Experimental Evaluation of Impact Force Caused by Collision of Expansion Joints for Seismic Isolated Structures

In seismically isolated buildings, expansion joints are installed in floors and ceilings to absorb the relative displacement between surround grounds and the seismic isolated buildings, ensuring safety and functional maintenance after earthquakes. In this study, collision experiments were conducted to determine the magnitude of the horizontal impact force generated by the collision of the main panel to a sloping section on the exterior structures. As the test results, it was clarified that the horizontal impact force was affected by the angle of the sloping section, the collision velocity, and the total mass of the main panel. The horizontal impact force increases in proportion to the collision velocity and the effective mass of the main panel, respectively. However, the effective mass on the horizontal impact force was dominated by the forward side of the main panel, influenced by the position of the additional weight. Also when the angle of the sloping section was reduced from the 45° to 30°, the horizontal impact force was roughly halved. On the other hand, when the angle was increased from 45° to 60°, the horizontal impact force was roughly doubled. Generally, 45° is used for the angle of the sloping section, however architects prefer a larger angle because it allows the expansion joint to be more compact. Based on the test results, it is recommended that employing a smaller angle for the sloping section is preferable from the point of protecting the exterior structure. For structural engineers, an evaluating method of the horizontal impact force for designing the exterior structure has been proposed.