Method for testing concrete shrinkage parameters of steel-concrete composite bridge deck

Abstract

The present application belongs to the field of concrete shrinkage, and relates to a steel-concrete composite bridge deck concrete shrinkage parameter testing method, comprising the following steps: S1, preparing a test model with the same proportion according to a steel-concrete composite bridge deck to be built; S2, collecting the measured strain forces of each strain force measuring point and the measured displacements of each perturbation measuring point in the test model in real time; S3, obtaining the theoretical strain forces of each strain force measuring point and the theoretical displacements of each perturbation measuring point in the test model; S4, obtaining the measured shrinkage equivalent temperature drop coefficient based on the measured strain forces of each strain force measuring point and the measured displacements of each perturbation measuring point in the test model and the theoretical strain forces of each strain force measuring point and the theoretical displacements of each perturbation measuring point; and S5, inputting the measured shrinkage equivalent temperature drop coefficient and the concrete shrinkage hyperbolic power function into an Origin model to fit the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent temperature drop coefficient curve. The present application solves the problem of inaccurate concrete shrinkage parameter testing results of the existing steel-concrete composite bridge deck.

Description

Technical Field

[0001] This invention relates to the field of concrete shrinkage, and specifically discloses a method for testing the shrinkage parameters of concrete in steel-concrete composite bridge decks. Background Technology

[0002] Concrete shrinkage is a characteristic property of concrete materials, varying with material origin, mix proportions, and environmental temperature and humidity. Concrete shrinkage causes concrete members to shorten and deform; when this deformation is constrained, it generates forces and further deformation. In steel-concrete composite structures, concrete shrinkage induces self-stress in the components, leading to stress and deformation in the steel structure. In the construction of long-span bridges, concrete shrinkage, influenced by steel components and statically indeterminate structures, results in significant complex stresses and deformations, which increase with span. These complex stresses and deformations affect the bridge's safety and durability. Therefore, shrinkage testing is essential for long-span steel-concrete composite bridges. Based on the test results, relevant technical measures can be implemented to control these complex stresses and deformations, thereby improving the bridge's safety and durability.

[0003] Existing concrete shrinkage testing primarily involves indoor standard specimens combined with deformation testing, which has the following problems: 1. The small size of the standard specimens leads to significant errors in testing even minor shrinkage deformations, resulting in inaccurate test results; 2. Indoor standard specimen testing cannot account for the influence of external environmental changes such as temperature and humidity, sunlight, and wind on the shrinkage performance of concrete, leading to inaccurate test results; 3. Existing concrete shrinkage testing is limited to testing the shrinkage of ordinary concrete and is not suitable for testing the shrinkage of concrete in steel-concrete composite structures. The accuracy of the test results directly affects the precision of deformation control during bridge construction, thus directly impacting the safety and durability of the bridge. Therefore, there is a need for an efficient shrinkage test for steel-concrete composite bridge decks that can reflect real-world conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for testing the shrinkage parameters of concrete in steel-concrete composite bridge decks, thereby solving the problem of inaccurate test results for shrinkage parameters of concrete in existing steel-concrete composite bridge decks.

[0005] The specific solution of the present invention is as follows: A method for testing the shrinkage parameters of concrete in steel-concrete composite bridge decks includes the following steps: S1. Construct a scaled-down test model based on the steel-concrete composite bridge deck to be built; S2. Real-time acquisition of the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the test model; S3. Using the ANSYS finite element model, the experimental model was analyzed under various cooling modes to obtain the theoretical strain force at each strain force measurement point and the theoretical displacement at each deflection measurement point in the experimental model. S4. Based on the measured strain force and measured displacement of each strain force measuring point in the experimental model, and the theoretical strain force and theoretical displacement of each strain force measuring point, the measured shrinkage equivalent cooling coefficient is obtained. S5. Input the measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage into the Origin model to obtain the parameters of the concrete shrinkage coefficient equation and the fitted shrinkage equivalent cooling coefficient curve.

