A spring damper with trigger function and self-restoration function is going to be installed at a curved cable-stayed bridge to raise the seismic performance. Since this type of devise has never been used for a bridge so far, two types of loading tests of the spring damper were performed to verify the performance under the conditions in the actual bridge; one is a cyclic loading test and the other was a long-term constant loading test. The cyclic loading test was to identify the force-displacement relationship, and its temperature and loading-speed dependencies, verifying the performance in case of large-scale earthquakes. The long-term constant loading test was to identify the durability of the spring damper, verifying the performance in case of a dead load condition. As a result, it was verified that the spring damper could meet the specified performance criteria under the conditions in the actual bridge although a minor temperature dependency in the force-displacement relationships was found.