PSI - Issue 78

Christoph Butenweg et al. / Procedia Structural Integrity 78 (2026) 1689–1696

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in EN 1998-1 (2004), even when the mass inertia force perpendicular to the infill plane is conservatively estimated using the formula for secondary elements in EN 1998-1 (2004), assuming installation in the top story, resonance with the building's natural frequency and a reference peak ground acceleration of 4 m/s². Furthermore, since structural design according to the draft standard FprEN 1998-1-2 (2025) of the second-generation Eurocodes limits interstory drift to 2%, and practical designs typically assume maximum drifts of 1.0 -1.5%, the INODIS system demonstrates additional reserves for the configurations investigated. A comprehensive experimental campaign was conducted on a RC frame with masonry infills decoupled using the INODIS system, as part of the Horizon Europe FLEJOI project (FLExible JOInts for seismic-resilient design of masonry-infilled RC frames), under the European framework ERIES (Engineering Research Infrastructures for European Synergies, 2022–2026). The tests were performed at the shaking table facility of the IZIIS Institute in Skopje. The test structure is shown in Fig. 4, that underwent two phases of shaking table excitation. In Phase 1, fully infilled walls were subjected to in-plane loading, aligned with the direction of excitation, while infilled walls with openings experienced out-of-plane loading. In Phase 2, the test specimens were rotated 90° around the vertical axis so that the walls with openings were loaded in plane, and the fully infilled walls were exposed to out-of-plane excitation. The ground motion excitations were applied with progressively increasing intensity, using the 1998 Adana earthquake (Mw 6.3) and a synthetic accelerogram generated according to the response spectrum for soil type C from EN 1998-1 (2004). Peak ground accelerations of up to 0.33 g were applied in both cases. A maximum interstory drift of 2.6% was recorded. While the RC frame reached its deformation capacity and formed plastic hinges, the masonry infills remained undamaged.

Fig. 4. Test structure with INODIS on the shaking table at IZIIS in Skopje.

4. Benefits of the REGUPOL INODIS system 4.1 Practical application

To assess the practical applicability of the INODIS system in everyday structural engineering, a case study was carried out on a six-story building. The complete design was performed in accordance with EN 1998-1 (2004). For comparative purposes, the RC frame was designed with both interacting (Fig. 5a: rigidly connected) and non interacting (Fig. 5b: decoupled) masonry infills.

a)

b)

Fig. 5. a) Design model with traditional infills and b) design model with decoupled infills.