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Publications (10 of 65) Show all publications
Nilsson, M., Nilimaa, J., Emborg, M., Hösthagen, A. & Westerholm, M. (2024). Analysmetodik och materialmodeller vid inmätning av ung betongs egenskaper för beräkning av temperatur, hållfasthet och spänningar under härdningsförlopp. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Analysmetodik och materialmodeller vid inmätning av ung betongs egenskaper för beräkning av temperatur, hållfasthet och spänningar under härdningsförlopp
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2024 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2024. p. 102
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
National Category
Infrastructure Engineering
Research subject
Structural Engineering; Building Materials
Identifiers
urn:nbn:se:ltu:diva-108191 (URN)978-91-8048-611-8 (ISBN)
Projects
Trafikverkets och Anläggning AMAs metoder för undvikande av tidig sprickbildning i betong – nyutveckling med hänsyn till miljökriterier
Funder
Swedish Transport Administration, FOI-BBTSvenska Byggbranschens Utvecklingsfond (SBUF)
Note

Funder: Heidelberg Materials, Cement och Betong

Available from: 2024-06-28 Created: 2024-06-28 Last updated: 2024-07-02Bibliographically approved
Najeh, T., Gamil, Y. & Nilimaa, J. (2024). Forecasting maximum formwork pressure for self-compacting concrete using ARX-Laguerre machine learning model. Developments in the Built Environment, 18, Article ID 100409.
Open this publication in new window or tab >>Forecasting maximum formwork pressure for self-compacting concrete using ARX-Laguerre machine learning model
2024 (English)In: Developments in the Built Environment, ISSN 2666-1659, Vol. 18, article id 100409Article in journal (Refereed) Published
Abstract [en]

Forecasting the maximum pressure exerted by cast-in-place self-compacting concrete (SCC) is a major concern for formwork designers, researchers, and site engineers to accurately design the bearing capacity of the formwork and control the casting rate for safe and fast construction. This article aims to utilize the ARX-Laguerre model, which is a data-driven model to forecast the maximum form pressure. A laboratory instrumented setup was used to cast a 2-m column using SCC made with two different types of cement. A pressure system consisting of four sensors was used to document the pressure during casting. The data were sent to the cloud at every 1-min interval for real-time monitoring. The data were used to develop the model. The results demonstrated that forecasting with the ARX-Laguerre model is highly accurate. The model can forecast the maximum pressure exerted by SCC with less complexity. The model performance was also found to be consistent with insignificant differences between actual experimental results and predicted results. With a recursive and straightforward representation, the resulting model, known as the ARX-Laguerre model, ensures the parameter number reduction. Providing fast prediction of the maximum pressure. The model enables formwork designers to forecast the form pressure to design safe formwork and also helps to control the casting rate when SCC is used.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Formwork, Pressure, Maximum, SCC, Casting rate, Cement types, Forecasting, ARX-Laguerre Model
National Category
Infrastructure Engineering
Research subject
Building Materials; Operation and Maintenance Engineering
Identifiers
urn:nbn:se:ltu:diva-104967 (URN)10.1016/j.dibe.2024.100409 (DOI)2-s2.0-85188842171 (Scopus ID)
Funder
Svenska Byggbranschens Utvecklingsfond (SBUF)
Note

Validerad;2024;Nivå 2;2024-04-04 (signyg);

Full text license: CC BY

Available from: 2024-04-04 Created: 2024-04-04 Last updated: 2024-04-09Bibliographically approved
Nilsson, M., Nilimaa, J., Emborg, M., Hösthagen, A. & Westerholm, M. (2024). Materialdata för beräkning av temperatur, hållfasthet och spänningar – betong med AnlFA-cement, flygaska och slagg. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Materialdata för beräkning av temperatur, hållfasthet och spänningar – betong med AnlFA-cement, flygaska och slagg
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2024 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2024. p. 38
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
National Category
Infrastructure Engineering Other Materials Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-106153 (URN)978-91-8048-597-5 (ISBN)
Projects
Trafikverkets och Anläggning AMAs metoder för undvikande av tidig sprickbildning i betong – nyutveckling med hänsyn till miljökriterier
Available from: 2024-06-10 Created: 2024-06-10 Last updated: 2024-06-10Bibliographically approved
Zhaka, V., Bridges, R., Riska, K., Nilimaa, J. & Cwirzen, A. (2024). Snow effects on brash ice and level ice growth. Journal of Glaciology
Open this publication in new window or tab >>Snow effects on brash ice and level ice growth
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2024 (English)In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652Article in journal (Refereed) Epub ahead of print
Abstract [en]

