## 5 Conclusions  
Three types of bolted gusset connections, featuring a two-sided slotted gusset plate with unidirectional sliding bolts, two-sided slotted gusset plate with bidirectional sliding bolts and one-sided slotted gusset plate configurations, respectively, were developed to reduce the negative opening-closing action effect on the seismic performance of BRB-RCBs. Finite element analysis was used to investigate their column-gusset-BRB interactions and the corresponding plastic responses. Comparisons were made between three strategies and the traditional one. The main conclusions can be drawn as follows based on the numerical results:  
(1) A strong opening-closing effect on the BRB-RCB was induced by the constraint between the welded gusset connection and its adjacent beam-column zone under severe earthquake conditions. The proposed bolted gusset connection consisted of a slotted gusset plate, end plates, square bolts and steel jackets, which effectively released the frame action through the sliding of the bolt group, as well as improved the seismic behavior of BRB-RCBs.  
(2) No shear failure of the cap beam or buckling failure of the gusset-to-BRB connection (except for the specimen NG-V) was found during the loading process, which indicated that the bolted gusset connection could delay the shear failure of the concrete beam and provide enough stiffness on the BRB-to-gusset connection. Meanwhile, the bolted gusset connection configuration was relatively simple and easy to construct, as well as being suitable for both the new and as-built structures.  
(3) BRB-RCBs with bolted gusset connections exhibited satisfactory and stable hysteretic responses, except for specimens NG-V and NG-S because of their excessive slippages of the bolt group. Among all BRB-RCB models, three specimens with the bidirectional sliding bolt group had the better energy dissipation capacity, while the lateral stiffnesses of the specimens with a one-sided slotted gusset plate were relatively high.  
Figure 21: PEEQ on right pier columns at 3% drift.  
(4) Compared to the BRB-RCB model with the welded gusset plate, the Von Mises stress at the gusset interfaces could be significantly reduced by adopting the slotted gusset plates, with a maximum decrease of 80.7% in the gusset-to-column interface, which would delay the rupture failure in the gusset plate connections.  
(5) By employing the bolted gusset connection, the plastic response level at the columns could be successfully decreased. The primary plastic hinges were formed and further developed on the top of the column near the gusset tip when story drift increased from 2% to 3%. The specimen NG-H had the lowest PEEQ value, which was even less than that of the bare bridge.  
Conceptualization, J.L. and P.C.; methodology, G.X.; software, P.J.; validation, P.J.; writing--original draft preparation, P.J.; writing--review and editing, J.L. 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 (Grant Nos. 51978213, 51778190), the Scientific Research Fund of the Institute of Engineering Mechanics, China Earthquake Administration (Grant No. 2020D04) and the Natural Science Foundation of Heilongjiang Province (Grant No. LH2022E005).  
No new data were created or analyzed in this study.  
The authors declare no conflict of interest.