Kentaro ISHII

Study on Evaluation of Stress Properties of Steel-Topped Arch Bridges by Replacing Deck Slabs

Eiji IWASAKI

In recent years, there has been an increasing need for large-scale construction work to extend the service life and improve the functions of steel bridges as a countermeasure against structural deterioration and functional obsolescence. In the replacement of slab slabs, it is necessary to select the appropriate slab replacement sequence according to the type of the bridge. In particular, for arch bridges, the sequence of slab replacement may cause unexpected deformation of the bridge due to the change in stress properties and the resulting localized high stresses.
The purpose of this study is to establish a modeling method for steel arch bridges to understand the changes in stress properties during slab replacement and to select an appropriate slab replacement sequence from the viewpoints of safety and workability of construction. Three analytical models with different coupling conditions between elements of vertical members were developed and the results of dead load analysis were compared. As a result, it is confirmed that the analytical results of each model for arch ribs and stiffening girders are generally consistent and are not affected by the edge of the vertical timber. On the other hand, in the case of vertical timbers, the difference between the results of each model is large, indicating that the results are affected by the vertical timber ends. Next, assuming that the slab is removed in one direction and symmetrical direction, stress tests are conducted for each slab replacement step. As a result, it was confirmed that the stress levels of the arch ribs, stiffening girders and vertical members exceeded the allowable stress level when the slab was removed in one direction up to the center of the span. On the other hand, when the slab was removed in the symmetrical direction, it was confirmed that the increase in the stress level due to the slab replacement was suppressed, indicating that the slab should be removed in the symmetrical direction.