Data-Based RC Dynamic Modelling to Assessing the In-Situ Thermal Performance of Buildings. Analysis of Several Key Aspects in a Simplified Reference Case toward the Application at On-Board Monitoring Level

This paper reports the application of RC dynamic models for assessing thermal performance of buildings from in-situ tests (obtaining the U value for the walls, and the UA value and gA value for the whole buildings). The following aspects which are relevant to this approach have been systematically analyzed: The effect of the solar radiation on the heat flux through the opaque walls versus the performance of the models including this effect, the optimum number of nodes required to represent the thermal systems, the assignment of inputs and outputs and the length of the test period. Additionally, several options modelling relevant effects using unmeasured variables were studied to evaluate the feasibility to reduce the cost and intrusiveness of the measurement devices required to obtain accurate results. Data series recorded under different experimental conditions were considered to analyze the robustness and validity of the results. The performance of the models for each of these different test conditions is discussed. The uncertainties estimated using the described method for the U values of the opaque walls, and the UA and gA values of the whole building, are, respectively, 2.8%, 4.2% and 2.3%. The feasibility to model relevant effects using unmeasured variables has been demonstrated. A simplified and well-known building has been used as a case study, reinforcing and complementing the validation criteria.

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Data-Based RC Dynamic Modelling Incorporating Physical Criteria to Obtain the HLC of In-Use Buildings: Application to a Case Study

Energies ◽

10.3390/en13020313 ◽

2020 ◽

Vol 13 (2) ◽

pp. 313

Author(s):

Heidi Paola Díaz-Hernández ◽

Pablo René Torres-Hernández ◽

Karla María Aguilar-Castro ◽

Edgar Vicente Macias-Melo ◽

María José Jiménez

Keyword(s):

Dynamic Models ◽

Dynamic Test ◽

Dynamic Modelling ◽

Electricity Consumption ◽

Energy Performance ◽

Electricity Production ◽

Data Series ◽

Electrical Networks ◽

Occupancy Patterns

This paper reports the application of RC dynamic models (network of resistances and capacitances analogous to electrical networks) to obtain the heat loss coefficient (HLC) from a dynamic test campaign carried out in an in-use building. It is a well-insulated building located in Gainsborough, U.K. This case study and data were made available to participants in the IEA–EBC Annex 71 project Building Energy Performance Assessment Based on In-Situ Measurements. The analysis reported in this paper is mainly focused on the identification of the main heat transfer contributions and also on the translation of these phenomena to the RC models used to obtain the required HLC. First pre-processing and qualitative analysis were carried out. Afterwards several candidate models were constructed according to different plausible assumptions and approximations. The validity of the results obtained using these models has been evaluated taking into account the agreement among different data series and also the levels of the residuals obtained using the different models. The work concludes obtaining accurate estimates of the HLC from the energy balance including the following relevant contributions: space heating, solar gains, internal gains due to appliances, and internal gains due to metabolic activity. These terms were modelled using the following driving variables: consumption of gas and water, electricity production by the photovoltaic (PV) panels and electricity consumption (modelling internal gains due to appliances and occupancy patterns).

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Integrated Testing of Building Fabric Thermal Performance for Calibration of Energy Models of Three Low-Energy Dwellings in the UK

Sustainability ◽

10.3390/su13052784 ◽

2021 ◽

Vol 13 (5) ◽

pp. 2784

Author(s):

Rajat Gupta ◽

Matt Gregg

Keyword(s):

Thermal Performance ◽

Thermal Imaging ◽

Energy Performance ◽

Low Energy ◽

In Situ Tests ◽

Building Regulations ◽

Energy Models ◽

Integrated Testing ◽

The Uk

This paper presents the methodology and results of in situ testing of building fabric thermal performance to calibrate as-built energy models of three low-energy dwellings in the UK, so as to examine the gap between as-designed and as-built energy performance. The in situ tests included repeat testing of air permeability (AP) integrated with thermal imaging survey and heat flux measurements of the building fabric elements, along with concurrent monitoring of indoor temperature during the pre-occupancy stage. Despite being designed to high thermal standards, wall and roof U-values were measured to be higher than expected. Thermal imaging surveys revealed air leakage pathways around door/window openings, penetrations and junctions between walls and ceilings, indicating poor detailing and workmanship. AP was found to have increased after the initial test due to post-completion alteration to the building fabric. Though the results did not meet design expectation, they were within the UK Building Regulations. Calibration of energy models with temperature monitoring provided a less extreme energy performance gap than simply replacing the designed values with test results. Insights from this study have reinforced the need for building regulations to require integrated testing of building fabric as part of housing delivery to ensure performance targets are realised.

