Fracture mechanics-based joint crack propagation judgment method for laminated component

Abstract

The invention belongs to the technical field of constructional engineering, and particularly relates to a laminated component joint crack propagation judgment method based on fracture mechanics, which comprises the following steps: establishing a weak joint surface inclined crack coordinate system based on a weak joint surface at a joint of a laminated component, and calculating a stress intensity factor of a weak joint surface inclined crack tip; calculating the tip circumferential stress of the inclined crack along the weak junction surface by combining a crack tip circumferential stress expression constructed on the basis of fracture mechanics; based on the circumferential stress of the tip of the oblique crack along the weak joint surface, determining the joint crack propagation and propagation direction of the laminated component in combination with the maximum circumferential stress criterion; and based on the concrete strength of the prefabricated component and the strength of post-poured concrete, comparing the circumferential stress of the tip of the inclined crack along the weak joint surface, and determining the propagation priority in the joint crack propagation process of the laminated component. The method can be used for judging whether the joint of the laminated component is cracked or not and judging the crack propagation direction and priority, so that the safety, stability and reliability of the structure are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of building engineering, and in particular relates to a method for distinguishing crack extension in a joint of a composite member based on fracture mechanics. Background Art

[0002] In the modern construction industry, with the rapid development of prefabricated construction technology, composite components, as an efficient and environmentally friendly structural form, are gradually becoming an important part of the construction field. Composite components, as components composed of prefabricated parts and cast-in-place parts superimposed in a specific way, are designed to increase construction speed, reduce wet work, and reduce material consumption.

[0003] Compared with traditional fully cast-in-place structures, the significant advantage of composite components is that they can significantly reduce the amount of formwork, shorten the construction period, and reduce labor costs, while maintaining the integrity and stability of the structure. Compared with traditional fully assembled structures, composite components have stronger advantages in seismic resistance and integrity due to their partial cast-in-place characteristics, and can better adapt to the test of natural disasters such as earthquakes, ensuring the safety and durability of buildings.

[0004] However, despite the many advantages of composite components, they also face some technical difficulties in practical applications, the most critical of which is the stress and crack propagation problems at the joints. Since there is a joint between the prefabricated part and the cast-in-place part of the composite component, the stress conditions in this area are extremely complex when subjected to various stresses (such as bending stress, shear stress, temperature stress, etc.). Especially under the influence of long-term loads and environmental factors, cracks are prone to appear at the joints, and the crack propagation path will directly affect the overall stability and failure mode of the structure. Summary of the invention

[0005] The present invention provides a method for distinguishing crack extension at the joint of a composite component based on fracture mechanics. The method forms a weak bonding surface at the joint of the composite component by using a shear key arranged on the bonding surface between the prefabricated component and the post-cast concrete, and combines the crack tip stress field at the joint of the composite component calculated by the crack tip stress field solution of fracture mechanics. The method further uses the maximum circumferential stress criterion to distinguish crack extension and extension direction at the joint of the composite component, so that it is possible to accurately calculate whether the joint of the composite component is cracked, and at the same time reasonably determine the priority of the crack extension direction, so as to avoid the crack extension path from damaging the entire structure, thereby ensuring the safety, stability and reliability of the structure.

[0006] A method for determining crack propagation in a composite component joint based on fracture mechanics, comprising:

[0007] Based on the weak bonding surface at the joint of the composite component, the oblique crack coordinate system of the weak bonding surface is established, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated, and the circumferential stress at the oblique crack tip along the weak bonding surface is calculated by combining the circumferential stress expression at the crack tip constructed based on fracture mechanics.

[0008] Based on the circumferential stress at the tip of the inclined crack along the weak bonding surface and the maximum circumferential stress criterion, the crack extension and propagation direction of the composite component joint are determined;

[0009] Based on the concrete strength of precast components and the post-cast concrete strength, the circumferential stress at the tip of the oblique crack along the weak bonding surface is compared to determine the expansion priority of the crack in the composite component joint during expansion.

[0010] By setting the shear key based on the bonding surface of the precast component and the post-cast concrete, a weak bonding surface is formed at the joint of the composite component, and the crack tip stress field at the composite component joint is calculated by combining the solution of the crack tip stress field in fracture mechanics. Then, the maximum circumferential stress criterion is used to judge the crack extension and extension direction of the composite component joint. It is possible to accurately calculate whether the composite component joint is cracked, and at the same time reasonably determine the priority of the crack extension direction to avoid the crack extension path from damaging the entire structure, thereby ensuring the safety, stability and reliability of the structure.