Brash ice formation and accumulation occur at a faster rate in ship channels, harbours and turning areas compared to the surrounding level ice. Accurate prediction of brash ice thickness plays an important role in addressing operational challenges and optimisation of ice management strategies. This study enhances existing brash ice growth models by considering the effects of snow and accounting for brash ice expulsion towards the sides of ship channels at each passage. To validate the influence of these critical factors on brash ice thickness, three distinct ship channels located in the Bay of Bothnia, Luleå, Sweden, were investigated. For two test channels formed for study purposes, the slower growth rate of brash ice caused by snow insulation was more prominent than the brash ice growth acceleration caused by the snow–slush–snow ice transformation. In the third channel characterised by frequent navigation, the transformation of slush into snow ice played a more substantial role than snow insulation. In both test channels, the brash ice growth model performed optimally, assuming a 10% expulsion of brash ice sideways at each vessel passage. In the third, wider and more frequently navigated channel, a 1.2% brash ice expelling coefficient predicted well the measured brash ice thicknesses.

Place, publisher, year, edition, pages
Cambridge University Press, 2024
Keywords
ice/atmosphere interactions, sea ice, sea-ice growth and decay, sea-ice modelling, snow physics
National Category
Infrastructure Engineering Water Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-101579 (URN)10.1017/jog.2024.5 (DOI)2-s2.0-85182884600 (Scopus ID)
Funder
Luleå University of Technology
Note

Funder: Total Energies SE, France;

Full text license: CC BY

Available from: 2023-10-05 Created: 2023-10-05 Last updated: 2024-04-18
Nilsson, M., Nilimaa, J., Emborg, M., Hösthagen, A. & Westerholm, M. (2024). Spänningsberäkningar, metodik och kriterier. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Spänningsberäkningar, metodik och kriterier
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2024 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2024. p. 30
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
National Category
Infrastructure Engineering
Research subject
Structural Engineering; Building Materials
Identifiers
urn:nbn:se:ltu:diva-108190 (URN)978-91-8048-610-1 (ISBN)
Projects
Trafikverkets och Anläggning AMAs metoder för undvikande av tidig sprickbildning i betong – nyutveckling med hänsyn till miljökriterier
Funder
Swedish Transport Administration, FOI-BBTSvenska Byggbranschens Utvecklingsfond (SBUF)
Note

Funder: Heidelberg Materials, Cement och Betong

Available from: 2024-06-28 Created: 2024-06-28 Last updated: 2024-07-02Bibliographically approved
Nilimaa, J. & Nilforoush, R. (2023). A Direct Tensile Strength Testing Method for Concrete from Existing Structures. CivilEng, 4(1), 333-344
Open this publication in new window or tab >>A Direct Tensile Strength Testing Method for Concrete from Existing Structures
2023 (English)In: CivilEng, E-ISSN 2673-4109, Vol. 4, no 1, p. 333-344Article in journal (Refereed) Published
Abstract [en]

Tensile strength is a crucial property for the function, safety and durability of all concrete structures. The general procedure to assess the tensile properties of concrete from existing structures is to perform indirect tests and predict the tensile strength based on established empirical relationships. In this study, the direct tensile strength of concrete was investigated using cylindrical specimens. The aim of the study was to propose, test and evaluate a general method for direct tensile tests of concrete from existing structures. A total of 16 specimens were tested under deformation-controlled tensile-loading until failure. The concrete samples were prepared with 10 or 15 mm grooves at mid-height to obtain cracking in the groove region, where the crack-opening sensors were installed. The load and corresponding deformation were recorded continuously during the test to obtain the load–crack-width relationship of the concrete. The tests showed that the method can be used to assess the tensile properties of concrete from existing structures. The study provides important insights regarding the assessment of direct tensile strength of concrete and the results can be used to improve the structural health monitoring of existing structures and thereby ensure their safety and durability.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
assessment, concrete, fracture energy, material properties, structural health monitoring, tensile strength, test methods
National Category
Infrastructure Engineering Building Technologies
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-96635 (URN)10.3390/civileng4010019 (DOI)2-s2.0-85151089700 (Scopus ID)
Note

