Numerical simulation method considering the effect of carbonization on the performance of reinforced concrete

Abstract

The present invention provides a numerical simulation method considering the influence of carbonization on the performance of reinforced concrete, which relates to the technical field of reinforced concrete performance analysis. The method comprises: establishing an initial concrete model QA; importing ZH into a preset finite element calculation software; predicting the carbonization depth X of ZH after N ΔTs through a preset concrete carbonization depth prediction mathematical model X. N ; QB N External surface facing inwards X N The thickness area of ​​QB is determined as the complete carbonization area. N Outer surface facing inwards X N To X N The thickness area of ​​+Δd is determined as the carbonization reaction zone, and QB N Outer surface facing inwards X N The thickness area from +Δd to the steel bar surface is determined as the uncarbonized area; set QB N The constitutive relations of the complete carbonization zone, carbonization reaction zone and uncarbonized zone are obtained to obtain QB N The corresponding updated Nth concrete model QB N '; Until the loading is completed; the present invention makes the difference between the simulated data and the actual data smaller.

Description

Technical Field

[0001] The invention relates to the technical field of reinforced concrete performance analysis, and in particular to a numerical simulation considering the influence of carbonization on reinforced concrete performance. Background Art

[0002] The carbonization of concrete is a complex physical and chemical process. After CO2 in the atmosphere diffuses into the concrete, it reacts chemically with the substances generated during the hydration process of concrete cement, which reduces the alkalinity of the concrete. After the concrete is carbonized, its density increases, its water absorption rate decreases, and its compressive strength and flexural strength increase. Studies have shown that after the cement mortar with a mix ratio of 1:3 is carbonized, its compressive strength increases by 50%-70%, and its flexural strength increases by 40%-60%. However, once the carbonization depth reaches the surface of the steel bar, it will lose its ability to protect the steel bar from rusting. Carbonization reduces the alkalinity of concrete, thereby weakening its ability to protect the steel bar, causing the steel bar to rust, reducing the stress area of ​​the steel bar, and posing certain safety hazards. The carbonization behavior of concrete is one of the most serious problems in the durability of concrete at present; existing numerical simulation methods usually do not consider the impact of carbonization on reinforced concrete, resulting in a large difference between the simulation data of concrete and the actual data. Summary of the invention

[0003] Based on the above technical problems, the present application provides a numerical simulation method considering the influence of carbonization on the performance of reinforced concrete, the method comprising the following steps:

[0004] S100, establishing an initial concrete model QA corresponding to the target concrete.

[0005] S200, obtaining a first preset value N=1 and an intermediate model ZH=QA.

[0006] S300, import ZH into the preset finite element calculation software, load the preset unit time length ΔT, and obtain the Nth concrete model QB N , enter S400.

[0007] S400, using a preset concrete carbonation depth prediction mathematical model X, predict the carbonation depth X of ZH after N ΔT N .

[0008] S500, QB N Outer surface facing inwards X N The thickness area of ​​QB is determined as the completely carbonized area. N Outer surface facing inwards X N To X N The thickness area of ​​+Δd is determined as the carbonization reaction zone, and QB N Outer surface facing inwards X NThe thickness area from +Δd to the steel bar surface is determined as the uncarbonized area; Δd is the preset carbonization reaction zone thickness.

[0009] S600, set QB N The constitutive relations of the complete carbonization zone, carbonization reaction zone and uncarbonized zone are obtained to obtain QB N The corresponding updated Nth concrete model QB N '.

[0010] S700, if the fully carbonized zone does not reach the steel bar surface, then obtain N=N+1 and ZH=QB N ', enter S300; otherwise, enter S800.

[0011] S800, update the steel bar diameter until the loading is completed.

[0012] The present invention has at least the following beneficial effects:

[0013] The numerical simulation method of the present invention that considers the influence of carbonization on the performance of reinforced concrete continuously updates the constitutive relationship of the model according to the change of the carbonization depth of concrete during the simulation of the target concrete, so that the simulation process is more consistent with the carbonization process in the actual environment; at the same time, the simulation process considers the influence of carbonization on concrete, and can more accurately simulate the performance of reinforced concrete; as the corrosion depth of the steel bar continues to increase, when the diameter of the steel bar is less than the minimum diameter requirement of the structure, it can be considered that the structure is damaged; it has a certain predictive effect on the service life of the structure; thereby reducing the difference between the simulation data and the actual data. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 A flow chart of a numerical simulation method considering the influence of carbonization on the performance of reinforced concrete provided in an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of the structure of different zones provided by an embodiment of the present invention;

[0017] Figure 3 A schematic diagram of a steel bar corrosion structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0019] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0020] The following will refer to Figure 1 The flowchart of the numerical simulation method considering the influence of carbonization on the performance of reinforced concrete is shown, which introduces the numerical simulation method considering the influence of carbonization on the performance of reinforced concrete.

