Issue 45

X.Z. Wang, Frattura ed Integrità Strutturale, 45 (2018) 100-107; DOI: 10.3221/IGF-ESIS.45.08 103 Experimental design The dimension of the specimen steel is Φ8×40 mm. Clean the oil of the specimen bar and place it in a dry container. Specimens were placed in four environments: close and damp, permanently soaked in water, wet and dry alternately, weak acidity aqueous soaking. The close and damp means that the specimen is hung above the water surface in the sealed con- tainer. The permanently soaked in water means that the specimen is located below the water level in the sealed container. The wet and dry alternately means that the specimen is located below the water level for 7 days, and the other 7 days is located above the water level in the container, and so on alternately, the container is open. The weak acidity aqueous soak- ing means that the dilute sulfuric acid and tap water was used to prepare soaking solution, and the soaking solution is used to simulate the acid environment, immerse the specimen permanently below the surface of the acid solution in the sealed container. All of the above corrosion environments change soaking liquid once a month [16-20]. Experimental result The experimental results are shown in Fig. 1. (1) As can be seen from Fig. 1, in the four different corrosion environments, the weight loss rate of steel is the largest in the weak acid aqueous solution and the minimum in the close and damp environment. Figure 1 : Distribution of anchor steel weight loss rate with time (2) The rate of weight loss of steel in wet and dry alternately is almost the same as that in permanently soaked in water, but the growth rate of weight loss rate in the wet and dry alternately condition is greater than the permanently soaked in water condition. (3) The weight loss rate of the anchor steel in close and damp condition is only about 1/5 of the anchor steel in the condi- tion of permanently soaked in water condition and wet and dry alternately condition. (4) In any experimental environment, the weight loss rate of anchor steel increases with time, but the increase rate de- creases with time. T HE ANALYSIS OF G REY PREDICTION Determination of the bearing capacity loss threshold of steel bars n practical engineering, the bearing capacity of steel bars direct influence on the structural safety, therefore, the bear- ing capacity loss rate of the steel bars is taken as the damage criterion. The bearing capacity loss rate of steel bars can be expressed as: %100 Δ 0 y0 1 ' y 0 y0    Sf Sf Sf P P (16) In the formula, P  —the decrement of bearing capacity (KN); P — initial bearing capacity (KN); f y0 —initial strength of the steel bars(N/mm 2 ); ' y f —strength damage threshold of steel bars (N/mm 2 ); S 0 —initial sectional area of steel I