笠原 華子 (Hanako KASAHARA)
Some experiments have shown that carbon fiber reinforcement polymer (CFRP) retrofitting is effective to repair steel bridges. However, since the design of CFRP retrofitting is generally based on elastic design assuming complete bonding of steel and CFRP, the limit state design method has not been established. In this study, in order to clarify the failure mechanism of CFRP-reinforced steel girders, a numerical model for nonlinear finite element analysis taking into account the elasto-plasticity of the material, debonding and fracture of CFRP is developed. The model is used to reproduce elemental tests to confirm the behavior of steel-CFRP composite members after steel material yields. As a result, although bonding of steel and CFRP is confirmed even after steel material yields, brittle fracture occurred in the case of CFRP failure or debonding. Furthermore, numerical analysis of CFRP-reinforced steel girders with concrete slab is conducted. As a result, the reinforcement effect is confirmed even after the steel girder yields. However, it is found that the load-carrying capacity is partially reduced due to the failure of CFRP, and that brittle failure occurred due to debonding. Therefore, we concluded that it is important that CFRP failure or debonding avoids becoming the ultimate limit state by selecting the modulus of elasticity and the strength of the CFRP used for retrofitting.It is also found that the anchorage of the CFRP edge is effective in avoiding brittle fracture due to debonding.
Key Words : FEM,CFRP, steel girder, energy release rate, cohesive model, fracture