# Macro-Modelling Approach for the In-Plane Cyclic Response of Cold-Formed Steel Partition Walls
## 4 Validation of the Proposed Analytical Model
### Validation of the Proposed Analytical Model
#### 4.2.2 Damage State Identification  
The damage estimated by the analytical model is confirmed in order to validate that the suggested methodology accomplished its objective of predicting the possible damage mechanism of partition walls. Figure 17 compares the estimated damage states in the analytical model with the experimental observations. The initial stiffness reduction in the screw connections is initiated at a 0.5% drift ratio, which is consistent with the observed damages in the experiment where screw tilting first occurred. As drift ratios increase, damaged screws suffered further damage and a higher number of screws were additionally damaged. After the eighth step of loading drift of 2.2%, several screws suffered pullout and pull-though damages to both the ST600 and ST450 specimens. This damage mechanism is also predicted by the analytical model in which the force-displacement relation of the screw connection starts to show strength degradation from the corresponding drift levels.  
Figure 17: Comparison of analytical and experimental damage states: **(a)** ST600; **(b)** ST450.  
Differences of damage to other components between the ST600 and ST450 specimens was negligible. During the tests, crushing or breaking of GBs at the corner of wall panels occurred in both the specimens in drifts ranging from 1.5% to 2.2% corresponding to 50 th percentile spots of the GB corners damaged. The predicted damage mechanisms include the interaction between GBs and concrete slabs. The initial gaps of GB-to-slab connections were analytically closed at 1.5% and 2.2% drift ratios and crushing strengths reached at 2.0% and 3.0% drift ratios for the ST600 and ST450 specimens, respectively. Although the analytical model produces a slight difference in the contact initiation, it can reasonably simulate the nonlinearity of the force-displacement relation at the GB-to-slab connection. The analytical model of studs installed in the ST600 specimen captures the interaction of the boundary stud-to-track connection at a 2.5% drift ratio and the bearing strength is developed due to such interaction. Rapid strength degradation in the force-displacement relation occurred at a drift ratio of 3.5% of drift, which resulted from the damage states such as local buckling and bending of studs. These damage mechanisms of studs are consistent with the observed damages in the experiment.  
The damage-to-drift correlation obtained from this study is compared to results of previous experimental studies [34; 35], of which the specimens were similar to those utilized in this study. As shown in Figure 18, screw tilting and stud buckling were, respectively, observed on 0.40% and 1.9% of drift ratios which are almost identical to those measured at the ST600 specimen. The noticeable difference is the occurrence of corner crushing of GBs. The early occurrence of crushing of GBs in this study results in the use of smaller gaps between the edge of GBs and slabs, and between the CFS stud and top tracks than used in the previous studies.