ABSTRACT
The Meishin Expressway, which opened in 1963, was the first expressway to be built in Japan. Its bridges incorporated a number of special forms of construction that are not used today. One type of bridge that was adopted particularly often was a bridge whose intermediate piers consisted of rocker piers with hinges at the top and bottom ends. With this construction, the intermediate piers bear only vertical forces from the superstructure and do not transmit horizontal forces. For this reason, it was an appropriate form of construction that did not generate large bending stress in column sections. Furthermore, since this form of construction was simple and inexpensive, it was used extensively in the early days of expressway construction in Japan.
However, following the Kobe Earthquake, some rocker piers were found to have developed horizontal cracks in the termination section. Therefore, given that the Mesnager hinges were surrounded by load-bearing concrete and shock-absorbing rubber, this suggests that in the event of a large horizontal displacement of the entire bridge during a major earthquake, the constraining effect of these elements contributes to rotational rigidity, and the behavior of the Mesnager hinge thus differs from the design assumptions.
Also, the rocker piers had an extremely thin wall thickness of about 300 mm and the yield strength was small; thus, the seismic performance of the piers themselves is presumed to have particularly diminished due to the effect of the rotational rigidity of the Mesnager hinges. Comparison of damaged conditions. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig191_1.jpg"/> Rotational rigidity of Mesnager hinge according to test results. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig191_2.tif"/> Model using simulation analysis. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig191_3.tif"/> Modeling of function-separating bearings. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig191_4.tif"/>
Japan is one of the most earthquake-prone countries in the world, and the strong possibility of a major earthquake with its epicenter in the Nankai Trough occurring in the future; thus, this paper presents the conclusions from a seismic analysis and seismic performance study of bridges with rocker piers, taking into account the results of tests that focused on the rotational rigidity and failure mechanism of the Mesnager hinges, and the stress properties of the columns.
