Examensarbeten för masterexamen // Master Theses
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- PostStability and Dynamic Properties of Tall Timber Structures - A parametric study of the structural response due(2019) Alalwan, Ahmad; Larsson, Joakim; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Al-Emrani, Mohammad; Al-Emrani, MohammadABSTRACT The interest in building taller structures in timber is increasing in the building sector. However, the high strength-to-weight ratio of timber leads to a relatively light structure which is often associated with vibrations. The dynamic properties are essential in the design of tall timber structures, where wind-induced vibrations of the building in service state is addressed. The dynamic response is influenced by mass, stiffness and damping. These parameters influence the acceleration of the building which can be perceived as a discomfort for human occupancy. The aim is to find a structural concept that makes a taller structure than the usual today feasible. The objective is to make a parametric study and investigate how a multi-storey residential building of timber can be optimized with respect to dynamic wind loading. With a combination of numerical and analytical methods, accelerations are calculated and evaluated against the criteria for human comfort according to ISO 10137 and ISO 6897. An analytical calculation sheet is set up according to SS-EN-1991-1-4 and EKS 10 to define wind-induced acceleration. Starting from a beam-column structure with a central core, the effect of adding inner walls and exterior bracing is studied to see what limits the number of storeys for an open plan building. Analysis of the dynamic response due to wind shows the fundamental mode shape in torsion before exterior bracing is added. Results have shown that the structure can reach 5-storeys with inner walls of cross-laminated timber and 4-storeys with no walls. Moreover, it’s found that diagonal bracing in the facades improves the torsional stiffness significantly and the fundamental mode becomes a transversal mode. An outrigger bracing system has been found to be the most efficient, leading to a structure of 12-storeys. The parameters mass and stiffness are modified by adding concrete floors and assigning larger sections to the structure. Results show that the building can achieve 15-storeys with pure timber and 21-storeys when concrete floors are added. Secondary parametric action i.e. adding another outrigger generates a gain of one-storey and modifying the truss-work to steel gives a structure of 23-storeys.
- PostThe 200 m timber tower - A study on the possibilities of constructing a 200 meter tall timber building(2020) Sebastian Gyllensten, Axel Modig; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Jockwer, RobertABSTRACT As the interest in timber buildings is increasing, more attention is pointed towards highrise timber buildings. Partly because it is one of the main areas pushing the development within the field of timber structures. As the current tallest timber building, Mjöstornet in Brumunddal is approximately 10 times shorter than the world’s tallest building, Burj Khalifa, the intuition says that there is room for major improvements regarding tall timber structures. The aim of this thesis is therefore to investigate the possibilities to build a 200 m tall timber tower while still fulfilling the requirements for strength, stability and dynamics. In order to anchor the project in reality, the assumed building location is Gothenburg with the ground conditions of solid rock. Early in the study it was concluded that in order to push the height limits, the building design had to be improved compared to the existing timber buildings. The main geometries of interest turned out to be the circular shape thanks to its aerodynamical benefits. This base shape was applied in various ways, generating five different concepts ready for evaluation. Each of the five concepts were modelled and preliminary sized using Grasshopper and Karamba 3D, whereafter they were evaluated based on their dynamic performance, global stiffness, and a few other evaluation criteria. The evaluation was primary made with structural performance in mind and secondary with regard to comfort, quality and economical aspects. The results show that one of the concepts have great potential of reaching 200 m despite the uncertainties regarding joint stiffness and structural damping. Also, a few of the other concepts might be able to reach 200 m if subject to some structural and dynamical improvements. Key words: Acceleration