Importance Sampling Method in V-Space

Based on the observation of importance sampling and second order information about the fail-ure surface of a structure,an importance sampling region is defined in V-space which is obtained by ro-tating a U-space at the point of maximum likelihood.The sampling region is a hyper-ellipsoid that con-sists of the sampling ellipse on each plane of main curvature in V-space.Thus,the sampling probabilitydensity function can be constructed by the sampling region center and ellipsoid axes.Several exampleshave shown the efficiency and generality of this method.