FEM-analys av betongvägg vid bortfall av bärande pelare : Prefabricerade betongelements robusthet mot ras och olyckslast

Sammanfattning: Total collapses of buildings are a rare occurrence in modern building construction, and while they are scarcely seen, their consequences are often extensive enough to encourage building projectors to invest in a structural framework capable of sustaining its stability through unforeseen events. This individually completed degree project aims to provide insight into the principles and techniques used to prevent these kinds of collapses and how they can be applied to future structural design. This is achieved by studying the expected reactions of precast concrete structures and by analyzing the building codes currently applied to concrete buildings in Sweden. The study analyses a fictional four-story concrete building and the resulting deflection of its precast walls as a loadbearing column is removed from its bottom floor. Results are generated using the software Strusoft FEM-design 3D structure, and the deflection is calculated for walls spanning 6, 7, 8 or 8.5 m. Different concrete qualities ranging from 20/25 to 45/55 are applied to each span with the objective of examining the properties of a precast concrete buildings ability to remain stable without the use of extensive attachment methods. The biggest impact is presented by increasing the concrete quality from 25/30 to 30/37, which further justifies the usage of 30/37 in most modern construction. Generally the impact of increasing the structures concrete quality increases as its original deflection increases, which suggests an increase of quality is more profitable for high-risk structures. Furthermore walls constructed with high quality concrete will allow for the usage of further spanning components, as the study shows a lesser increase of deflection under these circumstances. While some results presented in the study may appear minor, it is proven crucial to provide proper attachment of precast concrete components in order to reduce the potential of a disastrous collapse. Keywords: Collapse, deflection, attachment, deformation, concrete quality, diaphragm action, membrane action, span, FEM-design.