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Williams Portal, NatalieORCID iD iconorcid.org/0000-0002-0033-1841
Publications (10 of 32) Show all publications
Flansbjer, M., Williams Portal, N., Hall, S. & Engqvist, J. (2019). Analysis of Fiber-matrix Interaction in FRC using X-ray Tomography and Digital Volume Correlation. In: proc. of 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X): . Paper presented at 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X), Bayonne, France, 23-26 June 2019. Bayonne, France: International Association of Fracture Mechanics for Concrete and Concrete Structures
Open this publication in new window or tab >>Analysis of Fiber-matrix Interaction in FRC using X-ray Tomography and Digital Volume Correlation
2019 (English)In: proc. of 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X), Bayonne, France: International Association of Fracture Mechanics for Concrete and Concrete Structures , 2019, , p. 8Conference paper, Published paper (Refereed)
Abstract [en]

Fiber pull-out is generally considered to be the dominating failure mechanism in fiber reinforced concrete (FRC). Accordingly, pull-out tests are typically performed to characterize the fiber-matrix interaction. However, little direct insight can be gained on the actual mechanisms ofthe pull-out from such a test. Deeper understanding could however be gained through the addition of non-destructive techniques to pull-out tests to enable the visualization and quantification of the mechanical interaction. Pull-out mechanisms for different common steel fibers were investigated using adapted pull-out tests performed in-situ in an X-ray micro tomography (µXRT). High resolution volume images from the µXRT scans enable clear visualization of aggregates, pores, fiber and fiber-matrix interface. Furthermore, the natural density speckle pattern from aggregate distribution and pores was found to be suitable for Digital Volume Correlation (DVC) analysis. From the DVC results it was possible to visualize and quantify the strain distribution in the matrix around the fiber at different load levels up to final failure, being marked by either pull-out or fiber rupture. The load transfer mechanism was initially dominated by shear along the fiber. As the load increased, slip occurred in the end-hook region and mechanical locking became the governing mechanism. This study demonstrates that strain measurements within the concrete matrix and passive end-slip can be obtained successfully using µXRT imaging and DVC analysis, which leads to an increased understanding of the interaction mechanisms in fiber reinforced concrete under mechanical loading.

Place, publisher, year, edition, pages
Bayonne, France: International Association of Fracture Mechanics for Concrete and Concrete Structures, 2019. p. 8
Keywords
Fiber reinforced concrete; pull-out behavior; X-ray Computed Tomography, Digital Volume Correlation
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-39953 (URN)10.21012/FC10.233198 (DOI)
Conference
10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X), Bayonne, France, 23-26 June 2019
Available from: 2019-09-23 Created: 2019-09-23 Last updated: 2019-09-27Bibliographically approved
Williams Portal, N. & Flansbjer, M. (Eds.). (2019). Assessment of Fire Exposed Concrete with Full-field Strain Determination and Predictive Modelling. Paper presented at 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X). Bayonne, France: International Association of Fracture Mechanics for Concrete and Concrete Structures
Open this publication in new window or tab >>Assessment of Fire Exposed Concrete with Full-field Strain Determination and Predictive Modelling
2019 (English)Conference proceedings (editor) (Refereed)
Abstract [en]

A condition assessment of civil engineering structures is typically performed after the occurrence of a fire incident to determine the remedial actions required out of a structural point of view. A condition assessment is based on the mapping of damage on the given structure, which is traditionally executed via methods that yield indirect results related to surface and/or geometric properties. To be able to predict the accurate fire resistance performance of a given structure, it is most suitable to apply a mapping method which can be directly coupled to the change in material properties of concrete at high temperatures. The aim of this study is to explore the potential of applying an innovative damage mapping methodology directly coupled to the change in material properties of concrete at high temperatures. This methodology consists of optical full-field strain measurements based on Digital Image Correlation (DIC) coupled with a predictive model based on finite-element analysis (FEA). An experimental study was firstly conducted to expose concrete slabs to a standard fire curve. Subsequently, compression tests were performed on drilled cores taken from the damaged induced specimens, all while optically measuring the full-field strain on a specimen surface. As a preliminary step, an FE model of a fire exposed core was developed based on input data from standard temperature-dependent properties. The analysis consisted of a sequentially coupled thermal stress analysis to solve the multiphysics problem. The model was able to capture the temperature distribution in the concrete with enough certainty given the choice of input data. The resulting strain along the height of the core was also comparable to the experimental optical strain measurements, particularly as the distance increased from the fire exposed surface. These results can be practical when assessing the required strengthening actions to restore the load carrying capacity and durability of the concrete structure.

