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Utdragshållfasthet av inlimmade skruvar i limträ
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
2013 (Swedish)Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

In this thesis tests has been performed on the pull strength of screws glued into glulam beams.

The experiment is based on the already approved method whereby the diameter of the drilled holes is the same as the screw outer diameter of 1 mm or bigger. The screws strength class shall not be less than 4.6 (EN ISO 898-1:1999, 1999).

The difference in the experiments that were performed where that the drilled diameter were 1 mm smaller than the outer diameter of the screw so that the screw thread was worked into the wood.

In the tests the gluing where made on M8 glulam beams. The screws where drilled at and angel of 90°tangental to the fiber direction with a diameter of 7 mm. The gluing of the screws where made in three different depths and where later exposed to pulling forces. The results showed both pulling breaks and screw breaks when they reached their maximum capacity. This conforms to the assessments made before the tests.

From the evaluation of the tests the characteristic values have been calculated so that the method can be compared with nails and bolts in the roof trusses. The experiments showed that the glued screws with adapted drill-depths have similar pull strength as the corresponding wood screws and glued screws according to standards.

There is a great need for continued research in this method of glued screws if they are going to be used in roof trusses and fulfill the same function as bolted joints does today. Tests should then be made on amongst others glued screws in different fiber directions, drill diameters, screw dimensions, glue types and climate tests.

Abstract [sv]

I detta examensarbete har försök gjorts på utdragshållfasthet av inlimmade skruvar i limträbalkar.

Undersökningen i detta examensarbete bygger på den redan typgodkända metoden som innebär att borrhållsdiametern är densamma som skruvens yttrediameter eller 1 mm större. Skruvarnas hållfasthetklass får inte vara lägre än 4,6 (SS-EN ISO 898-1, 1999).

Skillnaden i försöken som utfördes var att borrhållsdiametern var 1 mm mindre än skruvens ytterdiameter, så att skruven gängades ner.

I försöken gjordes inlimning av M8 på limträbalkar. Skruvarna borrades 90° mot fiberriktningen med borrhålsdiametern på 7 mm. Inlimningen av skruvarna gjordes i tre olika borrdjup och utsattes sedan för utdragskrafter. Resultaten visade på både utdragsbrott och skruvbrott när de uppnådde sin maxkapacitet. Detta överensstämde väl med de bedömningar som gjordes innan proven.

I utvärderingen av försöken har karakteristiska värden beräknats för att metoden ska kunna jämföras med spik- och skruvförband i takstolar. Undersökningen visade på att inlimmade skruvar med anpassat borrdjup har en utdragshållfasthet i samma storleksordning motsvarande träskruv och inlimmad skruv enligt typgodkännande.

Det finns ett stort behov av fortsatt forskning kring denna metod av inlimmade skruvar om det skall kunna användas i takstolar och uppfylla samma funktion som skruvförband gör idag. Då bör tester göras på bland annat inlimmade skruvar i olika fiberriktningar, borrhålsdiametrar, skruvdimensioner, limtyper, belastningstider och klimattester.

Place, publisher, year, edition, pages
2013. , 68 p.
Keyword [sv]
Inlimmade skruvar, Limträ
National Category
Construction Management
Identifiers
URN: urn:nbn:se:hig:diva-14785OAI: oai:DiVA.org:hig-14785DiVA: diva2:633736
Subject / course
Building engineering
Educational program
Högskoleingenjör
Presentation
11:520, Kungsbäcksv. 47, Gävle (Swedish)
Supervisors
Examiners
Available from: 2013-08-19 Created: 2013-06-27 Last updated: 2013-08-19Bibliographically approved

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