel models and as high as 85% of the total model variance in the fuel model light logging slash. On the other hand, the fuel depth explains around 40% of the total variance in the fuel model light logging slash but only 12% of the total variance in the fuel model short grass. The quantification of the importance of parameters across fuel models helps identify the parameters for which additional resources should be used to lower their uncertainty, leading to effective fire management.

Download Full-text

Carotid endarterectomy following thrombolysis for acute ischaemic stroke

VASA ◽

10.1024/0301-1526/a000601 ◽

2017 ◽

Vol 46 (2) ◽

pp. 116-120 ◽

Cited By ~ 4

Author(s):

Naz Ahmed ◽

Damian Kelleher ◽

Manmohan Madan ◽

Sarita Sochart ◽

George A. Antoniou

Keyword(s):

Ischaemic Stroke ◽

Carotid Endarterectomy ◽

Acute Ischaemic Stroke ◽

Intravenous Thrombolysis ◽

Hospital Length ◽

Hospital Length Of Stay ◽

Wound Complications ◽

Cardiac Complications ◽

High Dependency ◽

Low Incidence

Abstract. Background: Insufficient evidence exists to support the safety of carotid endarterectomy (CEA) following intravenous thrombolysis (IVT) for acute ischaemic stroke. Our study aimed to report a single-centre experience of patients treated over a five-year period. Patients and methods: Departmental computerised databases were interrogated to identify patients who suffered an ischaemic stroke and subsequently underwent thrombolysis followed by CEA. Mortality and stroke within 30 days of surgery were defined as the primary outcome end points. Results: Over a five-year period, 177 out of a total of 679 carotid endarterectomies (26 %) were performed in patients presenting with acute ischaemic stroke. Twenty-five patients (14 %) received IVT prior to CEA in the form of alteplase. Sixty percent of patients were male with a mean age of 68 years. Sixteen patients (64 %) underwent CEA within 14 days of IVT and the median interval between thrombolysis and CEA was 7.5 days (range, 3–50 days). One female patient died of a further intraoperative stroke within 30 days of surgery, yielding a mortality rate of 4 %. Two patients (8 %) suffered from cardiac complications postoperatively resulting in a short high dependency unit stay. Another two patients (8 %) developed local wound complications, which were managed conservatively without the need for re-operation. The median hospital length of stay was 4.5 days (range, 1–33 days). Conclusions: Our experience indicates that CEA post-thrombolysis has a low incidence of mortality. Further high quality evidence is required before CEA can be routinely recommended following IVT for acute ischaemic stroke.

Download Full-text