دانلود رایگان مقاله انگلیسی رفتار سازه ای تیرهای بتن آرمه ترک خورده تحت بارگذاری پایدار - الزویر 2018

abstract

This paper presents the results of an experimental study designed to investigate the combined effects of corrosion and sustained loads on the structural performance of reinforced concrete beams. A total of eight RC beams, including both uncorroded beams and corroded ones accelerated by the impressed current method, were tested. All the beams were subjected to a four-point sustained bending load which was equivalent to 17%, 33% or 50% of the designed ultimate load, respectively. Corrosion degree, crack patterns, crack width and mid-span deflection of the beams were monitored during the test. The results showed that reinforcement corrosion had no obvious effect on the transverse crack spacing and a slight effect on the development of transverse crack width for the beams under simultaneous loading and corrosion. A higher load level and a lower current density allow for more sufficient oxidation of corrosion products with a larger volume expansion rate, leading to premature initiation and rapid propagation of corrosion cracking, and more obvious deflection development of RC beams. For a beam under simultaneous loading and reinforcement corrosion, the effect of reinforcement corrosion on its deflection cannot be ignored, because it may exceed creep effect at a relatively low corrosion degree.

5. Conclusions

(1) Transverse cracks appeared under loading prior to reinforcement corrosion in the test, and the reinforcement corrosion had no obvious effect on the transverse crack spacing but a slight effect on the crack width.

(2) The deflection development curves displayed obvious characteristics of all three stages under simultaneous loading and reinforcement corrosion. The deflection stable development stage before the corrosion crack initiation was followed by the rapid development stage. The other stable stage of the deflection began when the interface between the steel and the concrete and corrosion cracks were filled up by the corrosion product.

(3) For the specimens under the same current density, a lower load level might delay the initiation and propagation of corrosion cracking. Furthermore, for the specimens subjected to loading at the same level, a higher current density might also delay the initiation and propagation of corrosion cracking. This delayed initiation and propagation can be attributed to more insufficient oxidation and a lower volume expansion of corrosion products.

(4) Corrosion effect cannot be ignored on the calculation of the deflection of the beams under simultaneous loading and reinforcement corrosion. At a certain corrosion degree, the beams subjected to a higher load level and a lower current density would have a larger deflection.