Keita KIZAWA

Study on strengthening of concrete structures considering cooperative load carrying mechanism between existing and retrofitted part

Takumi SHIMOMURA

In this research, retrofitting design and construction method of concrete structures expecting the residual performance of deteriorated existing members was studied. In particular, the cooperative mechanism between the existing and the retrofitted part was focused.
Firstly, as the most fundamental study, strengthening of a simple RC beam member was examined. The influence of the degree of deterioration of existing members on structural performance after strengthening was investigated by finite element analysis. As a result, it was clarified that the degree of deterioration of the existing member affects the structural performance after strengthening. Considering this fact in retrofitting design, it was shown that the cross sectional dimensions of retrofitted part can be drastically reduced.
Furthermore, a case study was conducted on retrofitting cases of actual bridges deteriorated by salt attack. In this study, the design and construction method considering the cooperative mechanism were applied to strengthening of deteriorated existing PC bridge by box girder. As result of the finite element analysis, when soil was filled between the existing bridge and the box girder, the existing part showed a cooperative mechanism of load sharing. This implies that this sort of construction method is valid for utilization of residual structural performance of existing members.
Moreover, a case study on actual bridge that needed seismic retrofitting, was carried out. A detailed performance evaluation of the existing structures was conducted, and an appropriate reinforcing method was proposed. As result of detailed seismic analysis through FEM analysis, response values within elastic ranges were obtained for all analysis cases. Therefore, since the target bridge is a very rigid structure, it was concluded that there is no necessity of further strengthening considering its residual structural performance.