Investigation Of The Checking Method For Serviceability Limit State Of Wood Floors

The serviceability limit state of wood bending members includes deflections checking and vibrations checking,this thesis is mainly about the method of deflections checking.When determining the limiting values for deflections of wood bending members,Chinese codes GB 50005-2003 and GB 50005-2017(draft)didn't consider the interaction between the joists and sheathing correctly as well as the creep effect.The calculation process of this code also ignore the use of modern wood products like sawn timber and engineered wood,whose modulus of elasticity(MOE)parameter and ratio of load is quite different form Chinese traditional wood products.Accordingly,the limiting values for deflections given in Chinese codes is not accurate enough for engineering calculation.Groups of finite elements in different stiffness of nails,location of joist,MOE of joists were calculated by ABAQUS,to investigate the relationship between the stiffness of the floor and other parameters such as the cross section of joists,the spacing between joists,the stress level of the joists and the stiffness of nails between the joist and the sheathing.The equivalent modulus of elasticity was defined to consider the interaction between the joists and sheathing when calculating the reliability index,while the methods for calculating the stiffness of the floor was simplified.By refering existed research,the limit state of wood beams were defined and performance function considering about quasi-permanent combination of actions and creep effect was given.By the performance function and the equivalent MOE,the reliability index of wood beams according to Chinese code could be calculated.The result is,all of the limiting values except joists made by Chinese timber and dimension lumber are so easy that requirement of serviceability limit state could not be satisfied.Focusing on the inadequacy of Chinese codes,several new calculating methods were given,considering about the quasi-permanent combination of actions and the creep effect.The designers could check beams in different creep conditions more flexiblly,and the corresponding recommended values for the limiting values for deflections were also derived.