Probabilistic study of the behavior of steel frames with partially restrained connections

The reliability of steel frames with type PR (partially restrained) connections is dependent on the variability in the moment–rotation characteristics of the connections. In this paper, the contribution of this source of variability to the uncertainty in frame deformation is examined using stochastic finite element analysis to compare the effect of initial connection stiffness to that of bending stiffnesses of the beams and columns. The PR connections have top and seat angles connecting the beam and column flanges, and double web angles connecting the beam web to the column flange. A stochastic finite element analysis is used to develop system fragilities, which depict the probability of exceeding three limit states related to the maximum horizontal displacement, maximum interstory drift ratio and elastic bending moment capacity as a function of lateral force. The effect of the variability in initial connection stiffness on frame response is sufficiently important to require careful consideration in performance-based design.