[0011] Furthermore, based on the weak bonding surface at the joint of the composite component, the weak bonding surface oblique crack coordinate system is established, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated, and the circumferential stress at the oblique crack tip along the weak bonding surface is calculated in combination with the crack tip circumferential stress expression based on fracture mechanics, including:

[0012] Based on the weak bonding surface at the joint of the composite component, the weak bonding surface oblique crack coordinate system is established with the tip of the oblique crack on the weak bonding surface as the origin and the oblique crack oblique angle direction as the X-axis;

[0013] Based on the oblique crack coordinate system of the weak bonding surface, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated;

[0014] Based on fracture mechanics, the expression of circumferential stress at the crack tip is constructed;

[0015] The circumferential stress at the inclined crack tip along the weak bonding surface is calculated by combining the stress intensity factor at the inclined crack tip of the weak bonding surface and the circumferential stress at the crack tip.

[0016] Furthermore, based on the weak-bonding surface oblique crack coordinate system, the weak-bonding surface oblique crack is a I-II composite crack.

[0017] Furthermore, the method of determining the crack extension and extension direction of the composite component joint based on the circumferential stress at the tip of the oblique crack along the weak bonding surface and the maximum circumferential stress criterion includes:

[0018] The maximum circumferential stress at the tip of the I-type crack on the post-casting joint surface is calculated based on the expression of the circumferential stress at the crack tip. When the maximum circumferential stress at the tip of the oblique crack on the weak joint surface is greater than the strength of the post-cast concrete, it is determined that the joint crack of the composite component extends along the direction of the I-type crack on the joint surface.

[0019] Based on the circumferential stress at the tip of the oblique crack along the weak bonding surface, and when the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface is greater than the concrete strength of the prefabricated component, it is determined that the crack in the joint of the composite component extends in the direction of the oblique crack on the weak bonding surface.

[0020] Furthermore, the method of comparing the circumferential stress at the tip of the oblique crack along the weak bonding surface based on the concrete strength of the precast component and the post-cast concrete strength to determine the expansion priority of the crack in the composite component joint during the expansion process includes:

[0021] When the ratio of the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface to the strength of the precast component is greater than the ratio of the maximum circumferential stress at the tip of the type I crack on the post-cast bonding surface to the strength of the post-cast concrete, the bifurcated oblique crack will preferentially expand, that is, the crack in the joint of the composite component will preferentially expand along the oblique crack direction of the weak bonding surface.

[0022] Furthermore, the determination of the expansion priority of the crack in the composite component joint during the expansion process also includes:

[0023] The critical strength ratio of the crack propagation of the composite component joint at the weak bonding surface is set, and the ratio of the concrete strength of the precast component to the strength of the post-cast concrete is defined as the strength ratio;

[0024] When the value of the critical strength ratio is smaller, it means that the strength ratio of the concrete strength of the precast component required for the composite component joint crack to expand along the weak bonding surface is smaller, that is, the condition for the oblique crack expansion along the weak bonding surface is more difficult to meet;

[0025] The larger the value of the critical strength ratio, the larger the strength ratio of the concrete strength of the precast component required for the composite component joint crack to propagate along the weak bonding surface, that is, the condition for the oblique crack propagation along the weak bonding surface is easier to meet.

[0026] A system for determining crack propagation of a composite component joint based on fracture mechanics, comprising:

[0027] A calculation module is used to establish a weak bonding surface oblique crack coordinate system based on the weak bonding surface at the joint of the composite component, calculate the stress intensity factor at the oblique crack tip of the weak bonding surface, and calculate the circumferential stress at the oblique crack tip along the weak bonding surface in combination with the crack tip circumferential stress expression based on fracture mechanics;

[0028] The first judgment module is used to determine the crack extension and extension direction of the composite component joint based on the circumferential stress at the tip of the oblique crack along the weak bonding surface and the maximum circumferential stress criterion;

[0029] The second judgment module is used to compare the circumferential stress at the tip of the oblique crack along the weak bonding surface based on the concrete strength of the prefabricated component and the post-cast concrete strength, and determine the expansion priority of the joint crack of the composite component during the expansion process.

