Tatsuya HAMA
Fundamental Study on Seismic Retrofit for Steel Bridge Using Carbon Fiber Sheet
Takeshi MIYASHITA
A carbon fiber reinforced polymer (CFRP) sheet has the characteristics such as light weight, high strength and durability. CFRP sheet has begun to been applied to repair or reinforcement for steel bridges. This research aims to conduct fundamental study on seismic retrofit for steel bridge using CFRP sheet, which can reduce stress and increase load-carrying capacity and toughness.
Firstly, uniaxial compression test for steel box short columns reinforced by carbon fiber sheets were conducted. Herein, with aim of prevention of delamination and improvement of toughness, high-elongation and low elastic putty layer was inserted between steel and carbon fiber sheet. Experiment revealed that load-carrying capacity was improved by 10 % compared to the case without carbon fiber sheet when ten sheets were bonded on each surface of the column. Toughness was also improved. However, increment rate of load-carrying capacity was two-thirds of expected value, and stress reduction was also less than the expected. This is because bonding and edge shift length of the sheet are not enough. Then, uniaxial compression of steel long column was planned. Herein, bonding and edge shift length of the sheet were 250 mm and 25 mm respectively. As a result, expected stress reduction was achieved, but increment rate of load-carrying capacity was 13 % while expected rate was 17 %. In this experiment, number of carbon fiber sheet was determined by the calculation that thickness of the sheet was converted to one of steel based on the ratio of Young¡Çs modulus of steel and carbon fiber. Since it was observed that buckling of steel plate was not sufficiently suppressed, it is needed to improve design method which determines number of carbon fiber sheet based on observed mechanical behavior
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