Reinforced concrete structure bonding failure monitoring and early warning method

Abstract

The invention discloses a reinforced concrete structure bonding failure monitoring and early warning method. An ultrasonic sensor is mounted on the surface of a test piece and connected with ultrasonic acquisition equipment; performing a pull-out test on the reinforced concrete test piece, synchronously starting ultrasonic acquisition equipment, and recording a group of ultrasonic signals when a load of 10kN is applied; calculating to obtain decorrelation coefficients corresponding to different loads in the failure process of the bonding performance of the reinforcing steel bar and the concrete in the test piece; establishing a change relation between an external load and a decorrelation coefficient in a failure process of the bonding performance of the reinforcing steel bar and the concrete in the test piece; and monitoring the reinforced concrete structure by using ultrasound, calculating the decorrelation coefficient and the decorrelation coefficient change rate corresponding to each ultrasonic response, substituting the decorrelation coefficient and the decorrelation coefficient change rate into the change relation, and judging the bonding condition of the reinforcing steel bars and the concrete in the reinforced concrete structure. According to the method, the bonding condition of the reinforced concrete can be accurately evaluated, early warning can be carried out on the structure which cannot meet the bearing requirement, and the durability of the reinforced concrete structure and the safety in the service period are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of reinforced concrete structure monitoring, and in particular relates to a reinforced concrete structure bonding failure monitoring and early warning method. Background Art

[0002] In the prior art, the monitoring of bond failure in reinforced concrete structures generally adopts empirical methods, dynamic and static load test methods or reliability theory evaluation methods.

[0003] The empirical method is affected by the level of the evaluator and is highly subjective. It lacks precision, is not systematic, and has a limited scope of application.

[0004] The quantitative analysis of the structure by dynamic and static load test methods is limited to the comparison between measured parameters and design parameters, and cannot provide a specific bearing capacity assessment value.

[0005] Reliability theory assessment methods calculate the probability that a structure or component will complete its intended function within a specified time and under specified conditions. However, there are many uncertainties in the operation of a structure, and different operating environments can lead to differences in performance, thus affecting the assessment results. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for monitoring and early warning of bond failure in reinforced concrete structures. The method is easy to implement, does not require sampling on existing structures, and will not damage existing structures. It can accurately assess the bonding condition of reinforced concrete and issue early warnings for structures that cannot meet the load-bearing requirements, thereby ensuring the durability of reinforced concrete structures and their safety during service.

[0007] To achieve the above object, the present invention provides a method for monitoring and early warning of bond failure in reinforced concrete structures, comprising the following steps:

[0008] S1. Construct reinforced concrete structures and make a batch of test pieces made of the same material at the same time;

[0009] S2. Install an ultrasonic sensor on the surface of the specimen;

[0010] S3, connecting the ultrasonic acquisition equipment;

[0011] S4. Conduct a pull-out test on the reinforced concrete specimen and simultaneously start the ultrasonic acquisition equipment to record a set of ultrasonic signals U for each 10kN load applied. i , the ultrasonic signal in the initial state is recorded as U0;

[0012] S5. Conduct signal analysis and i The decorrelation coefficient DC corresponding to different loads in the failure process of the bond performance between steel bars and concrete in the specimen is obtained by cross-correlation calculation with U0;

[0013] S6. Establish the relationship between the applied load and the decorrelation coefficient during the failure process of the steel bar and concrete bond performance in the specimen;

[0014] S7. Monitor the reinforced concrete structure using ultrasound, and calculate the decorrelation coefficient and the rate of change of the decorrelation coefficient corresponding to each ultrasonic response;

[0015] S8. Substitute the decorrelation coefficient obtained in S7 into the change relationship in S6 to determine the bonding condition between the steel bars and concrete in the reinforced concrete structure.

[0016] As a further solution of the present invention: the calculation formula for the decorrelation coefficient corresponding to different loads during the failure process of the bond performance between the structural steel bar and concrete in the specimen S5 is as follows:

[0017]

[0018] Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is , T is the center point of the coda time window, and ΔT is the length of the time window.

[0019] As a further solution of the present invention: the change relationship includes three stages: in the first stage, the DC value increases slowly, and the corresponding DC change rate is basically less than 0.5%; in the second stage, the DC value increases rapidly, and the DC change first increases and then decreases, and the change rate is basically above 0.5%; in the third stage, the DC value increases slowly, and the DC change rate is less than 0.5%; when the change relationship is in the third stage, it is necessary to issue an early warning of the bonding state between the steel bars and the concrete.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Ultrasound is used to monitor the pull-out failure process of the specimens, and the ultrasonic responses of the failure process of the bond performance between steel bars and concrete of different specimens are obtained. Subsequently, the decorrelation coefficients corresponding to different loads in the failure process of the bond performance between steel bars and concrete in the specimens are obtained by analysis, and the changing relationship between the external load and the decorrelation coefficient in the failure process of the bond performance between steel bars and concrete in the specimens is established. The established changing relationship is then used to infer the bonding condition of the reinforced concrete structure. The overall steps are easy to implement, and there is no need to take samples on existing structures, and the existing structures will not be damaged. The bonding condition of reinforced concrete can be accurately evaluated, and early warning can be given for structures that cannot meet the load-bearing requirements, thereby ensuring the durability of reinforced concrete structures and their safety during service. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a graph showing the change of DC value with the applied load on the specimen.

