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Utvärdering av styvhetsegenskaper hos ett nyutvecklat träbjälklag
Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
2006 (Swedish)Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesisAlternative title
Evaluation of stiffness properties of a novel wooden floor system (English)
Abstract [sv]

I samband med att intresset för att bygga högre trähus har ökat så krävs nya lösningar för att t.ex. kunna möta efterfrågan på stora öppna ytor och långa spännvidder. Träbjälklag med lång spännvidd har dock oftast svårigheter med att klara kraven på svikt och vibrationer. Ett nyutvecklat förslag på träbjälklag som förmodas klara dessa krav bättre än traditionella träbjälklag har varit utgångspunkten för detta examensarbete där syftet har varit att undersöka bjälklagets styvhet. Detta gjordes laborativt genom att bygga och testa en prototyp av det föreslagna bjälklaget och genom att en numerisk modell baserad på finita element metoden togs fram och användes för att studera hur olika parametrar påverkar bjälklagets styvhetsegenskaper.

Bjälklagets design bygger på fackverksprincipen i primärriktningen och på balkverkan i sekundärriktningen. De ingående komponenterna har kommit prefabricerade till Växjö universitet där de har monterats ihop till ett fullskaligt bjälklagselement. Elementet har sedan utsatts för ett antal belastningsfall där nedböjningarna uppmätts vilka sedan givit underlag för att få värden på bjälklagets effektiva styvhetsegenskaper.

Både de laborativa och de simulerade resultaten visar på en hög böjstyvhet i primärriktningen d.v.s. 18,9•106 Nm2/m [EI/b] respektive 18,6•106 Nm2/m [EI/b]. Även böjstyvheten i sekundärriktningen är hög d.v.s. motsvarar 21,2 % respektive 17,1 % av styvheten i primärriktningen.

I beräkningsmodellen har det dessutom undersökts hur ett övre lager av spånskivor inverkar på bjälklagets styvhet.

Abstract [en]

The interest for building higher and larger wooden houses has increased in Sweden during the last decade resulting in higher requirements on the technical performance of such structures in order to met demands on large open surfaces and large spans of floors. Wooden floor systems with large spans often have difficulties, however, to meet the vibration requirements. A novel floor system, likely to handle the vibration requirements better than traditional wooden floor systems, is the basis for this master thesis. The purpose is to examine the stiffness of the floor by building and testing a prototype and by producing a numerical model based on the finite element method.

In the longitudinal, main load-bearing direction the floor system works as a truss with flanges of longitudinal oriented timber members and web diagonals of transversely oriented members. In the transverse direction the web diagonals work as beams. The components were prefabricated elsewhere and assembled at Växjö University into a prototype. The prototype was then exposed to a number of different load cases. Deflections were measured and stiffness properties of the floor were derived. In addition to the experimental analysis the numerical model was used to calculate deflections when subjected to different load cases and for evaluating the principal stiffness properties of the floor.

Both the experimental and the calculated results using the numerical model show high bending stiffness in the longitudinal direction, EI/b = 18,9•106 Nm2/m and 18,6•106 Nm2/m respectively. Also the bending stiffness in the transversal direction is high and equivalent to 21,2 % or 17,1 % (testing and simulation respectively) of the bending stiffness in the longitudinal direction. Using numerical analysis, also the effect on the stiffness of adding an upper layer of a 22 mm particleboard was examined.

Place, publisher, year, edition, pages
2006. , p. 44
Series
Reports from Växjö University: Mathematics, natural sciences and technology, ISSN 1404-045X ; TD 073/2006
Keywords [en]
wooden floor system, wood-based beams, bending stiffness, FE-modelling
Keywords [sv]
Träbjälklag, lättbalkar, böjstyvhet, FE-modellering
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:vxu:diva-937OAI: oai:DiVA.org:vxu-937DiVA, id: diva2:207264
Uppsok
teknik
Supervisors
Examiners
Available from: 2006-10-27 Created: 2006-10-27 Last updated: 2010-03-10Bibliographically approved

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