Method for calculating severity of fatigue crack of steel box girder based on geometric figure

Abstract

The invention discloses a geometric figure-based method for calculating the severity of fatigue cracks of a steel box girder. The calculation method comprises the following steps of: acquiring basic information of typical fatigue cracks of the steel box girder according to detection data; the method comprises the following steps: establishing a body-surface-line multi-scale geometric model from the perspective of geometry according to a fatigue and vulnerable part of a steel box girder; determining a body geometric model or a surface geometric model or a line geometric model according to the local fatigue crack characteristics of the steel box girder; enveloping all local fatigue cracks by using an imaginary geometric body / plane / line with a unit length, and statistically calculating the total length l0 of a welding seam in the geometric body / plane / line and the total length l1 of the fatigue cracks; the formula Cs = l1 / l0, Cs is the fatigue crack severity body / plane / line coefficient, l1 is the total length of the fatigue crack in the geometry / plane / line, and l0 is the total length of the welding seam in the geometry / plane / line, and quantifying the fatigue crack severity. And the fatigue damage degree of the steel box girder bridge deck slab in the actual operation state is accurately evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of local fatigue crack damage detection of steel box girder bridges, and in particular to a geometric figure-based steel box girder fatigue crack severity calculation method. BACKGROUND

[0002] As a key load-bearing component of long-span bridges, orthotropic steel bridge decks are subjected to repeated vehicle wheel loads for a long time, and are prone to fatigue cracks at welding and structural details, such as the butt weld of longitudinal ribs, the weld between longitudinal ribs and top plates, the weld between longitudinal ribs and transverse diaphragms, and the weld between top plates and vertical stiffening ribs. Once cracks occur, fatigue damage inside the structure will continue to accumulate, and if not repaired and reinforced in time, the components will fatigue and break, leading to bridge collapse and causing significant economic losses. Therefore, it is crucial to regularly inspect, assess and quantify the local fatigue crack damage of steel box girders during the entire life cycle of the bridge.

[0003] In the 2020 annual inspection report of a certain long-span cable-stayed bridge, a total of 104 fatigue cracks were found, including 94 U-rib embedded sections, 4 transverse diaphragms, 3 top plates and 3 webs. However, the crack information in the report is limited to location, length and width, and these descriptions cannot accurately determine the severity of fatigue cracks from a quantitative perspective. In addition, the existing specification "Design Specification for Highway Steel Structure Bridges" (JTG D64-2015) only provides fatigue detail classification and stress limitation, and lacks quantitative indicators for the severity of existing cracks. Therefore, how to handle a large amount of fatigue crack data, quantify the local fatigue damage of steel box girders, and quickly generate a scientific and reliable data report is a difficult problem that needs to be solved.

[0004] The existing technology has the technical problem that the basic description of fatigue cracks in the literature or bridge inspection report cannot be quantified, so the fatigue damage degree of the steel box girder bridge deck under actual operating conditions cannot be accurately assessed. SUMMARY

[0005] In view of the above problems, the present application is proposed to provide a geometric figure-based steel box girder fatigue crack severity calculation method to overcome the above problems or at least partially solve the above problems.

[0006] According to one aspect of the present application, a geometric figure-based steel box girder fatigue crack severity calculation method is provided, which comprises: obtaining basic information of typical fatigue cracks of the steel box girder according to detection data; establishing a volume-surface-line multi-scale geometric model from the perspective of geometry according to fatigue prone positions of the steel box girder; determining the volume geometric model or the surface geometric model or the line geometric model according to the characteristics of the local fatigue cracks of the steel box girder; All fatigue cracks are enveloped by a hypothetical unit length geometry / surface / line, and the total length of welds l0 and the total length of fatigue cracks l1 in the geometry / surface / line are calculated statistically; Formula C s =l1 / l0, Wherein C s is the fatigue crack severity coefficient of the geometry / surface / line, l1 is the total length of fatigue cracks in the geometry / surface / line, l0 is the total length of welds in the geometry / surface / line, and the fatigue crack severity is quantified.

