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Publications (10 of 15) Show all publications
Björngrim, N., Fjellström, P.-A. & Hagman, O. (2017). Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges. BioResources, 12(4), 7218-7227
Open this publication in new window or tab >>Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges
2017 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 4, p. 7218-7227Article in journal (Refereed) Published
Abstract [en]

The biggest threats to the longevity of a timber bridge are rot and decay. Wood protection by design, inspections, and monitoring of the bridge for elevated moisture content will ensure that the full service life of the structure can be achieved. Today's sensors for moisture content measurements are limited in their functionality and range. This paper presents a sensor that can be both factory installed and retrofitted, which can measure the moisture content through the cross-section of the member in a timber bridge. The sensor has been mounted on Sundbron bridge during manufacturing and retrofitted on Gislaved bridge. The ensuing measurements helped to adjust a design flaw on Gislaved bridge. Monitoring of Sundbron showed that the bridge deck dried up after the bridge had been exposed to sleet and snow during the on-site assembly of the stress laminated bridge deck

Place, publisher, year, edition, pages
North Carolina State University, 2017
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63538 (URN)10.15376/biores.12.4.7218-7227 (DOI)000422879900024 ()2-s2.0-85032702721 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-15 (andbra)

Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-05-18Bibliographically approved
Björngrim, N. (2017). Monitoring and Inspections of Timber Bridges: Moisture Content Measurements Adapted for Large Timber Constructions. (Doctoral dissertation). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Monitoring and Inspections of Timber Bridges: Moisture Content Measurements Adapted for Large Timber Constructions
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2017
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63540 (URN)978-91-7583-918-9 (ISBN)978-91-7583-919-6 (ISBN)
Public defence
2017-09-22, Hörsal A, Skellefteå, 09:00 (English)
Opponent
Supervisors
Available from: 2017-05-30 Created: 2017-05-26 Last updated: 2018-05-18Bibliographically approved
Björngrim, N., Fjellström, P.-A. & Hagman, O. (2017). Resistance measurements to find high moisture content inclusions adapted for large timber bridge cross-sections. BioResources, 12(2), 3570-3582
Open this publication in new window or tab >>Resistance measurements to find high moisture content inclusions adapted for large timber bridge cross-sections
2017 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 2, p. 3570-3582Article in journal (Refereed) Published
Abstract [en]

One challenge of monitoring and inspecting timber bridges is the difficulty of measuring the moisture content anywhere other than close to the surface. Damage or design mistakes leading to water penetration might not be detected in time, leading to costly repairs. By placing electrodes between the glulam beams, the moisture content through the bridge deck can be measured. Due to the logarithmic decrease of the resistance in wood as a function of electrode length, the model must be calibrated for measurement depth. Two models were created: one for electrode lengths of 50 mm and one for electrode lengths up to 1355 mm. The model for short electrodes differed by no more than 1 percentage points compared with the oven dry specimens. The model for long electrodes differed up to 2 percentage points for lengths up to 905 mm, and over that it could differ up to 4 percentage points.

Place, publisher, year, edition, pages
North Carolina State University, 2017
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63537 (URN)10.15376/biores.12.2.3570-3582 (DOI)000402883700098 ()2-s2.0-85018882673 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-05-30 (andbra)

Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-07-10Bibliographically approved
Björngrim, N., Hagman, O. & Wang, X. (. (2016). Moisture Content Monitoring of a Timber footbridge (ed.). BioResources, 11(2), 3904-3913
Open this publication in new window or tab >>Moisture Content Monitoring of a Timber footbridge
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, p. 3904-3913Article in journal (Refereed) Published
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-8165 (URN)10.15376/biores.11.2.3904-3913 (DOI)2-s2.0-84965178404 (Scopus ID)6a1c5eb0-a974-485c-bf86-4d05f781ef85 (Local ID)6a1c5eb0-a974-485c-bf86-4d05f781ef85 (Archive number)6a1c5eb0-a974-485c-bf86-4d05f781ef85 (OAI)
Note

Validerad; 2016; Nivå 2; 20150126 (nicbjo)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Björngrim, N., Hagman, O. & Wang, A. (2016). Multivariate Screening of the Weather Effect on Timber Bridge Movements (ed.). BioResources, 11(4), 8890-8899
Open this publication in new window or tab >>Multivariate Screening of the Weather Effect on Timber Bridge Movements
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8890-8899Article in journal (Refereed) Published
Abstract [en]

Monitoring displacements and weather impact of complex structures such as a large cable stayed footbridge generates large amount of data. In order to extract, visualize and classify health-monitoring data to get a better comprehension multivariate statistical analysis is a powerful tool. This paper is a screening to evaluate if principal component analysis is useful on health monitoring data. Principal component analysis (PCA) and projections to latent structures by means of partial least squares (PLS) modeling were used to achieve a better understanding of the complex interaction between bridge dynamics and weather effects. The results show that principal component analysis (PCA) give good overview of the collected data, and PLS modeling show that winds from east and west best explain bridge movements.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-7218 (URN)10.15376/biores.11.4.8890-8899 (DOI)000391801300058 ()58c8f6c1-1179-4252-9da2-f01a1369859b (Local ID)58c8f6c1-1179-4252-9da2-f01a1369859b (Archive number)58c8f6c1-1179-4252-9da2-f01a1369859b (OAI)
Note

