Static and dynamic properties of connections in timber-frame structures : BOOST + FBBB project

Connections play an important role in timber frame structures, especially when approaching the market of multi-story buildings. Two questions faced by practitioners were studied: for the first is the deformation behavior of such structures, where connections between wall and floor elements play an important role for the global stability of the timber structure. For the second is the sound transmission within elements of high importance, particularly timber building systems face challenges. For that reason, the static and dynamic behavior of such connections was studied in a joined experimental program. Two different building systems were investigated in 13 different test setups of how a floor and wall elements were connected to each other. By adjusting connection elements, the influence of various parameters on the dynamic and static behavior was studied. Sound/vibration transmission over the wall-floor connection was the special interest of the dynamic study. The floor element was excited by a shaker, and the response of floor and wall element was measured by accelerometers. This allowed to identify eigenfrequencies and eigenmodes as well as the damping of the structure and the insertion loss over the connection, respectively. Distinct differences between the building systems of the different producers were seen, while adjustments within building systems influenced only slightly the dynamic behavior. For the static part of the study, the moment-rotation behavior of the wall-floor connection was investigated. Variations of connection designs and layouts were tested to better understand the load-transfer and the mechanical interaction using different connectors and connector arrangements. The nailed connection between vertical studs and the bottom rail of the wall element was identified as a soft point when loaded by a horizontal force perpendicular to the plane of the wall element. Using screws this connection showed a substantial improvement of the connection strength. Further adjustments on the connector arrangements showed only partly influence on connection stiffness and strength.FBBB Framtidens biobaserade byggande och boendeBOOST - Boende- och bostadsutveckling för stärkt tillväx