[0006] In some embodiments, the experimental model includes: The bridge consists of a pier and two cantilevered sections. The two cantilevered sections are symmetrically arranged on both sides of the pier to form a double cantilever. The pier includes multiple reinforcing bars and pier concrete. The double cantilever consists of a double cantilever steel structure and concrete. The double cantilever steel structure includes a steel bridge deck, two parallel longitudinal ribs and multiple ordinary reinforcing bars. The longitudinal ribs are set on the steel bridge deck and the ordinary reinforcing bars pass through the longitudinal ribs.

[0007] In some embodiments, creating a scaled-down experimental model includes: The template for installing the test model is used to pour concrete into the multiple steel bars of the platform in the template to form the platform. The double cantilever steel structure was placed on a pedestal, and concrete was poured into the double cantilever steel structure to form a test model.

[0008] In some embodiments, creating a scaled-down experimental model includes: After the test model is removed from the template, paint is applied to both ends of the test model.

[0009] In some embodiments, creating a scaled-down experimental model includes: Multiple strain measurement points were set at the root section and mid-span section of the steel bridge deck and concrete surface, respectively. Multiple strain measurement points are set on the root section of ordinary steel bars; One deflection measuring point is set at each of the end sections and the mid-span section of the cantilever.

[0010] In some embodiments, the measured strain force at each strain force measuring point is collected in real time by multiple resistive strain gauges of the data collection system, and the measured displacement at each deflection measuring point is collected in real time by multiple electromechanical dial gauges.

[0011] In some embodiments, step S3 includes: A spatial solid finite element model was constructed based on the experimental model using the ANSYS finite element model. Finite element analysis was performed on the spatial solid finite element model under various cooling modes to obtain the simulated strain force and simulated displacement of each strain force measurement point under various cooling modes. The measured strain force and measured displacement of each strain force measurement point in the experimental model were compared with the simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model under various cooling modes. The cooling mode with the smallest difference between the simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model and the measured strain force and measured displacement of each strain force measurement point in the experimental model was selected as the shrinkage equivalent cooling mode. The simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model under the shrinkage equivalent cooling mode are used as the theoretical strain force and theoretical displacement of each strain force measurement point in the experimental model.

[0012] In some embodiments, the multiple cooling modes include: The modes include: uniform cooling of concrete by 10℃, inverted triangular cooling of concrete by 10℃, and trapezoidal cooling of concrete by 10℃.

[0013] In some embodiments, step S4 includes: The average values ​​of the measured strain at the root of the first cantilever, the average value of the measured strain at the mid-span of the first cantilever, the average value of the measured strain at the root of the second cantilever, and the average value of the measured strain at the mid-span of the second cantilever are obtained based on the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the test model. The theoretical strain values ​​at the root of the first cantilever, the theoretical strain values ​​at the mid-span of the first cantilever, the theoretical strain values ​​at the root of the second cantilever, and the theoretical strain values ​​at the mid-span of the second cantilever are obtained based on the theoretical strain force at each strain force measuring point and the theoretical displacement at each deflection measuring point in the test model. The measured average strain at the root of the first cantilever, the measured average strain at the mid-span of the first cantilever, the measured average strain at the root of the second cantilever, and the measured average strain at the mid-span of the second cantilever are respectively compared with the theoretical average strain at the root of the first cantilever, the theoretical average strain at the mid-span of the first cantilever, the theoretical average strain at the root of the second cantilever, and the theoretical average strain at the mid-span of the second cantilever to obtain the equivalent cooling coefficient of shrinkage at the root of the first cantilever, the equivalent cooling coefficient of shrinkage at the mid-span of the first cantilever, the equivalent cooling coefficient of shrinkage at the root of the second cantilever, and the equivalent cooling coefficient of shrinkage at the mid-span of the second cantilever in the test model. The average value of the equivalent cooling coefficient of the first cantilever root contraction, the equivalent cooling coefficient of the first cantilever mid-span contraction, the equivalent cooling coefficient of the second cantilever root contraction, and the equivalent cooling coefficient of the second cantilever mid-span contraction is taken as the measured equivalent cooling coefficient of contraction.