Validerad;2023;Nivå 1;2023-04-18 (hanlid)

Available from: 2023-04-18 Created: 2023-04-18 Last updated: 2023-04-18Bibliographically approved
Nilimaa, J. & Zhaka, V. (2023). An Overview of Smart Materials and Technologies for Concrete Construction in Cold Weather. Eng, 4(2), 1550-1580
Open this publication in new window or tab >>An Overview of Smart Materials and Technologies for Concrete Construction in Cold Weather
2023 (English)In: Eng, E-ISSN 2673-4117, Vol. 4, no 2, p. 1550-1580Article, review/survey (Refereed) Published
Abstract [en]

Cold weather conditions pose significant challenges to the performance and durability of concrete materials, construction processes, and structures. This paper aims to provide a comprehensive overview of the material-related challenges in cold weather concrete construction, including slow setting, reduced curing rate, and slower strength development, as well as frost damage, early freezing, and freeze–thaw actions. Various innovative materials and technologies may be implemented to address these challenges, such as optimizing the concrete mix proportions, chemical admixtures, supplementary cementitious materials, and advanced construction techniques. The paper also examines the impact of weather-related challenges for personnel, equipment, and machinery in cold environments and highlights the importance of effective planning, communication, and management strategies. Results indicate that the successful implementation of appropriate strategies can mitigate the challenges, reduce construction time, and enhance the performance, durability, and sustainability of concrete structures in cold and freezing temperatures. The paper emphasizes the importance of staying updated about the latest advancements and best practices in the field. Future trends include the development of smart and functional concrete materials, advanced manufacturing and construction techniques, integrated design, and optimization of tools, all with a strong focus on sustainability and resilience.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
concrete, cold construction, engineering challenges, freezing, concrete setting, construction materials
National Category
Construction Management
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-99222 (URN)10.3390/eng4020089 (DOI)2-s2.0-85168668409 (Scopus ID)
Note

Godkänd;2023;Nivå 0;2023-07-18 (sofila)

Available from: 2023-07-18 Created: 2023-07-18 Last updated: 2024-03-07Bibliographically approved
Gamil, Y., Nilimaa, J., Cwirzen, A. & Emborg, M. (2023). Experimental based assessment of formwork pressure theoretical design models for self-compacting concrete. Journal of Building Engineering, 68, Article ID 106085.
Open this publication in new window or tab >>Experimental based assessment of formwork pressure theoretical design models for self-compacting concrete
2023 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 68, article id 106085Article in journal (Refereed) Published
Abstract [en]

Self-Compacting Concrete (SCC) offers favourable properties which help accelerate the casting time, especially in congested reinforced structures but when casting with SCC uncertainty remains a challenge on the behaviour of its formwork pressure. Researchers have introduced several design models to predict pressure and its behaviour. This research aims to assess the design models that have been reported in the literature. The assessment was carried out through a series of rigorous laboratory tests and the results from the tests served as input for the mathematical model evaluation. Twelve concrete columns with 2 m height were cast in the laboratory to study the effect of varying the input parameters in the existing design models. The formwork pressure was documented by a pressure monitoring system, with the capacity to produce instant results for real-time remote monitoring of the pressure development during and after concrete casting. The formwork pressures were calculated according to the current design models and were compared with pressure data acquitted from the laboratory tests. The results showed that the pressure predicted by the design models was typically greater than the pressure observed during the laboratory tests. The DIN18218 design model showed a relatively close approximation of the pressure distribution over the formwork height and casting time. The limitation of the models is observed when the casting rate varies, and models are sensitive to the input parameters. Thus, additional development of the current design models is needed to enable reliable estimations of the pressure, for example, in the case of low and high casting rates. The laboratory tests also showed that high casting rates and high slump flows generate higher pressures whereas higher thixotropy results in faster pressure reduction during construction.

