Structural Reliability Assessment of Composite Columns in Steel and Concrete using Non-linear Finite Element Analysis

In Eurocode 0, the ultimate limit state is related to the structural failure (collapse) of a part e.g., column, beam, foundation or the entire structure. Mathematically, this can be expressed in terms of limit-state function g(x) = R(x) – S(x), and the probability of failure as Pf = P [g(x)<0] where R is the resistance of the structure and S is the loading part. In Eurocode 0, the target reliability index β for reference period of 50 years is β=3.8 which represents the probability of failure of 0.1%. The probability of failure is related to reliability index β as Pf=Φ(−β), where Φ is cumulative distribution function of the standard normal distribution. In finite element analysis (FEM), the input parameters e.g., geometry of the structure, materials, loads, and other structural properties are deterministic, while the stochastic finite element analysis is an extension of FEM, which allows variation of these parameter as random variable. In this study the stochastic finite element analyses for composite columns in steel and concrete were performed using OpenSeesPy and QuoFEM. First the deterministic model was developed in OpenSeesPy and validated with experimental results and ABAQUS then, the model is transformed in probabilistic one using QuoFEM which is an open-source research application software with focus on providing uncertainty qualification methods. To generate sampling of the random variables, The Latin Hypercube Sampling (LHS) and Monte Carlo (MS) were used. The results from parametric SFEM analyses were compared with safety level provided by Eurocode 4 according to general and simplified method for design of composite columns in steel and concrete under compressive axial load.