Reliability Assessment Of Bending Wood Members In Servicebility Limit State

Sufficient reliability of structural system or structural members should be ensuredin structural design. The deflection limit value of bending member is an importantdesign index in serviceability limit state for the design of timber structures. Therefore,determination of deflection limit value for bending member needs to ensure that it hassufficient reliability. In china, the determination of deflection limit value for bendingmember in Code for Design of Timber Structures GB50005-2003only covers thereliability of sawn and round timber without considering the reliability of dimensionlumber and glulam in serviceability limit state. In addition, creep is one of the importantfactors that influence the long-term deformation. GB50005-2003only checks thereliability of bending members for short-term deformation without consideringdeformation due to creep in serviceability limit state, and there is no evidence to suggestthat checking short-term deflection of bending member can ensure that it has sufficientreliability in the design reference period,50years in China.In order to investigate the creep effect on the deformation of wood bendingmembers, creep experiment of full size bending members of dimension lumber havebeen conducted, and the50-year creep deformation coefficient has been predicted usingthe creep models derived from the90-day creep test data.The design methods of serviceability limit state including long-term and short-termdeflection for bending members are recomemded by referring to relevant specificationsboth home and abroad, and the proposed values of corresponding deflection limit fordifferent types of bending members are given. The reliability of different types ofbending members in serviceability limit state has been examined by using JC and MonteCarlo methods. It was found out that some of the suggested deflection limit values fordifferent types of bending members in GB50005-2003are inadequate and can notsatisty the target reliability indices in serviceability limit state specified by Unifiedstandard for reliability design of building structures GB50068-2001. Therefore, theaverage deflection limit values for different types of bending members that satisfy thetarget reliability indices were calculated in this study by using JC method, thusproviding reference for future compiling and revising the relevant codes.