Availability evaluation method of existing bridges in highway reconstruction and expansion projects

Abstract

The present invention discloses a method for judging the availability of existing bridges in a highway reconstruction and expansion project, including: step 1, evaluating the technical status and bearing capacity of existing bridges in the highway reconstruction and expansion project, and for bridges rated as Class 3, Class 4 and Class 5 in terms of technical status, and bridges rated as Class 1 and Class 2 but whose bearing capacity does not meet the requirements, it is not recommended to continue using them in the reconstruction and expansion project; step 2, for bridges rated as Class 1 and Class 2 and whose bearing capacity is evaluated as meeting the requirements, the main structural component categories are divided, and the score of the appearance durability state of any main structural component category is calculated. If the score reaches the threshold range, it is not recommended to continue using them in the reconstruction and expansion project. The present invention proposes a combination of qualitative and quantitative evaluation of bridge durability, fully considering the current safety status and future durability status of the bridge, so that the reuse of the bridge in the reconstruction and expansion project has more sufficient safety guarantees, and guarantees the long-term safety performance of the bridge in the later operation.

Description

Technical Field

[0001] The present invention relates to the technical field of extending the life of bridge structures, and more specifically, to a method for evaluating the availability of existing bridges in a highway reconstruction and expansion project. Background Art

[0002] With the rapid development of the social economy along the route, the traffic volume of expressways has increased rapidly. Some sections of the early domestic construction have reached or are close to saturation, and the service level has seriously declined. The current traffic conditions cannot adapt to its important road network status and the development requirements of future traffic needs, and it is urgently needed to be rebuilt and expanded. Bridges are key nodes in the transportation network. In the highway reconstruction and expansion projects, the existing bridges have been in service for many years. After years of overload operation, the performance of the existing bridge structures has deteriorated, and the service performance and durability of a large number of bridge structures have generally decreased. Due to complex environmental factors, frequent natural disasters, overload and over-limit service, backward maintenance technology, and limited early construction technology, a large number of bridge structures that are theoretically in the middle or even early stages of their design life have "aged" in advance. Although some old bridges appear to be in good overall technical condition, there may be certain safety hazards in some parts or they are basically close to the durability limit state. In some reconstruction and expansion projects, in order to ensure the coordinated service performance of the bridge structure system, all the old bridges on the line are uniformly demolished and rebuilt, and the sustainable utilization value of the old bridges has not been brought into play, resulting in a major waste of resources and not in line with the concept of green and environmental protection development. Many existing bridges can achieve the same service life as newly built bridges through some life extension measures, but there is a lack of a reasonable evaluation method. In some renovation and expansion projects, existing bridges with good apparent conditions are directly used, and the bridge is judged to continue to be used based only on the apparent technical condition and bearing capacity of the bridge at that time, but the internal deterioration of the structural material is not analyzed. Later, it is found that the bridge deteriorates rapidly. For example, the protective layer is too thin, resulting in large-scale corrosion after carbonization to the surface of the steel bar, which greatly increases the maintenance cost. In this case, demolition and reconstruction are more economical than direct use. How to adopt the development concept of "innovation, coordination, green, openness, and sharing" in the renovation and expansion process, make reasonable judgments on the continued use of existing bridges in highway renovation and expansion projects, formulate life extension criteria and take long-term life extension measures to make them have the same durability and safety as newly built bridges, is an important problem faced by the implementation of engineering renovation and expansion. Summary of the invention

[0003] The present invention provides a method for evaluating the availability of existing bridges in highway reconstruction and expansion projects, which combines qualitative (appearance durability status) and quantitative (remaining durability years) evaluation of bridge durability, fully considering the current safety status and future durability status of the bridge, considering both the appearance manifestations of durability degradation of structural components and the internal degradation process of structural materials, with both specimens and comprehensive evaluation content, so that the reuse of bridges in reconstruction and expansion projects has more sufficient safety guarantees, and the durability evaluation can guarantee the long-term safety performance of the bridge in later operations.

