Corrugated steel web box girder lining concrete cracking risk analysis method and system

Abstract

The present application provides a corrugated steel web box girder lining concrete cracking risk analysis method and system, sets up displacement boundary conditions and temperature boundary conditions, establishes a corrugated steel web lining concrete model, carries out numerical calculation on the corrugated steel web lining concrete model, analyzes the numerical calculation results; based on the numerical calculation results, taking shrinkage effect, creep, concrete mold temperature and concrete surface heat preservation measures as the consideration factors, the influence of each consideration factor on the cracking risk of corrugated steel web lining concrete is analyzed; according to the influence of each consideration factor, the cracking risk of target corrugated steel web lining concrete in target environment is determined and adjusted. The present application analyzes the influence of hydration heat release efficiency, elastic modulus change and shrinkage and creep behavior of concrete on the crack resistance of lining concrete, which helps to determine the cracking risk.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a method and system for analyzing the cracking risk of concrete lining in corrugated steel web box girders. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Corrugated steel web is a type of steel-concrete composite structure with advantages such as lightweight, good seismic performance, reasonable stress distribution, simple construction, and economical project cost. When the span of a corrugated steel web box girder bridge is large, the height of the box girder root section is correspondingly high. In the design, concrete is generally poured inside the corrugated steel web near the pier top, i.e., the inner lining concrete. The cracking mechanism of the inner lining concrete is relatively complex. Cracking of the corrugated steel web under strong constraint in early age is the main cause. The early age cracking of concrete is caused by the combined effect of factors such as the heat of hydration of cement in concrete, early age shrinkage and creep of concrete, and the gradual development of the elastic modulus.

[0004] Currently, there are existing engineering cases of cracking in corrugated steel web box girders. However, there are few research results on the crack prevention mechanism and engineering suggestions for the construction process of corrugated steel web box girders, both domestically and internationally. The analysis of the causes of early-age cracking of the inner lining concrete of corrugated steel web box girders is relatively simple, and there is a lack of accurate and effective analysis methods for cracking risk. Therefore, there is an urgent need for a method that comprehensively considers the heat release efficiency of hydration, changes in elastic modulus, and shrinkage and creep behavior to reveal the early-age cracking risk of the inner lining concrete. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for analyzing the cracking risk of the inner lining concrete in corrugated steel web box girders. Based on considerations of the heat release efficiency of concrete hydration, changes in elastic modulus, and shrinkage and creep behavior, this invention conducts numerical simulations and analyzes the crack resistance of the inner lining concrete from four aspects: shrinkage effect, creep, concrete placement temperature, and convection coefficient, using actual corrugated steel web continuous beam bridges. This analysis helps determine the cracking risk and yields relatively accurate results.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A method for analyzing the cracking risk of concrete lining in corrugated steel web box girders includes the following steps:

[0008] Displacement boundary conditions and temperature boundary conditions are set, a corrugated steel web inner lining concrete model is established, numerical calculations are performed on the corrugated steel web inner lining concrete model, and the numerical calculation results are analyzed.

[0009] Based on the numerical calculation results, the impact of shrinkage effect, creep, concrete placement temperature and concrete surface insulation measures on the cracking risk of the corrugated steel web lining concrete is analyzed.

[0010] Based on the influence of various factors, during the design stage of the corrugated steel web box girder lining concrete, the effects of shrinkage and creep on the crack resistance of the lining concrete are calculated, and relevant design parameters are adjusted accordingly. During the construction stage of the corrugated steel web box girder lining concrete, the concrete pouring temperature is adjusted and the concrete surface is insulated to reduce the risk of early-age cracking of the corrugated steel web box girder lining concrete.

[0011] As an alternative implementation, when setting the displacement boundary, the constraint effect of the diaphragm and the constraint effect of the cast-in-place portion on the uncast portion are considered.

[0012] As a further step, the corrugated steel web lining concrete model includes multiple segments, wherein segment N-1 simulates the already poured segment, and it is assumed that the concrete has solidified and the heat of hydration of the concrete is not considered; segment N is the currently poured part of the concrete, and it is assumed that the heat of hydration of the concrete exists in this part.

[0013] The three-directional displacement is constrained at the concrete interface of the poured segments N-1 and N-2. In segment N, the influence of the diaphragm at the front end of the concrete is considered to constrain the lateral displacement, while the three-directional displacement is constrained at the top and bottom.

