Introduction – Cross-laminated timber (CLT) is a product that is becoming increasingly common in the construction industry. CLT is categorized as homogeneous or combined, where homogeneous has the same strength classes throughout the entire cross-section and combined has varying strength classes across the cross-section. The strength and stiffness are compensated in the combined material by placing the highest strength class furthest out in the cross-section. When it comes to stiffness in timber structures, however, joints often represent the weakest link. This is particularly relevant in the construction of taller buildings where stiffness becomes a crucial variable for stability. To broaden the knowledge of screw connections in CLT this study aims to investigate the comparison of homogeneous and combined CLT with regards to strength and stiffness in axially loaded screw connections in CLT. Method – A literature review was conducted to design a test setup for measuring the strength and stiffness of axially loaded screw connections in CLT. Relevant studies and standards were examined to develop a suitable setup for the study. Tensile tests were conducted to determine the difference in strength and stiffness between homogenous and combined CLT as well as between strength class C24 and C35, providing numerical values for comparison. Result – The literature study resulted in empirical data presenting various test setups for measuring axially loaded screws connections in CLT. The experiment, conducted in the form of tensile tests, resulted in data in the form of measured force in relation to displacement, which could be used to calculate strength and stiffness.  Analysis – The test setup which was designed to measure the strength and stiffness of axially loaded screw connections in CLT was based on guidelines from SS-EN 1382 (SIS, 2016) and ISO 6891 (ISO, 1983), as well as inspiration from previous studies with similar test setups. The tensile tests showed that no significant difference in strength and stiffness could be observed between the combined and homogeneous CLT elements that were tested. Discussion – The results show no significant percentage differences in relation to the coefficient of variation between combined CLT and homogeneous CLT. However, the results do show a significant difference when only strength class C35 and C24 are tested separately. Additionally, the experiments show that displacement measurements should be made locally due to deformations in the tensile testing machine and equipment. Due to deformations in the screw, it also turns out to matter where in relation to the test specimen and screw the local measurements are made.

Introduktion: Håldäck är ett prefabricerat bjälklag med en viktig betydelse för en byggnads stomstabilitet. Bjälklaget har som egenskap att fånga upp de horisontallaster som påverkar konstruktionen och fördelar krafterna vidare i konstruktionen. För överföring av skjuvkrafter och dragkrafter mellan bjälklag och vägg används kopplingar i håldäckets långsida. Denna studie syftar till att med hjälp av praktiska försök pröva om det finns en högre kapacitet i sidokoppling i håldäck mot vad som framgår av den beräkningsmodell som används idag vid dimensionering. Metod: Studiens metod är huvudsakligen experiment då primärdata samlas in för vidare analys. En fullskaleprovning har genomförts där kopplingen av typen pinnskruv med mutter har provats i två olika dimensioner av håldäck. För insamling av sekundärdata används metoden dokumentstudie då en fördjupning av lagar, standarder och riktlinjer är det huvudsakliga syftet. Resultat: Studien redogör resultat av Betongelementbokens validitet för beräkning av sidokopplingars kapacitet i håldäck. Resultatet visar att kopplingen i praktiken har en starkare hållfasthet än vad beräkningsmodellen från Betongelementboken redogör för.  Analys: Den beräkningsmodell som används idag för beräkning av kapacitet hos sidokoppling av håldäck ger överdimensionerande värden i jämförelse med resultat från provning. Metod för provning gav resultat med hög validitet och reliabilitet. Diskussion: Genom fullskaleprovning och riktlinjer för dimensionering genom provning gav experimentet jämförbara resultat. Metod för experimentet har gett goda resultat och studien kan användas som underlag för vidare studier.

To achieve structural integrity in precast concrete systems, connections between elements must be capable to transfer both vertical and horizontal loads which puts high demands on single ties. Hollow-core slabs are often used to stabilize the structural system which puts high demands on the connections between the slab and the buildings stabilizing units. Because of this, the connections need to withstand high tensile and shear forces. The purpose of this report is to investigate the tensile capacity of tie-connections used between hollow-core slabs that are parallel with e.g. stabilizing walls and compare with current design methods. Current design methods suggest that tensile failure will occur in the roof and bottom of the cores which provides low design capacities. Two connections are investigated through full scale pull-out tests where the results are compared with the design methods. The results from testing the tensile capacity show that the failure module occurred as suggested. However, the tests show significantly higher capacity than proposed by the design methods. Eurocodes Design assisted by testing are applied to the test result and a new design method is proposed. Both provides design values that are approximately twice as large as the values suggested in previous design methods.