Place, publisher, year, edition, pages
Bayonne, France: International Association of Fracture Mechanics for Concrete and Concrete Structures, 2019. p. 10
Keywords
concrete, fire, damage assessment, digital image correlation, finite element analysis
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:ri:diva-39952 (URN)10.21012/FC10.232063 (DOI)
Conference
10th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-X)
Available from: 2019-09-23 Created: 2019-09-23 Last updated: 2019-09-27Bibliographically approved
Gustavsson, B., Williams Portal, N. & Antonsson, U. (2019). Skydd av befintliga byggnadsfasader – en förstudie.
Open this publication in new window or tab >>Skydd av befintliga byggnadsfasader – en förstudie
2019 (Swedish)Report (Other academic)
Abstract [en]

© RISE Research Institutes of Sweden

Abstract

Protection of existing building façades

– preliminary study

General concepts related to explosive loading and associated effects on buildings have been discussed. Requirements pertaining to the explosive and vehicle impact resistance of various building components were also elaborated along with the mention of relevant safety measures. Assessing the explosive resistance of existing buildings, with a focus on facades, was discussed in combination with design requirements and potential strength-ening approaches. Relevant literature covering the developments of this field was re-ferred to throughout the report.

It was suggested that a future quality assurance method be devised with the title of

"By-ggaS – Method for quality assurance of safe buildings". ByggaS is a method of working with safety issues related to the entire construction process. This encompasses quality assurance requirements (phased), planning and production. With the help of quality management routines and checklists, this method ensures that quality is met in each process through continuous documenting, communicating, checking and verifying the work. Overall, ByggaS allows for an increased quality and safety of the building to be delivered. It facilitates the work of individual construction projects and provides a more efficient process by offering the project participants a complete working method with associated tools/templates.

Series
RISE Rapport ; 2019:24
Keywords
security, quality, critical infrastructure, democracy, enforcement, building technology, fortification, façade, structural protection, antagonist, threat
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38990 (URN)978-91-88907-50-9 (ISBN)
Available from: 2019-06-13 Created: 2019-06-13 Last updated: 2019-06-13Bibliographically approved
Williams Portal, N. & Boubitsas, D. (2019). Sprickor i betong.
Open this publication in new window or tab >>Sprickor i betong
2019 (Swedish)Report (Other academic)
Abstract [en]

The Swedish Fortifications Agency

’s (FORTV) property stock consists of numerous concrete structures built both above and below rock. Some of these structures have experienced cracking overtime which, in turn, can lead to subsequent problems such as reinforcement corrosion and deterioration of structural performance. Due to the fact that in many cases there are building requirements related to protection against forced entry and weapon attacks, it is of great importance for FORTV to gain an understanding of how cracks are developed, the significance of the crack development, how do cracks affect the performance, as well as how cracks can be remediated. A similar project, with a focus on so-called access protection, has earlier been managed by FORTV. During the project, it was ascertained that there is inadequate knowledge pertaining to crack repair.

The goals of this project were the following:

  • Suggest a method or a tool to evaluate the extent of cracking in concrete structures which are included in protective facilities.
  • Describe which parameters can initiate cracking.
  • Describe repair methods to reinstate the functionality of concrete structures.

Cracking naturally takes place during the normal use of a concrete structure without influencing

the structure’s functionality given that it is designed correctly. However, there are other mechanisms which can initialize cracking in concrete structures. These mechanisms take place during various time periods (hardening, after hardening and

during the service life). Three crack groups have been identified accordingly: a) cracks due to poor workmanship, b) cracks due to chemical deterioration mechanisms and c) loading cracks.

