# Seismic Responses of a Cable-Stayed Bridge with Consideration of Uniform Temperature Load
## 5 Case Study and Discussion
### Deck to pylon Connections  
The connection form between the deck and the pylons is an important issue when designing cable-stayed bridges, which determines the path of the forces transformed to the substructure. It is noted that the forces of the superstructure can be transmitted either from cables or from the connection between the deck and the pylons. Three types of connections, in Figure 5, are considered in current research: Connection 1 (deck to pylon is connected by movable bearings), Connection 2 (deck to pylon is not connected), and Connection 3 (deck to pylon is restrained in longitudinal direction). Although Connection 3 is not adopted in the real structure, it is used here to illustrate the effects of different connections on the seismic responses of the bridge with uniform temperature. The seismic responses of the bridge for different deck to pylon connections with temperature changes of \(\pm 0\,^{\circ}\)C and \(\pm 35\,^{\circ}\)C are listed in Table 5. The results show that the seismic responses of the bridge with and without temperature changes are notably different for various connections. Notably, the bending moment at the pylon bottom in Connection 3 is much larger than that in Connection 1 and Connection 2. This can be attributed to the strong restraints between the deck and the pylons in the longitudinal direction. The ratios between the internal forces and displacement of Connection 1, Connection 2, and Connection 3 with temperature change of \(\pm 35\,^{\circ}\)C and with temperature of \(\pm 0\,^{\circ}\)C are listed in Figure 6. The result indicates that Connection 2 does not have a better performance compared with Connection 1 because of the different paths of force transmission. In Connection 1, the forces of the superstructure \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Cable No.** & **0 (\({}^{\circ}\)C)** & \(\pm\)**20 (\({}^{\circ}\)C)** & **Increase (\%)** & \(\pm\)**35 (\({}^{\circ}\)C)** & **Increase (\%)** \\ \hline
1 & 2827 & 2863 & 1.273 & 2872 & 1.592 \\
18 & 2475 & 2485 & 0.404 & 2496 & 0.848 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Earthquake records used in time history analysis. Figure 5: Schematic models of different deck to pylon connections; (**a**) Connection 1—connected by bearings in longitudinal direction; (**b**) Connection 2—not restrained in longitudinal direction; (**c**) Connection 3—restrained in longitudinal direction. are transmitted both from cables and bearingss, whereas, in Connection 2, the forces are transmitted mainly from cables. Therefore, the distances between the shear forces transmitted to the pylon and pylon bottom are significantly different for Connection 1 and Connection 2. Meanwhile, most of the responses of the bridge with different connections are significantly affected by the temperature loading. For example, the bending moments at the pylon bottom of the bridge with different connections are increased by 15%, 17% and 64% respectively with the temperature change of \(\pm\)35 \({}^{\circ}\)C. Pylons, as a critical component of cable-stayed bridges, are vulnerable to strong earthquake. Therefore, the increase of the bending moment demand on the pylon due to temperature loading will further increase the risk of the bridge under strong earthquake. The type of the deck to pylon connection has a significant effect on the responses of the bridge during a strong earthquake with consideration of temperature loading. Generally speaking, Connection 3 is not  
Figure 6: The ratios of the responses of the bridge with temperature change of \(\pm\)35 \({}^{\circ}\)C to their counterparts with changing temperature of \(\pm\)0 \({}^{\circ}\)C for different deck/ pylon connections.