[0004] In order to achieve these purposes and other advantages according to the present invention, a method for evaluating the availability of existing bridges in a highway reconstruction and expansion project is provided, comprising:

[0005] Step 1: Evaluate the technical status and load-bearing capacity of existing bridges in the highway reconstruction and expansion project. For bridges rated as Class 3, Class 4 and Class 5 in terms of technical status, and bridges rated as Class 1 and Class 2 but with load-bearing capacity that does not meet the requirements, it is not recommended to continue using them in the reconstruction and expansion project;

[0006] Step 2: For bridges rated as Class 1 and Class 2 and whose bearing capacity is assessed to meet the requirements, classify the main structural components and calculate the score of the appearance durability status of any main structural component category. If the score reaches the threshold range, it is not recommended to continue using it in the renovation and expansion project.

[0007] Preferably, in step 2, any main structural component category is divided into a plurality of durability assessment units, the level of the appearance durability state of each durability assessment unit is assessed, and the corresponding appearance durability state score is determined to obtain the appearance durability state score of each main structural component category:

[0008]

[0009] Where A is the score of the appearance durability status of any main structural component category;

[0010] A i It is the score corresponding to the grade of the appearance durability state of a durability assessment unit in the category of the main structural component;

[0011] n i The number of durability assessment units with the same score in the category of the main structural component;

[0012] n is the number of durability assessment units classified by the category of the main structural component.

[0013] Preferably, when the score of the appearance durability status of any main structural component category does not reach the threshold range, each durability assessment unit in the main structural component category is assessed separately. If the remaining durability life of the durability assessment unit is not less than the design service life, it is recommended that the durability assessment unit continue to be used in the renovation and expansion project.

[0014] Preferably, the life coefficient and the usable life coefficient of each durability assessment unit of any main structural component category are calculated.

[0015] k y When ≥1, the durability assessment unit can continue to be used in the renovation and expansion project;

[0016] When the durability assessment unit is used for a longer period of time in the renovation and expansion project;

[0017] When the durability assessment unit is damaged, it is not suitable to continue to be used in the renovation and expansion project;

[0018] Among them, k y is the life coefficient, is the useful life factor;

[0019]

[0020] Among them, t e The remaining durability of the durability assessment unit;

[0021] T is the target useful life of the renovation and expansion project;

[0022]

[0023] Among them, T 0i The effective guarantee period for the i-th type of life extension technology;

[0024] m i A value for implementing a certain type of maintenance measure;

[0025] j is the number of types of maintenance measures to be taken on the existing bridges within the target service life of the renovation and expansion project;

[0026] j value and m i The value should satisfy:

[0027]

[0028] Among them, C 0i is the cost of the ith maintenance measure;

[0029] C r The cost of demolition and reconstruction.

[0030] Preferably, for concrete bridges in general atmospheric environments, the remaining durability of the durability assessment unit is calculated as t e When the carbonization depth reaches the steel bar surface, the durability limit state is:

[0031]

[0032]

[0033] Where c is the thickness of the steel bar protective layer;

[0034] t0 is the operating time of the bridge;

[0035] k c is the carbonization coefficient;

[0036] d is the carbonation depth of concrete.

[0037] Preferably, for concrete bridges subject to chloride ion corrosion in marine environments, the remaining durability of the durability assessment unit is calculated as t e When the chloride ion concentration on the steel bar surface reaches the critical value of corrosion, it is taken as the durability limit state:

[0038]

[0039]

[0040] Among them, k D is the chloride ion corrosion coefficient;

[0041] D is the chloride ion diffusion coefficient in concrete;

[0042] erf -1 is the inverse function of the error function;

[0043] C cr is the critical concentration of chloride ions;

[0044] γ s is the chloride ion surface concentration coefficient;

[0045] C s is the surface chloride ion concentration;

[0046] D value and C s The value should satisfy:

[0047]

[0048] Among them, C x,t is the chloride ion concentration at depth x at age t;

[0049] C0 is the initial chloride ion concentration in concrete;

[0050] erf is the error function;

[0051] x is the depth from the surface of the structure.

