6. A technique to reinforce RC rigid-frame viaduct beams using arch-shaped steel plates

  • RTRI developed an effective method for reinforcing the beams of existing RC rigid-frame viaducts.
  • It also confirmed that this technique reduced work time and cost compared to existing reinforcement methods.

Many existing RC rigid-frame viaducts in urban areas were constructed a long time ago, and extensive repair work may be necessary not only for columns but also for beams due to insufficient durability and seismic capacity. In practice, however, it is difficult to perform extensive repair work that involves the stopping train services. Accordingly, there is a need to develop a renovation technique which can be used to improve performance of structures without stopping operations.

The method presented here is intended for the reinforcement of beams on which repair work is difficult. First, an arch-shaped piece made of H-section steel and steel plates is installed at the lower face, reinforcing bars are then put in place, and finally high-fluidity concrete is cast to restructure the beams (Fig. 1). Such reinforcement improves structures where flexural and shear capacity is insufficient. In relation to this, the effects of using bending reinforcing bars, shear reinforcing bars and arch-shaped steel plates for reinforcement were investigated in loading tests including a full-scale model test, and a design method was proposed. An example in which the flexural capacity is doubled is shown in Fig. 2.

In addition, since arch-shaped steel plates can be utilised as hanging formwork, shoring can be avoided, the construction period can be reduced and costs can be cut, in comparison to existing methods for increasing RC thickness.

This reinforcement method has already been applied to repair work on existing rigid-frame viaducts, and has been confirmed as being an effective technique (Fig. 3).

The gentle curves of the reinforced beams are aesthetically pleasing.

  • fig 1
    Fig. 1 Outline of the reinforcement method using arch-shaped steel plates
  • fig 2
    Fig. 2 Example of flexural reinforcement of beams
  • fig 3
    Fig. 3 Example of repair work with the reinforcement method using arch-shaped steel plates