| A study of characters of reinforced concrete members under corrosion fatigue conditions is an important aspect of engineering durability problems. Generally, the failure of reinforced concrete members is the fatigue fracture of corroded steel bars.Based on the fatigue crack initialed mainly from the pitting corrosion theory and experimental study, this paper investigated the pitting evolution and the mechanical properties deterioration laws of corroded members. Moreover, the effect of corrosion on fatigue life of steel bars is studied based on the test data are obtained. The main research work is set out as follows:(1) Natural corrosion of steel bars test were conducted in this study. the results show that the corrosion pit morphology have developed from deep and narrow semi-elliptic into shallow and wide semi-elliptic, however, few have developed into wide grooves.(2) This paper also has carried on axial tensile static and fatigue tests of corroded specimens test and fracture analysis. The results show that the mechanical properties of corroded reinforced have get degraded, Moreover, a significant reduction of fatigue life of corroded reinforcement with the appearance and development of corrosion. The macro static fracture is mainly divided into normal fracture and shear fracture, and the micrographics showed that the fracture surface of fatigue is mainly divided into three zones such as the crack initiation, steady crack propagation and instantaneous fracture. Fatigue cracks mainly initiated at the root of etch pits and fatigue cracks propagated radially.(3) According to the stress field analysis around crack tips of corroded members and pitting evolution law, the fatigue crack growth threshold of corroded steel bar is established. Based on pitting evolution law of steel bars which embedded in concrete, the fatigue crack growth threshold of corroded steel bar which embedded in concrete is also established.(4) A calculation model is established for the fatigue life of corroded reinforced, according to the Paris formula, and applied to corroded specimens of fatigue tests. The result of calculation showed that fracture toughness were not sensitive to residual fatigue life, which depended on the initial crack length and shape parameter. Afterwards, a fatigue life predicting method of the concrete structure was put forward. This paper has45figures,17tables and77references. |
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