# Seismic Design Procedure for Low-Rise Cold-Formed Steel-Special Bolded Moment Frames
## 6 Conclusions  
The original cold-formed steel-special bolted moment frames (CFS-SBMFs) were introduced in an AISI seismic standard. However, the current ASCE 7 only permits buildings using this system to be one storey in height. Therefore, this study aimed to extend the concept of the original CFS-SBMFs to multi-storey low-rise buildings by utilising the advantage of system ductility provided by bolted connections' slippage and bearing.  
This study was divided into two parts. In the first part, a new beam-to-column moment connection detail was proposed for utilisation in multi-storey structures. Additionally, a design procedure for this connection was proposed to ensure ductility from the bolted connections rather than the beams or columns. Full-scale specimens were prepared, and the structure's performance was clarified through cyclic testing. The testing showed that the proposed bolted beam-to-column connection performed as designed; inelastic behaviour was delivered by the bolted connection, while the beam and column essentially remained elastic. It was also demonstrated that the inelastic behaviour of the proposed bolted beam-to-column connection could be predicted through mathematical modelling with reasonable accuracy.  
In the second part of the study, nonlinear analyses of archetype frames were conducted by following the FEMA P695 methodology. Four configurations of archetype frames were designed using the proposed connection design procedure. Seismic design factors (SDFs) were considered during the frame design, assuming their use in multi-storey low-rise buildings (see Table 5). A static nonlinear pushover analysis demonstrated that the assumed design system overstrength factor was appropriate. Moreover, the ultimate limit state mechanism formed after the storey drift ratio exceeded 4.0%. Two different dynamic  
\begin{table}
\begin{tabular}{c c c} \hline
**Total Collapse Uncertainty** & **Collapse Probability of 10\%** & **Collapse Probability of 20\%** \\ \(\beta_{\text{TOT}}\) & \(ACMR_{10\%}\) & \(ACMR_{20\%}\) \\ \hline
0.525 & 1.96 & 1.56 \\ \hline \end{tabular}
\end{table}
Table 10: Acceptable collapse margin ratio corresponding to the collapse probability.  
analyses were carried out to assess the dynamic characteristics. The first nonlinear time history analysis was conducted with a seismic intensity equal to the design base earthquake (DBE) level. The average maximum storey drift ratio of the archetype frames did not exceed the criterion provided in ASCE 7, which was 2.0%. Additionally, the deflection amplification factor computed in the dynamic analysis was smaller than the assumed design value, indicating that the assumed design value was appropriate. A second nonlinear time history analysis was conducted using incremental dynamic analysis (IDA), and the collapse margin ratio of the archetype frames was assessed. Based on the probabilistic approach, the designed multi-storey low-rise CFS-SBMF building met the requirements of FEMA P695, and the assumed response modification coefficient was shown to be appropriate.  
Conceptualisation, A.S.; methodology, A.S.; software, A.S. and H.K.; validation, A.S. and H.K.; formal analysis, A.S. and H.K.; investigation, A.S. and H.K.; resources, A.S. and H.K.; data curation, A.S. and H.K.; writing--original draft preparation, A.S.; writing--review and editing, A.S.; visualisation, A.S. and H.K.; supervision, A.S.; project administration, A.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare that they have no personal circumstances or interests that could improperly influence the representation or interpretation of the reported study results.