[0021] First, the principle of the method in this embodiment is introduced:

[0022] The carbonization of concrete is a complex physical and chemical process in which gas diffuses into the concrete, dissolves in the pore water of the concrete to become carbonic acid, and then reacts with cement hydration products. There is a band-shaped range of about 10 mm in width inside the carbonized concrete, which is called the carbonization zone. The outer side is the carbonized area, called the fully carbonized zone, and the inner side is the uncarbonized area, called the uncarbonized zone. Carbonization only changes the properties of reinforced concrete in the fully carbonized zone and the carbonization reaction zone, and the properties of reinforced concrete in the uncarbonized zone do not change. The carbonization depth changes with time. If the corresponding constitutive relationship can be given to the fully carbonized zone and the partially carbonized zone in real time during the simulation process and the steel bar section can be reduced, the influence of carbonization can be better reflected. For simplification, the preset unit time length ΔT is taken as the unit, that is, every ΔT, the above model is replaced to change the constitutive relationship of concrete and reduce the cross-sectional area of ​​the steel bar to consider the influence of carbonization.

[0023] In this embodiment, in order to measure the constitutive relationship of the concrete after carbonization, the constitutive relationship of the standard concrete specimen after carbonization at a carbon dioxide concentration of (20±3)% for 28 days is used as the constitutive relationship of the concrete after carbonization. Carbonation at a carbon dioxide concentration of (20±3)% for 28 days is roughly equivalent to the carbonation depth of 50 years in the natural environment, which is consistent with the general durability requirements. The initial constitutive relationship is based on the standard cubic specimen measured in the laboratory.

[0024] The numerical simulation method considering the influence of carbonization on the performance of reinforced concrete may include the following steps:

[0025] S100, establishing an initial concrete model QA corresponding to the target concrete.

[0026] In this embodiment, the target concrete can be any concrete in an actual environment; the initial concrete model QA can be obtained according to the actual parameters corresponding to the target concrete; the initial concrete model QA can be obtained by measuring a standard cubic specimen corresponding to the target concrete.

[0027] It should be noted that those skilled in the art can use the existing concrete model construction method to establish the initial concrete model QA corresponding to the target concrete according to actual needs, which will not be elaborated here.

[0028] S200, obtaining a first preset value N=1 and an intermediate model ZH=QA.

[0029] In this embodiment, N and ZH are used for cyclic operation in subsequent steps.

[0030] S300, import ZH into the preset finite element calculation software, load the preset unit time length ΔT, and obtain the Nth concrete model QB N , enter S400.

[0031] In this embodiment, ΔT can be set to be smaller to improve the accuracy of the simulation; ΔT can also be set to be larger to improve the simulation efficiency; those skilled in the art can set ΔT according to actual needs to achieve better simulation effects.

[0032] Furthermore, the preset finite element calculation software includes: HyperMesh software.

[0033] S400, using a preset concrete carbonation depth prediction mathematical model X, predict the carbonation depth X of ZH after N ΔT N .

[0034] In this embodiment, an initial concrete model corresponding to the target concrete is established in the finite element software; the loading time history is set, and when the loading time reaches 1 ΔT, the calculation is stopped, and the model at this time is exported using the HyperMesh software.

[0035] Furthermore, the preset concrete carbonization depth prediction mathematical model X conforms to the following relationship:

[0036] .

[0037] Among them, C CO2 is the carbon dioxide concentration corresponding to the environment in which the target concrete is located; t is the time the target concrete is in the environment; H is the annual average relative humidity of the environment in which the target concrete is located.

[0038] In this embodiment, it can be understood that X is a general calculation model, X is the carbonation depth; different carbonation depths can be calculated according to different loading durations; in the specific simulation process, the duration t of the target concrete in the environment corresponding to 1 ΔT can be obtained according to the mapping relationship between the simulation duration and the actual duration, so that X1 can be obtained according to X.

