CN-115828570-B - Corrosion reinforcing steel bar mechanical property degradation reliability assessment method based on average corrosion rate

Abstract

The invention relates to a method for evaluating the reliability of the mechanical property degradation of a rusted steel bar based on average corrosion rate. The method comprises the steps of 1) taking the diameter, length and mass of a steel bar sample before rusting, weighing the rusted steel bar sample after rust removal to obtain the residual mass, calculating the average rusting rate eta s of the steel bar sample, 2) determining parameter position parameters mu Rλ and scale parameters sigma Rλ of the rusted non-uniform coefficient R λ according with I-type extremum distribution based on the average rusting rate eta s , the diameter and the length of the steel bar, and 3) calculating the normal distribution mean value and standard deviation of all mechanical property parameters after the rusting of the steel bar according to the yield strength f y , the ultimate strength f u , the elastic modulus E s , the reinforced modulus k and the ultimate strain epsilon u of the steel bar before rusting based on the obtained position parameters mu Rλ and the scale parameters sigma Rλ . The invention finds out the optimal parameter for measuring the uneven corrosion, and adopts the parameter as a key intermediate variable to establish a corrosion reinforcing steel bar mechanical property reliability calculation method based on the average corrosion rate.

Inventors

• WANG XIAOGANG
• QIN YU

Assignees

• 烟台大学

Dates

Publication Date

20260512

Application Date

20230117

Claims (2)

1. 1. The evaluating method for the degradation reliability of the mechanical property of the rusted steel bar based on the average corrosion rate is characterized by comprising the following steps: 1) The diameter of a steel bar sample before rusting is D, the length is L, the mass is m 0 , the rusted steel bar sample is derusted and then weighed to obtain the residual mass m 1 , the average rusting rate eta s is calculated, and the calculation formula (1) is as follows: 2) The corrosion non-uniformity coefficient R λ accords with the I-type extremum distribution, and based on the average corrosion rate eta s , the diameter D and the length L of the steel bar, the parameter position parameter mu Rλ and the scale parameter sigma Rλ of the steel bar are determined, and the calculation formula (2) is as follows: wherein c 5 is a comprehensive parameter, c 5 ＝0.32ln(η s ) +2.41; Based on statistical analysis, sigma Rλ is normally distributed as a whole, the mean value is 0.038, the standard deviation is 0.016, and in practical application, the quantile value of 95% guarantee rate is 0.064; 3) Based on the obtained position parameter mu Rλ and the scale parameter sigma Rλ , calculating the normal distribution mean value and standard deviation of each mechanical property parameter after the corrosion of the steel bar according to the yield strength f y , the ultimate strength f u , the elastic modulus E s , the strengthening modulus k and the ultimate strain epsilon u before the corrosion of the steel bar, The mean μ FY and standard deviation σ FY of the nominal yield strength f' y are calculated as follows: The mean μ FU and standard deviation σ FU of the nominal ultimate strength f' u , the calculation formula (4) is as follows: The mean μ ES and standard deviation σ ES of the nominal elastic modulus E' s , the calculation formula (5) is as follows: The mean μ EU and standard deviation σ EU of the nominal limit strain ε' u are calculated as follows: 。
2. 2. The method for evaluating the reliability of the mechanical property degradation of the rusted steel bar based on the average corrosion rate according to claim 1, wherein the method further comprises the following steps between the step 2) and the step 3): If the rusted steel bar is obtained by a laboratory accelerated rusting method, the obtained position parameter mu Rλ and the scale parameter sigma Rλ are adjusted as follows: When the number of test pieces is n <30, the position parameter mu Rλ is multiplied by a coefficient gamma to correct, the scale parameter sigma Rλ is kept unchanged, the coefficient gamma is determined by actually measuring the R λ value of each test piece, setting the actually measured corrosion rate of the ith test piece as eta s,i , calculating a theoretical value mu Rλ,i through eta s,i , actually measuring the corrosion non-uniformity coefficient as R λ,i , obtaining a correction coefficient gamma i ＝R λ,i /μ Rλ,i of the ith test piece, and taking the average value of all gamma i to obtain a final correction coefficient The number n of the test pieces is more than or equal to 30, the R λ value of each test piece is actually measured, and the parameter estimation is directly carried out by adopting a maximum likelihood estimation method to obtain the position parameter mu Rλ and the scale parameter sigma Rλ .

