## 5 Non-Linear Static Analyses  
Two lateral force distributions were used to perform the pushover analyses of the structures: one proportional to the masses and another consistent with the fundamental mode of vibration. For the sake of brevity, the comparison between the capacity curves varying the loading pattern is only shown for MEG structures in Figure 4. In fact, the trend is almost the same for all of the other investigated buildings; specifically, the capacity curves evaluated for the mass-proportional loads are systematically characterized by greater stiffness and resistance, as well as smaller displacement capacity, than those evaluated under first-mode proportional loads. As anticipated, the push-over analyses were performed considering the deletion of links once their capacity was reached during the analyses. In conf. 2, a larger demand on the very short links can be observed, one which led to their anticipated failure and a sudden loss of structural capacity. Therefore, the push-over resistance increases up to the attainment of the maximum capacity of the first link; after that, a sudden resistance drop can be pointed out. The re-loading branch of the response curve is due to the contribution of the other links. Figure 3: Link element (shear spring) model in Seismostruct. In all the investigated cases, the structural displacement capacity was verified against the target values for Damage limitation, Significant Damage, and Near Collapse limit states. The comparison between the two investigated configurations (i.e., the ones with short and very short links) is depicted in Figure 5.  
From the force-displacement curves, it can be observed that the structures with shorter links show a slightly higher lateral stiffness and peak resistance, mainly due to the different diagonal slopes. However, this configuration shows a smaller ductility with respect to the structure equipped with very short links. Indeed, the structures equipped with very short links fulfill the drift displacements at both DL and SD but are not able to meet the required displacements at the Near Collapse limit state. In particular, in all the investigated cases with configuration 2, the failure of the links was observed (which corresponds to the sudden loss of capacity of the pushover curves) prior to the NC drift demand. This result suggests that the use of very short links may be not effective, because the shorter the link, the greater is their ductility demand at the same drift with respect to the links of configurations 1. However, the advantage of very short links (configuration 2) is mainly limited to the smaller forces expected on the connections at the link ends and thus simpler connection details. This aspect can be economically convenient, especially if the detachable links are used with deep sections. Unfortunately, the primary drawback in adopting this type of configuration is that explicit checks have to be made in the design stage to ensure that the deformation capacity of such very-short links suffices for the overall displacement demand, thus requiring at least pushover analyses to check the consistency of the design procedure,  
Figure 4: Comparison of the capacity curves varying the loading pattern (mass vs. first-mode loads) for the 8-, 4-and 2-story buildings ((**a**–**c**), respectively). since the conventional elastic analyses may not be an efficient way to estimate the ultimate deformations of the building. Nevertheless, the presence of MRFs in combination with EBFs is highly important, because a secondary resisting mechanism activates once the links fail, thus guaranteeing an important reserve of ductility and residual resistance. Figure 5 depicts the comparison between the three sets of investigated structures (i.e., GEG, MEG, and MEM) in terms of force-displacement curves. As expected, the structure configurations with two MRFs in conjunction with the EBFs are characterized by higher levels of post-yield rigidity and resistance.