[0052] The present invention has at least the following beneficial effects:

[0053] First, in the process of judging the availability of existing bridges in reconstruction and expansion, the present invention proposes a three-level evaluation method of "technical condition level" ["Technical Condition and Bearing Capacity Evaluation Standard for Highway Bridges" (JTG / TH21-2011)], "bearing capacity requirements" ["Highway Bridge Bearing Capacity Testing and Evaluation Procedure" (JTG / T J21-2011)], and "durability condition" on the basis of existing technical specifications, which fully considers the current safety status and future durability status of the bridge, so that the reuse of the bridge in the reconstruction and expansion project has more sufficient safety guarantee, and the durability evaluation can guarantee the long-term safety performance of the bridge in the later operation;

[0054] Second, the present invention proposes a durability evaluation method that combines qualitative (appearance durability status) and quantitative (remaining durability years) evaluation for bridge durability, which not only takes into account the appearance of durability degradation of structural components, but also reflects the internal degradation process of structural materials. It has both specimens and comprehensive evaluation content. Compared with the current relevant evaluation methods at home and abroad, it is very advanced in terms of evaluation methods;

[0055] Third, the present invention provides a basis for the scientific and reasonable disposal of existing bridges, taking the operational safety of existing bridges during reconstruction and expansion as a prerequisite, the consistency of long-term performance and service life of existing bridges and newly built bridges as a goal, and the economic rationality of long-term maintenance of bridges as a criterion. It fully considers economic rationality and the expansion of the utilization value of existing bridges, and ensures the safe and reasonable use of existing bridge structures within the target service life after reconstruction and expansion at the lowest cost, supports and ensures the service safety, reliability, green environmental protection and sustainable development capabilities of the reconstruction and expansion project, and ensures the consistency of long-term performance and service life of existing bridges and newly built bridges.

[0056] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below with reference to examples so that those skilled in the art can implement the invention with reference to the description.

[0058] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0059] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified; in the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected, set, or detachably connected, set, or integrally connected, set. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] The evaluation method of the availability of existing bridges in highway reconstruction and expansion projects includes:

[0061] Step 1: According to the "Technical Status and Load-bearing Capacity Assessment Standard for Highway Bridges" (JTG / T H21-2011), the technical status and load-bearing capacity of existing bridges in the highway reconstruction and expansion project are assessed. For bridges rated as Class 1 and Class 2, the bridge load-bearing capacity is assessed according to the "Highway Bridge Load-bearing Capacity Testing and Assessment Procedure" (JTG / T J21-2011). For bridges rated as Class 3, Class 4 and Class 5 in technical status, and bridges rated as Class 1 and Class 2 but whose load-bearing capacity does not meet the requirements, it is not recommended to continue to use them in the reconstruction and expansion project;

[0062] Step 2: For bridges rated as Class 1 and Class 2 and whose bearing capacity is assessed to meet the requirements, the main structure components are classified according to the cross-sectional form, stress characteristics and construction materials of the components. The main structure includes multiple component categories. For example, the pier structure can include pier cap component categories, pier column component categories, etc. Calculate the score of the appearance durability status of any main structure component category. If it reaches the threshold range (for example, greater than 3), it is not recommended to continue using it in the renovation and expansion project.

[0063] In step 2, any main structural component category is divided into multiple durability assessment units. The durability assessment units are divided according to environmental conditions and apparent characteristics. Components with basically the same environmental effects, material properties and apparent characteristics in the same component category are taken as one durability assessment unit. For example, in the pier component category, there are 5 piers, 3 of which are corroded and cracked, and 2 are intact. Then they can be divided into two durability assessment units based on the apparent disease characteristics. The components in the durability assessment unit are tested for the appearance durability of the bridge, and the grade of the appearance durability of each durability assessment unit is assessed, and the corresponding score of the appearance durability is determined. The score corresponding to the grade of the appearance durability of the durability assessment unit should be taken according to the provisions of Table 1.

[0064] Table 1

[0065] Appearance durability level Ia IIa IIIa IVa Corresponding score 1 2 3 4

[0066] The appearance durability of the main structural component category is used as the first-level evaluation index to obtain the appearance durability score of each main structural component category:

[0067]

[0068] Where A is the score of the appearance durability status of any main structural component category;

[0069] A i It is the score corresponding to the grade of the appearance durability state of a durability assessment unit in the category of the main structural component;

[0070] n i The number of durability assessment units with the same score in the category of the main structural component;

[0071] n is the number of durability assessment units classified by the category of the main structural component.

