4. Method for reinforcing or repairing deteriorated slabs on viaducts

Recent years have seen progressive aging of slabs on RC rigid frame viaducts, which has led to concerns about weakening load bearing capacity. At the same time, with increasing speeds of high speed trains, there is a growing demand for means to reduce vibrations and noise.

A viaduct slab reinforcement method has therefore been developed with UFC (ultra high strength fiber reinforced concrete) boards or deck plates.

In both methods a UFC board or deck plate is affixed to the underside of the slab and shrinkage compensating mortar is injected to bind them together into a single unit (Figs. 1 and 2). Compared with traditional repair methods involved the whole section of a unit, the new method should be more practical since it does not require large scaffolding and is expected to offer considerably higher resistance force.

The UFC boards affixed to the underside of the slabs are thin and light weight, and do not therefore add any significant burden on the foundations. The bonding method with deck plates on the other hand considerably increases slab rigidity, and therefore have the added feature of helping to reduce vibration and noise.

Loading tests validated that both methods not only greatly increased load bearing capacity of the slabs, but also significantly raised rigidity (Fig.3). Further analyses demonstrated that when deck plates were used for reinforcement, structural noise from trains running over the structure was lower.

Up until now, various proposals have been made for restoring piers and girders, however, this new method is expected to lead to a reinforcement proposal for the complete overhaul of a deteriorated viaduct.