[0023] Figure 2 This is a graph showing the DC change rate versus the applied load on the specimen. DETAILED DESCRIPTION

[0024] The present invention will be further described below by way of examples.

[0025] A method for monitoring and early warning of bond failure of reinforced concrete structures, comprising the following steps:

[0026] S1. Construct reinforced concrete structures (Structure 1 and Structure 2) and simultaneously produce a batch of test specimens made of the same material.

[0027] S2. Install an ultrasonic sensor on the surface of the specimen.

[0028] S3. Connect the ultrasonic acquisition device.

[0029] S4. Conduct a pull-out test on the reinforced concrete specimen and simultaneously start the ultrasonic acquisition equipment to record a set of ultrasonic signals U for each 10kN load applied. i , the ultrasonic signal in the initial state is recorded as U0.

[0030] S5. Conduct signal analysis and i The decorrelation coefficient DC corresponding to different loads in the failure process of the bond performance between steel bars and concrete in the specimen is obtained by cross-correlation calculation with U0; the calculation formula is as follows:

[0031]

[0032] Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is , T is the center point of the coda time window, and ΔT is the length of the time window.

[0033] S6. Establish the relationship between the applied load and the decorrelation coefficient during the failure process of the steel bar and concrete bond performance in the specimen;

[0034] In this embodiment, a set of ultrasonic data is collected every time a load of 10 kN is applied, and the collected ultrasonic data is analyzed in S5 to obtain the following: Figure 1 The DC value changes with the applied load of the specimen as shown in the figure and Figure 2 The graph shows the DC change rate as the applied load on the specimen changes.

[0035] As the external load increases, the change relationship includes three stages: in the first stage, the DC value increases slowly, and the corresponding DC change rate is basically less than 0.5%; in the second stage, the DC value increases rapidly, and the DC change first increases and then decreases, and the change rate is basically above 0.5%; in the third stage, the DC value increases slowly, and the DC change rate is less than 0.5%; when the change relationship is in the third stage, it is necessary to issue an early warning on the bonding state between steel bars and concrete.

[0036] S7. Monitor the reinforced concrete structure using ultrasound, and calculate the decorrelation coefficient and the rate of change of the decorrelation coefficient corresponding to each ultrasonic response;

[0037] S8. Substitute the decorrelation coefficient obtained in S7 into the change relationship in S6 to determine the bonding condition between the steel bars and concrete in the reinforced concrete structure.

[0038] According to the formula in S5, the DC value of structure 1 is 0.28, which is in the second stage of the change relationship. The corresponding DC change rate is 1.3%, which is greater than 0.5%. Therefore, it is judged that the bond performance between the specimen steel bar and concrete is good and is not close to failure. No warning is required. The DC value of structure 2 is 0.37, which is in the third stage of the change relationship. The corresponding DC change rate is 0.46%, which is less than 0.5%. Therefore, it is judged that the bond performance between the specimen steel bar and concrete is close to failure, and a quick warning is required.

Claims

1. A method for monitoring and early warning of bond failure of reinforced concrete structures, characterized in that: The following steps are involved: S1. Construct reinforced concrete structures and make a batch of test pieces made of the same material at the same time; S2. Install an ultrasonic sensor on the surface of the specimen; S3, connecting the ultrasonic acquisition equipment; S4. Conduct a pull-out test on the reinforced concrete specimen and simultaneously start the ultrasonic acquisition equipment to record a set of ultrasonic signals U for each 10kN load applied. i , the ultrasonic signal in the initial state is recorded as U0; S5. Conduct signal analysis and i The decorrelation coefficient DC corresponding to different loads in the failure process of the bond performance between steel bars and concrete in the specimen is obtained by cross-correlation calculation with U0; S6. Establish the relationship between the applied load and the decorrelation coefficient during the failure process of the bond performance between steel and concrete in the specimen; S7. Monitor the reinforced concrete structure using ultrasound, and calculate the decorrelation coefficient and the rate of change of the decorrelation coefficient corresponding to each ultrasonic response; S8. Substitute the decorrelation coefficient obtained in S7 into the change relationship in S6 to determine the bonding condition between the steel bars and concrete in the reinforced concrete structure.

2. A reinforced concrete structure bond failure monitoring and early warning method according to claim 1, characterized in that: The calculation formula for the decorrelation coefficient corresponding to different loads during the failure process of the bond performance between the structural steel bars and concrete in specimen S5 is as follows: Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is , T is the center point of the coda time window, and ΔT is the length of the time window.

3. The method for monitoring and early warning of bond failure of reinforced concrete structure according to claim 1, characterized in that: The change relationship includes three stages: in the first stage, the DC value increases slowly, and the corresponding DC change rate is basically less than 0.5%; in the second stage, the DC value increases rapidly, and the DC change first increases and then decreases, and the change rate is basically above 0.5%; in the third stage, the DC value growth slows down, and the DC change rate is less than 0.5%; when the change relationship is in the third stage, it is necessary to issue an early warning on the bonding state between steel bars and concrete.

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