Hanshin Expressway Large-scale Renewal Project
No.11 Ikeda Line, vicinity of Ootoyohashi
~opened in 1967~

Meeting New Traffic Demands

Major causes and damage

Additional concrete casting to turn an existing bridge into an expressway in preparation for the Osaka Expo (held in 1970) or an increasing number of large vehicles using the thus constructed expressway turned out to be a great burden to the deck slabs and girders and ultimately caused cracking in the bridge structure.

Causes and Condition of Damage

This section was originally designed as an ordinary road (Osaka municipal road).
An expressway was constructed on this ordinary road structure.
Additional concrete load and an increase in large vehicle traffic, which were never considered in the original design conditions, have given large loads to the bridge girders and caused cracking in the concrete.
Cracks allow entry of water to eventually corrode reinforcing bars inside the concrete.

Back in the Days of Construction

In the days when the bridge was constructed, urban development and road construction were accelerated at a high speed toward holding of the Osaka Expo in 1970.
Construction of expressways was also part of the urgent construction projects.
As a solution to swift road network development, the Hanshin Expressway was constructed using part of the roads originally built as ordinary roads (Osaka municipal roads).
Namely,it was the girders of the Otoyo Bridge over which the expressway road was constructed.
However, to construct the Hanshin Expressway road, the formation level had to be raised by up to 50 cm for height adjustment.
The concrete was thus cast over the existing structure for height adjustment.
This additional concrete, which was not considered in the initial design conditions, gave extra burdens on the bridge structure.