Statistical Analysis Method of Cable-stayed Bridges Behavior by Method of Moment Estimation Ho Jin Jeon   ABSTRACT This paper presents the dispersion characteristic of cable-stayed bridges behavior by method of moment estimation and predicts probabilistic distributions of the responses of structures.    Designing or analyzing cable-stayed bridges studies its mechanical behavior by structural type and design variable etc. and has to investigate sufficiently effects of design variable on total structural system. However, if this design variable is constant random variables, it is difficult to evaluate correctly structural behavior. The method of moment estimation approximates the probabilistic distribution of structural responses by using the probabilistic distribution of random variables considering Taylor series about random variables. Monte Carlo simulation is not suitable to analyze complicated structures, because it need long time to conduct repeatedly the probabilistic analysis from the structural analysis. This paper proposes the secondorder third-moment method to predict the probabilistic distribution of structural responses and evaluates the mean, standard deviation, skewness of the cable-stayed bridge responses.    The sensitivity analysis of cable elements for a second-order third-moment method is directly calculated by using the elastic catenary cable elements that are different from the existing equivalent truss elements proposed by Ernst. Applied input random variables in this study are independent Modulus of elasticity and Girder weight of cables respectively, and considering this variables, this paper is studied the mean, the standard deviation, the skewness of the responses of structures by using the second-order Taylor series of multi-random variable. Also, as a result of probability analysis, the non-linear probability distribution of the responses is approximated as three-parameter lognormal distribution. Monte-Carlo simulations were used for the verification of the developed program. The validity of the proposed method is demonstrated by cable stayed bridge examples and compared with the results of the Monte Carlo simulation.   Key Word The Method of Moment Estimation, Second-Order Third-Moment Method, Monte Carlo simulation, Elastic Catenary Cable Element, Three-Parameter Lognormal