ABSTRACT A full‐scale three‐storey one‐bay‐by‐two‐bay steel rocking structure designed for the RObust BUilding SysTem (ROBUST) project consists of a central gravity frame (GF) and two exterior rocking frames (RFs) in the loading direction. Energy dissipation is provided by tension‐only friction dissipators and by moment connections in the beams extending from the central GF, which have the effect of partially restraining RF uplift. These beams, which span perpendicular to the loading direction, have nominally pinned connections adjacent to the exterior RFs and moment connections at the interface with the central GF. The moment connections on the two sides of the GF have different connection details with similar moment‐rotation loading characteristics but different unloading behaviour. Tests on the friction connection component of the tension‐only dissipators indicated that the sliding force varied during piecewise monotonic elongation. Shaking table tests with peak table accelerations up to 0.6 g exhibited RF uplift and showed the structure fully self‐centred with almost no damage. Despite similar loading characteristics, differences in unloading behaviour of the connections in the transverse beams on each side of the central GF caused significant floor plan torsion, and north and south RF peak absolute roof drifts of 0.92% and 0.42%, respectively. Three‐dimensional finite element model results matched the experimental behaviour well for the maximum applied shaking intensity. A parametric study using the experimental ground motion record showed roof displacements increased 54% due to the moment connection unloading difference, but this average value decreased to <8% considering multiple ground motion records.
Zhang et al. (2026) studied this question.