[0039] S500, QB N Outer surface facing inwards X N The thickness area of ​​QB is determined as the completely carbonized area. N Outer surface facing inwards X N To X N The thickness area of ​​+Δd is determined as the carbonization reaction zone, and QB N Outer surface facing inwards X N The thickness area from +Δd to the steel bar surface is determined as the uncarbonized area; Δd is the preset carbonization reaction zone thickness.

[0040] In this embodiment, the carbonization of concrete is a complex physical and chemical process in which gas diffuses into the concrete, dissolves in the pore water of the concrete to become carbonic acid, and then reacts with cement hydration products. There is a band-shaped range of about 10 mm in width inside the carbonized concrete, which is called the carbonization progressing area. The outer side is the carbonized area, which is called the completely carbonized area, and the inner side is the uncarbonized area, which is called the uncarbonized area.

[0041] Further, Δd=10mm.

[0042] S600, set QB N The constitutive relations of the complete carbonization zone, carbonization reaction zone and uncarbonized zone are obtained to obtain QB N The corresponding updated Nth concrete model QB N '.

[0043] In this embodiment, the constitutive relations of the complete carbonization zone and the initial constitutive relation are both known, and the average of the constitutive relation of the complete carbonization zone and the initial constitutive relation can be used as the constitutive relation of the concrete in the carbonization reaction zone.

[0044] Specifically, Figure 2 As shown, the carbonization depth X1 of the first ΔT is calculated and recorded as X1+10mm as X1'; X1 is used as the boundary between the complete carbonization zone and the carbonization reaction zone, and X1' is used as the boundary between the carbonization reaction zone and the uncarbonized zone.

[0045] The exported model was re-imported into the finite element calculation software, and the constitutive relationship after carbonization was assigned to the concrete in the completely carbonized zone. The average of the constitutive relationship after carbonization and the initial constitutive relationship was used as the constitutive relationship of the concrete in the carbonization reaction zone. The initial constitutive relationship was assigned to the uncarbonized zone and recalculated.

[0046] After another ΔT, the calculation is stopped and the model at this time is exported using HyperMesh. Thereafter, the exported model is re-imported into the finite element calculation software, and the boundary position is calculated based on twice the ΔT moment, with X2 as the boundary between the completely carbonized zone and the carbonization reaction zone, and X2' as the boundary between the carbonization reaction zone and the uncarbonized zone. The concrete in the completely carbonized zone is assigned the constitutive relationship after carbonization, and the average of the constitutive relationship after carbonization and the initial constitutive relationship is used as the constitutive relationship of the concrete in the carbonization reaction zone. The uncarbonized zone is assigned the initial constitutive relationship, and the calculation is repeated again, in a cycle.

[0047] S700, if the fully carbonized zone does not reach the steel bar surface, then obtain N=N+1 and ZH=QB N ', enter S300; otherwise, enter S800.

[0048] S800, update the steel bar diameter until the loading is completed.

[0049] Further, step S800 may include the following steps:

[0050] S810, obtaining a second preset value k=1.

[0051] S820, obtain the corrosion depth δ of the steel bar within k ΔT k .

[0052] S830, set the diameter of the steel bars of ZH to δ-δ k , and update the corresponding constitutive relation to obtain the kth specified model QC k .

[0053] S840, if the steel bar is not completely corroded, obtain k=k+1 and set QC k Import into the preset finite element calculation software, load the preset unit time length ΔT, and enter S820; otherwise, jump out of the current process.

[0054] In this embodiment, it is assumed that the carbonization depth of concrete reaches the steel bar surface at (N+1)×ΔT, that is, the carbonization depth does not reach the steel bar surface at n×ΔT; ​​the steel bar corrosion depth can be calculated using the following formula:

[0055] ;

[0056] Where C is the target concrete cover thickness; f cu is the standard value of the target concrete cube compressive strength; T is the average temperature of the environment in which the target concrete is located.

[0057] The corrosion depth δ1 of the steel bar is calculated, and the initial steel bar diameter is assumed to be δ, and δ-δ1 is used as the steel bar diameter at the time (N+1)×ΔT to be introduced into the model; thereafter, at each time interval, the corresponding corrosion depth is obtained using the above formula, and the steel bar diameter at each time is changed until the loading is completed, thereby completing the simulation process of the target concrete and obtaining the relevant change curve corresponding to the target concrete; the steel bar corrosion structure is shown in Figure 3 shown.