[0014] In some embodiments, the formula for the hyperbolic power function of concrete shrinkage is: , in,ε cs ( t ) for a certain t The concrete shrinkage coefficient at time t. A and B These are all parameters from the concrete shrinkage coefficient equation. t For time.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention utilizes a full-scale test model with a double cantilever structure to measure the strain force at each strain point and the displacement at each deflection point under natural environmental conditions. Using an ANSYS finite element model, the theoretical strain force at each strain point and the theoretical displacement at each deflection point are obtained through finite element analysis under various cooling modes. Based on the measured strain force and displacement at each strain point and the theoretical displacement at each deflection point, the measured shrinkage equivalent cooling coefficient is obtained. The measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage are then input into an Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent cooling coefficient curve. This improves the effectiveness and accuracy of the concrete shrinkage coefficient equation parameters for steel-concrete composite bridge decks, thereby enhancing the safety and durability of the bridge. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete in Embodiment 1 of the present invention.

[0017] Figure 2 This is a front view of the experimental model in Embodiment 1 of the present invention.

[0018] Figure 3 This is a top view of the experimental model in Embodiment 1 of the present invention.

[0019] Figure 4 The measured shrinkage equivalent cooling coefficient curve and the fitted shrinkage equivalent cooling coefficient curve of C40 in Embodiment 2 of the present invention are shown.

[0020] Figure 5 The measured shrinkage equivalent cooling coefficient curve and the fitted shrinkage equivalent cooling coefficient curve of C50 in Embodiment 2 of the present invention are shown.

[0021] Reference numerals: 1-Platform, 2-Cantilever, 3-Steel bridge deck, 4-Longitudinal rib, 5-Ordinary reinforcing steel, 6-Concrete t -time, ε cs - Concrete shrinkage coefficient. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Example 1 A method for testing the shrinkage parameters of concrete in steel-concrete composite bridge decks, such as... Figure 1 As shown, it includes the following steps: S1. Construct a scaled-down test model based on the steel-concrete composite bridge deck to be built; First, based on the test model of the double cantilever structure of the steel-concrete composite bridge deck to be built, a platform 1 is set in the middle of the test model, which is used to support the symmetrical cantilever 2 on both sides.

[0024] like Figure 2 and Figure 3 As shown, the test model includes a platform 1, on which a double cantilever steel structure including a first cantilever and a second cantilever is set. The double cantilever steel structure includes a steel bridge deck 3, two parallel longitudinal ribs 4, and multiple ordinary steel bars 5. The longitudinal ribs 4 are set on the steel bridge deck, and the multiple ordinary steel bars 5 pass through the longitudinal ribs 4. The platform 1 and the double cantilever steel structure are cast into a whole by concrete 6. The longitudinal ribs 4 are PBL plates, which refer to plastic barrier laminated pipes. The steel bridge deck 3 and ordinary steel bars 5 in the test model are made of the same materials as the steel-concrete composite bridge deck in actual construction. The concrete 6 uses 2 to 3 different mix proportions of the actual steel-concrete composite bridge deck for comparative testing. 1 to 3 test models are set up for each concrete mix proportion for comparative testing. The platform 1 includes multiple steel bars, which are cast into the platform 1 by the platform concrete. The platform concrete uses concrete 6 of grade not lower than C40 and is set on a hardened site with a stable foundation.

[0025] The experimental model uses a double cantilever structure as a control group to ensure the accuracy of the experimental data and to guarantee the overall self-balancing of the experimental model.

