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Testing of CLT-Concrete Composite decks

Thilén, Joakim LU (2017) In TVBK-5259 VBK920 20171
Division of Structural Engingeering
Abstract
When massive timber decks are used in buildings the design is often regulated by serviceability limit state (SLS), mainly the vibration criteria. To decrease the risk for vibrations of a deck the bending stiffness needs to be increased. To increase the bending stiffness of the deck either the depth of the deck can be increased or the stiffness of the used material. The most common way to increase the bending stiffness is to increase the depth of the deck. In this thesis it was tested if a composite deck could be used. Composite decks consisting of timber and concrete are often referred to as TCC meaning Timber-concrete composite. TCC can be an alternative by combining the two above mentioned methods of increasing the bending stiffness. By... (More)
When massive timber decks are used in buildings the design is often regulated by serviceability limit state (SLS), mainly the vibration criteria. To decrease the risk for vibrations of a deck the bending stiffness needs to be increased. To increase the bending stiffness of the deck either the depth of the deck can be increased or the stiffness of the used material. The most common way to increase the bending stiffness is to increase the depth of the deck. In this thesis it was tested if a composite deck could be used. Composite decks consisting of timber and concrete are often referred to as TCC meaning Timber-concrete composite. TCC can be an alternative by combining the two above mentioned methods of increasing the bending stiffness. By creating a TCC deck by adding and connecting a concrete slab to the upper-side of the timber deck the bending stiffness can be increased while keeping the depth of the deck to a minimum.

To make TCC a possible alternative to be used in modern buildings it is necessary to be able to accurately predict necessary quantities such as the load-bearing capacity and bending stiffness. In this report the main objective is to investigate how well an existing calculation method, the gamma-method, can predict the bending stiffness and therefore the deflections. To reach the aim of the report tests are performed on the TCC's and the connections that are used. Shear tests are performed on the connections in order to determine their stiffness. Bending tests are performed on four TCC-decks, two of which are tested to failure.

The bending stiffness of the TCC is dependent on the stiffness of the connection between the different parts of the cross-section. Two types of connections to connect the concrete slab to the wooden deck were investigated. The first type is a connection through notches cut in the wooden deck and the second is by applying an epoxy adhesive to the wooden deck prior to casting the concrete.

The experimental test results showed that the prediction of the mid-span deflections with the gamma-method could be accurate. The level of accuracy could not be determined due to that it is dependent on several parameters such as the stiffness of the timber and concrete as well as the stiffness of the connections used, of which the concrete's compressive stiffness was not tested. The test results also showed the difficulty to accurately determine the stiffness of the connection by performing shear tests. One part of the experimental study was to check the bearing capacity of two of the TCC-decks by performing a destructive bending test. The results from the destructive bending test revealed that a high load-bearing capacity can be expected from a TCC. (Less)
Popular Abstract (Swedish)
När massiva träbjälklag används i byggnader är dimensioneringen ofta styrd av krav på utböjningen. För att minska utböjningen för ett bjälklag måste böjstyvheten ökas. Ökning av böjstyvheten för ett bjälklag kan antingen ske genom en ökad höjd eller genom användning av material med högre styvhet. Den vanligaste metoden för att öka böjstyvheten är genom att öka höjden på bjälklaget. I denna rapport undersöktes det om samverkansbjälklag kan användas. Samverkansbjälklag som består av trä och betong refereras ofta till som TCC vilket står för Timber-Concrete Composite. TCC kan vara ett alternativ som kombinerar de två tidigare nämnda metoderna för att öka böjstyvheten. Genom att skapa ett TCC där ett betongbjälklag kopplas mot ovansidan av... (More)
När massiva träbjälklag används i byggnader är dimensioneringen ofta styrd av krav på utböjningen. För att minska utböjningen för ett bjälklag måste böjstyvheten ökas. Ökning av böjstyvheten för ett bjälklag kan antingen ske genom en ökad höjd eller genom användning av material med högre styvhet. Den vanligaste metoden för att öka böjstyvheten är genom att öka höjden på bjälklaget. I denna rapport undersöktes det om samverkansbjälklag kan användas. Samverkansbjälklag som består av trä och betong refereras ofta till som TCC vilket står för Timber-Concrete Composite. TCC kan vara ett alternativ som kombinerar de två tidigare nämnda metoderna för att öka böjstyvheten. Genom att skapa ett TCC där ett betongbjälklag kopplas mot ovansidan av träbjälklaget kan böjstyvheten ökas samtidigt som höjden hålls till ett minimum.

