## 5 Discussion
As depicted in Figure 12, the displacement trace associated with the TnT-enhanced frame shows a significant peak in amplitude, which seems to manifest marginally earlier than that observed in the trace corresponding to the X-type braced system. Additionally, the evidence of residual displacements in the TnT enhanced frame is clearly illustrated in the figure. It shows that this frame experienced approximately 5 mm of residual displacement, which aligns closely with the observed hysteretic response. This alignment suggests that the TnT effectively yielded after absorbing a significant amount of energy. Furthermore, these findings are consistent with the results obtained from the shake table tests. While both experimental and numerical findings affirm the effectiveness of the TnT system at a model scale, several significant limitations hinder their direct application to full-scale edifices. Initially, the specimens utilized in the shake table experiments were fabricated at a one-third geometric scale; although the slenderness ratios of the cross-sections adhered to similitude principles, the absolute thickness of the restrainer tube walls was unavoidably diminished. This scaling methodology may inhibit critical phenomena such as localized denting, interfacial bearing stresses, and frictional dynamics between the inner and outer tubes, which could result in discrepancies in hysteretic behavior when scaled up. Moreover, the scaled clearances between the tubes may exhibit divergent behaviors under full-scale conditions, influenced by the tolerances, imperfections, and variability inherent to real-world construction practices. Furthermore, the concrete mixture employed in the scaled models was deliberately formulated to emulate the low compressive strength characteristic of inadequate Turkish residential buildings. However, various attributes of this simulant, including aggregate  
Figure 12: Displacement time trace plots for TnT and X-type frames. grading, moisture content, curing conditions, and shrinkage behavior, are bound to differ from those of actual construction materials. As a result, the specific patterns, densities, and propagation rates of micro-cracks that develop under cyclic shear loading at full scale may not be accurately captured, leading to discrepancies in damage progression and stiffness deterioration in prototype structures. Additionally, the effects of strain rate on material properties, particularly under the dynamic loading conditions experienced during actual earthquakes, may vary significantly at larger scales and were thus not entirely elucidated by the present experimental framework. These constraints underscore the imperative for further experimental investigations at larger scales, utilizing authentic construction materials and methodologies, to substantiate the generalizability of the observed advantages. Such prospective studies should ideally encompass a variety of ground-motion scenarios to enhance comprehension of variability in structural responses and to bolster broader confidence in the applicability and dependability of the proposed TnT retrofit system for extensive practical deployment. In synthesizing the empirical evidence with contemporary theory, it is instructive to interpret the TnT brace through the lens of the \"four R\" resilience construct--robustness, redundancy, resourcefulness, and rapidity--that underpins FEMA P-58 [52]. Robustness, defined as the inherent capacity of a system to resist damage without losing essential functions, is enhanced because the TnT's continuous outer shell restrains both global and local buckling, thereby arresting the brittle column-shear and joint-punching failures that characterized the control specimen. Redundancy, the provision of alternative load paths to accommodate unexpected demand, is elevated once axial forces are shared between the existing concrete columns, the yielding steel core, and the restraining tube; this redistribution mitigates the single-point vulnerability that non-ductile Turkish frames typically exhibit.