[0026] The platform height ranges from 40cm to 100cm, and the platform width ranges from 40cm to 80cm, providing testing space for the experimental model and ensuring good long-term stability. The thickness of the double cantilever steel structure, the size and spacing of the longitudinal rib openings, and the thickness of the concrete bridge deck of the experimental model are all the same as those of the actual constructed steel-concrete composite bridge deck. The width of the experimental model is the width of the steel-concrete composite bridge deck corresponding to 2 to 4 longitudinal ribs, ranging from 0.6m to 1.5m. The cantilever length of the experimental model is the relatively larger length preferred when the cantilever steel structure bears the weight of the concrete and the weight of the cantilever steel structure, provided that the stress on the cantilever steel structure does not exceed the yield strength. This allows the experimental model to have greater deformation and stress under concrete shrinkage, which helps to reduce the influence of test data errors. Typically, the cantilever length ranges from 2m to 4m.

[0027] Secondly, the casting of the test model and the setting of measuring points.

[0028] The casting process of the test model includes: tying multiple reinforcing bars of the pedestal, installing the template of the test model, placing the tied pedestal reinforcing bars in the corresponding positions within the template, and pouring pedestal concrete into the reinforcing bars to form pedestal 1; placing the double cantilever steel structure on the pedestal, and pouring concrete 6 into the double cantilever steel structure to form the test model. The double cantilever steel structure is pre-cambered during fabrication. Concrete 6 is poured using the double cantilever steel structure as support, and the wet weight of the concrete is borne by the double cantilever steel structure without the need for supports. After casting, the cantilever 2 is used to bear the weight of the double cantilever steel structure and the weight of the concrete. The concrete surface of the test model is cured according to the curing methods of actual constructed steel-concrete composite bridge decks. After the test model is removed from the template, paint is applied to its sides to prevent water loss and shrinkage, simulating the continuous side surface of the steel-concrete composite bridge deck. During the casting process, pedestal 1 first bears the weight of the double cantilever steel structure, and then the double cantilever steel structure bears the weight of the poured concrete, ensuring that concrete 6 is essentially in a stress-free state.

[0029] The measurement point setup includes: selecting root sections and mid-span sections on the steel bridge deck and concrete surface in the cantilever of the steel-concrete composite bridge deck, and setting 2 to 4 strain measurement points symmetrically on the left and right sides of each section, and setting 1 strain measurement point at the middle position of each section; selecting root sections on ordinary reinforcing bars and setting 2 to 4 strain measurement points on them; setting strain measurement points on the concrete surface, steel bridge deck, and ordinary reinforcing bars to measure the strain on the upper surface of the steel-concrete composite bridge deck, the upper surface of the steel bridge deck, and the strain of ordinary reinforcing bars, respectively. All measurement points adopt single-point compensation to form a half-bridge test to eliminate the influence of factors such as changes in ambient temperature; selecting cantilever end sections and mid-span sections in the cantilever of the steel-concrete composite bridge deck, and setting 1 deflection measurement point on each section.

[0030] Strain force measuring points are used to measure strain force, and strain force measurement focuses on the local stress distribution of the material; deflection measuring points are used to measure displacement, and deflection measurement focuses on the overall deformation of the structure, such as the bending deformation of beams and plates.

[0031] S2. Real-time acquisition of the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the test model; The data collection system collects the measured strain force at each strain gauge point and the measured displacement at each deflection gauge point in the test model in real time. Three days after the test model was poured, the strain force at each strain gauge point and the displacement at each deflection gauge point in the test model were measured, and the data was monitored regularly for more than 180 days a day.

[0032] The data acquisition system includes: multiple resistance strain gauges, fiber optic sensors, multiple electromechanical dial gauges, a static data acquisition unit, sensor connecting wires, a smart socket, and a computer. Resistance strain gauges are installed at various strain measurement points on the test model, and electromechanical dial gauges are installed at various deflection measurement points. The fiber optic sensors are connected to the resistance strain gauges and electromechanical dial gauges via sensor connecting wires to collect data from these gauges and transmit the collected data to the static data acquisition unit. The static data acquisition unit receives the data from the fiber optic sensors and transmits it to the computer for data storage. The computer's power is remotely controlled via the smart socket to remotely control the computer system, remote control software, and data testing software to start and stop at fixed times each day, enabling daily remote control of the computer to collect and archive data from each measurement point. This data acquisition system facilitates remote data collection, improving work flexibility and efficiency. After the test model is installed in the open field, a test chamber is installed nearby to shelter the data acquisition system from wind and rain.