Description

Corrosion reinforcing steel bar mechanical property degradation reliability assessment method based on average corrosion rate Technical Field The invention relates to a rust steel bar mechanical property degradation reliability assessment method based on average rust rate, and belongs to the technical field of rust steel bar mechanical property assessment methods. Background Steel bar corrosion is one of the most major durability problems of concrete structures, and the degradation of the mechanical properties of steel bars after rust is one of the major factors causing the loss of bearing capacity, shortened service life and premature failure of the rust members. However, no mature and effective method is available at present for quantitatively analyzing the mechanical property degradation of the rusted steel bars, the model proposed by a few existing researchers is rough and is only a simple regression of few test results, and the obtained results have huge differences because of the adopted accelerated rusting technology differences, the different rusting rate indexes (such as section rusting rate, volume rusting rate, weightlessness rate, rusting depth and the like), the different diameters and lengths of the steel bars and the like, and the problems of degradation mechanism, whether the elastic modulus is degraded or not and the like are still controversial. In view of the shortcomings of the prior art, there is a need to develop a method for evaluating the reliability of the mechanical property degradation of rusted steel bars based on average rusting rate, which can solve the technical problems. Disclosure of Invention The invention defines the mechanical property degradation mechanism of the rusted steel bar, reveals that the uneven rusting is a main cause of nominal material degradation, finds out the optimal parameter for measuring the uneven rusting on the basis, and establishes a calculation method for the mechanical property reliability of the rusted steel bar based on the average rusting rate by adopting the parameter as a key intermediate variable. In order to achieve the above purpose, the present invention provides the following technical solutions: The evaluating method for the degradation reliability of the mechanical property of the rusted steel bar based on the average corrosion rate is characterized by comprising the following steps of: 1) The diameter of a steel bar sample before rusting is D, the length is L, the mass is m 0, the rusted steel bar sample is derusted and then weighed to obtain the residual mass m 1, the average rusting rate (weightlessness rate) eta s is calculated, and the calculation formula (1) is as follows: 2) The corrosion non-uniformity coefficient R λ accords with the I-type extremum distribution, and based on the average corrosion rate eta s, the diameter D and the length L of the steel bar, the parameter position parameter mu Rλ and the scale parameter sigma Rλ of the steel bar are determined, and the calculation formula (2) is as follows: wherein c 5 is a comprehensive parameter, c 5＝0.32ln(ηs) +2.41; Based on statistical analysis, sigma Rλ is normally distributed as a whole, the mean value is 0.038, the standard deviation is 0.016, and in practical application, the quantile value of 95% guarantee rate is 0.064; 3) If the rusted steel bar is obtained by a laboratory accelerated rusting method, the obtained position parameter mu Rλ and the scale parameter sigma Rλ are adjusted as follows: When the number of test pieces is n <30, the position parameter mu Rλ is multiplied by a coefficient gamma to correct, the scale parameter sigma Rλ is kept unchanged, the coefficient gamma is determined by actually measuring the R λ value of each test piece, setting the actually measured corrosion rate of the ith test piece as eta s,i, calculating a theoretical value mu Rλ,i through eta s,i, actually measuring the corrosion non-uniformity coefficient as R λ,i, obtaining a correction coefficient gamma i＝Rλ,i/μRλ,i of the ith test piece, and taking the average value of all gamma i to obtain a final correction coefficient The number n of the test pieces is more than or equal to 30, the R λ value of each test piece is actually measured, and the parameter estimation is directly carried out by adopting a maximum likelihood estimation method to obtain a position parameter mu Rλ and a scale parameter sigma Rλ; 4) Based on the obtained position parameter mu Rλ and the scale parameter sigma Rλ, calculating the normal distribution mean value and standard deviation of each mechanical property parameter after the corrosion of the steel bar according to the yield strength f y, the ultimate strength f u, the elastic modulus E s, the strengthening modulus k and the ultimate strain epsilon u before the corrosion of the steel bar, The mean μ FY and standard deviation σ FY of the nominal yield strength f y' are calculated as follows: The mean μ FU and standard deviation μ FU of the nominal ult