[0007] Optionally, the fatigue vulnerable parts of the steel box girder include: longitudinal rib butt welds, longitudinal rib and top plate connecting welds, longitudinal rib and transverse diaphragm connecting welds, and top plate and vertical stiffening rib connecting welds.

[0008] Optionally, the geometry shape of the body geometry model includes a cylinder, a sphere, a square pyramid, a cube, a cuboid, a cone, a circular truncated cone, a triangular prism, a triangular pyramid, a regular polyhedron, a prism, and an ellipsoid.

[0009] Optionally, the body geometry model is applicable to enveloping longitudinal rib and top plate connecting welds and longitudinal rib butt welds.

[0010] Optionally, the enveloping longitudinal rib and top plate connecting welds and longitudinal rib butt welds are a unit length 1m cubic geometry model; The total length of welds in the enveloping part and the body includes the welds at both ends of the embedded section U rib, the top plate butt weld, and the welds between the longitudinal rib and the top plate.

[0011] Optionally, the enveloping part of the cube is according to the vertical and horizontal placement of the cube, the orthogonal and oblique angle of the top plate; The welds between the longitudinal rib and the top plate are divided into 12 calculation conditions, and the maximum total length of welds l 0,v,max , the minimum total length of welds l 0,v,min , and the total length of fatigue cracks l 1,v in the cube are defined in the 12 conditions.

[0012] Optionally, the maximum total length of welds l 0,v,max , the minimum total length of welds l 0,v,min , and the ratio of the total length of fatigue cracks to the total length of welds are used to obtain the maximum value C s,v,max and the minimum value C s,v,min of the local fatigue crack severity coefficient of the steel box girder.

[0013] Optionally, the surface geometry model is a unit length 1m plane, which envelops the top plate crack or transverse diaphragm section crack part.

[0014] Optionally, the cross diaphragm section crack includes the surrounding welding of each side length of the cross diaphragm beam, the stiffened plate welding seam and the stiffened plate surrounding welding, and the total length of the in-plane fatigue crack l is defined 1,p And the total length of the welding seam l 0,p The severity coefficient of the plane crack C s,p .

[0015] Optionally, the line geometry model is a reference line with a length of 1m, which is suitable for the length of a single crack or for tracking and observing the condition of a certain crack. The line geometry model envelopes the crack with a reference line with a length of 1m, and the total length of the in-line fatigue crack l 1,l And the total length of the welding seam l 0,l The severity coefficient of the line crack C s,l .

[0016] The application provides a steel box girder fatigue crack severity calculation method based on geometry, and the calculation method comprises the following steps: acquiring basic information of typical fatigue cracks of a steel box girder according to detection data; from the perspective of geometry, establishing a body-surface-line multi-scale geometric model according to fatigue vulnerable parts of the steel box girder; determining a body geometric model or a surface geometric model or a line geometric model according to local fatigue crack characteristics of the steel box girder; enveloping all local fatigue cracks with a unit length geometric body / surface / line, and statistically calculating the total length of the welding seam l0 and the total length of the fatigue crack l1 in the geometric body / surface / line; and the formula C s =l1 / l0, wherein C s is a body / surface / line coefficient of the fatigue crack severity, l1 is the total length of the fatigue crack in the geometric body / surface / line, and l0 is the total length of the welding seam in the geometric body / surface / line, and the fatigue crack severity is quantified. The problem of ambiguous definition of the fatigue crack severity of the steel box girder in the existing literature and bridge detection reports is effectively solved, technical support is provided for formulating a scientific management and maintenance scheme for the steel box girder bridge, and the fatigue damage degree of the steel box girder bridge deck under the actual operation state is accurately evaluated.

[0017] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the content of the specification can be implemented, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described below. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical scheme of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creating labor.