[0072] When the score of the appearance durability status of any main structure component category does not reach the threshold range (for example, less than or equal to 3), the main structure component category is rated as Class A, and the components in Class A need to be evaluated for availability. When the appearance durability status score of the main structure component category of the bridge reaches the threshold range (for example, greater than 3), the main structure component category is rated as Class B, and the components in Class B are not recommended to continue to be used. As shown in Table 2, the components in Class A need to be evaluated separately for each durability assessment unit in the main structure component category. If the remaining durability life of the durability assessment unit is not less than the design service life, then the durability assessment unit is recommended to continue to be used in the renovation and expansion project.

[0073] Table 2

[0074] First-level indicator score ≤3 >3 First-level indicator evaluation Category A Category B Availability Notes Conduct secondary assessment It is not recommended to continue using

[0075] Since the actual durability of an existing bridge structure is not only related to its remaining durability, but also to the maintenance measures taken during its service life, and whether the remaining durability meets the requirements is also related to the target service life, the concept of life coefficient is introduced to better measure the availability of the remaining durability of the existing bridge structure in the renovation and expansion project, taking into account the maintenance status during service and the target service life.

[0076] For the components in category A, each durability assessment unit needs to be judged by the secondary evaluation index - life coefficient according to the remaining durability and the maintenance method to be adopted during the service life. The life coefficient and usable life coefficient of each durability assessment unit of any main structural component category are calculated.

[0077] k yWhen ≥1, the durability assessment unit can continue to be used in the renovation and expansion project;

[0078] When the durability assessment unit is used for a longer period of time in the renovation and expansion project;

[0079] The durability assessment unit should not be used in the renovation and expansion project.

[0080] Among them, k y is the life coefficient, is the useful life factor;

[0081]

[0082] Among them, t e The remaining durability of the durability assessment unit is determined through durability testing and assessment;

[0083] T is the target service life of the renovation and expansion project, which can be the designed service life or the service life expected by the renovation and expansion project manager, and is determined by the renovation and expansion project manager based on actual conditions;

[0084]

[0085] Among them, T 0i The effective guarantee period for the life extension technology of category i shall be determined based on the life extension technology;

[0086] m i The numerical value for implementing a certain type of maintenance measure is formulated according to Table 3 based on the difficulty of implementing the maintenance measure;

[0087] j is the number of types of maintenance measures to be taken on the existing bridges within the target service life of the renovation and expansion project, which shall be prepared in advance by the renovation and expansion project manager based on the actual operation status and technical development level of the renovation and expansion project;

[0088] Table 3

[0089]

[0090] j value and m i The value should satisfy:

[0091]

[0092] Among them, C 0i is the cost of the ith maintenance measure;

[0093] C r The cost of demolition and reconstruction;

[0094] Formula IV is used to determine and restrict the economic feasibility of reusing existing bridges during reconstruction and expansion.

[0095] From formula III, we can see that the availability life coefficient Related to the following factors:

[0096] 1) Target service life T of the reconstruction and expansion project: The larger the target service life T of the reconstruction and expansion project, the larger the availability life coefficient needs to be. That is, the longer the normal service life of the bridge in the reconstruction and expansion project is required, the larger the availability life coefficient of the existing bridge components is, and the longer the remaining durability requirement for the existing bridge to continue to be used is.

[0097] 2) The effective protection period of a single life extension is T 0i :When the effective protection period of a single life extension is T 0i The longer the service life, the lower the availability life coefficient can be. That is, the more effective the life extension technology is, the lower the requirement for the existing bridge to continue its remaining durability, and the availability of the existing bridge is improved. On the contrary, the availability life coefficient needs to be increased, and the availability of the existing bridge is reduced.