[0033] A resistance strain gauge is a sensor based on the strain effect, and it is commonly used for stress analysis of civil structures, such as stress analysis of bridge surfaces and stress analysis of building surfaces.

[0034] An electromechanical dial indicator is a precision measuring tool that combines mechanical transmission and electronic technology. It is mainly used to detect minute dimensional changes and shape and position errors of workpieces.

[0035] S3. Using the ANSYS finite element model, the experimental model was analyzed under various cooling modes to obtain the theoretical strain force at each strain force measurement point and the theoretical displacement at each deflection measurement point in the experimental model. Based on the experimental model, a refined spatial solid finite element model was constructed using the ANSYS finite element model. This model was used to perform finite element analysis on the stress and deformation patterns caused by concrete shrinkage under various cooling modes. Specifically, finite element analysis was conducted on the spatial solid finite element model under different cooling modes to obtain the simulated strain force at each strain measurement point and the simulated displacement at each deflection measurement point under each cooling mode. The various cooling modes included: a uniform 10℃ cooling mode for the entire concrete structure, a 10℃ cooling mode for an inverted triangle cooling mode, and a 10℃ cooling mode for a trapezoidal cooling mode. The inverted triangle cooling mode resulted in the maximum temperature drop at the concrete surface, with a linear decrease along the thickness until the temperature at the steel plate reached 0℃. The trapezoidal cooling mode resulted in the maximum temperature drop at the concrete surface, with a relatively lower but not zero temperature drop at the steel plate, such as 2.5℃, 5.0℃, and 7.5℃. The measured strain forces and measured displacements of each strain force measurement point in the experimental models at different ages were collected and compared with the simulated strain forces and simulated displacements of each strain force measurement point in the spatial solid finite element model under various cooling modes. The cooling mode with the smallest difference between the simulated strain forces and simulated displacements of each strain force measurement point in the spatial solid finite element model and the measured strain forces and measured displacements of each strain force measurement point in the experimental model was selected as the shrinkage equivalent cooling mode. The simulated strain forces and simulated displacements of each strain force measurement point in the spatial solid finite element model under the shrinkage equivalent cooling mode were taken as the theoretical strain forces and theoretical displacements of each strain force measurement point in the experimental model.

[0036] S4. Based on the measured strain force and measured displacement of each strain force measuring point in the experimental model, and the theoretical strain force and theoretical displacement of each strain force measuring point, the measured shrinkage equivalent cooling coefficient is obtained. Based on the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the experimental model, the average measured strain values ​​at the root and mid-span of the two cantilever arms are calculated to obtain the average measured strain values ​​at the root of the first cantilever, the average measured strain value at the mid-span of the first cantilever, the average measured strain value at the root of the second cantilever, and the average measured strain value at the mid-span of the second cantilever. Based on the theoretical strain force at each strain force measuring point and the theoretical displacement at each deflection measuring point in the experimental model, the average theoretical strain values ​​at the root and mid-span of the two cantilever arms are calculated to obtain the average theoretical strain values ​​at the root of the first cantilever, the average theoretical strain value at the mid-span of the first cantilever, the average theoretical strain value at the root of the second cantilever, and the average theoretical strain value at the mid-span of the second cantilever. The average measured strain values ​​at the root of the first cantilever, the average measured strain value at the mid-span of the first cantilever, and the average measured strain value at the mid-span of the second cantilever are then calculated. The average measured strain at the root and the average measured strain at the mid-span of the second cantilever are calculated by comparing them with the average theoretical strain at the root of the first cantilever, the average theoretical strain at the mid-span of the first cantilever, the average theoretical strain at the root of the second cantilever, and the average theoretical strain at the mid-span of the second cantilever. This yields the equivalent cooling coefficients for shrinkage at the root and mid-span of the first cantilever, the equivalent cooling coefficients for shrinkage at the mid-span of the first cantilever, the equivalent cooling coefficients for shrinkage at the root of the second cantilever, and the equivalent cooling coefficients for shrinkage at the mid-span of the second cantilever. The average value of these coefficients is taken as the measured equivalent cooling coefficient. The measured equivalent cooling coefficient curve is generated by the change of the measured equivalent cooling coefficient over time.