[0019] Figure 1A flow chart of a steel box girder fatigue crack severity calculation method based on geometric figures provided by the embodiment of the present application is shown in the figure. Figure 2 A schematic diagram of a typical plane structure detail of a steel box girder provided by the embodiment of the present application is shown in the figure. Figure 3 A schematic diagram of a partial geometric body model provided by the embodiment of the present application is shown in the figure. Figure 4 A cubic horizontal and vertical roof orthogonal calculation working condition plan view provided by the embodiment of the present application is shown in the figure. Figure 5 A cubic vertical roof oblique calculation working condition plan view provided by the embodiment of the present application is shown in the figure. Figure 6 A cubic horizontal roof oblique calculation working condition plan view provided by the embodiment of the present application is shown in the figure.

[0020] The figure shows a schematic diagram of a steel box girder, in which 1 represents a roof, 2 represents an upper inclined roof, 3 represents a lower inclined bottom plate, 4 represents a bottom plate, 5 represents a lower inclined web plate, 6 represents a straight web plate, 7 represents a longitudinal rib (U rib), 8 represents a longitudinal rib butt joint weld, 9 represents a longitudinal rib and roof connecting weld, 10 represents a longitudinal rib and transverse partition plate connecting weld, 11 represents a roof butt joint weld, 12 represents a roof and vertical stiffening rib connecting weld, 13 represents a transverse partition beam each side length surrounding weld, 14 represents a stiffening plate weld, 15 represents a stiffening plate surrounding weld, 16 represents a transverse partition plate, 17 represents a stiffening rib, 18 represents a spherical geometric body model, 19 represents a cubic geometric body model, 20 represents a conical geometric body model, and 21 represents a cylindrical geometric body model. DETAILED DESCRIPTION

[0021] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood and so that the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0022] The terms in the specification embodiments of the present application and claims and drawings include and have as well as their any variations, which are intended to cover non-exclusive inclusion, for example, including a series of steps or units.

[0023] The technical solutions of the present application will be described in further detail below in combination with the drawings and embodiments.

[0024] Embodiment 1 The application provides a steel box girder fatigue crack severity calculation method based on geometry, and the calculation method comprises the following steps: According to the local fatigue vulnerable position of the steel box girder, a body-surface-line fatigue crack severity calculation method is provided from the perspective of geometry, a unit length geometric body (including but not limited to a cylinder, a sphere, a square pyramid, a cube, a cuboid, a cone, a circular truncated cone, a triangular prism, a triangular pyramid, a regular polyhedron, a prism, an ellipsoid and the like) is used to envelope a part of fatigue cracks, the ratio of the total length of welds in the geometric body / surface to the total length of fatigue cracks is calculated, a coefficient C s,v and C s,p is defined; if a single crack is longer (exceeds the total length of welds in the unit geometric body / surface) or an important crack needs to be tracked and compared, a geometric line model is used to calculate the ratio of the length of a single fatigue crack to the total length of an important weld or the length of a unit weld at the position of the fatigue crack, and a coefficient C s,l is defined.

[0025] Based on the body-surface-line multi-scale geometric model, the steel box girder fatigue crack severity calculation method can accurately judge the fatigue crack severity from the quantitative perspective, can realize rapid evaluation of the fatigue crack severity, and provides technical support for formulating a scientific management and maintenance scheme for the steel box girder bridge.

[0026] The application aims to provide a steel box girder fatigue crack severity calculation method, and solve how to quantize the basic description of fatigue cracks in the literature or bridge detection report and accurately evaluate the fatigue damage degree of the steel box girder bridge deck in the actual operation state.

[0027] As shown in Figure 1 , the application provides a steel box girder fatigue crack severity calculation method based on geometry, which comprises the following steps: Basic information of typical fatigue cracks of the steel box girder is acquired according to detection data; A body-surface-line multi-scale geometric model is established from the perspective of geometry according to the fatigue vulnerable position of the steel box girder; A body geometric model or a surface geometric model or a line geometric model is determined according to the local fatigue crack characteristics of the steel box girder; A unit length geometric body / surface / line is used to envelope all local fatigue cracks, and the total length l0 of welds in the geometric body / surface / line and the total length l1 of fatigue cracks are calculated and counted; A formula C s =l1 / l0 is used, wherein C s is a body / surface / line coefficient of fatigue crack severity, l1 is the total length of fatigue cracks in the geometric body / surface / line, and l0 is the total length of welds in the geometric body / surface / line; The fatigue crack severity is quantized.