[0030] The beneficial effects of the present invention are:

[0031] The present invention forms a weak bonding surface at the joint of the composite component by means of shear keys arranged based on the bonding surface of the prefabricated component and the post-cast concrete, and calculates the crack tip stress field at the joint of the composite component by combining the crack tip stress field solution of the fracture mechanics, and then uses the maximum circumferential stress criterion to judge the crack extension and extension direction of the composite component joint, so that it is possible to accurately calculate whether the joint of the composite component is cracked, and at the same time reasonably determine the priority of the crack extension direction, so as to avoid the crack extension path from damaging the entire structure, thereby ensuring the safety, stability and reliability of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of the present invention;

[0033] Figure 2 Schematic diagram of the angle between the I-type crack and the oblique crack surface of the weak bonding surface;

[0034] Figure 3 Schematic diagram of the coordinate system of the oblique crack of the weak bonding surface;

[0035] Figure 4 It is a schematic diagram of the system structure in the present invention. DETAILED DESCRIPTION

[0036] 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] 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 can 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 can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can 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 can be used to implement this device and / or practice this method.

[0038] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples, and a person of ordinary skill in the art can understand the specific meanings of the above terms in this application under specific circumstances.

[0039] Example 1

[0040] Figure 1 The method shown is a method for judging crack extension at the joint of composite components based on fracture mechanics. The weak bonding surface is formed at the joint of composite components by setting the shear key based on the bonding surface of prefabricated components and post-cast concrete, and the crack tip stress field at the joint of composite components is calculated by combining the crack tip stress field solution of fracture mechanics. Then, the maximum circumferential stress criterion is used to judge the crack extension and extension direction of the composite component joint. This method can accurately calculate whether the composite component joint is cracked, and reasonably determine the priority of the crack extension direction to avoid the crack extension path from damaging the entire structure, thereby ensuring the safety, stability and reliability of the structure. The method specifically includes the following steps:

[0041] S1: Based on the weak bonding surface at the joint of the composite component, the oblique crack coordinate system of the weak bonding surface is established, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated, and the circumferential stress at the oblique crack tip along the weak bonding surface is calculated by combining the circumferential stress expression at the crack tip constructed based on fracture mechanics;

[0042] In this embodiment, the shear keys generally provided at the joint surface of the precast component and the post-cast concrete will form a weak joint surface at the joint of the composite component, and according to JGJ1-2014 "Technical Code for Prefabricated Concrete Structures", the strength of the post-cast concrete cannot be lower than the concrete strength of the precast component.

[0043] like Figure 2 As shown, the angle between the oblique crack of the weak bonding surface and the vertical I-type crack surface is set to β, that is, the angle is the inclination angle of the oblique surface of the weak bonding surface.

[0044] S11: Based on the weak bonding surface at the joint of the composite component, the weak bonding surface oblique crack coordinate system is established with the tip of the oblique crack on the weak bonding surface as the origin and the oblique crack oblique angle direction as the X-axis;

[0045] Figure 3 The coordinate system of the weak bonding surface oblique crack is shown. The X-axis is the direction of the I-type crack. The axis is the oblique crack direction of the weak bonding surface.

[0046] S12: Based on the oblique crack coordinate system of the weak bonding surface, calculate the stress intensity factor at the oblique crack tip of the weak bonding surface;

[0047] According to the continuity assumption, the I-type crack surface and the oblique crack on the weak bonding surface are continuous and uninterrupted, that is, when the length of the oblique crack on the weak bonding surface is very small, it can be considered that the tip stress and displacement field of the oblique crack on the weak bonding surface are still equivalent to the original stress and displacement field at that point on the I-type crack surface.

[0048] That is, the expression of the tip stress of the oblique crack on the weak bonding surface is:

[0049]

[0050] In the formula, Indicates the length of the oblique crack; represents the coordinate value on the Y axis in the coordinate system constructed with the inclined crack tip of the weak bonding surface as the origin; β represents the angle between the inclined crack of the weak bonding surface and the vertical I-type crack surface; θ represents the angle starting from the crack tip in the weak bonding surface inclined crack coordinate system;

[0051] The expression of displacement field of oblique crack on weak bonding surface is:

[0052]

[0053] In the formula, It represents the coordinate value in the coordinate system constructed when the inclined crack tip of the weak bonding surface is taken as the origin, the radial distance r is the radius, and the angle θ starting from the crack tip is equal to the angle β between the inclined crack of the weak bonding surface and the vertical I-mode crack surface.

