Hanshin Expressway Large-scale Renewal Project
No.3 Kobe Line, vicinity of Kyobashi
~opened in 1966~
The State-of-the-art Technology in Those Days and Rapid Progress of Damage Beyond Expectation
Major causes and damage
Hinge-type joints located near the center of the bridge girder sagged more than expected in the original design, which resulted in subsidence of the road surface.
Causes and Condition of Damage
Although the method regarded rational in those days was employed to match the locational conditions of this section, the hinge type joints near the center of the bridge girder gradually sagged, and the road level then greatly settled.
As an emergency measure, the sagging bridge girder was pulled up with cables laid inside. This solution, however, showed no sufficient recovery, and subsidence is likely to start aggravation again.
Back in the Days of Construction
The structure in this section is a bridge over the sea. To reduce the number of bridge piers, the bridge length had to be long enough to stride over the sea. The method that uses hinge type joints near the center of the bridge girder was one of the state-of-the art techniques for construction in those days as it was considered highly rational in terms of structural dynamics when a bridge structure with a long span and shorter bridge girders was constructed. However, because of aging, the central part greatly sagged more than expected in the original design. It is necessary to take measures to control sagging and make radical improvement of the structure by large-scale renewal.