Design of floor-to-wall connections in hybrid structures - Study of robustness in CLT floor to concrete wall connections

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Examensarbete för masterexamen
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2021
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ALIBASIC, ARMEL
VOCAL, VIDAL
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The construction industry has taken an approach towards implementing sustainable alternatives combining conventional concrete or steel elements with timber. Concrete has been the most popular construction material in the past century, but the amount consumed has considerable negative environmental impacts compared to its alternatives. In an effort towards a sustainable industry, construction of hybrid structures is encouraged. These types of structures combine different materials, allowing more diversity in the structural design. However, replacing structural elements with “green” materials needs further study about its performance regarding robustness and the prevention of progressive collapse. Following the availability of prefabricated timber in the Swedish construction industry, this material is to gradually replace concrete elements. Limited research currently exists regarding robustness criteria when combining timber and concrete. The Eurocode and national design guidelines provide design procedures for each individual material, but not the effects when combined in a hybrid structure. Additionally, cross-laminated timber has different material properties and structural behavior than regular solid timber which are not considered. Referral to external research articles and foreign guidelines were studied to understand the mechanical behavior and determine a design approach to reach robustness demands. The aim of this thesis is to study and design the connection of a CLT floor to a precast concrete wall by performing a case study of a housing project in Malmö. Results showed that a combination of the tying method with an alternate load path analysis, cross-laminated timber could provide the ductility and strength necessary for load redistribution to alternate load paths. Precast concrete walls together with CLT floors worked together to each contribute to the overall robustness with the capability of triggering different collapse resistance mechanisms such as hanging action and deep beam behavior. The replacement of hollow-core slabs with CLT floors provided a reduction of 30% in the self-weight and negative values in carbon dioxide equivalent emissions where timber stored more carbon dioxide than the amount required for their production.
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Robustness, progressive collapse, deep beam behavior, alternate load path, analysis, hybrid connections, redundancy, cross-laminated timber, carbon dioxide, equivalents
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