För att möjliggöra användningen av TCC i moderna byggnader är det nödvändigt att med hög noggrannhet kunna fastställa att det uppfyller de krav som finns på bärande delar i en byggnad. De krav som undersöks i denna rapport är främst böjstyvheten och till viss del bärförmågan. I denna rapport är huvudmålet att undersöka hur väl en redan existerande beräkningsmetod, gammametoden, kan förutse böjstyvheten och därmed utböjningen. För att uppnå målet görs tester på bjälklagen och kopplingarna som används. Skjuvtester utförs på kopplingarna för att fastställa deras styvhet. Böjtester utförs på fyra stycken bjälklag för att mäta deras böjstyvhet. Två bjälklag böjtestas även till brott för att testa deras bärförmåga.

Ett samverkansbjälklags böjstyvhet är beroende på hur de olika delarna i bjälklaget har fästs mot varandra. Två olika kopplingar testas i rapporten. Den första kopplingen består av att skåror fräses ur träbjälklaget som fylls med betong vid gjutningen av betongen. Den andra kopplingen består av att ett epoxilim som appliceras på träbjälklaget innan gjutning sker.

De experimentella testresultaten visade att gammametoden kan vara precis. Precisionen hos gammametoden kunde inte fastställas då den är beroende av flera parametrar, såsom träbjälklagets böjstyvhet, kopplingens styvhet samt betongens styvhet. Betongens styvhet testades inte och är den parameter som saknades för att uttala sig om metodens precision. Testresultaten visade också på svårigheten med att bestämma styvheten hos en koppling genom skjuvtester. Bärförmågan för de TCC som belastades till brott var tillräckligt hög för att inte ses som begränsande vid framtida användning. (Less)
Please use this url to cite or link to this publication:
author
Thilén, Joakim LU
supervisor
organization
course
VBK920 20171
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Notch, Adhesive, Composite Decks, Deflection, Gamma-method, CLT, TCC
publication/series
TVBK-5259
report number
TVBK-5259
ISSN
0349-4969
language
English
additional info
Examinator: Eva Frühwald Hansson
id
8917463
date added to LUP
2017-07-13 16:31:07
date last changed
2017-07-13 16:31:07
@misc{8917463,
  abstract     = {When massive timber decks are used in buildings the design is often regulated by serviceability limit state (SLS), mainly the vibration criteria. To decrease the risk for vibrations of a deck the bending stiffness needs to be increased. To increase the bending stiffness of the deck either the depth of the deck can be increased or the stiffness of the used material. The most common way to increase the bending stiffness is to increase the depth of the deck. In this thesis it was tested if a composite deck could be used. Composite decks consisting of timber and concrete are often referred to as TCC meaning Timber-concrete composite. TCC can be an alternative by combining the two above mentioned methods of increasing the bending stiffness. By creating a TCC deck by adding and connecting a concrete slab to the upper-side of the timber deck the bending stiffness can be increased while keeping the depth of the deck to a minimum.

To make TCC a possible alternative to be used in modern buildings it is necessary to be able to accurately predict necessary quantities such as the load-bearing capacity and bending stiffness. In this report the main objective is to investigate how well an existing calculation method, the gamma-method, can predict the bending stiffness and therefore the deflections. To reach the aim of the report tests are performed on the TCC's and the connections that are used. Shear tests are performed on the connections in order to determine their stiffness. Bending tests are performed on four TCC-decks, two of which are tested to failure.

The bending stiffness of the TCC is dependent on the stiffness of the connection between the different parts of the cross-section. Two types of connections to connect the concrete slab to the wooden deck were investigated. The first type is a connection through notches cut in the wooden deck and the second is by applying an epoxy adhesive to the wooden deck prior to casting the concrete.

The experimental test results showed that the prediction of the mid-span deflections with the gamma-method could be accurate. The level of accuracy could not be determined due to that it is dependent on several parameters such as the stiffness of the timber and concrete as well as the stiffness of the connections used, of which the concrete's compressive stiffness was not tested. The test results also showed the difficulty to accurately determine the stiffness of the connection by performing shear tests. One part of the experimental study was to check the bearing capacity of two of the TCC-decks by performing a destructive bending test. The results from the destructive bending test revealed that a high load-bearing capacity can be expected from a TCC.},
  author       = {Thilén, Joakim},
  issn         = {0349-4969},
  keyword      = {Notch,Adhesive,Composite Decks,Deflection,Gamma-method,CLT,TCC},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVBK-5259},
  title        = {Testing of CLT-Concrete Composite decks},
  year         = {2017},
}