[0028] The steel box girder fatigue crack severity calculation method based on geometry provided by the application is: (1) The main locations prone to fatigue cracks in orthotropic steel bridge decks include: butt welds of longitudinal ribs, welds connecting longitudinal ribs and top plate, welds connecting longitudinal ribs and transverse diaphragms, and welds connecting top plate and vertical stiffening ribs. Based on literature research and statistical analysis of actual test data, the basic information (location, length, and width) of typical fatigue cracks in steel box girders is compiled.

[0029] (2) Based on the fatigue-prone parts of the steel box girder, a multi-scale geometric model of volume, surface and line is established from a geometric perspective; (3) Determine the volume geometric model, surface geometric model, or line geometric model based on the local fatigue crack characteristics of the steel box girder; (4) Enclose all local fatigue cracks with an imaginary geometric body / surface / line of unit length, and statistically calculate the total weld length l0 and the total fatigue crack length l1 within the geometric body / surface / line; (5) Propose the calculation formula C s =l1 / l0, where C s The coefficients for fatigue crack severity are: l1 represents the total length of fatigue cracks within the geometric body / surface / line, and l0 represents the total length of welds within the geometric body / surface / line, thus quantifying the severity of fatigue cracks.

[0030] Solid geometry models include various geometric shapes, including but not limited to cylinders, spheres, square pyramids, cubes, cuboids, cones, frustums, triangular prisms, triangular pyramids, regular polyhedra, prisms, ellipsoids, etc.

[0031] The solid geometry model takes a cube with a unit length of 1m as an example. This cube model is applicable to fatigue crack locations such as the weld connecting the longitudinal ribs and the top plate and the butt weld of the longitudinal ribs.

[0032] The total length of the welds within the cube envelope includes the welds at both ends of the U-ribs of the insert section, the butt welds of the top plate (transverse bridge direction), and the welds between the longitudinal ribs and the top plate (excluding the welds of the transverse diaphragms for the time being).

[0033] For the cube envelope portion, based on whether the cube is placed vertically or horizontally, and whether the top plate is orthogonal or oblique, the weld between the U-rib and the top plate can be divided into 12 calculation cases. Among these 12 cases, the maximum total weld length l of the cube is defined. 0,v,max Minimum total weld length l 0,v,min The total length of fatigue cracks within the cube is l 1,v .

[0034] The maximum and minimum total weld lengths of the cube, and the ratio of the total fatigue crack length to the total weld length, can be used to obtain the maximum system number C of the severity of local fatigue cracks in the steel box girder. s,v,max and minimum value C s,v,min .

[0035] The plane geometry model is a plane with a unit length of 1m, and is suitable for enveloping a long crack in a top plate or a large number of cracks in a cross partition plate section.

[0036] The cross partition beam section weld includes the weld around each side of the cross partition beam, the stiffener plate weld and the weld around the stiffener plate, and defines the total length l of the in-plane fatigue crack 1,p and the total length l of the weld 0,p , and the plane crack severity coefficient C s,p is calculated.

[0037] The line geometry model is a reference line with a length of 1m, and is suitable for enveloping a single long crack or tracking and observing an important crack.

[0038] The line geometry model envelops the crack with a reference line with a length of 1m, defines the total length l of the in-line fatigue crack 1,l and the total length l of the weld 0,l , and the line crack severity coefficient C s,l is calculated.