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Experimental and CFD Simulations of the Aerosol Flow in the Air Ventilating the Underground Excavation in Terms of SARS-CoV-2 Transmission

Energies ◽

10.3390/en14164743 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4743

Author(s):

Tomasz Janoszek ◽

Zbigniew Lubosik ◽

Lucjan Świerczek ◽

Andrzej Walentek ◽

Jerzy Jaroszewicz

Keyword(s):

Numerical Calculations ◽

Mining Institute ◽

Ventilation Network ◽

Underground Excavation ◽

In Situ Tests ◽

Ansys Fluent ◽

Aerosol Emission ◽

Ansys Cfx ◽

Computational Fluid Dynamics Cfd

The paper presents the results of experimental and model tests of transport of dispersed fluid droplets forming a cloud of aerosol in a stream of air ventilating a selected section of the underground excavation. The excavation selected for testing is part of the ventilation network of the Experimental Mine Barbara of the Central Mining Institute. For given environmental conditions, such as temperature, pressure, relative humidity, and velocity of air, the distribution of aerosol droplet changes in the mixture of air and water vapor along the excavation at a distance was measured at 10 m, 25 m, and 50 m from the source of its emission. The source of aerosol emission in the excavation space was a water nozzle that was located 25 m from the inlet (inlet) of the excavation. The obtained results of in situ tests were related to the results of numerical calculations using computational fluid dynamics (CFD). Numerical calculations were performed using Ansys-Fluent and Ansys-CFX software. The dimensions and geometry of the excavation under investigation are presented. The authors describe the adopted assumptions and conditions for the numerical model and discuss the results of the numerical solution.

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Experimental Evaluation of Shear Behavior of Stone Masonry Wall

Materials ◽

10.3390/ma14092313 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2313

Author(s):

Maria Luisa Beconcini ◽

Pietro Croce ◽

Paolo Formichi ◽

Filippo Landi ◽

Benedetta Puccini

Keyword(s):

Shear Behavior ◽

Stone Masonry ◽

Masonry Walls ◽

Mechanical Parameters ◽

In Situ Tests ◽

Capacity Curves ◽

Historical Structures ◽

Definition Of

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

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Predicting the Energy Consumption of a Robot in an Exploration Task Using Optimized Neural Networks

Electronics ◽

10.3390/electronics10080920 ◽

2021 ◽

Vol 10 (8) ◽

pp. 920

Author(s):

Liesle Caballero ◽

Álvaro Perafan ◽

Martha Rinaldy ◽

Winston Percybrooks

Keyword(s):

Neural Network ◽

Energy Consumption ◽

Mobile Robot ◽

Energy Budget ◽

Dynamic Models ◽

Pearson Correlation ◽

Experimental Conditions ◽

Grid Map ◽

Proposed Model ◽

Exploration Task

This paper deals with the problem of determining a useful energy budget for a mobile robot in a given environment without having to carry out experimental measures for every possible exploration task. The proposed solution uses machine learning models trained on a subset of possible exploration tasks but able to make predictions on untested scenarios. Additionally, the proposed model does not use any kinematic or dynamic models of the robot, which are not always available. The method is based on a neural network with hyperparameter optimization to improve performance. Tabu List optimization strategy is used to determine the hyperparameter values (number of layers and number of neurons per layer) that minimize the percentage relative absolute error (%RAE) while maximize the Pearson correlation coefficient (R) between predicted data and actual data measured under a number of experimental conditions. Once the optimized artificial neural network is trained, it can be used to predict the performance of an exploration algorithm on arbitrary variations of a grid map scenario. Based on such prediction, it is possible to know the energy needed for the robot to complete the exploration task. A total of 128 tests were carried out using a robot executing two exploration algorithms in a grid map with the objective of locating a target whose location is not known a priori by the robot. The experimental energy consumption was measured and compared with the prediction of our model. A success rate of 96.093% was obtained, measured as the percentage of tests where the energy budget suggested by the model was enough to actually carry out the task when compared to the actual energy consumed in the test, suggesting that the proposed model could be useful for energy budgeting in actual mobile robot applications.

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Digital Image Correlation for Evaluation of Cracks in Reinforced Concrete Bridge Slabs

Infrastructures ◽

10.3390/infrastructures6070099 ◽

2021 ◽

Vol 6 (7) ◽

pp. 99

Author(s):

Christian Overgaard Christensen ◽

Jacob Wittrup Schmidt ◽

Philip Skov Halding ◽

Medha Kapoor ◽

Per Goltermann

Keyword(s):

Reinforced Concrete ◽

Digital Image Correlation ◽

Crack Initiation ◽

Laboratory Test ◽

Digital Image ◽

Crack Detection ◽

Image Correlation ◽

In Situ Tests ◽

Stop Criterion

In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.