[0014] As an alternative implementation method, when setting the temperature boundary, a thermal convection model is used to simulate external heat loss, and the temperature boundary is set based on the simulation results.

[0015] As an alternative implementation method, when analyzing the crack resistance of the lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the lining concrete is compared under the two conditions of considering and not considering the shrinkage effect, so as to determine the influence of the shrinkage effect on the crack resistance of the lining concrete.

[0016] As an alternative implementation method, when analyzing the crack resistance of the lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the lining concrete under two conditions—concrete shrinkage plus creep and concrete shrinkage—is compared to determine the influence of creep on the crack resistance of the lining concrete.

[0017] As an alternative implementation method, when analyzing the crack resistance of the lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the lining concrete at different concrete placement temperatures is compared to determine the influence of the concrete placement temperature on the crack resistance of the lining concrete.

[0018] As an alternative implementation method, when analyzing the crack resistance of the inner lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the inner lining concrete under different convection coefficients on the surface of the inner lining concrete is compared to determine the influence of the surface convection coefficient on the crack resistance of the inner lining concrete, and then the influence of concrete surface insulation measures on the crack resistance of the inner lining concrete is determined.

[0019] As an alternative implementation method, the process of determining the cracking risk of the target corrugated steel web lining concrete in the target environment includes: based on the influence of various factors and combined with the results of numerical simulation, determining whether the target corrugated steel web lining concrete has a cracking risk under the set concrete placement temperature and the proposed concrete surface insulation measures in the target area's service environment.

[0020] A risk analysis system for cracking of concrete lining in corrugated steel web box girder includes:

[0021] The model simulation module is configured to set displacement boundary conditions and temperature boundary conditions, establish a corrugated steel web inner lining concrete model, perform numerical calculations on the corrugated steel web inner lining concrete model, and analyze the numerical calculation results.

[0022] The impact analysis module is configured to analyze the impact of shrinkage effect, creep, concrete placement temperature and concrete surface insulation measures on the cracking risk of the corrugated steel web lining concrete based on numerical calculation results.

[0023] The parameter adjustment module is configured to calculate the impact of shrinkage and creep effects on the crack resistance of the corrugated steel web box girder lining concrete during the design stage, based on various considerations, and then adjust the relevant design parameters. During the construction stage of the corrugated steel web box girder lining concrete, the concrete pouring temperature is adjusted and the concrete surface is insulated to reduce the risk of early-age cracking of the corrugated steel web box girder lining concrete.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention comprehensively considers the heat release efficiency of hydration, changes in elastic modulus, and shrinkage and creep behavior to reveal the early-age cracking risk of the inner lining concrete. Furthermore, during the design phase of the actual corrugated steel web box girder inner lining concrete, the influence of shrinkage and creep effects on the crack resistance of the inner lining concrete is calculated. Relevant design parameters are then adjusted. During the actual construction phase of the corrugated steel web box girder inner lining concrete, the concrete placement temperature is adjusted and surface insulation treatment is performed to reduce the early-age cracking risk of the inner lining concrete, thus contributing to improved bridge engineering safety.

[0026] This invention conducts numerical simulations based on considerations of concrete hydration heat release efficiency, elastic modulus change, and shrinkage and creep behavior. Furthermore, it analyzes the crack resistance of the inner lining concrete from four aspects: shrinkage effect, creep, concrete placement temperature, and convection coefficient, using actual corrugated steel web continuous beam bridges. This analysis helps determine the cracking risk and yields relatively accurate results.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 Construction diagram of a corrugated steel web lining concrete model established for one embodiment;

[0030] Figure 2 This is a boundary condition definition diagram for a corrugated steel web lining concrete model according to one embodiment.

[0031] Figure 3 A numerical model selection and analysis location diagram for a corrugated steel web lining concrete model of one embodiment;

[0032] Figure 4 This is a diagram showing the selected stress analysis locations in a corrugated steel web lining concrete model according to one embodiment.

[0033] Figure 5 This is a diagram illustrating the effect of shrinkage on stress in one embodiment.

[0034] Figure 6 This is a diagram illustrating the effect of creep on stress in one embodiment.

[0035] Figure 7 This is a diagram illustrating the effect of concrete placement temperature on stress in one embodiment.

[0036] Figure 8 This is a diagram illustrating the influence of the convection coefficient on stress in one embodiment.