[0039] Example 2 The accompanying drawings are combined Figures 2-6 A steel box girder fatigue crack severity calculation method based on geometry of the present application is described in detail: 1) The fatigue crack prone positions of the orthotropic steel bridge deck mainly include: the longitudinal rib butt weld 8, the longitudinal rib and top plate connecting weld 9, the longitudinal rib and cross partition plate connecting weld 10, and the top plate and vertical stiffening rib connecting weld 12. Based on literature research and actual detection data statistics, the basic information (position, length, width) of the typical fatigue cracks of the steel box girder is sorted out;

[0040] 2) According to the fatigue prone positions of the steel box girder, a body-surface-line multi-scale geometry model is established from the perspective of geometry; 3) The body geometry model or the plane geometry model or the line geometry model is determined according to the characteristics of the local fatigue cracks of the steel box girder; 4) All local fatigue cracks are enveloped by a hypothetical unit length geometry body / surface / line, and the total length l0 of the weld and the total length l1 of the fatigue crack in the geometry body / surface / line are calculated and counted; 5) The calculation formula C s =l1 / l0 is proposed, wherein C s is the fatigue crack severity body / surface / line coefficient, l1 is the total length of the fatigue crack in the geometry body / surface / line, and l0 is the total length of the weld in the geometry body / surface / line, so as to realize the quantification of the fatigue crack severity.

[0041] The body geometry model includes various geometric shapes, including but not limited to cylinder 18, sphere 19, four-pyramid 20, cube 21, cuboid, conical body, circular truncated cone, three-prism, three-pyramid, regular polyhedron, prism, ellipsoid, etc.

[0042] Body geometry model takes a cube with unit length 1m as an example, and is applicable to envelope fatigue crack positions such as longitudinal rib and top plate connecting weld 9 and longitudinal rib butt weld 8.

[0043] The total length of the weld in the cube includes the weld at both ends of the embedded section U rib 7, the top plate butt weld 11 (horizontal bridge direction), and the weld 9 between the longitudinal rib and the top plate (not including the weld of the horizontal partition plate 16).

[0044] In combination Figures 2-4 , according to the vertical and horizontal placement of the cube, the orthogonal and oblique angle of the top plate 1, and the weld between the U rib 7 and the top plate 1, the total weld can be divided into 12 calculation conditions, and the maximum total weld length l 0,v,max and the minimum total weld length l 0,v,min of the cube are defined in the 12 conditions. 1,v

[0045] The maximum and minimum total weld lengths of the cube can be obtained by using the ratio of the total fatigue crack length to the total weld length, and the maximum value C s,v,max and the minimum value C s,v,min of the local fatigue crack severity system coefficient of the steel box girder can be obtained.

[0046] The plane geometry model is a unit length 1m plane, which is applicable to envelope the longer cracks of the top plate 1 or the more cross-sectional cracks of the horizontal partition plate 16.

[0047] The cross section weld of the horizontal partition beam 16 includes the surrounding weld 13 of each side length of the horizontal partition beam, the stiffener weld 14 and the stiffener surrounding weld 15, the total fatigue crack length l 1,p and the total weld length l 0,p in the plane are defined, and the crack severity plane coefficient C s,p is calculated.

[0048] The line geometry model is a reference line with a length of 1m, which is applicable to a single crack with a longer length or tracking and comparing observation of an important crack.

[0049] The line geometry model envelopes the crack with a reference line with a length of 1m, defines the total fatigue crack length l 1,l and the total weld length l 0,l in the line, and calculates the crack severity line coefficient C s,l .

[0050] Advantages: ​The application proposes a calculation method of the severity of the fatigue cracks of the steel box girder according to the fatigue vulnerable position of the steel bridge deck, from the geometric point of view, and based on the multi-scale geometric model of "volume-surface-line", the local all fatigue cracks are enveloped by the imaginary unit length geometric volume / surface / line, the ratio of the total length of the weld l0 and the total length of the fatigue cracks l1 in the geometric volume / surface / line is calculated, and the volume / surface / line coefficient C of the severity of the fatigue cracks is obtained s , and the quantification of the severity of the fatigue cracks is realized. The method is strong in implementation, effectively solves the problem of the fuzzy definition of the severity of the fatigue cracks of the steel box girder in the existing literature and the bridge detection report, and provides technical support for formulating a scientific management and maintenance scheme for the steel box girder bridge.

