Hanshin Expressway Large-scale Renewal Project
No. 13 Higashi-osaka Line, vicinity of Houenzaka
~opened in 1978~

Handing down the Naniwa Palace Remains Buried Underground to Future Generations

Major causes and damage

Special structure of the Route 13 Higashi-Osaka Line employed to preserve the historical remains became the cause of fatigue cracking of steel girders.
Even despite repeated repair, the damage never stopped, and faulting once occurred on the road surface.

Causes and Condition of Damage

A special structural solution was employed in this section to meet special site requirements, which was the foundation without piles and a light-weight superstructure.
However, the light-weight structure repeatedly received large vehicle loads as the section had a large traffic volume.
Eventually cracks have occurred at various parts of the steel girders by metal fatigue, and faulting occurred on the road surface.
Emergency repair was conducted by structural reinforcement.
However, repeated loading is expected to continuously cause damage to the section.
It is therefore necessary to make a drastic change in the road structure.

Back in the Days of Construction

Construction site in those days

Although the site of the Naniwa Palace, one of ancient capital palaces of Japan, had been unknown for many years, a survey conducted in around 1960 found that a vast stretch of remains spread southwest of the Osaka Castle.
When construction of an expressway crossing over the remains was planned, it was decided that the expressway road be constructed in a pile-free structure in order to protect the remains and preserve the environment around the Osaka Castle.