Stability Of Wood Members In Axial Compression And The Reliability Analysis

The equations for calculation of the stability coefficient of wood members in axial compression in current Chinese code for design of timber structures GB 50005-2003 follows the equations in the code,GBJ 5-88,which was based on tests of traditional sawn or round timber members in axial compression.It can not fully apply to members made of modern wood products like glued laminated wood,dimension lumber,imported lumber.The code in amending adopted the new equation to calculate stability coefficient.However,whether it meets reliability requirement requires further study.The finite element models of wood members in axial compression were developed,with material nonlinearity and geometric nonlinearity of timber members considered.Stochastic models of modulus of elasticity,tensile strength,compressive strength of timber and initial deflection of members were developed.Stochastic finite element analysis of members in axial compression about glued laminated timber,dimension lumber,North American timber of different strength grades and different slenderness ratio was completed.The buckling carrying capacity of statistical significance of columns was predicted and it can afford distribution parameter of stochastic model of residence for reliability analysis.Performance function of wood members in axial compression was developed.Based on results of stochastic finite element analysis of wood members in axial compression,reliability analysis on stability of members of glued laminated timber,dimension lumber,North American timber was completed.The analysis results show that the reliability index of three kinds of timber products can totally meet the target reliability index,3.2.However,reliability indexes of members with slenderness near to the break-point of equations for calculation of the stability coefficient are usually lower than those with other slenderness.And those lower reliability indexes can not be partially adjusted simply by adjusting the parameters in the formula.Analysis of cause of reliability indexes near to break-point lower than others was given.Based on the former work,a solution was promoted to times stability coefficients of those slenderness near break-point calculated by the formula by a coefficient less than 1 to achieve the aim of partial adjustment.After adjustment,the problem of that the reliability index near break-point is lower than others is solved.