[0058] Mechanical properties and durability in the numerical simulation process are important simulation indicators. Conventional numerical simulation methods are difficult to consider the differences in mechanical properties and durability caused by concrete carbonization, especially for large reinforced concrete structures such as bridges, tunnels, and high-rise buildings. This method takes into account the impact of carbonization on concrete and can more accurately simulate the performance of reinforced concrete. At the same time, as the depth of steel corrosion continues to increase, when the diameter of the steel bar is less than the minimum diameter requirement of the structure, the structure can be considered damaged. It has a certain predictive effect on the service life of the structure.

[0059] The numerical simulation method of this embodiment that considers the influence of carbonization on the performance of reinforced concrete continuously updates the constitutive relationship of the model according to the change of the carbonization depth of concrete during the simulation of the target concrete, so that the simulation process is more consistent with the carbonization process in the actual environment; at the same time, the simulation process considers the influence of carbonization on concrete, and can more accurately simulate the performance of reinforced concrete; as the corrosion depth of the steel bar continues to increase, when the diameter of the steel bar is less than the minimum diameter requirement of the structure, the structure can be considered to be damaged; it has a certain predictive effect on the service life of the structure; thereby reducing the difference between the simulation data and the actual data.

[0060] In addition, although the steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps, etc.

[0061] Although some specific embodiments of the present invention have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present invention. It should also be understood by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the present invention.

Claims

1. A numerical simulation method considering the effect of carbonization on the performance of reinforced concrete, characterized in that: The method comprises the following steps: S100, establishing an initial concrete model QA corresponding to the target concrete; S200, obtaining a first preset value N=1 and an intermediate model ZH=QA; S300, import ZH into the preset finite element calculation software, load the preset unit time length ΔT, and obtain the Nth concrete model QB N , enter S400; S400, using a preset concrete carbonation depth prediction mathematical model X, predict the carbonation depth X of ZH after N ΔT N ; S500, QB N External surface facing inwards X N The thickness area of ​​QB is determined as the complete carbonization area. N External surface facing inwards X N To X N The thickness area of ​​+Δd is determined as the carbonization reaction zone, and QB N External surface facing inwards X N The thickness area from +Δd to the steel bar surface is determined as the uncarbonized area; Δd is the preset carbonization reaction zone thickness; S600, set QB N The constitutive relations of the complete carbonization zone, carbonization reaction zone and uncarbonized zone are obtained to obtain QB N The corresponding updated Nth concrete model QB N '; The constitutive relation corresponding to the carbonization reaction zone is the average of the constitutive relation of the complete carbonization zone and the initial constitutive relation of the uncarbonized zone; S700, if the fully carbonized zone does not reach the steel bar surface, then obtain N=N+1 and ZH=QB N ', enter S300; otherwise, enter S800; S800, update the steel bar diameter until the loading is completed; Step S800 includes the following steps: S810, obtaining a second preset value k=1; S820, obtain the corrosion depth δ of the steel bar within k ΔT k ; S830, set the diameter of the steel bars of ZH to δ-δ k , and update the corresponding constitutive relation to obtain the kth specified model QC k ; S840, if the steel bar is not completely corroded, obtain k=k+1 and set QC k Import into the preset finite element calculation software, load the preset unit time length ΔT, and enter S820; otherwise, jump out of the current process.

2. The numerical simulation method considering the influence of carbonization on the performance of reinforced concrete according to claim 1 is characterized in that: The preset concrete carbonization depth prediction mathematical model X conforms to the following relationship: ； Among them, C CO2 is the carbon dioxide concentration corresponding to the environment in which the target concrete is located; t is the time the target concrete is in the environment; H is the annual average relative humidity of the environment in which the target concrete is located.

3. The numerical simulation method considering the influence of carbonization on the performance of reinforced concrete according to claim 2 is characterized in that: δ k The following relationship is met: ； Where C is the target concrete cover thickness; f cu is the standard value of the target concrete cube compressive strength; T is the average temperature of the environment in which the target concrete is located.

4. The numerical simulation method considering the influence of carbonization on the performance of reinforced concrete according to claim 1 is characterized in that: The preset finite element calculation software includes: HyperMesh software.

5. The numerical simulation method considering the influence of carbonization on the performance of reinforced concrete according to claim 1 is characterized in that: Δd=10mm.

Images