*3.2. The SBC Scheme*

It can be seen from Section 2.2 that the compressive stress of the horizontal diagonal brace of the transverse connection system of the main arch exceeds the allowable compressive stress, which may lead to buckling instability. Therefore, it is necessary to implement seismic lateral measures to improve the seismic performance of this arch bridge in the transverse direction.

In this project, CHIPFM is proposed for the arch-rib construction. After an archrib construction is completed, the buckle tower and all SBCs are removed. The SBCs used can only assist in the construction, and the SBCs removed after the completion of the construction cannot assist in the construction of other arch bridges again. The SBCs are discarded, causing a certain level of waste. Therefore, the SBCs removed after the construction were reused in the present work. After the completion of the bridge's construction, the SBCs are not removed directly, but remain as the "fuses" to support the arch bridge's seismic resistance. The specific method is as follows: the end of SBC connected with the arch rib (called the A end) does not need to be moved, but the other end of the SBC (called the B end) is anchored in the canyon bedrock, and the arch bridge's transverse stiffness is increased through the reasonable arrangement of SBCs, so as to improve the arch bridge's transverse seismic performance. Moreover, SBCs are easy to replace and can be replaced directly in case of damage after an earthquake. The schematic diagram of the SBC scheme is shown in Figure 9.

**Figure 9.** Schematic diagram of SBC scheme.

The seismic-performance-improvement effects of several SBCs layout schemes were compared, and the best scheme was obtained, as illustrated in Figure 10. This scheme is called Model 2. Compared with the construction-layout scheme, the SBCs near the arch foot in Model 2 are removed, leaving only the SBCs of the <sup>1</sup> <sup>4</sup> -arch-to- <sup>3</sup> <sup>4</sup> -arch-rib section. The nodes (called the A end) connecting the remaining SBC and the arch rib remain unchanged, but the other end of the SBC (called the B end) needs to be adjusted, as follows. The B ends of the six SBCs at the top of each side are moved 50 m to the lateral outer side, and the B ends of the other SBCs are moved 30–40 m in the vertical downward direction. The B ends of the SBCs move a certain distance in the vertical downward direction to prevent the SBCs from bearing the self-weight of the structure as far as possible, so as not to change the structural system of the original model, while endowing the arch0bridge structure with greater lateral stiffness and better seismic-performance improvements.

**Figure 10.** Layout of SBC. (**a**) Front view. (**b**) Top view. (**c**) Stereogram.
