Eaves is something that is common to see on buildings. But what is the purpose of the eaves and how do they affect the building? To get an answer to that and if you really need to build eaves is the main purpose of this work. The work is mostly done as a literature study in which existing literature concerning eaves is compiled. As a completion to that, interviews have been performed with people that has a lot of knowledge about eaves to see what they have to say about the effect eaves have on a building. In today’s building regulations it’s hard to tell when you should build with eaves and how long the eaves should be because they are formed as functional requirements. If you instead look at older building regulations, recommendations on how to build with eaves can be found. Many clients require eaves on their buildings, but they do not give any reasons to it. The common picture based on answers from interviews with people in the industry is that eaves protects the façade and mostly the upper parts. It is possible to build without eaves, but it should be considered a risk. Some materials are extra sensitive to wind driven rain and then it’s more important to build eaves. The research that has been done about eaves is mostly simulations, but field measurements have also been made. Both the simulations and measurements show that it is the upper parts of the facade that is exposed to the most wind driven rain and it is also the upper parts of the facade that is mostly protected by eaves. So even if the impact that the eaves have on a build is not too well determined it’s clear that the eaves have a function. The eaves do not only protect the building as an extra roof it also changes the wind flow around the building and gives good protection to the upper parts of the facade that is the most exposed part of the faced for wind driven rain for buildings without eaves.

Samverkanskonstruktioner ger goda förutsättningar för att använda material på ett optimalt sätt både gällande momentbärförmåga och materialanvändning. Vid dimensionering av takfoten på Lättelement AB:s takelement utnyttjas samverkan mellan taktass och plywood. Vid samverkan ges bra förutsättningar att nå god momentbärförmåga men tvärkraftsbärförmågan gällande skjuvning i plywood invid limfogen blir ofta dimensionerande i företagets takfotslösning. Ett behov av att kunna bredda limfogen mot plywood utan att behöva öka dimension eller antal taktassar är vad detta examensarbete har utgått ifrån. Att tunn stålplåt som redan används i Lättelements produkter monteras mellan taktass och plywood sågs som en potentiell lösning på problemet. Syftet med denna studie är att genom provningar göra en första utvärdering av lösningen för att ge företaget underlag för fortsatta undersökningar.   Då den faktiska konstruktionen och verkligt lastfall var problematisk att återskapa i en provningssituation med tillgänglig provningsutrustning utformades förenklade provkroppar för att företräda ursprungskonstruktionen. Provkroppar till två försöksserier utformades för att genom tryckprovning testa skjuvbärförmågan i limfog mellan träregel och plywoodstycken. Provkroppen till kontrollserien bestod endast av Lättelements specialanpassade konstruktionsplywood och regel av konstruktionsvirke i klass C24 vilka limmades samman med tvåkomponents polyuretanlim. Den hade enligt teoretiskt värden en karakteristisk bärförmåga på 8,4 kN. Plåtseriens provkropp hade samma utformning som kontrollserien med skillnaden att två 0,7 mm tjock stålplåt, som var fyra gånger så bred som träregeln, limmas fast mellan respektive plywood och träregel för att bredda limfogen mot plywood. Stålplåten var en SSAB produkt som var polyesterlackad på dess synlig sida och hade epoxybaserad baksidesfärg på dess baksida. Synliga sidan vändes mot träregel vid limning. Plåtseriens karakteristiska skjuvbärförmåga enligt teoretiska värden var 33,6 kN Provserierna bestod av fem provkroppar vardera.   I kontrollserien gick samtliga provkroppar till brott genom rullskjuvning i plywood, som planerat. Uppmätta brottlaster varierade från 20,2 kN till 34,0 kN och beräkning enligt standard SS-EN 14358:2016 gav en karakteristisk brottslast på 15, 7 kN. Av plåtserien gick tre av fem provkroppar till brott på samma sätt genom att vidhäftning av limmet mot polyesterlackade sidan av plåten släppte. Brottlasterna varierade mellan 26,9 kN och 47,5 kN och gav en karakteristisk brottlast på 14,0 kN. En av de övriga två provningarna i serien avbröts vid en last på 49,1 kN på grund av begränsning i provningsutrustningens avläsningskapacitet.   Resultatet bekräftade teorin att plywoodens rullskjuvningsbärförmåga var dimensionerande för kontrollserien. Dock var den uppmätta karakteristiska lasten över 87 % högre än den teoretiska. Dock bör ej det resultatet läggas för stor vikt vid då urvalet var litet.   