Snedfördelning av laster på sadeltak av trä: Förslag på detaljlösning
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
An uneven load distribution on roofs allows a shear force to occur in the ridge. This shear force should be able to move between the two roof beams that are the roof truss, which is accomplished through a ridge bond. The magnitude of this force is dependent on the difference between the loads on each half of the roof and the span of the roof truss.The loads that contribute to this uneven distribution are often variable, such as snow- and wind loads. This in combination with a large span of the roof truss allows for a large shear force that the ridge bond should carry. With the transition from the Swedish standard BKR to EC this uneven load distribution has increased even more due to the significant change in snow load shape coefficient.Wood structures are especially vulnerable to this shear force due to their low tensile strength perpendicular to the fiber. The ridge bond transfers the force in a way that tensile forces act in perpendicular to the fiber, which puts the beam in risk of splitting.To get a grip on the magnitude of this shear force a calculation has been done on a hall with a wooden structure. The loads on the hall have been calculated with BKR and EC to show the difference between these two standards. Furthermore a simple ridge bond has been designed for each load case to see how it fairs up against the shear force.How can a bond be designed to manage the high shear forces present in the ridge and at the same time avoid the beam to split?When the problem is identified and what is needed to minimize the risk of splitting a number of bonds has been produced in excess of the ones Svensk Hallteknik uses as of now. Of the bonds produced only two has been fully designed to verify their capacity to handle the shear force.The two bonds that is designed is then put against each other through a number of criterions to choose one bond that is favorable at high shear forces.In the paper a bond with steel plates configured in a cross over the ridge has been the one to fulfill the criterions.
Place, publisher, year, edition, pages
2014. , 95 p.
IdentifiersURN: urn:nbn:se:ltu:diva-58676Local ID: f3f3c989-e44e-405f-9b81-acedcd5c52feOAI: oai:DiVA.org:ltu-58676DiVA: diva2:1032064
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20140123 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved