PSI - Issue 78

Melina Bosco et al. / Procedia Structural Integrity 78 (2026) 1087–1094

1088

elastic (Damage Limitation limit state). For earthquakes with probability of exceedance of 10% in 50 years, links are expected to yield in shear and/or flexure - depending on their mechanical length - and dissipate energy, while members of MRF should remain in the elastic range of behavior (Significant Damage limit state). This ensures rapid return to occupancy after earthquakes. For rarer earthquakes with probability of exceedance of 3% in 50 years, yielding of beams is accepted; however, the Near Collapse limit state should not be reached (Shoeibi et al., 2019). Over the last decade, some design procedures have been proposed for the structural system under investigation. Some of these procedures are formulated according to the displacement-based approach (Tazarv and Mohebkhah, 2019a-b), some others rely on simplified force-based approach (Shoeibi et al., 2019) or on the plastic mechanism control (Montuori et al., 2023). More recently, the authors of this paper have formulated a force-based design procedure (Bosco et al., 2024a) that is consistent with the design procedures included in the upcoming version of Eurocode 8 for other structural types. Although the effectiveness of this design procedure in ensuring a global collapse mechanism and limiting the damage to beams and columns has been validated through nonlinear dynamic analyses, relatively low values of the behavior factor have been used in design to limit the maximum interstory drift below the upper limit of 2% of the interstorey height. This limit is provided for seismic events with a probability of exceedance equal to 10% in 50 years. This issue can make the use of LC framed systems economically disadvantageous for mid rise buildings. In this paper a modified structural configuration featuring three linked columns is proposed in order to reduce the interstorey drift demands and make the use of higher values of the behavior factor possible.

Fig. 1. (a) linked column frame system; (b), (c), (d) performance objectives at the DL, DS and NC limit states.

2. Deformability of the linked columns The two subsystems that cooperate within the LCF systems, separately considered, are characterized by a different heightwise distribution of lateral stiffness. This section focuses on the primary system (i.e., dual columns connected by links). For simplicity, column continuity is neglected and the case of a single link positioned at an intermediate height is examined. Accordingly, the system is analyzed starting from the modular configuration depicted in Fig. 2a where h /2 represents the distance between two links and e is the link length. When the above system is subjected to lateral loads, the lateral displacements are given by the sum of two deformative contributions: (1) that due to the shear and flexural deformation of members (Fig. 2b), and (2) that due to the axial elongation or shortening of the columns (Fig. 2c). The significance of the latter contribution increases with building height and becomes more pronounced in the case of short links. Indeed, the axial deformation of columns Δ h causes a rotation θ that is equal to

2

h



θ

(1)



e

To limit the deformative contribution due to the axial elongation or shortening of the columns, this paper proposes the use of a structural configuration featuring three linked columns (Fig. 2d). In this configuration, the central column