[0098] 3) The number of maintenance measures to be implemented for a certain type m i : The number of maintenance measures to be implemented is related to the difficulty of their construction, provided that the economic requirements of Formula IV are met. Construction includes the treatment of the original structural components and the implementation of maintenance measures. For example, the difficulty of implementing the structural surface coating in the maintenance of atmospheric zone components can be considered medium, but it is very difficult to implement it for components in water level fluctuation zones and splash zones; the first implementation is relatively easy, but the second implementation is more difficult because the failed coating of the first implementation needs to be removed. Normally, the number of similar structural and surface treatment measures should not exceed 2 times.

[0099] 4) The number j of types of maintenance measures to be taken for existing bridges within the target service life of the renovation and expansion project: Within the target service life, provided that the economic requirements of Formula IV are met, the more life extension technical measures that can be taken and are planned to be taken, the smaller the availability life coefficient, and the lower the requirement for the remaining durability of the existing bridge.

[0100] According to the research results of current maintenance technology, the availability life coefficients of the commonly used life extension methods are calculated by taking the target service life T of 50 years and 100 years as examples, see Table 4. The cost of new construction and life extension is related to the economic development of various regions, the environmental conditions of the bridge, the bridge structure type, etc., and can also be determined according to the specific conditions of the project during actual engineering judgment. The life coefficient is calculated according to the evaluation method given in the present invention. According to the existing technical level, the economic cost values ​​of the commonly used life extension measures used in the present invention when calculating the life coefficient are as follows:

[0101] 1) Cost of building a new bridge

[0102] Prestressed small box girder, 5,000 yuan / square meter;

[0103] Prestressed T-beam, 6,000 yuan / square meter;

[0104] Hollow slab beam, 5,000 yuan / square meter;

[0105] Piers, 2,000 yuan / square meter (diameter 2 meters)

[0106] 2) Demolition cost: 600 yuan / square meter;

[0107] 3) Life extension measures costs:

[0108] ① Protective coating, 10 years, 150 yuan / m2 for the first time, (150+150) yuan / m2 from the second time onwards;

[0109] ②Silane impregnation, 15 years, 300 yuan / square meter;

[0110] ③ Paste carbon fiber cloth, 20 years, 900 yuan / square meter; from the second time onwards (900+900) yuan / square meter;

[0111] ④Electrochemical protection + penetrating rust inhibitor, 20 years, 2,000 yuan / square meter

[0112] ⑤ Increase section protection, 30 years, 3,000 yuan / square meter;

[0113] The available life coefficients corresponding to different life extension measures and target service life are shown in Table 4.

[0114] Table 4

[0115]

[0116]

[0117] For the selection of the usable life coefficient, the principles of minimum life extension cost and maximum life extension period can be adopted. When the principle of minimum life extension cost is adopted, it is mainly limited by the maintenance cost during the operation of the renovation and expansion project. At this time, the requirements for the remaining durability of the existing structure are relatively high; when the principle of maximum life extension period is adopted, it is mainly to consider the full utilization of the existing structure, but it will cost a high maintenance cost during the operation period and may affect the normal use of the structure.

[0118] Formula II calculates the remaining durability of the durability assessment unit t e Consider a concrete bridge in two contexts:

[0119] 1) For concrete bridges in general atmospheric environment, calculate the remaining durability of the durability assessment unit t eWhen the carbonization depth reaches the steel bar surface, it is taken as the durability limit state. Concrete is carbonized by the carbon dioxide in the air. The carbonization depth is proportional to the 0.5 power of time. This rule can be used to calculate the time when carbonization reaches the steel bar surface:

[0120]

[0121]

[0122] Where c is the thickness of the steel bar protective layer;

[0123] t0 is the operating time of the bridge;

[0124] k c is the carbonization coefficient;

[0125] d is the carbonation depth of concrete.

