Moment resistance statistical distribution of beam-to-column composite joints

In seismic design of steel–concrete composite moment resisting frames, the randomness of beam-to-column joint rotational response can affect the location of dissipative zones. In fact, in case of full-strength joints, the dissipation of the earthquake input energy occurs at the beam ends; conversely, in case of partial-strength joints, the connection components of beam-to-column joints are involved. Within this framework, random material variability of joint components plays an important role, because it affects the joint flexural strength and, as a consequence, also the plastic rotation supply. Therefore, within the framework of a research program aimed at the evaluation of the seismic reliability of steel–concrete composite frames including random material variability, this paper focuses the attention on the analysis of the influence of random material variability on the rotational response of beam-to-column joints. In particular, the aim of the work is the evaluation, by means of Monte Carlo simulations, of the statistical distribution laws of the parameters describing, from the overall point of view, the rotational behaviour of beam-to-column joints. Such distribution laws represent important input data for a complete probabilistic seismic demand analysis of steel–concrete composite moment-resisting frames where the joint modelling is performed by using rotational spring elements whose parameters are selected as random values satisfying the distribution laws previously derived.