[0054] At the same time, based on the weak bonding surface oblique crack coordinate system, in the stress field near the tip of the weak bonding surface oblique crack, the displacement field of the original crack along the direction of the weak bonding surface provides shear stress for the tip of the weak bonding surface oblique crack, and then the weak bonding surface oblique crack becomes a I-II composite crack. The stress intensity factors at the tip of the weak bonding surface oblique crack are:

[0055]

[0056] In the formula, It represents the stress intensity factor at the tip of the I-II type composite crack in the weak bonding surface; It represents the stress intensity factor at the tip of the mode II oblique crack in the I-II composite crack of the weak bonding surface;

[0057] Combined with the angle β between the oblique crack on the weak bonding surface and the vertical I-mode crack surface, the stress intensity factor at the tip of the oblique crack on the weak bonding surface can be expressed as:

[0058]

[0059] In the formula, K I Indicates the mode I fracture strength factor; K II represents the mode II fracture strength factor;

[0060] S13: Based on fracture mechanics, construct an expression for the circumferential stress at the crack tip;

[0061] The expression of circumferential stress near the crack tip is:

[0062]

[0063] In the formula, σ θ represents the circumferential stress near the crack tip; r represents the radial distance from the crack tip, that is, the radius of the critical crack extension area; θ represents the angle from the crack tip, that is, the angle between the line from the positive direction of the crack surface to the point under consideration rotated counterclockwise and the positive direction of the crack surface; T represents stress.

[0064] S14: Calculate the circumferential stress at the inclined crack tip along the weak bonding surface by combining the stress intensity factor at the inclined crack tip of the weak bonding surface and the circumferential stress at the crack tip.

[0065] Among them, the expression of the circumferential stress at the inclined crack tip along the weak bonding surface is:

[0066]

[0067] In the formula, represents the circumferential stress at the inclined crack tip along the weak bonding surface; It represents the angle of the crack tip in the weak bonding surface oblique crack coordinate system;

[0068] By non-dimensionalizing the stress T, the critical crack extension region radius r, and the crack length a, we obtain:

[0069]

[0070] Wherein, B represents the first coefficient factor; a represents the crack length; α represents the second coefficient factor.

[0071] Combined with the dimensionless expression, the expression of the circumferential stress at the inclined crack tip along the weak bonding surface can be transformed into:

[0072]

[0073] S2: Based on the circumferential stress at the tip of the oblique crack along the weak bonding surface and combined with the maximum circumferential stress criterion, the crack extension and propagation direction of the composite component joint are determined;

[0074] In this embodiment, according to the maximum circumferential stress criterion, brittle fracture occurs in the direction where the circumferential stress at the crack tip is the largest. The post-cast concrete strength is defined as S t , the concrete strength of precast components is

[0075] S21: Calculate the maximum circumferential stress at the tip of the post-casting joint surface I-type crack based on the expression of the circumferential stress at the crack tip, and when the maximum circumferential stress at the tip of the oblique crack on the weak joint surface is greater than the strength of the post-casting concrete, it is determined that the joint crack of the composite component extends along the direction of the I-type crack on the joint surface;

[0076] Among them, the expression of the maximum circumferential stress at the tip of the I-type crack on the post-casting joint surface is:

[0077]

[0078] In the formula, σ θ | θ＝0 It indicates the maximum circumferential stress at the tip of the I-type crack of the post-casting joint surface when the angle θ from the crack tip is 0;

[0079] When the maximum circumferential stress at the tip of the oblique crack on the weak bonding surface is greater than the strength of the post-cast concrete, that is, when When S t Indicates the strength of post-cast concrete;

[0080] S22: Based on the circumferential stress at the tip of the oblique crack along the weak bonding surface, and when the circumferential stress at the tip of the bifurcated crack along the direction of the oblique crack on the weak bonding surface is greater than the concrete strength of the prefabricated component, it is determined that the crack in the joint of the composite component extends in the direction of the oblique crack on the weak bonding surface.

[0081] Based on the expression of the circumferential stress at the inclined crack tip along the weak bonding surface, it can be seen that when the angle in the direction of the inclined crack tip is 0, the circumferential stress at the inclined crack tip along the weak bonding surface is:

[0082]

[0083] When the circumferential stress at the crack tip of the bifurcated crack along the weak bonding surface is greater than the concrete strength of the precast component, that is, When the crack in the joint of the composite component is determined to extend in the direction of the oblique crack on the weak bonding surface.

