Modelling rocking steel inter-module (RSI) connections: parametric analysis of cyclic behavior and wind load performance

This paper presents a novel modelling approach for simulating Rocking Steel Inter-module (RSI) connections within the OpenSees framework. The accuracy of the proposed model is validated against existing experimental tests, and its sensitivity to key design parameters is assessed. Given that such connections are often simplified as either hinges or rigid springs in practice, this study evaluates the impact of a more accurate representation by analysing six twelve-story modular structures under both static and dynamic wind loads. A reliability-based analysis is conducted using the First-Order Reliability Method (FORM) to compare the probability of failure across models and to evaluate the sensitivity of the reliability index to variables such as slab thickness, beam depths, column sizes, and rod diameter. The results demonstrate that the influence of the proposed RSI model is design-dependent. For strong-beam configurations under serviceability wind loads, its global response can be reasonably approximated by a simpler hinged connection model. However, for scenarios where pinching behaviour or significant moment–shear interaction is anticipated, or when reliably predicting acceleration-sensitive performance metrics is needed, the proposed model provides essential accuracy that simplified approaches cannot capture. Furthermore, the reliability analysis reveals that approximating the inter-module connections with rigid behaviour consistently yield higher reliability indices than the accurate modelling approach, with the strong-column weak-beam configuration proving more reliable than its weak-column strong-beam counterpart. The sensitivity measures indicate that slab thickness and column depth are the most influential parameters on system reliability, whereas rod diameter has a negligible effect under service-level wind loads.