رفتار تیرهای ترک خورده تحت بارگذاری پایدار
Abstract
1- Introduction
2- Experimental program
3- Crack patterns and crack widths
4- Deflection development of beams
5- Conclusions
Acknowledgement
References
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.
Introduction
Reinforced concrete (RC) is one of the most widely used construction materials in the world. RC structures are usually regarded as permanent structures that can be free of severe degradation problems for a long period time owing to their good service performance. Although steel bars embedded in concrete are normally protected against corrosion during the service life of a structure, the concrete cover can deteriorate under the effects of some aggressive agents, leading to corrosion of the steel bars in concrete. For RC structures, corrosion of steel bars is one of the most important factors causing durability problems [1]. On the one hand, corrosion can lead to the cross-sectional loss of steel bars and degradation of their mechanical properties thereby reducing the bearing capacity of a structural member. On the other hand, steel bars corrosion can also degrade the bonding behavior between the concrete and steel, thereby inducing stiffness reduction, which can increase the deflection during the service life.