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  • 1.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Monitoring and Inspections of Timber Bridges: Moisture Content Measurements Adapted for Large Timber Constructions2017Doctoral thesis, comprehensive summary (Other academic)
  • 2.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Monitoring of a Timber Footbridge2015Licentiate 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.

  • 3.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellström, Per-Anders
    Science Partner.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 4, p. 7218-7227Article in journal (Refereed)
    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

  • 4.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fjellström, Per-Anders
    SP - Science Partner.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Resistance measurements to find high moisture content inclusions adapted for large timber bridge cross-sections2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 2, p. 3570-3582Article in journal (Refereed)
    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.

  • 5.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gustafsson, Anders
    SP Trätek.
    Pousette, Anna
    SP Trätek.
    Health monitoring of timber bridges2010In: Proceedings International Conference Timber Bridges: ICTB 2010 / [ed] Lasse Postmyr, Trondheim: Tapir Academic Press , 2010, p. 213-222Conference paper (Refereed)
  • 6.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Gustafsson, Anders
    SP Trätek, SP Technical Research Institute of Sweden, Skellefteå.
    Pousette, Anna
    Luleå tekniska universitet, SP Trätek.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Health monitoring of a cable-stayed timber footbridge2011Conference paper (Refereed)
  • 7.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate Screening of the Weather Effect on Timber Bridge Movements2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8890-8899Article in journal (Refereed)
    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.

  • 8.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wang, Xiaodong (Alice)
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture Content Monitoring of a Timber footbridge2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, p. 3904-3913Article in journal (Refereed)
  • 9.
    Björngrim, Niclas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Laitila, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Forsman, Samuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Model-based production for engineered-to-order joinery products2012In: World Conference on Timber Engineering, WCTE: Final Papers / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 697-701Conference paper (Refereed)
    Abstract [sv]

    När det levereras snickeri-produkter till byggindustrin som utvecklas mot kundorder, tar tillverkaren tar ofta ansvar för hela värdeflödet från offertförfrågan till slutmontering på byggarbetsplatsen. Det finns dock luckor i informationsflödet mellan varje aktör i den interna leveranskedjan, vilket leder till osäkerheter i kvalitet och påverkar processeffektiviteten. En del av problemen kommer från avsaknaden av rutiner för dokumentation av både ändringar och tillägg till den ursprungliga planen. För att kompensera för bristen på dokumentation, hantverkare förlita sig på sina färdigheter och erfarenhet, vilket ofta leder till onödiga och tidskrävande ad hoc-lösningar. Varje aktör i kedjan tillbringar tidåterupptäcka tidigare känd information istället för att hänvisa till dokumentationen. I denna artikel föreslås ett modell-baserad angreppsätt, som utnyttjar informations-och kommunikationsteknik (IKT) för att förbättra information- och kunskapsutbytet genom värdekedjan för bättre spridningav relevant information till berörda aktörer.

  • 10.
    Cibecchini, Daniele
    et al.
    GESAAF - Department of Agricultural, Food and Forestry Systems, University of Florence, Italy.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sousa, Hélder
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Jorge, Marco
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Branco, Jorge
    ISISE - Department of Civil Engineering, University of Minho, Guimarães, Portugal.
    Repairing of a timber truss through two different techniques using timber elements and screwed metal plates2015In: Historical Earthquake-Resistant Timber Framing in the Mediterranean Area: HEaRT 2015, 2015, p. 371-381Conference 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.

  • 11.
    Forsman, Samuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bystedt, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Laitila, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Need for innovation in supplying engineer-to-order joinery products to construction: a case study in Sweden2012In: Construction Innovation, ISSN 1471-4175, E-ISSN 1477-0857, Vol. 12, no 4, p. 464-491Article in journal (Refereed)
    Abstract [en]

    Purpose – The construction industry has been criticized for not keeping up with other production industries in terms of cost efficiency, innovation, and production methods. The purpose of this paper is to contribute to the knowledge about what hampers efficiency in supplying engineer-to-order (ETO) joinery-products to the construction process. The objective is to identify the main contributors to inefficiency and to define areas for innovation in improving this industry. Design/methodology/approach – Case studies of the supply chain of a Swedish ETO joinery-products supplier are carried out, and observations, semi-structured interviews, and documents from these cases are analysed from an efficiency improvement perspective. Findings – From a lean thinking and information modelling perspective, longer-term procurement relations and efficient communication of information are the main areas of innovation for enhancing the efficiency of supplying ETO joinery-products. It seems to be possible to make improvements in planning and coordination, assembly information, and spatial measuring through information modelling and spatial scanning technology. This is likely to result in an increased level of prefabrication, decreased assembly time, and increased predictability of on-site work. Originality/value – The role of supplying ETO joinery-products is a novel research area in construction. There is a need to develop each segment of the manufacturing industry supplying construction and this paper contributes to the collective knowledge in this area. The focus is on the possibilities for innovation in the ETO joinery-products industry and on its improved integration in the construction industry value chain in general.

  • 12.
    Forsman, Samuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Laitila, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    3-D measuring for an engineer-to-order secondary wood processing industry2012In: World Conference on Timber Engineering, WCTE: Final Papers - Poster presentations / [ed] Pierre Quenneville, New Zealand Timber Design Society , 2012, p. 498-504Conference paper (Refereed)
  • 13.
    Hagman, Olle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Projekt: Smart träbro i smart stad2013Other (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.

  • 14.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gong, Guan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wixe, David
    Luleå University of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moisture absorption behaviour and its impact on the mechanical properties of polyvinyl acetate (PVAc) based cellulose nanocomposites2011In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 51, no 11, p. 2136-2142Article in journal (Refereed)
    Abstract [en]

    Cellulose nanowhisker (CNW) reinforced polyvinyl acetate (PVAc) nanocomposites were prepared by melt-extrusion using a master batch process. Microscopy images showed no visible aggregation of whiskers in the matrix. The influence of CNWs and moisture absorption on the mechanical behavior of the nanocomposites was studied. The water sorption studies indicated low water uptake (<10 wt%) for all the materials. However, higher moisture uptake was obtained in the nanocomposites compared to the matrix though the diffusion co-efficient of the nanocomposites was lower. The tensile strength and modulus were decreased with the addition of CNWs to PVAc, but the reduction is lower at higher CNW concentration indicating that the plasticizing effect of the moisture was counteracted to some extent by the reinforcing effect of CNWs. Higher tensile ductility and toughness, which were dependent on moisture absorption, were achieved in the nanocomposites than pure PVAc.

  • 15.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Engineered wood in cold climate: application to monitoring of a new Swedish suspension bridge2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 639-640, p. 96-104Article in journal (Refereed)
    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.

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