[0037] Figure 9 This is a diagram showing the location of cracks in the inner lining concrete of a corrugated steel web inner lining concrete model according to one embodiment. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0042] Example 1

[0043] A method for analyzing the cracking risk of concrete lining in corrugated steel web box girders includes the following steps:

[0044] Step 1: Set displacement boundary conditions and temperature boundary conditions, establish a corrugated steel web inner concrete lining model, perform numerical calculations on the corrugated steel web inner concrete lining model, and analyze the numerical calculation results.

[0045] Step 2: Based on the numerical calculation results, the impact of shrinkage effect, creep, concrete placement temperature and concrete surface insulation measures on the cracking risk of the corrugated steel web lining concrete is analyzed.

[0046] Step 3: Based on the influence of each factor, determine the cracking risk of the concrete lining of the target corrugated steel web under the target environment.

[0047] In step 1, when establishing the concrete model of the corrugated steel web lining, the constraint effect of the diaphragms and the constraint effect of the cast-in-place portion on the uncast portion are considered when setting the displacement boundary, such as... Figure 2 As shown.

[0048] In step 1, when establishing the corrugated steel web with inner concrete lining, a thermal convection boundary is used to simulate the heat exchange between the inner concrete lining and the atmospheric environment when setting the temperature boundary. Specifically, the corrugated steel web and the concrete share a node, and the heat caused by the hydration heat of the inner lining is directly transferred to the steel web. Convection coefficients are set on both the surface of the steel web in contact with the atmosphere and the surface of the inner concrete lining in contact with the atmosphere to simulate heat dissipation in the form of thermal convection. The specific parameters are thermal conductivity k = 1.87 W / (m·K), thermal expansion coefficient α = 8.53E-06K-1, specific heat capacity cp = 1045 J / (kg·K), and convection coefficient h = 7.9 W / (m2·K). At the same time, indoor model experiments are conducted to verify the effectiveness of the model.

[0049] like Figure 1 As shown, in step 1 of this invention, a concrete model of the corrugated steel web lining was established. The actual dimensions are: the concrete lining is 3.2m long, 7m high, and 0.3m thick. The corrugated steel web uses 1600-type corrugated steel plate, made of Q420qD steel. The horizontal section of the corrugated steel web is 430mm long, the inclined section is 430mm long, the horizontal length of the inclined section is 370mm, the wave height is 220mm, and the thickness is 28mm. Densely packed studs are welded inside the corrugated steel web; therefore, the steel web and concrete are bonded using TIE (Tightening over Iron). Figure 3 In the construction diagram, segment N-1 simulates the already poured segment, and it is assumed that the concrete has solidified and the heat of hydration of the concrete is not considered; segment N is the part where the concrete is currently poured, and it is assumed that the heat of hydration of the concrete exists in this part.

[0050] like Figure 2 As shown in the boundary condition definition diagram, segments N-1 and N-2 are both cast segments. The concrete interface of segments N-1 and N-2 is constrained in three directions of displacement. In segment N, the influence of the diaphragm is considered at the front end of the concrete, constraining the lateral displacement. At the same time, the top and bottom are constrained in three directions of displacement.

[0051] like Figure 3 As shown, in step 2, calculations are performed on the corrugated steel web lining concrete model, and the results collected by the field sensors are compared with the calculation results of the numerical model. Point P is selected as the numerical analysis point, and the elastic strain at point P is compared with the measured strain sensor data to determine whether the established corrugated steel web lining concrete model can accurately reflect the actual structural strain.

[0052] like Figure 4 As shown, in step 2 of this invention, calculations are performed on the concrete lining model of the corrugated steel web, and the calculation results of the numerical model are analyzed. The stress of the corrugated steel web is analyzed to obtain the location and magnitude of the maximum vertical tensile stress in the corrugated steel web; the distribution of the vertical stress field of the lining concrete at different times is analyzed to determine the location where the lining concrete first cracks. Figure 4 In this study, four points A, B, C, and D were selected on the model as the stress analysis locations for the inner lining concrete. The vertical stress time history of the four points was analyzed to obtain the tensile and compressive stress conditions of the concrete at different times and the location and value of the maximum vertical tensile stress.

