The effect of steel corrosion on the behavior of bond between steel and the surrounding concrete was investigated. Pullout tests were carried out to demonstrate bond stress-slip response for reinforcing steel bars of ...The effect of steel corrosion on the behavior of bond between steel and the surrounding concrete was investigated. Pullout tests were carried out to demonstrate bond stress-slip response for reinforcing steel bars of a series of corrosion level. Specimens either confined or unconfined were investigated for evaluation of the effect of confinement on bond strength and failure mode. Also, the tests were analyzed using nonlinear finite element analysis. It was shown that for both confined and unconfined steel bars, bond strength generally decreases as the corrosion level increases when corrosion level is relatively high. Confinement was demonstrated to provide excellent means to conteract bond loss for corroded reinforcing steel bars. It was shown that unconfined specimens generally split at a small slip with a large crack width and result in splitting failure while confined specimens contribute to a small crack width and generally cause a pullout failure. The analysis results agree reasonably well with the experiments.展开更多
The mechanical peratures and cooling rates properties and microstructure of as-cast Nb-Ti microalloyed steel at different tern- are investigated in this paper. The III brittle zone （700--900~C） is revealed. The redu...The mechanical peratures and cooling rates properties and microstructure of as-cast Nb-Ti microalloyed steel at different tern- are investigated in this paper. The III brittle zone （700--900~C） is revealed. The reduction of the hot ductility is due to the film-like proeutectoid ferrite or the Nb（C, N） precipitates along the austenitic grain boundaries. In the temperature range of 850 1000~C, with the increase of the cooling rate, the hot ductility decreases. However, in the range of 650--850 ~C, the appearance of large volume fractions of ferrite on austenite grain boundaries minimizes the effect of cooling rate on hot ductility. When the cooling rate is 10 ℃/s, austenite transforms more quickly to ferrite and at a lower temperature a larger amount of ferrite nucleates and precipitates in the grain, which leads to a sharper improvement in the hot ductility at 650 ℃.展开更多
文摘The effect of steel corrosion on the behavior of bond between steel and the surrounding concrete was investigated. Pullout tests were carried out to demonstrate bond stress-slip response for reinforcing steel bars of a series of corrosion level. Specimens either confined or unconfined were investigated for evaluation of the effect of confinement on bond strength and failure mode. Also, the tests were analyzed using nonlinear finite element analysis. It was shown that for both confined and unconfined steel bars, bond strength generally decreases as the corrosion level increases when corrosion level is relatively high. Confinement was demonstrated to provide excellent means to conteract bond loss for corroded reinforcing steel bars. It was shown that unconfined specimens generally split at a small slip with a large crack width and result in splitting failure while confined specimens contribute to a small crack width and generally cause a pullout failure. The analysis results agree reasonably well with the experiments.
文摘The mechanical peratures and cooling rates properties and microstructure of as-cast Nb-Ti microalloyed steel at different tern- are investigated in this paper. The III brittle zone （700--900~C） is revealed. The reduction of the hot ductility is due to the film-like proeutectoid ferrite or the Nb（C, N） precipitates along the austenitic grain boundaries. In the temperature range of 850 1000~C, with the increase of the cooling rate, the hot ductility decreases. However, in the range of 650--850 ~C, the appearance of large volume fractions of ferrite on austenite grain boundaries minimizes the effect of cooling rate on hot ductility. When the cooling rate is 10 ℃/s, austenite transforms more quickly to ferrite and at a lower temperature a larger amount of ferrite nucleates and precipitates in the grain, which leads to a sharper improvement in the hot ductility at 650 ℃.
