PSI - Issue 78

Maria Maglio et al. / Procedia Structural Integrity 78 (2026) 153–160

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4.1. Configuration 1 The first scissor-toggle configuration (Fig. 2a) follows the geometry proposed by Sigaher and Constantinou (2003). The internal angle between the inclined links is set to 9°, while the angle between the diagonal brace and the base is 51°, resulting in an amplification factor =3.97 . The relatively large angle Ψ notably influences the system’s connections and thus the expected behaviour of the deformable model. In this configuration, the knee-brace is connected to the beam rather than directly to the beam-column joint. When member deformability is accounted for, the structure does not exhibit any plastic response within the analyzed displacement range. Consequently, the dissipative element remains inactive. This happens because this configuration is particularly sensitive to the flexural deformability of the beam, which plays a dominant role in the global deformation mechanism. This behaviour is clearly visible in the amplification factor – displacement diagram (Fig. 3), which shows no significant amplification effect throughout the pushover analysis and in the deformed shape shown in Fig. 4.

Fig. 3. Amplification factor – displacement diagram for C1 configuration

As Fig. 4 shows, the beam undergoes significant flexural deformation, evident from its pronounced curvature. As a result, a substantial portion of the interstorey drift is accommodated by bending of the beam rather than being transferred axially to the knee-brace device. This deformation pattern reduces the relative axial displacement between the two ends of the knee-brace, which is the primary driver for the activation of the energy dissipation mechanism. In other words, the deformability of the beam acts as a mechanical buffer, absorbing horizontal displacements and hindering the effective engagement of the device. This explains why the device remains inactive or only marginally engaged, even under significant global drift.

Fig. 4. Deformed shape of C1 configuration under lateral loading, accounting for member deformability