[0053] like Figure 5 As shown, in step 4 of this invention, based on numerical simulation, the effects of shrinkage, creep, concrete placement temperature, and concrete surface insulation measures on the maximum vertical stress of the inner lining concrete are analyzed. Furthermore, the influence of different factors on the crack resistance of the corrugated steel web inner lining concrete is analyzed. The main analysis consists of the following four parts:

[0054] (1) Concrete shrinkage causes internal constraints, thereby generating additional stress in the concrete. Analyzing the effect of shrinkage on the vertical stress of the lining concrete, and comparing the vertical stress of the lining concrete with and without considering shrinkage, reveals that shrinkage has a certain degree of influence on the cracking of the lining concrete. Regarding the research object of this invention, compared to the model considering shrinkage, the model without considering shrinkage... Figure 4 The vertical tensile stress at point D decreases by approximately 8%, such as... Figure 5 As shown, this indicates that by providing sufficient water curing to the model, the tensile stress of the concrete can be reduced to a certain extent, thus reducing the risk of cracking in the inner lining concrete.

[0055] (2) After creep occurs in concrete, it will reduce the stress level of the concrete. Analyzing the effect of creep on the vertical stress of the lining concrete and comparing the vertical stress of the lining concrete under the two conditions of concrete shrinkage + creep and concrete shrinkage, it is found that the effect of creep needs to be considered in order to accurately simulate the stress level of the lining concrete in the early age. For the research object of this invention, if the material characteristics of creep are not considered, the stress level of the concrete will be greatly overestimated. Figure 4 The vertical tensile stress at point D increased by 46.2%, such as... Figure 6 As shown;

[0056] (3) The concrete placement temperature affects the form of vertical stress. An analysis of the influence of placement temperature on the vertical stress of the lining concrete was conducted. Comparison of the vertical stress of the lining concrete under four conditions (10℃, 15℃, 20℃, and 25℃) revealed that reducing the placement temperature of the lining concrete can effectively reduce the risk of cracking. For the research object of this invention, every 1℃ change in placement temperature... Figure 4 The vertical tensile stress at point D will increase by 0.345 MPa, such as Figure 7 As shown, this indicates that a lower concrete placement temperature can be achieved by cooling the aggregate with cold water.

[0057] (4) The convection coefficient affects the heat transfer efficiency between concrete and the atmosphere. After implementing thermal insulation measures on the concrete surface, the convection coefficient changes. The influence of the convection coefficient on the vertical stress of the inner lining concrete is analyzed, comparing values ​​of 8.4, 14.2, 20, and 28.4 kJ / (m²). 2 The vertical stress of the inner lining concrete under four conditions (h℃) was analyzed. It was found that the smaller the convection coefficient of the inner lining concrete surface, the lower the tensile stress of the concrete, and the lower the risk of cracking of the inner lining concrete. For the research object of this invention, when the convection coefficient is from 8400 J / (m²), the vertical stress is lower. 2 h℃) changed to 28400J / (m 2 After h℃), Figure 4 The vertical tensile stress at point D increased from 1.6 MPa to 3.1 MPa, approximately doubling. Figure 8 As shown, this indicates that foam plastic boards (1cm thick, with a convection coefficient of 9600kJ / (m²)) can be used in practical engineering. 2 h℃)) Implement insulation for actual engineering projects.

[0058] In step 3, based on the influence of various factors and combined with the numerical simulation results, it is determined whether there is a risk of cracking in the concrete lining of the target corrugated steel web under the set concrete pouring temperature and the proposed concrete surface insulation measures in the target area's usage environment.