[0126] 2) For concrete bridges corroded by chloride ions in marine environments, calculate the remaining durability of the durability assessment unit t e When the chloride ion concentration on the steel bar surface reaches the critical value of corrosion, it is taken as the durability limit state. The diffusion of chloride ions into concrete in the marine environment is non-steady-state diffusion, and the diffusion law conforms to Fick's second law:

[0127]

[0128]

[0129] Among them, k D Chloride ion corrosion coefficient

[0130] D is the diffusion coefficient of chloride ions in concrete (mm 2 / a);

[0131] erf -1 is the inverse function of the error function;

[0132] C cr is the critical concentration of chloride ions (%, accounting for the mass of concrete), which is determined according to the actual corrosion status of the steel bars. The value is 0.6% in the splash zone and water level change zone, and 0.2% to 0.45% in the atmospheric zone;

[0133] γ s is the chloride ion surface concentration coefficient, which is 1.2 at the corner and 1.0 at the non-corner;

[0134] C s is the surface chloride ion concentration (%, accounting for the mass of concrete);

[0135] The diffusion of chloride ions in the marine environment into concrete can be expressed by Fick's second law. The chloride ion content of each layer within about 10 cm of the surface layer was measured by sampling the bridge concrete. The unknown coefficients "chloride ion diffusion coefficient D in concrete" and "chloride ion concentration C on the surface of concrete" were converted into s "The fitting results show that the D value and C s The value should satisfy:

[0136]

[0137] Among them, C x,t is the chloride ion concentration at depth x at age t (%, based on concrete mass);

[0138] C0 is the initial chloride ion concentration in concrete (%, accounting for the mass of concrete);

[0139] erf is the error function;

[0140] x is the depth from the structure surface (mm).

[0141] In the above calculation process, the chloride ion diffusion coefficient D in concrete and the chloride ion concentration C on the surface of concrete are calculated. s The solution of " is relatively complex. This is the key to assessing the remaining durability of concrete bridges in marine environments. The inventor designed a calculation program to solve this unknown. The program is written in Python and is as follows:

[0142]

[0143]

[0144] Verification of the economic benefits of the method of this application:

[0145] The method of the present invention is used to evaluate the availability of a bridge in a general atmospheric environment in a line reconstruction and expansion project.

[0146] The bridge has been assessed for technical condition [Standard for Assessment of Technical Condition of Highway Bridges (JTG / T H21-2011)] and bearing capacity [Procedure for Testing and Assessment of Bearing Capacity of Highway Bridges (JTG / T J21-2011)], and its technical condition grade is 2, and its bearing capacity meets the requirements.

[0147] According to step 2, the main structural components are classified according to their cross-sectional form, stress characteristics and construction materials, and then the component durability assessment units are divided according to environmental conditions and surface characteristics. Components in the same component category with basically the same environmental effects, material properties and surface characteristics are regarded as a durability assessment unit.

[0148] After the appearance durability test and evaluation, it was found that the appearance durability scores of each main structural component category of the bridge were all less than 3, the first-level indicator was evaluated as Class A, and the second-level evaluation was carried out.

[0149] The carbonization remaining durability of each durability assessment unit is evaluated by testing relevant parameters. The target service life is 50 years, and the life coefficient k is obtained, see Table 5.

[0150] Table 5

[0151]

[0152] Through calculation, the life coefficient k of the middle beam unit in the main beam structure of the bridge on this expansion line is greater than 1, and it can be used directly. Other assessed units need to be treated to extend their life before they can continue to be used. Combined with the life extension measures in Table 4, the life of the units that need to be extended is extended, and the guaranteed years and usable life coefficient are shown in Table 6.

[0153] Table 6

[0154]

[0155]

[0156] For hollow slab girder bridges, the new construction cost of the main beam structure is about 5,000 yuan / m2, the new construction cost of the pier structure is about 2,000 yuan / m2 (diameter 2 meters), and the demolition cost is 600 yuan / m2. After corresponding life extension measures, the life extension cost of the side beam unit in the main beam structure is 150 yuan / m2, which is significantly lower than the cost of demolishing and rebuilding the main beam structure. The life extension measures for the cap beam and pier in the pier structure are both 450 yuan / m2, which is significantly lower than the cost of demolishing and rebuilding the pier structure.

[0157] In summary, under the condition that the target service life is 50 years, the cost of life extension treatment is significantly lower than the cost of demolition and reconstruction. Therefore, it is recommended that the bridge continue to be used after taking corresponding life extension measures. This provides a reasonable analysis for the treatment of existing bridges during expansion and avoids waste of resources.