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Cast in place, Casting rate, Concrete construction, Formwork pressure, Modelling, Self compacting concrete, Slump flow, Thixotropy
National Category
Other Materials Engineering Infrastructure Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-95818 (URN)10.1016/j.jobe.2023.106085 (DOI)001012837700001 ()2-s2.0-85149059320 (Scopus ID)
Funder
Svenska Byggbranschens Utvecklingsfond (SBUF)
Note

Validerad;2023;Nivå 2;2023-03-08 (joosat);

Funder: NCC AB

Licens fulltext: CC BY License

Available from: 2023-03-08 Created: 2023-03-08 Last updated: 2024-03-07Bibliographically approved
Nilimaa, J., Gamil, Y. & Zhaka, V. (2023). Formwork Engineering for Sustainable Concrete Construction. CivilEng, 4(4), 1098-1120
Open this publication in new window or tab >>Formwork Engineering for Sustainable Concrete Construction
2023 (English)In: CivilEng, E-ISSN 2673-4109, Vol. 4, no 4, p. 1098-1120Article in journal (Refereed) Published
Abstract [en]

This study provides a comprehensive review of the engineering challenges of formwork in concrete construction. The paper investigates different formwork systems, their design based on form pressure, and the difficulties of form stripping. Alternative binders are gaining more and more interest by opening new opportunities for sustainable concrete materials and their impact on form pressure and concrete setting is also investigated in this paper. The discussion involves several engineering challenges such as sustainability, safety, and economy, while it also explores previous case studies, and discusses future trends in formwork design. The findings pinpoint that choosing an appropriate formwork system depends significantly on project-specific constraints and that the development of innovative materials and technologies presents significant benefits but also new challenges, including the need for training and regulation. Current trends in formwork design and use show promising possibilities for the integration of digital technologies and the development of sustainable and ‘smart’ formwork systems. Continued research within the field has the possibility to explore new formwork materials and technologies, which will contribute to the implementation of more effective and sustainable practices in concrete construction.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
formwork systems, concrete construction, form pressure, form stripping, alternative binders, sustainability, formwork design, digital technologies
National Category
Infrastructure Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-103523 (URN)10.3390/civileng4040060 (DOI)2-s2.0-85180426136 (Scopus ID)
Funder
Swedish Research Council FormasLuleå University of TechnologySvenska Byggbranschens Utvecklingsfond (SBUF)
Note

Godkänd;2024;Nivå 0;2024-02-26 (signyg);

Full text license: CC BY

Available from: 2024-01-08 Created: 2024-01-08 Last updated: 2024-04-19Bibliographically approved
Gamil, Y., Nilimaa, J., Najeh, T. & Cwirzen, A. (2023). Formwork pressure prediction in cast-in-place self-compacting concrete using deep learning. Automation in Construction, 151, Article ID 104869.
Open this publication in new window or tab >>Formwork pressure prediction in cast-in-place self-compacting concrete using deep learning
2023 (English)In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 151, article id 104869Article in journal (Refereed) Published
Abstract [en]

The prediction of formwork pressure exerted by self-compacting concrete (SCC) remains a challenge not only to researchers but also to engineers and contractors on the construction site. This article aims to utilize shallow neural networks (SNN) and deep neural networks (DNN) using Long Short-Term Memory (LSTM) approach to develop a prediction model based on real-time data acquitted from controllable laboratory testing series. A test setup consisting of a two-meter-high column, ø160 mm, was prepared and tested in the laboratory. A digital pressure monitoring system was used to collect and transfer the data to the cloud on a real-time basis. The pressure was monitored during- and after casting, following the pressure build-up and reduction, respectively. The two main parameters affecting the form pressure, i.e., casting rate and slump flow, were varied to collect a wide range of input data for the analysis. The proposed model by DNN was able to accurately predict the pressure behavior based on the input data from the laboratory tests with high-performance indicators and multiple hidden layers. The results showed that the pressure is significantly affected by the casting rate, while the slump flow had rather lower impact. The proposed model can be a useful and reliable tool at the construction site to closely predict the pressure development and the effects of variations in casting rate and slump flow. The model provides the opportunity to increase safety and speeding up construction while avoiding costly and time-consuming effects of oversized formwork.

Place, publisher, year, edition, pages
Elsevier B.V., 2023
Keywords
Artificial neural networks, Casting in place, Deep learning, Formwork pressure, Self-compacting concrete
National Category
Other Civil Engineering
Research subject
Building Materials; Operation and Maintenance Engineering
Identifiers
urn:nbn:se:ltu:diva-97045 (URN)10.1016/j.autcon.2023.104869 (DOI)000983677200001 ()2-s2.0-85152943941 (Scopus ID)
Note

Validerad;2023;Nivå 2;2023-05-09 (joosat);

Funder: Swedish Construction Industry SBUF; NCC;

Full text license: CC BY

Available from: 2023-05-09 Created: 2023-05-09 Last updated: 2024-03-07Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1398-6118

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