# Nonlinear Seismic Response of Multistory Steel Frames with Self-Centering Tension-Only Braces
## 5 Conclusions  
This work presents an extensive investigation of the nonlinear seismic response of multistory steel frames built with self-centering tension-only braces (SC-TOBs) to internal force, drift, and energy dissipation. Pushover analysis adopting two lateral load distributions and nonlinear dynamic analysis under four suites of 16 ground motions corresponding to four hazard levels were conducted. The conclusions from the investigation can be summarized as follows:  
* As expected, the SC-TOBs serve as conventional TOBs only providing necessary lateral stiffness when subjected to low level seismic hazard and begin to function with energy dissipation as the intensity of ground motions increases. All structural elements, such as cables, always remain elastic both in pushover analysis within 2% roof drift angle and in dynamic analysis under the severe hazard level, displaying a full self-centering capability without any residual deformations.
* The SC-TOB frames (SC-TOBFs) exhibit a bilinear base shear response with a significant stiffness reduction when the yield-like activation is attained, which facilitates the capping of seismic forces induced in the structures similar to the softening behavior of yielding systems. Besides, the internal force distributions of structural elements are observed to be nearly identical with the increase of intensity as long as the SC-TOBs are triggered.
* Although drift is prone to be concentrated around the middle stories of the SC-TOBFs when subjected to parabolic load distribution and at bottom stories under uniform load distribution, it is  
Figure 14: Energy dissipation distributions under (**a**) GM 1; (**b**) GM 2; (**c**) GM 3; and (**d**) GM 4.  
Figure 15: Total cumulative energy dissipation.  
reliably limited within the code-prescribed limit of 2.0% under maximum considered earthquakes, and the SC-TOBFs are confirmed to have full self-centering capacity even when the maximum inter-story drift angle reaches twice the limit. In addition, the drifts develop as the intensity increases, but their distribution remains nearly unchanged.
* With the intensity getting higher, the energy dissipation of the SC-TOBFs continuously increases without stagnating at certain stories of the building, reflecting good structural interoperability of the bracing members along the structure height. For the prototype building, the lower and middle stories generally dissipate more seismic energy than the upper stories, and almost no energy is dissipated in the upper stories under certain load conditions, suggesting that the SC-TOBs on those stories could be replaced by conventional TOBs, thereby reducing costs while retaining fully the self-centering capability.  
Conceptualization, P.C. and J.D.; Formal analysis, P.C. and W.T.; Funding acquisition, P.C. and D.C.; Writing--original draft, P.C. and W.T.; Writing--review & editing, J.D. and D.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (Grants No. 51708482 and No. 51578478), the China Postdoctoral Science Foundation (Grant No. 2017M621593), and the Six Talent Peaks Project in Jiangsu Province (Grant No. JZ-035).  
The authors declare no conflict of interest.