[0059] By determining the cracking risk of the target corrugated steel web lining concrete under the target environment, and then calculating the impact of shrinkage and creep effects on the crack resistance of the lining concrete during the design stage of the corrugated steel web box girder lining concrete, relevant design parameters can be adjusted. During the construction stage of the corrugated steel web box girder lining concrete, the concrete pouring temperature can be adjusted and the concrete surface can be insulated to reduce the risk of early-age cracking of the corrugated steel web box girder lining concrete, which helps to improve the safety of bridge engineering.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the cracking risk of concrete lining in corrugated steel web box girders, characterized in that, Includes the following steps: Displacement boundary conditions and temperature boundary conditions were set, and a concrete model of the corrugated steel web lining was established. Numerical calculations were performed on the concrete model of the corrugated steel web lining, and the results were analyzed. When setting displacement boundaries, the constraint effect of the diaphragm and the constraint effect of the cast-in-place portion on the uncast portion were considered. The stress of the corrugated steel web was analyzed to obtain the location and magnitude of the maximum vertical tensile stress in the corrugated steel web. The distribution of the vertical stress field of the inner lining concrete at different times is analyzed to determine the location where the inner lining concrete first cracks. Based on numerical calculation results, the effects of shrinkage, creep, concrete placement temperature, and concrete surface insulation measures on the cracking risk of the corrugated steel web lining concrete are analyzed. After the concrete surface is insulated, the convection coefficient will change, and the influence of the convection coefficient on the vertical stress of the lining concrete is analyzed. Based on the influence of various factors, during the design stage of the corrugated steel web box girder inner lining concrete, the effects of shrinkage and creep on the crack resistance of the inner lining concrete are calculated, and then the relevant design parameters are adjusted. During the construction stage of the corrugated steel web box girder inner lining concrete, the concrete pouring temperature is adjusted and the concrete surface is insulated.

2. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, The corrugated steel web lining concrete model includes multiple segments, where segment N-1 simulates the already poured segment, assuming the concrete has solidified and ignoring the heat of hydration; segment N is the currently poured concrete portion, assuming that this portion contains the heat of hydration. The three-directional displacement is constrained at the concrete interface of the poured segments N-1 and N-2. In segment N, the influence of the diaphragm at the front end of the concrete is considered to constrain the lateral displacement, while the three-directional displacement is constrained at the top and bottom.

3. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, When setting the temperature boundary, a thermal convection model is used to simulate external heat loss, and the temperature boundary is set based on the simulation results.

4. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, When analyzing the crack resistance of the inner lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the inner lining concrete is compared under the two conditions of considering and not considering shrinkage effect, so as to determine the influence of shrinkage effect on the crack resistance of the inner lining concrete.

5. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, When analyzing the crack resistance of the lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the lining concrete under two conditions, namely concrete shrinkage plus creep and concrete shrinkage, is compared to determine the influence of creep on the crack resistance of the lining concrete.

6. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, When analyzing the crack resistance of the inner lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the inner lining concrete at different concrete placement temperatures is compared to determine the influence of the concrete placement temperature on the crack resistance of the inner lining concrete.

7. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, When analyzing the crack resistance of the inner lining concrete based on the numerical simulation results, the magnitude of the vertical stress of the inner lining concrete under different convection coefficients on the surface of the inner lining concrete is compared to determine the influence of the surface convection coefficient on the crack resistance of the inner lining concrete, and then the influence of the concrete surface insulation measures on the crack resistance of the inner lining concrete.

8. The method for analyzing the cracking risk of concrete lining in a corrugated steel web box girder as described in claim 1, characterized in that, The process of determining the cracking risk of the target corrugated steel web lining concrete in the target environment includes: based on the influence of various factors and combined with the numerical simulation results, determining whether the target corrugated steel web lining concrete has a cracking risk under the set concrete pouring temperature and the proposed concrete surface insulation measures in the target area's service environment.

9. A risk analysis system for cracking of concrete lining in corrugated steel web box girder, characterized in that, include: The model simulation module is configured to set displacement boundary conditions and temperature boundary conditions, establish a concrete model of the corrugated steel web lining, perform numerical calculations on the concrete model of the corrugated steel web lining, and analyze the numerical calculation results; when setting displacement boundaries, the constraint effect of the diaphragm and the constraint effect of the cast-in-place part on the uncast part are considered; the stress of the corrugated steel web is analyzed to obtain the location and magnitude of the maximum vertical tensile stress in the corrugated steel web; The distribution of the vertical stress field of the inner lining concrete at different times is analyzed to determine the location where the inner lining concrete first cracks. The impact analysis module is configured to analyze the impact of shrinkage effect, creep, concrete placement temperature and concrete surface insulation measures on the cracking risk of the corrugated steel web lining concrete based on numerical calculation results. After the concrete surface is insulated, the convection coefficient will change, and the impact of the convection coefficient on the vertical stress of the lining concrete will be analyzed. The parameter adjustment module is configured to calculate the impact of shrinkage and creep effects on the crack resistance of the corrugated steel web box girder lining concrete during the design stage, based on various considerations, and then adjust the relevant design parameters. During the construction stage of the corrugated steel web box girder lining concrete, the module adjusts the concrete pouring temperature and performs concrete surface insulation treatment.

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