PROPOSAL OF COUNTERMEASURES AGAINST DLIFTWOOD BLOCKAGE OF BRIDGES

Abstract

 In recent years, heavy rain disasters have become more frequent, and extensive damage to road bridges has been reported. A new concept of road risk assessment in Japan is presented for the purpose of constructing a highly reliable road network. Going forward, it is of utmost importance to clarify the damage risk presented by driftwood blockages of road bridges adjacent to rivers in the event of excessive flooding. In this study, we conducted basic experiments on bridges considered to be at high risk, as indicated in previous studies, and investigated how to prevent bridge outflow and flooding to the surrounding area due to driftwood blockage. In addition, the importance of the relationship between bridge girder position and water level, and the blocking mechanism of driftwood for bridges (girders and balustrade columns), are discussed. Finally, girder protection is proposed as a measure to reduce clogging around the girder under the floor slab, and its effectiveness was demonstrated.