[0084] S3: Based on the concrete strength of precast components and the post-cast concrete strength, the circumferential stress at the tip of the oblique crack along the weak bonding surface is compared to determine the expansion priority of the crack in the composite component joint during expansion.

[0085] In this embodiment, whether the crack will start to crack along the weak bonding surface when encountering the weak bonding surface during crack propagation is determined by the ratio of the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface to the strength of the precast component and the ratio of the maximum circumferential stress at the tip of the I-type crack at the post-cast bonding surface to the strength of the post-cast concrete. In other words, when the ratio of the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface to the strength of the precast component is greater than the ratio of the maximum circumferential stress at the tip of the I-type crack at the post-cast bonding surface to the strength of the post-cast concrete, the bifurcated oblique crack will preferentially propagate, that is, the crack in the joint of the composite component will preferentially propagate along the oblique crack direction of the weak bonding surface. That is:

[0086]

[0087] That is, combining the maximum circumferential stress at the tip of the I-type crack on the post-casting joint surface and the circumferential stress at the tip of the oblique crack along the weak bonding surface, the judgment condition for the extension of the oblique crack direction along the weak bonding surface of the composite component joint is further obtained as follows:

[0088]

[0089] In this embodiment, when determining the expansion priority of the crack in the composite component joint during the expansion process, it also includes:

[0090] S31: Set the critical strength ratio of the crack propagation of the composite component joint at the weak bonding surface, and define the ratio of the concrete strength of the precast component to the strength of the post-cast concrete as the strength ratio;

[0091] In this embodiment, the critical strength ratio of the crack extension of the composite component joint at the weak bonding surface is set to Define the ratio of the concrete strength of the precast component to the strength of the post-cast concrete as the strength ratio S c (0 c <1).

[0092] S32: When the value of the extended critical strength ratio The smaller it is, the smaller the strength ratio of the concrete strength of the precast component required for the composite component joint crack to propagate along the weak bonding surface, that is, the oblique crack propagation condition along the weak bonding surface is. More difficult to satisfy;

[0093] S33: When the value of the extended critical strength ratio The larger the value is, the greater the strength ratio of the concrete strength of the precast component required for the composite component joint crack to propagate along the weak bonding surface, that is, the condition for the oblique crack to propagate along the weak bonding surface is. Easier to satisfy.​

[0094] Example 2

[0095] Based on the same design concept, Figure 4 As shown, this embodiment provides a system for judging crack propagation of composite component joints based on fracture mechanics, including a calculation module, a first judgment module and a second judgment module.

[0096] Specifically, the calculation module is used to establish the oblique crack coordinate system of the weak bonding surface based on the weak bonding surface at the joint of the composite component, calculate the stress intensity factor at the oblique crack tip of the weak bonding surface, and calculate the circumferential stress at the oblique crack tip along the weak bonding surface in combination with the circumferential stress expression at the crack tip constructed based on fracture mechanics;

[0097] Specifically, the first judgment module is used to determine the crack extension and extension direction of the composite component joint based on the circumferential stress at the tip of the oblique crack along the weak bonding surface combined with the maximum circumferential stress criterion;

[0098] Specifically, the second judgment module is used to compare the circumferential stress at the tip of the oblique crack along the weak bonding surface based on the concrete strength of the prefabricated component and the post-cast concrete strength, and determine the expansion priority of the crack in the composite component joint during expansion.

[0099] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0100] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for determining crack propagation in composite component joints based on fracture mechanics, characterized in that: include: Based on the weak bonding surface at the joint of the composite component, the oblique crack coordinate system of the weak bonding surface is established, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated, and the circumferential stress at the oblique crack tip along the weak bonding surface is calculated by combining the circumferential stress expression at the crack tip constructed based on fracture mechanics. Based on the circumferential stress at the tip of the inclined crack along the weak bonding surface and the maximum circumferential stress criterion, the crack extension and propagation direction of the composite component joint are determined; Based on the concrete strength of precast components and the post-cast concrete strength, the circumferential stress at the tip of the oblique crack along the weak bonding surface is compared to determine the expansion priority of the crack in the composite component joint during expansion.