Damage identification and a condition assessment can be conducted in different stages to determine the extent of cracking. It is firstly recommended to review the existing documentation coupled to the structure, followed by a preliminary inspection (visual), additional non-destructive testing and lastly destructive testing. Repairs are selected according to the source of the damage, it is to say concrete defects or corroded reinforcement. In addition, the functionality requirements for the structure shall be evaluated and the selected methods shall be assessed according to e.g. lifespan and cost.

Publisher
p. 33
Series
RISE Rapport
Keywords
Concrete, crack development; reinforcement; damage identification, condition assessment, non-destructive testing (NDT), repair
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37811 (URN)978-91-88907-47-9 (ISBN)
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-02-21Bibliographically approved
Bedon, C., Honfi, D., Machalická, K. V., Eliášová, M., Vokáč, M., Kozłowski, M., . . . Williams Portal, N. (2019). Structural characterisation of adaptive facades in Europe – Part I: Insight on classification rules, performance metrics and design methods. Journal of Building Engineering, 25
Open this publication in new window or tab >>Structural characterisation of adaptive facades in Europe – Part I: Insight on classification rules, performance metrics and design methods
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2019 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 25Article in journal (Refereed) Epub ahead of print
Abstract [en]

Adaptive facades are increasingly used in modern buildings, where they can take the form of complex systems and manifest their adaptivity in several ways. Adaptive envelopes must meet the requirements defined by structural considerations, which include structural safety, serviceability, durability, robustness and fire safety. For these novel skins, based on innovative design solutions, experimentation at the component and / or assembly level is required to prove that these requirements are fulfilled. The definition of appropriate metrics is hence also recommended. A more complex combination of material-related, kinematic, geometrical and mechanical aspects should in fact be properly taken into account, compared to traditional, static facades. Accordingly, specific experimental methods and regulations are required for these novel skins. As an outcome of the European COST Action TU1403 ‘Adaptive facades network’ - ‘Structural’ Task Group, this paper collects some recent examples and design concepts of adaptive systems, specifically including a new classification proposal and the definition of some possible metrics for their structural performance assessment. The aim is to provide a robust background and detailed state-of-the-art information for these novel structural systems, towards the development of standardised and reliable procedures for their mechanical and thermo-physical characterisation.

Keywords
Adaptive facades, Structural performance parameters, Metrics, Experimentation, Design
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38668 (URN)10.1016/j.jobe.2019.02.013 (DOI)
Available from: 2019-05-10 Created: 2019-05-10 Last updated: 2019-05-10Bibliographically approved
Bedon, C., Honfi, D., Machalická, K., Eliášová, M., Vokáč, M., Kozłowski, M., . . . Williams Portal, N. (2019). Structural characterisation of adaptive facades in Europe - Part II: Validity of conventional experimental testing methods and key issues. Journal of Building Engineering, 25, Article ID 100797.
Open this publication in new window or tab >>Structural characterisation of adaptive facades in Europe - Part II: Validity of conventional experimental testing methods and key issues
Show others...
2019 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 25, article id 100797Article in journal (Refereed) Published
Abstract [en]

