# Friction Behavior of Ceramic Materials for the Development of Bridge-Bearing Friction Materials
## 4 Test Results and Analysis of Bridge Bearings with Ceramic Applications
### Compression Test Results of Bridge Bearings by Friction Material  
The results of the compression tests for bridge bearings with ceramic and PTFE friction materials are shown in Figure 9. Both the ceramic and PTFE materials demonstrated sufficient compressive stress under a load of 4500 kN, which is 1.5 times the capacity of the 3000 kN bridge bearing, showing ideal compressive behavior during both the loading and unloading phases. Additionally, when subjected to a load of 9000 kN, representing 3.0 times the bearing capacity to simulate extreme conditions, both ceramic and PTFE materials exhibited compressive stress with adequate load-bearing capability, indicating that both  
Figure 8: Optimal application for ceramic-friction materials. materials are capable of maintaining sufficient performance under standard and extreme loading conditions, suggesting their suitability for use in bridge-bearing applications. Ceramics exhibit sufficient compressive durability under both normal and extreme compressive loads, which can be attributed to their superior strength and hardness. Bridge bearings are structural components subjected to significant continuous compressive forces owing to the self-weight of the superstructure and live loads. Although the magnitude of the compressive force varies momentarily owing to the external dynamic loads, these variations are relatively small compared with the continuous compressive load, with a minimal fluctuation range. In addition, even if impacts and vibrations occur, the energy dissipates as it travels to the location of the ceramic-friction material, effectively damping the forces. Although ceramics are brittle materials, they do not require special consideration for impacts and vibrations under typical bridge conditions. Figure 10 presents the friction test results of the 3000 kN bridge bearings with ceramic and PTFE friction materials. For a bridge bearing with a ceramic material, the friction test results showed that the horizontal load gradually increased with the number of friction cycles and eventually converged to a consistent horizontal load level. Similarly, the COF increased with the number of friction cycles, but gradually stabilized, converging toward an average COF of 0.16. This indicates that, although the frictional behavior of the ceramic material initially increased, the rate of increase diminished over time, resulting in a consistent frictional performance. This stability suggests that ceramic materials do not exhibit defects or failures under repeated friction, confirming their potential as durable materials for bridge bearings. In contrast, the friction test results of the bridge bearing with PTFE exhibited stable horizontal loads, regardless of the number of friction cycles, with an average COF of 0.0027. The low COF of PTFE is influenced by the inherent properties of the material, which are significantly enhanced by the application of lubricants, resulting in a markedly improved frictional performance. These findings underscore the potential of ceramic-friction materials to provide durable and stable frictional behavior under repeated loading, and highlight the efficiency of PTFE in achieving extremely low friction through the use of lubricants. After completing all the compression and friction tests, the bridge bearings with the ceramic and PTFE friction materials were disassembled for visual inspection, and the results are shown in Figure 11. The ceramic material exhibited no damage or defects on its edges or surface, and was confirmed to remain securely in place within the bridge bearing without any displacement. This indicates that ceramic materials maintain excellent wear resistance and durability, even under high compressive forces and repeated frictional behavior. Figure 9: Compression test results of bridge bearing by friction material. In contrast, although no damage or defects were observed in the PTFE friction material, most of the applied lubricant migrated toward the edge of the friction material.