Plåtseriens resultat gav ett annat brottmod än planerat då vidhäftning mellan lim och plåtens polyesterlackade sida var otillräcklig. På grund av stor spridning och minimalt urval blev den karakteristiska uppmätta bärförmågan för plåtserien lägre än för kontrollgruppen. Dock kan en tendens ses att plåtserien klarade mer last med en median på 47,1 kN jämfört med kontrollseriens median på 25,0 kN. Det kombinerat med det faktum att limningen mot plywood i plåtserien inte gick till brott på någon provkropp indikerar på att lösningen har potential om vidhäftningen kan göras likvärdig på båda sidor av plåten. / Composite constructions provide good conditions for using materials in an optimal way both in terms of bending resistance and material use. When performing structural design of the eaves on Lättelement AB's prefabricated roof element, the interaction between structural wood stud and plywood is applied. In this composite construction, good conditions for god bending resistance are achieved, but the shear resistance in plywood next to the glue joint is often the limiting design resistance. A need to be able to widen the glue joint to plywood without having to increase the dimension or number of wood studs is what this thesis has been based on. Mounting a thin steel plate, usually used in Lättelement's products, between the structural wood stud and plywood was seen as a potential solution to the problem. The purpose of this study is to conduct tests to make an initial evaluation of the solution to provide the company with a basis for further investigations.   Since the actual design and actual load case were problematic to recreate in a test situation with available testing equipment, a simplified test specimen was designed to represent the original design. Test specimens for two different test series were designed. By compression testing, the shear resistance of the glue joint between wood studs and plywood pieces was tested. The test specimen for the control series consisted only of Lättelement's specially adapted structural plywood and a stud of structural wood in class C24 which was glued together with two-component polyurethane adhesive. According to theoretical values, it had a characteristic load capacity of 8.4 kN. The test specimen of the plate series had the same design as the one for the control series with the only difference that two 0.7 mm thick steel sheets, which were four times as wide as the wood stud, were glued between the respective plywood and wood stud to widen the glue joint on to the plywood. The steel sheet was a SSAB product that was polyester lacquered on its visible side and had epoxy-based backing paint on the other side. The visible side was turned against the wood stud when glued together. The characteristic shear resistance of the plate series was according to theoretical values 33.6 kN. The test series consisted of five test specimens each.   All the test specimens in the control series had the failure mode of roll shear in plywood as predicted. Measured ultimate loading ranged from 20.2 kN to 34.0 kN and calculation according to standard SS-EN 14358:2016 gave a characteristic value of ultimate loading of 15, 7 kN. Of the plate series, three out of five test specimens went to failure in the same way, by failed adhering of the adhesive to the polyester lacquered side of the steel sheet. Measured ultimate loading ranged from 26.9 kN and 47.5 kN, giving a characteristic value of ultimate loading of 14,0 kN. One of the other two tests in the series was interrupted at a load of 49.1 kN due to limitation in the test equipment's reading capacity.   The result confirmed the theory that the plywood's shear bearing capacity was the limiting design resistance for the control series. However, the measured characteristic ultimate loading was over 87% higher than the theoretical one. Nevertheless, this result should not be overestimated as the number of test values was scarce. The test of the plate series shows in a different failure mode than anticipated due to that the adhesion between the adhesive and the polyester lacquered side of the plate was insufficient. Because of the large spread and minimal number of test values the measured characteristic ultimate loading for the plate series was lower than for the control group. However, a tendency can be seen that the plate series could withstand more applied load with a median of 47.1 kN compared to the control series median of 25.0 kN. That combined with the fact that the bonding to plywood in the plate series did not fail in any specimen, indicates that the solution has potential if the adhesion can be sufficient to both sides of the sheet.