Research Of Probabilistic Design Methods Based On Global Reliability For Static Stabilitiy Of Single-layer Latticed Domes

The traditional design method of the spatial structure fails in precisely considering the uncertainties of random variables,for taking a rough and experiencing global safety factor.This dissertation selects the kiewitt8 structure for global stability analysis based on ANSYS and MATLAB.Furthermore,the probabilistic design method is proposed based on global reliability.The main research contents of this dissertation are summarized as follows:(1)Establishment of finite element model of K8 single-layer latticed domes in ANSYS.The tube members are modeled by BEAM189 element,the nodes are fixed and the bearings are constrained all degrees of freedom.The proper ty of the steel is simulated by bilinear constitutive model,which means a small tangent modulus.The uniform load is concentrated to nodes in the form of concentrated loads.The force-displacement curve is coincide with the earlier research,which demonstrates the reliability of the model.(2)The probabilistic models of uncertainty factors are analyzed.The initial imperfection of the shell and the external diameter and thickness are described by normal distribution.The yield stress,elastic modulus and Poisson's ratio are described by logarithmic normal distribution.The normal distribution is for dead load,and the type ? extreme value distribution is for live and snow loads.(3)The Monte Carlo simulation(MCS)is conducted for sensitivity analysis.The initial imperfection,yield stress,elastic modulus and Poisson's ratio,the initial imperfection of the shell,the external diameter and thickness of the tube are analyzed.(4)The process of snow drift is simulated by ANSYS,the Monte Carlo simulation and response surface method(RSM)are both carried out for computing the failure probability of the K8 structure.Besides,the failure probability of the structure is calculated based on the design formula from the Technical specification for space frame structures,and comparative analysis with the failure probability under actual conditions is done.(5)Parameters analysis is done based on RSM,six parameters are taken into consideration,which are external diameter and thickness of the tube,yield strength and dead,live and snow loads.Span ratio is considered.MCS is done based on limit state functions which are calculated by RSM,and a probability distribution model is proposed for K8 single-layer latticed domes.(6)The target reliability index is calibrated according to the Unified standard for reliability design of building structures.Global safety factor are calculated based on limit state function,and comparative analysis is done via a known target reliability index.Moreover,the partial safety factors are calculated.