Given their intrinsic features, adaptive facades are required to satisfy rigid structural performances, in addition to typical insulation, thermal and energy requirements. These include a minimum of safety and serviceability levels under ordinary design loads, durability, robustness, fire resistance, capacity to sustain severe seismic events or other natural hazards, etc. The overall design process of adaptive facades may include further challenges and uncertainties especially in the case of complex assemblies, where multiple combinations of material-related phenomena, kinematic effects, geometrical and mechanical characteristics could take place. In this context, experimental testing at the component and/or at the full-scale assembly level has a fundamental role, to prove that all the expected performance parameters are properly fulfilled. Several standards and guideline documents are available in the literature, and provide recommendations and procedures in support of conventional testing approaches for the certification and performance assessment of facades. These documents, however, are specifically focused on ordinary, static envelopes, and no provisions are given for the experimental testing of dynamic, adaptive skins. In this regard, it is hence expected that a minimum of conventional experimental procedures may be directly extended from static to dynamic facades. However, the validity of standardized procedures for adaptive skins is still an open issue. Novel and specific experimental approaches are then necessarily required, to assess the structural characteristics of adaptive facades, depending on their properties and on the design detailing. In this paper, existing fundamental standards for testing traditional facades are first recalled and commented. Special care is spent for the validity and reliability of conventional testing methods for innovative, adaptive envelopes, including a discussion on selected experimental methods for facade components and systems. Non-conventional testing procedures which may be useful for adaptive skins are then also discussed in the paper, as resulting from the research efforts of the European COST Action TU1403 ‘Adaptive facades network’ - ‘Structural’ Task Group.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Adaptive facades, Experimental facilities, Experimental testing, Metrics, Structural performance parameters, Testing methods, Fire resistance, Seismic design, Structural analysis, Testing, Thermal insulation, Structural performance, Testing method, Facades
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38956 (URN)10.1016/j.jobe.2019.100797 (DOI)2-s2.0-85065988691 (Scopus ID)
Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2019-06-10Bibliographically approved
Flansbjer, M., Williams Portal, N. & Vennetti, D. (2019). Verification of the structural performance of textile reinforced reactive powder concrete sandwich facade elements. Applied Sciences, 9(12), Article ID 456.
Open this publication in new window or tab >>Verification of the structural performance of textile reinforced reactive powder concrete sandwich facade elements
2019 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 12, article id 456Article in journal (Refereed) Published
Abstract [en]

As a part of the SESBE (Smart Elements for Sustainable Building Envelopes) project, non-load bearing sandwich elements were developed with Textile Reinforced Reactive Powder Concrete (TRRPC) for outer and inner facings, Foam Concrete (FC) for the insulating core and Glass Fiber Reinforced Polymer (GFRP) continuous connectors. The structural performance of the developed elements was verified at various levels by means of a thorough experimental program coupled with numerical analysis. Experiments were conducted on individual materials (i.e., tensile and compressive tests), composites (i.e., uniaxial tensile, flexural and pull-out tests), as well as components (i.e., local anchorage failure, shear, flexural and wind loading tests). The experimentally yielded material properties were used as input for the developed models to verify the findings of various component tests and to allow for further material development. In this paper, the component tests related to local anchorage failure and wind loading are presented and coupled to a structural model of the sandwich element. The validated structural model provided a greater understanding of the physical mechanisms governing the element's structural behavior and its structural performance under various dead and wind load cases. Lastly, the performance of the sandwich elements, in terms of composite action, was shown to be greatly correlated to the properties of the GFRP connectors, such as stiffness and strength

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
Finite element analysis (FEA), Foam concrete (FC), Reactive powder concrete (RPC), Sandwich elements, Textile reinforced concrete (TRC), Wind loading
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-39376 (URN)10.3390/app9122456 (DOI)2-s2.0-85068191709 (Scopus ID)
Available from: 2019-07-08 Created: 2019-07-08 Last updated: 2019-07-08Bibliographically approved
Flansbjer, M., Williams Portal, N., Hall, S. & Engqvist, J. (2018). Analysis of Failure Modes in Fiber Reinforced Concrete Using X-rayTomography and Digital Volume Correlation. In: : . Paper presented at 18th International Conference on Experimental Mechanics, Brussels, Belgium, 1–5 July 2018..
Open this publication in new window or tab >>Analysis of Failure Modes in Fiber Reinforced Concrete Using X-rayTomography and Digital Volume Correlation
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Pull-out mechanisms for different common steel fibers were investigatedusing adapted pull-out tests performed in-situ in an x-ray micro tomograph(µXRT). High-resolution volume images from the µXRT scans enable clearvisualization of aggregates, pores, the fiber and the fiber-matrix interface.Furthermore, the natural density speckle pattern from aggregate distributionand pores was found suitable for Digital Volume Correlation (DVC) analysis.From the DVC results it was possible to visualize and quantify the straindistribution in the matrix around the fiber at the different load levels up tofinal failure, being marked by either pull-out or fiber rupture. This studydemonstrates that strain measurements within the concrete matrix can beobtained successfully using µXRT imaging and DVC analysis, which leads to anincreased understanding of the interaction mechanisms in fibre reinforcedconcrete under mechanical loading.