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Effects of corrosion on a steel bowstring bridge in marine environment: A case-study of assessment and retrofit

Bridge Structures ◽

10.3233/brs-200178 ◽

2021 ◽

Vol 16 (4) ◽

pp. 121-137

Author(s):

Michele Fabio Granata

Keyword(s):

Corrosion Protection ◽

Marine Environment ◽

Spray Coating ◽

Thermal Spray Coating ◽

In Situ Tests ◽

Limit States ◽

Intervention Measures ◽

Near Future

The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with the inefficiency of the successive maintenance interventions. The paper presents assessment of the bridge and retrofit measures, including replacement of the hangers and galvanization through thermal spray coating technology, in order to increase its service life. The results of the investigations and the intervention measures are outlined and discussed.

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Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Water ◽

10.3390/w13081131 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1131

Author(s):

Soonkie Nam ◽

Marte Gutierrez ◽

Panayiotis Diplas ◽

John Petrie

Keyword(s):

Hydraulic Conductivity ◽

Field Measurements ◽

Natural Soil ◽

In Situ Tests ◽

Seepage Analysis ◽

Soil Deposits ◽

Seepage Modeling ◽

Sample Disturbance

This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

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Sub-Level Stoping in an Underground Limestone Quarry: An Analysis of the State of Stress in an Evolutionary Scenario

Archives of Mining Sciences ◽

10.1515/amsc-2016-0015 ◽

2016 ◽

Vol 61 (1) ◽

pp. 199-216 ◽

Cited By ~ 1

Author(s):

Marilena Cardu ◽

Sergio Dipietromaria ◽

Pierpaolo Oreste

Keyword(s):

Numerical Models ◽

The State ◽

In Situ Tests ◽

Future Scenario ◽

Limestone Quarry ◽

Geomechanical Properties ◽

State Of Stress ◽

Upper Level ◽

Pillar Structure

Abstract The aim of this study was to evaluate the state of stress of a „voids-pillar“ structure excavated by means of the sub-level stoping method in an underground limestone quarry near Bergamo (Italy). Both the current structure of the quarry (i.e. the rooms exploited till now) and a possible future scenario were analysed using the (FDM) FLAC 2D code. The quarry has been in operation since 1927; at present, exploitation is carried out underground via the sub-level stoping method. Exploitation involves two levels, with 5 rooms on the upper level and 9 rooms on the lower level. After analysing data obtained from laboratory and in situ tests carried out on rock samples and natural discontinuities, the geomechanical properties of the medium, knowledge of which is essential in order to establish the parameters that must be included in the numerical model, were evaluated. The implementation of three numerical models made it possible to study both the present conditions of quarry exploitation and the evolution of the exploited rooms, as well as a possible expansion involving a third level of rooms. Using the results obtained regarding the stress-strain present in the pillars, a potential change in room geometry was proposed aimed at reducing the stress state inside the pillars, decreasing plasticity and increasing overall quarry safety.

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In situ monitoring of isophorone diisocyanate-based flexible polyurethane foams formation

Journal of Cellular Plastics ◽

10.1177/0021955x16670579 ◽

2016 ◽

Vol 54 (1) ◽

pp. 37-52 ◽

Cited By ~ 3

Author(s):

I Eceiza ◽

L Irusta ◽

A Barrio ◽

MJ Fernández-Berridi

Keyword(s):

Foam Height ◽

Polyurethane Foams ◽

In Situ Monitoring ◽

Generation Process ◽

Isophorone Diisocyanate ◽

Experimental Conditions ◽

Foaming Process ◽

Foam Generation ◽

Flexible Polyurethane

Novel isophorone diisocyanate-based flexible polyurethane foams were prepared by the one-step method in a computerized foam qualification system (FOAMAT). The experimental conditions to obtain this type of foams, in relation to the nature and concentration of catalysts as well as the reaction temperature, were established as no data were available in scientific literature. The chemical reactions occurring during the foam generation process were monitored in situ by attenuated total reflectance-FTIR spectroscopy. The kinetics of the foam generation was fitted to an nth order model and the data showed that the foaming process adjusted to a first-order kinetics. The physical changes as pressure, foam height, and dielectric polarization were monitored by the FOAM software (FOAMAT). According to these parameters, the foaming process was divided into four steps: bubble growth, bubble packing, cell opening, and final curing.

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