Validerad; 2017; Nivå 2; 2017-02-10 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Björngrim, N. (2015). Monitoring of a Timber Footbridge (ed.). (Licentiate dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>Monitoring of a Timber Footbridge
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Alvsbacka Bridge was erected in the summer of 2011. During the planningof the construction researchers from LTU and SP Tr¨a designed ahealth monitoring system that constantly measures different parameterson the bridge. The motivation for health monitoring systems is several:Bridge safety, verification of the design and complement during inspections.Health monitoring of infrastructure is common, many bridges areequipped with health monitoring systems. Timber bridges are rarely monitored.This research project is looking to answer what type of sensorsis suitable for bridges in order to make them smart. The smartness ofthe bridge in this case is to help optimize bridge maintenance, assurethe service life and build knowledge about measurements on large timberconstructions. This thesis presents the monitoring system of the bridge,moisture content monitoring and studies the weather effects on the bridge.The monitoring system of ¨Alvsbacka Bridge consists of several differentsensor systems that continuously measure temperature, moisture content,movements, cable forces, wind velocity, wind direction. The monitoringsystem had some problems with sensors not communicating. Long termmoisture content monitoring show anticipated results and the bridge deckmovements are close to the theoretical values.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2015. p. 87
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Other Mechanical Engineering
Research subject
Wood Products Engineering
Identifiers
urn:nbn:se:ltu:diva-17617 (URN)44fbe73c-7784-4803-b86b-3bf21e98375c (Local ID)978-91-7583-218-0 (ISBN)978-91-7583-219-7 (ISBN)44fbe73c-7784-4803-b86b-3bf21e98375c (Archive number)44fbe73c-7784-4803-b86b-3bf21e98375c (OAI)
Note
Godkänd; 2015; 20150126 (nicbjo)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-18Bibliographically approved
Cibecchini, D., Björngrim, N., Sousa, H., Jorge, M. & Branco, J. (2015). Repairing of a timber truss through two different techniques using timber elements and screwed metal plates (ed.). In: (Ed.), Historical Earthquake-Resistant Timber Framing in the Mediterranean Area: HEaRT 2015. Paper presented at International Conference on Historic Earthquake-Resistant Timber Frames in the Mediterranean Region : 02/12/2015 - 04/12/2015 (pp. 371-381).
Open this publication in new window or tab >>Repairing of a timber truss through two different techniques using timber elements and screwed metal plates
Show others...
2015 (English)In: Historical Earthquake-Resistant Timber Framing in the Mediterranean Area: HEaRT 2015, 2015, p. 371-381Conference paper, Published paper (Refereed)
Abstract [en]

Structural reinforcement of timber buildings may be needed due to different reasons such as change of use, deterioration, lack of maintenance, exceptional damaging incidents or loading, to comply with regulatory changes and being retrofitted, or interventions to increase structural resistance.In this work, two different techniques were considered for repair of a timber truss, subjected only to vertical loads, that was previously assessed on laboratory (test facilities of University of Minho) and taken up to failure during a load-carrying test. A collar beam truss, with more than one hundred years, was tested carrying a vertical point load on each main rafter. Failure of the timber truss was located in the sections of the rafters near the loading positions by bending.Repairing techniques, based on the use of timber elements for one of the rafters and on screwed metal plates for the other rafter, were evaluated and compared to the original unstrengthened condition. The efficiency of the combined repairing techniques was evaluated taking into consideration the structural performance of the collar truss, namely its displacement and ultimate load capacity.In this paper, the results of the experimental tests are discussed attending to the analytical calculation of the contribution of the repairing techniques. Also, the different failure scenarios, for original and strengthened truss, were analyzed and compared.

Series
Lecture Notes in Civil Engineering, ISSN 2366-2557 ; 1
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-38445 (URN)10.1007/978-3-319-39492-3_31 (DOI)000392437200031 ()cda7e3a3-904d-49f6-9bdb-cb81182f3535 (Local ID)978-3-319-39491-6 (ISBN)978-3-319-39492-3 (ISBN)cda7e3a3-904d-49f6-9bdb-cb81182f3535 (Archive number)cda7e3a3-904d-49f6-9bdb-cb81182f3535 (OAI)
Conference
International Conference on Historic Earthquake-Resistant Timber Frames in the Mediterranean Region : 02/12/2015 - 04/12/2015
Note

Godkänd; 2015; 20151201 (nicbjo)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-07-10Bibliographically approved
Wang, X. (., Hagman, O., Björngrim, N. & Elfgren, L. (2013). Engineered wood in cold climate: application to monitoring of a new Swedish suspension bridge (ed.). Paper presented at International Conference on Advances of Civil Infrastructure Engineering : 15/09/2012 - 16/09/2012. Advanced Materials Research, 639-640, 96-104
Open this publication in new window or tab >>Engineered wood in cold climate: application to monitoring of a new Swedish suspension bridge
2013 (English)In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 639-640, p. 96-104Article in journal (Refereed) Published
Abstract [en]

