Impact of Semi-Rigid Joints in Light-Wood Framed Structures on the Serviceability Limit State

Timber structure especially light-wood framed structures depending on semi-rigid behaviour of its work have got lower spatial stiffness than theoretical model with full-fixed joints. Semi-rigid behaviour of the joints is a function of material and structural stiffness. Joints deformation are the results of material properties of wood as well as internal force redistribution onto individual elements intersected in analyzed joint. The force distribution between individual components depends on the direction of the grain in analyzed parts of the structure. Joints deformation as the result of its semi-rigid characteristics cause the reduction of the stiffness so the values of the displacements rise. Increase of the displacement allows possibility to exceed the limits imposed by the requirements of Serviceability Limit State. The exceeding of the safe values causes the structure lost its function due to the safety and comfortable use. The paper will present main concepts connected with non-linear and semi-rigid behavior of the joints as well the models and static schemes of joints work in the light-wood framed structures. The experimental researches were conducted in Bialystok University of Technology. The experiments were carried out on the specimen in micro-scale 1:3. The translational stiffness k and rotational stiffness κ were analyzed. The researches were conducted for stud-to-bottom plate joint as well floor joist-to-top plate of wall joint in the floor to wall connection. There were observed dependencies between the loads applied to the joint and the translational and rotational deformation of the connection. Selected results of these experimental tests present the behavior of the analyzed joints and expose its semi-rigid manner of work. For single-span beam with semi-rigid joints the calculation formulas presenting the change of extreme values of the displacement in relationship to the translational and rotational stiffness of the support joints is presented. The paper will be summarized by conclusions coming from the carried out analyses.