[0051] The above specific embodiments further specifically describe the purposes, technical solutions and beneficial effects of the application, and it should be understood that the above are only specific embodiments of the application and are not used to limit the protection scope of the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for calculating the severity of a fatigue crack in a steel box girder based on a geometric figure, characterized by, The calculation method comprises: According to the detection data, basic information of typical fatigue cracks of the steel box girder is acquired; According to fatigue vulnerable parts of the steel box girder, a volume-surface-line multi-scale geometric model is established from the perspective of geometry; According to characteristics of local fatigue cracks of the steel box girder, a volume geometric model or a surface geometric model or a line geometric model is determined; All fatigue cracks are enveloped by a hypothetical unit length geometric volume / surface / line, and total length l0 of welds and total length l1 of fatigue cracks in the geometric volume / surface / line are calculated and counted; Formula C s = l1 / l0, where C s is the fatigue crack severity body / surface / line factor, li is the total length of fatigue cracks within the geometric body / surface / line, lo is the total length of weld within the geometric body / surface / line, quantifying the fatigue crack severity.

2. The method according to claim 1, wherein, The fatigue vulnerable parts of the steel box girder comprise butt welds of longitudinal ribs, welds connecting longitudinal ribs and top plates, welds connecting longitudinal ribs and cross diaphragms, and welds connecting top plates and vertical stiffening ribs.

3. The method according to claim 1, wherein, The geometric shape of the volume geometric model comprises a cylinder, a sphere, a quadrangular pyramid, a cube, a cuboid, a conical body, a circular truncated cone, a triangular prism, a triangular pyramid, a regular polyhedron, a prism, and an ellipsoid.

4. The method according to claim 1, wherein, The volume geometric model is suitable for enveloping the welds connecting longitudinal ribs and top plates and the butt welds of longitudinal ribs.

5. The method according to claim 4, wherein, The enveloped welds connecting longitudinal ribs and top plates and the butt welds of longitudinal ribs are cubic geometric volume models with a unit length of 1 m. Total length of welds in the enveloped part and in the volume comprises welds at both ends of embedded segment U ribs, butt welds of top plates, and welds connecting longitudinal ribs and top plates.

6. The method according to claim 5, wherein, The enveloped part of the cube is according to vertical and horizontal placement of the cube, and normal and oblique angles of the top plate. The welds between the longitudinal ribs and the top plate are divided into 12 calculation conditions, and the maximum total length of the welds in the cube is defined as l 0,v,max , the minimum total length of the welds is defined as l 0,v,min , and the total length of the fatigue cracks in the cube is defined as l 1,v .

7. The method according to claim 6, wherein, The total length of the maximum weld l of the cube 0,v,max The total length of the minimum weld l 0,v,min The maximum value C of the local fatigue crack severity system number of the steel box girder is obtained by using the ratio of the total length of the fatigue crack to the total length of the weld s,v,max And the minimum value C s,v,min .

8. The method according to claim 1, wherein, The surface geometric model is a plane with a unit length of 1 m, which envelops top plate cracks or cross diaphragm section crack parts.

9. The method according to claim 8, wherein, The cross section crack of the transverse bulkhead includes the girth welding of each side length of the transverse beam, the welding seam of the stiffened plate and the girth welding of the stiffened plate, and defines the total length l of the in-plane fatigue crack 1,p and the total length l of the welding seam 0,p , calculates the plane crack severity surface coefficient C s,p .

10. The method of claim 1, wherein the method is characterized by: The line geometric model is a reference line with a length of 1 m, which is suitable for single crack length or tracking and comparison observation of a certain crack condition. The line geometry model, with 1 m length of the reference line enveloping the crack, defines the total length of the fatigue crack in the line l 1,l and the total weld length l 0,l , calculates the crack severity line coefficient C s,l .

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