DEVICES FOR CF SHEET POST-TENSION STRENGTHENING FOR STEEL BRIDGE GIRDER

摘要

In Japan, 20 tons track load had been adopted for bridge design codes since 1956, and it was upgraded to 25 tons in 1993. Although newly constructed bridges have been designed based on this code, most of the old bridges are still remaining under poor load capacity and are supporting heavy traffic until they would be strengthened. As well known, post-tension strengthening method has mainly been used for concrete bridges. However, this method becomes useful to strengthen existing steel bridges because additional load can be applied to meet the upgraded codes. In the present study, carbon fiber reinforced composites (CFRP) was tried as post-tension strengthening materials. The post-tension load was introduced into bridge girders by newly developed devices to pull and install carbon fiber sheet on the bottom of bridge girders. Then epoxy resin was impregnated into carbon fiber sheet. Finite element analysis has also been carried out to find out the design policy of this post-tension strengthening. With increasing the post-tension load, onset of delamination was expected. The analysis was mainly focused on how to prevent possible delamination at the end of CFRP. One of the smart and cheap way to avoid onset of delamination between CFRP and girder bridge is to suppress opening defection at the end of bonded CFRP by attaching the holding plates. The experimental results are also be presented. It is important to develop devices to introduce post-tension load in the bridge girder. Newly developed devices are also shown in this report.