[0158] If the target service life is 100 years, the life coefficient k of each assessment unit is shown in Table 7. It is difficult to achieve the useable life coefficient k with existing technical measures. If it is controlled below 0.3, the cost will increase greatly. In this case, it is not recommended to continue using the bridge.

[0159] Table 7

[0160]

[0161] The above analysis is an application example of the present invention, which is used to explain the application analysis process and economic rationality of the present invention. The specific amount of the cost needs to be determined in combination with the specific project.

[0162] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

[0163] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. A method for evaluating the availability of existing bridges in highway reconstruction and expansion projects, characterized in that: include: Step 1: Evaluate the technical status and load-bearing capacity of existing bridges in the highway reconstruction and expansion project. For bridges rated as Class 3, Class 4 and Class 5 in terms of technical status, and bridges rated as Class 1 and Class 2 but with load-bearing capacity that does not meet the requirements, it is not recommended to continue using them in the reconstruction and expansion project; Step 2: For bridges rated as Class 1 and Class 2 and with bearing capacity assessed as meeting the requirements, classify the main structural components into categories, calculate the score of the appearance durability status of any main structural component category, and if it reaches the threshold range, it is not recommended to continue using it in the renovation and expansion project; In step 2, any main structural component category is divided into a plurality of durability assessment units, the level of the appearance durability state of each durability assessment unit is assessed, and the corresponding appearance durability state score is determined to obtain the appearance durability state score of each main structural component category: Where A is the score of the appearance durability status of any main structural component category; A i It is the score corresponding to the grade of the appearance durability state of a durability assessment unit in the category of the main structural component; n i The number of durability assessment units with the same score in the category of the main structural component; n is the number of durability assessment units classified by the main structural component category; When the score of the appearance durability status of any main structural component category does not reach the threshold range, each durability assessment unit in the main structural component category shall be assessed separately. If the remaining durability of the durability assessment unit is not less than the design service life, it is recommended that the durability assessment unit continue to be used in the renovation and expansion project; Calculate the life factor and usable life factor of each durability assessment unit of any main structural component category, k y When ≥1, the durability assessment unit can continue to be used in the renovation and expansion project; When the durability assessment unit is used for a longer period of time in the renovation and expansion project; When the durability assessment unit is damaged, it is not suitable to continue to be used in the renovation and expansion project; Among them, k y is the life coefficient, is the useful life factor; Among them, t e The remaining durability of the durability assessment unit; T is the target useful life of the renovation and expansion project; Among them, T 0i The effective guarantee period for the i-th type of life extension technology; m i A value for implementing a certain type of maintenance measure; j is the number of types of maintenance measures to be taken on the existing bridges within the target service life of the renovation and expansion project; j value and m i The value should satisfy: Among them, C 0i is the cost of the ith maintenance measure; C r The cost of demolition and reconstruction.

2. The method for evaluating the availability of existing bridges in a highway reconstruction and expansion project as claimed in claim 1, characterized in that: Calculation of the remaining durability of the durability assessment unit for concrete bridges in general atmospheric environments e When the carbonization depth reaches the steel bar surface, the durability limit state is: Where c is the thickness of the steel bar protective layer; t0 is the operating time of the bridge; k c is the carbonization coefficient; d is the carbonation depth of concrete.

3. The method for evaluating the availability of existing bridges in a highway reconstruction and expansion project as claimed in claim 2, characterized in that: Calculation of the remaining durability of the durability assessment unit for a concrete bridge subject to chloride ion corrosion in a marine environment e When the chloride ion concentration on the steel bar surface reaches the critical value of corrosion, it is taken as the durability limit state: Among them, k D is the chloride ion corrosion coefficient; D is the chloride ion diffusion coefficient in concrete; erf -1 is the inverse function of the error function; C cr is the critical concentration of chloride ions; γ s is the chloride ion surface concentration coefficient; C s is the surface chloride ion concentration; D value and C s The value should satisfy: Among them, C x,t is the chloride ion concentration at depth x at age t; C0 is the initial chloride ion concentration in concrete; erf is the error function; x is the depth from the surface of the structure.

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