2. A method for determining crack propagation in composite component joints based on fracture mechanics according to claim 1, characterized in that: The method is based on the weak bonding surface at the joint of the composite component, establishes a weak bonding surface oblique crack coordinate system, calculates the stress intensity factor at the oblique crack tip of the weak bonding surface, and calculates the circumferential stress at the oblique crack tip along the weak bonding surface in combination with the crack tip circumferential stress expression based on fracture mechanics, including: Based on the weak bonding surface at the joint of the composite component, the weak bonding surface oblique crack coordinate system is established with the tip of the oblique crack on the weak bonding surface as the origin and the oblique crack oblique angle direction as the X-axis; Based on the oblique crack coordinate system of the weak bonding surface, the stress intensity factor at the oblique crack tip of the weak bonding surface is calculated; Based on fracture mechanics, the expression of circumferential stress at the crack tip is constructed; The circumferential stress at the inclined crack tip along the weak bonding surface is calculated by combining the stress intensity factor at the inclined crack tip of the weak bonding surface and the circumferential stress at the crack tip.

3. A method for determining crack propagation in composite component joints based on fracture mechanics according to claim 2, characterized in that: Based on the weak bonding surface oblique crack coordinate system, the weak bonding surface oblique crack is a I-II composite crack.

4. A method for determining crack propagation in composite component joints based on fracture mechanics according to claim 2, characterized in that: The method of determining crack extension and extension direction of a composite component joint based on the circumferential stress at the tip of an inclined crack along a weak bonding surface and a maximum circumferential stress criterion includes: The maximum circumferential stress at the tip of the I-type crack on the post-casting joint surface is calculated based on the expression of the circumferential stress at the crack tip. When the maximum circumferential stress at the tip of the oblique crack on the weak joint surface is greater than the strength of the post-cast concrete, it is determined that the joint crack of the composite component extends along the direction of the I-type crack on the joint surface. Based on the circumferential stress at the tip of the oblique crack along the weak bonding surface, and when the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface is greater than the concrete strength of the prefabricated component, it is determined that the crack in the joint of the composite component extends in the direction of the oblique crack on the weak bonding surface.

5. The method for determining crack propagation of composite component joints based on fracture mechanics according to claim 1, characterized in that: The method of comparing the circumferential stress at the tip of the oblique crack along the weak bonding surface based on the concrete strength of the precast component and the post-cast concrete strength to determine the expansion priority of the crack in the composite component joint during the expansion process includes: When the ratio of the circumferential stress at the tip of the bifurcated crack along the oblique crack direction of the weak bonding surface to the strength of the precast component is greater than the ratio of the maximum circumferential stress at the tip of the type I crack on the post-cast bonding surface to the strength of the post-cast concrete, the bifurcated oblique crack will preferentially expand, that is, the crack in the joint of the composite component will preferentially expand along the oblique crack direction of the weak bonding surface.

6. A method for determining crack propagation in composite component joints based on fracture mechanics according to claim 5, characterized in that: The step of determining the expansion priority of cracks in the composite component joint during expansion also includes: The critical strength ratio of the crack propagation of the composite component joint at the weak bonding surface is set, and the ratio of the concrete strength of the precast component to the strength of the post-cast concrete is defined as the strength ratio; When the value of the critical strength ratio is smaller, it means that the strength ratio of the concrete strength of the precast component required for the composite component joint crack to expand along the weak bonding surface is smaller, that is, the condition for the oblique crack expansion along the weak bonding surface is more difficult to meet; The larger the value of the critical strength ratio, the larger the strength ratio of the concrete strength of the precast component required for the composite component joint crack to propagate along the weak bonding surface, that is, the condition for the oblique crack propagation along the weak bonding surface is easier to meet.

7. A system for the composite component joint crack propagation identification method based on fracture mechanics according to claim 1, characterized in that: include: A calculation module is used to establish a weak bonding surface oblique crack coordinate system based on the weak bonding surface at the joint of the composite component, calculate the stress intensity factor at the oblique crack tip of the weak bonding surface, and calculate the circumferential stress at the oblique crack tip along the weak bonding surface in combination with the crack tip circumferential stress expression based on fracture mechanics; The first judgment module is used to determine the crack extension and extension direction of the composite component joint based on the circumferential stress at the tip of the oblique crack along the weak bonding surface and the maximum circumferential stress criterion; The second judgment module is used to compare the circumferential stress at the tip of the oblique crack along the weak bonding surface based on the concrete strength of the prefabricated component and the post-cast concrete strength, and determine the expansion priority of the joint crack of the composite component during the expansion process.

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