Conventional simple girder bridges are often not cost-effective while vulnerable to disasters by earthquakes, floods etc. due to a number of technical deficiencies (★) shown below:
This type of bridge structurally integrates both ends of a simple girder to the top of RC vertical walls:
The backfill is reinforced with a number of geogrid layers that are firmly connected to the full-height rigid (FHR) facing. Both ends of a continuous girder are structurally integrated to the top of a pair of FHR facings. In this way, the girder, the FHR facings and the reinforced backfill are all integrated. As a result, RRR GRS Integral Bridges become much more stable than conventional simple girder bridges, in particular against severe seismic loads.
As the bearings are not used to support the girder, the top of the FHR facings is laterally displaced cyclically by seasonal thermal expansion and contraction of the girder. This may result in settlements in the active zone of the backfill and the development of elevated passive earth pressure. With RRR GRS Integral Bridge, however, as the backfill is reinforced with geogrid layers connected to the FHR facings, these phenomena are effectively restrained and associated harmful problems do not take place. The development of a bump at the back of the abutment due to settlement of the backfill caused by traffic loads and seismic loads is also effectively restrained.
The girder and FHR facings become slender due to structural integration. Moreover, as the FHR facing and girder are constructed after the deformation of supporting ground and backfill has taken place, pile foundations becomes unnecessary.
All these features make RRR GRS Integral Bridge highly cost-effective in construction and maintenance while very stable during long lifecycle service and against severe natural disasters by seismic loads and scouring and over-flow by floods and tsunami.