Keywords
Fiber reinforced concrete; pull-out behavior; X-ray Computed Tomography, Digital Volume Correlation
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-35557 (URN)
Conference
18th International Conference on Experimental Mechanics, Brussels, Belgium, 1–5 July 2018.
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-05Bibliographically approved
Williams Portal, N., Flansbjer, M. & Mueller, U. (Eds.). (2018). Analysis of the Flexural Behavior of Textile Reinforced Reactive Powder Concrete Sandwich Elements Using Optical Measurements. Paper presented at 18th International Conference on Experimental Mechanics, Brussels, Belgium, 1–5 July 2018.. MDPI
Open this publication in new window or tab >>Analysis of the Flexural Behavior of Textile Reinforced Reactive Powder Concrete Sandwich Elements Using Optical Measurements
2018 (English)Conference proceedings (editor) (Refereed)
Abstract [en]

Prefabricated and non-load bearing sandwich façade elements were developed using Textile Reinforced Reactive Powder Concrete (TRRPC) along with low density Foamed Concrete (FC) and Glass Fiber Reinforced Polymer (GFRP) continuous connecting devices. Four-point bending tests were performed on large-scale TRRPC sandwich element beams to characterize the structural performance, which included the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on Digital Image Correlation (DIC) were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behavior of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
Reactive Powder Concrete; Textile Reinforced Concrete; Foam Concrete; Glass Fiber
National Category
Building Technologies
Identifiers
urn:nbn:se:ri:diva-33930 (URN)10.3390/ICEM18-05221 (DOI)
Conference
18th International Conference on Experimental Mechanics, Brussels, Belgium, 1–5 July 2018.
Funder
EU, FP7, Seventh Framework Programme, 608950
Available from: 2018-06-11 Created: 2018-06-11 Last updated: 2018-08-16Bibliographically approved
Flansbjer, M., Williams Portal, N., Vennetti, D. & Mueller, U. (2018). Composite Behaviour of Textile Reinforced Reactive Powder Concrete Sandwich Façade Elements. International Journal of Concrete Structures and Materials, 12(1), Article ID 71.
Open this publication in new window or tab >>Composite Behaviour of Textile Reinforced Reactive Powder Concrete Sandwich Façade Elements
2018 (English)In: International Journal of Concrete Structures and Materials, ISSN 1976-0485, E-ISSN 2234-1315, Vol. 12, no 1, article id 71Article in journal (Refereed) Published
Abstract [en]

Within the EC funded project smart elements for sustainable building envelopes, carbon textile reinforcement was incorporated into reactive powder concrete, namely textile reinforced reactive powder concrete (TRRPC), to additionally improve the post-cracking behaviour of the cementitious matrix. This high-performance composite material was included as outer and inner façade panels in prefabricated and non-load bearing sandwich elements along with low density foamed concrete (FC) and glass fibre reinforced polymer continuous connecting devices. Experiments and finite element analysis (FEA) were applied to characterize the structural performance of the developed sandwich elements. The mechanical behaviour of the individual materials, components and large-scale elements were quantified. Four-point bending tests were performed on large-scale TRRPC-FC sandwich element beams to quantify the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on digital image correlation were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behaviour of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels. As for the FEA, the applied modelling approach was found to accurately describe the stiffness of the sandwich elements at lower load levels, while describing the stiffness in a conservative manner after the occurrence of connector failure mechanisms. © 2018, The Author(s).

Keywords
finite element analysis (FEA), foam concrete (FC), four-point bending test, reactive powder concrete (RPC), sandwich elements, textile reinforced concrete (TRC), Bending tests, Cracks, Fiber reinforced plastics, Finite element method, Intelligent buildings, Optical correlation, Reinforced concrete, Sandwich structures, Stiffness, Structural analysis, Textiles, Foam concretes, Reactive powder concrete, Sandwich element, Textile reinforced concretes, Failure (mechanical)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36594 (URN)10.1186/s40069-018-0301-4 (DOI)2-s2.0-85057099836 (Scopus ID)
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2018-12-06Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0033-1841

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