12. Low-cost girder movement restriction device provides improved restorability for existing steel railway bridges

In past large earthquakes, the existing bearings of steel bridges failed, causing the girders to move significantly in the direction perpendicular to the bridge axis. As a countermeasure, girder movement restriction devices (such as side blocks) and anti-bridge-collapse devices (such as widening the girder seats) have been implemented (Figure 1).
However, while this method helps prevent bridges from collapsing, it has a drawback: during a large-scale earthquake, the girder movement restriction device can break, leading to increased movement. This can cause the girder to slide down from its bearings and make post-earthquake restoration more difficult.

We have developed a device that can absorb the energy of earthquake motion by means of high tensile bolt friction grip connection couplings added to a conventional girder movement restriction device, thereby restraining girder movement and preventing sliding down from the bearings (Table 1).
As shown in Figure 2, the couplings of this device have slit-shaped bolt holes to allow greater slippage than conventional couplings, increasing the absorbed energy.

This device can reduce the amount of girder movement during a large-scale earthquake to about 1/3 of that of a conventional girder movement restriction device while maintaining the same cost, and also allows anti-bridge-collapse devices to be omitted (Figure 3).
The design methods are also available and can be applied to bridges of various specifications.