Engineered wood is increasingly used in large structures in Europe, though little is known of its behavior in cold climate. This paper presents the structural health monitoring (SHM) system of a newly built suspension bridge with a deck of glulam timber as well as a bond stability study regarding cold climate performance of engineered wood. The bridge is located in Skellefteå in northern Sweden, and it connects two parts of the city situated on opposite shores of the Skellefteå river. In this ongoing study of the timber-bridge, a structural health monitoring system is employed to verify structural design and long-term performance. This 130m-span bridge is monitored using GNSS receivers, MEMS accelerometers, laser positioning systems, wireless moisture content sensors, strain gauges and weather stations. Data from the monitoring systems is analyzed regarding accuracy, complexity, costs and reliability for long time use. Engineered wood application in bridges, sports centers and timber buildings are discussed. Bond stability of glulam structures in cold climate is also examined in a range of experiments ranging from small glued wood joints to full size glulam bridge performance over time. From an engineered wood material point of view, the study is relevant to cold regions such as Scandinavia, Canada, Alaska, Russia, and the northern parts of China and Japan etc. The engineered wood constructions in these areas will be exposed to low temperature in a quite long period each year. The goal is to determine how engineered wood behaves when exposed to temperatures between 20 °C to -60 °C.

Keywords
Civil engineering and architecture - Building engineering, Träkonstruktioner, Kallt klimat, Samhällsbyggnadsteknik och arkitektur - Byggnadsteknik
National Category
Other Mechanical Engineering Infrastructure Engineering
Research subject
Wood Products Engineering; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-27461 (URN)10.4028/www.scientific.net/AMR.639-640.96 (DOI)000320199700007 ()2-s2.0-84873148688 (Scopus ID)0ebc0cb7-36c5-4113-8a8e-d1aeee80ca4d (Local ID)0ebc0cb7-36c5-4113-8a8e-d1aeee80ca4d (Archive number)0ebc0cb7-36c5-4113-8a8e-d1aeee80ca4d (OAI)
Conference
International Conference on Advances of Civil Infrastructure Engineering : 15/09/2012 - 16/09/2012
Note
Validerad; 2013; 20121123 (elfgren); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Hagman, O. & Björngrim, N. (2013). Projekt: Smart träbro i smart stad. Paper presented at .
Open this publication in new window or tab >>Projekt: Smart träbro i smart stad
2013 (Swedish)Other (Other (popular science, discussion, etc.))
Abstract [sv]

Smart Träbro i Smart Stad är ett projekt som genom gränsöverskridande samarbete ska ta fram data, modeller och verktyg för att mäta prestanda och kvalitet på en träbrokonstruktion. Genom ett samarbete mellan Luleå Tekniska Universitet (LTU) och Skellefteå kommun skapas exklusiva förutsättningar för att mäta och analysera träkonstruktioner i syfte att stärka konkurrenskraften för trävaruindustrin.

National Category
Other Mechanical Engineering
Research subject
Wood Products Engineering
Identifiers
urn:nbn:se:ltu:diva-36059 (URN)4bdef448-ddc0-4e97-bf45-e929425f4503 (Local ID)4bdef448-ddc0-4e97-bf45-e929425f4503 (Archive number)4bdef448-ddc0-4e97-bf45-e929425f4503 (OAI)
Note

Status: Avslutat; Period: 01/01/2010 → 31/12/2012; Externt projekt-ID: 348-2013-184

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-18Bibliographically approved
Forsman, S., Laitila, L. & Björngrim, N. (2012). 3-D measuring for an engineer-to-order secondary wood processing industry (ed.). In: (Ed.), Pierre Quenneville (Ed.), World Conference on Timber Engineering, WCTE: Final Papers - Poster presentations. Paper presented at World Conference on Timber Engineering : 15/07/2012 - 19/07/2012 (pp. 498-504). : New Zealand Timber Design Society
Open this publication in new window or tab >>3-D measuring for an engineer-to-order secondary wood processing industry
2012 (English)In: World Conference on Timber Engineering, WCTE: Final Papers - Poster presentations / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 498-504Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
New Zealand Timber Design Society, 2012
National Category
Other Mechanical Engineering
Research subject
Wood Technology; Wood Products Engineering
Identifiers
urn:nbn:se:ltu:diva-28083 (URN)1bcc9fd2-cd0b-458d-b112-322ba088e6ea (Local ID)9781622763054 (ISBN)1bcc9fd2-cd0b-458d-b112-322ba088e6ea (Archive number)1bcc9fd2-cd0b-458d-b112-322ba088e6ea (OAI)
Conference
World Conference on Timber Engineering : 15/07/2012 - 19/07/2012
Note
Godkänd; 2012; 20120629 (samuelfo)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-18Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7076-9494

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