## 7 Summary and Conclusions  
In this study, the behavior and design method of the plate-to-RHS K-connections stiffened by chord face stiffener were investigated. Cyclic loading tests were performed to investigate the stiffening effects of the chord face stiffener, and the applicability of current design codes such as AISC 360-10 and CIDECT Design Guide 3 was discussed. The conclusions are as follows.  
1. The plate-to-RHS K-connections exhibited the deformation-controlled hardening behavior dissipating considerable energy after slip occurred at the bolted joint of branch members. Overall, the joint behavior was flexible due to out-of-plane deformations of the connecting chord face and longitudinal plate, and thus, there was not brittle failure such as weld rupture.
2. The behavior of the plate-to-RHS K-connections stiffened by chord face stiffeners was governed first by slip at the bolted joint of branch members and then by the plastification of the connecting chord face. For S15-150 and S25-200, as the chord face stiffener reduced the deformation of the connecting chord face, the initial stiffness and ultimate strength were greatly increased.  
Figure 12: Results of FEM analysis: Mises stress contours and deformations at peak load points: (a) N00-150 (unstiffened); (b) S15-150 (stiffened).  
3. The provisions of current design codes, such as AISC 360-10 and CIDECT Design Guide 3, yielded a reasonable estimate of the chord face plastification strength of plate-to-RHS K-connections. The CIDECT Design Guide 3 resulted in the conservative estimate of the connection strengths, whereas AISC 360-10 slightly overestimated the strength of the stiffened connections.  
If the post-slip-bearing resistance of the bolted joint of branch members is large enough to achieve stable cyclic behavior, the seismic performance of stiffened plate-to-RHS connections can be greatly improved by allowing slip at the slip-critical bolted joint. Thus, for the seismic design of RHS trusses, the following two-phase design may be applicable.  
1. In the first phase, the plate-to-RHS connections are designed for unfactored service loads (i.e., serviceability limit state). The governing limit state of the truss connections is connection slip at the bolted joint of branch members.
2. In the second phase, the plate-to-RHS connections are designed for factored loads at the ultimate limit state. The governing limit state of the truss connections is the plastification of connecting chord face. The bolted joint of branch members should be checked for post-slip failure modes, such as hole-bearing failure and block shear rupture.  
[PERSON] and [PERSON] contributed to experimental and numerical investigations of the behavior of plate-to-RHS k-connections. [PERSON]-[PERSON] contributed to experimental campaign. [PERSON]-[PERSON] contributed to research funding and writing of the paper. All authors have read and agreed to the published version of the manuscript.  
This work was supported by C&S ENG Co., the National Research Foundation of Korea funded by the Korean Government (NRF-R-2019-01064 and NRF-2018R1A6A1A07025819), and the Urban Architecture Research Program of KAIA (19 AUDP-B106327-05).  
The authors declare no conflicts of interest.