[0037] S5. Input the measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage into the Origin model to obtain the parameters of the concrete shrinkage coefficient equation and the fitted shrinkage equivalent cooling coefficient curve.

[0038] The measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage are input into the Origin model to obtain the parameters of the concrete shrinkage coefficient equation. The parameters of the concrete shrinkage coefficient equation are then substituted into the hyperbolic power function of concrete shrinkage to obtain the fitted value of the shrinkage equivalent cooling coefficient. The fitted value of the shrinkage equivalent cooling coefficient changes with time to generate the fitted shrinkage equivalent cooling coefficient curve.

[0039] The formula for the hyperbolic power function of concrete shrinkage is: , in, ε cs ( t ) for a certain t The concrete shrinkage coefficient at time t. A and B These are all parameters from the concrete shrinkage coefficient equation. t For time.

[0040] Origin Model is a scientific plotting and data analysis software developed by OriginLab. It has functions such as statistics, signal processing, curve fitting, and peak analysis, and features powerful data import and diverse graphical output formats.

[0041] By measuring the strain force at each strain point and the displacement at each deflection point under natural environmental conditions using a full-scale test model with a double cantilever structure, and then performing finite element analysis on the test model under various cooling modes using ANSYS finite element model, the theoretical strain force at each strain point and the theoretical displacement at each deflection point in the test model were obtained. Based on the measured strain force and displacement at each strain point and the theoretical strain force and displacement at each deflection point in the test model, the measured shrinkage equivalent cooling coefficient was obtained. The measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage were input into the Origin model for fitting to obtain the parameters of the concrete shrinkage coefficient equation and the fitted shrinkage equivalent cooling coefficient curve. This improved the effectiveness and accuracy of the concrete shrinkage coefficient equation parameters for steel-concrete composite bridge decks, thereby improving the safety and durability of the bridge.

[0042] Example 2 A specific embodiment of a method for testing the shrinkage parameters of concrete in steel-concrete composite bridge decks includes the following steps: S1. Construct a scaled-down test model based on a certain steel-concrete composite bridge deck; The stiffening rib spacing of a certain steel-concrete composite bridge deck is 40 cm. The range of 20 cm outward from the two stiffening ribs and the stiffening ribs on both sides is selected. The platform width is 80 cm, the platform height is 86 cm, the cantilever length on both sides of the platform is 240 cm, and the total length of the test model is 560 cm. It is a steel-concrete composite bridge deck with double PBL plates.

[0043] Two sets of identical test models were cast using C40 and C50 steel fiber reinforced concrete, respectively. C40 steel fiber reinforced concrete is a composite material in which a certain amount of short, fine steel fibers are incorporated into ordinary concrete, with a standard compressive strength of 40 MPa. C50 steel fiber reinforced concrete is a novel multiphase composite material formed by incorporating randomly distributed short steel fibers into ordinary concrete, with a standard compressive strength of 50 MPa. The C40 and C50 test models were placed in an open-air environment, their concrete surfaces covered with plastic film, and cured with water. After being removed from the formwork, waterproof paint was applied to the sides of both models to prevent water loss and shrinkage, simulating the continuous side surfaces of the C40 and C50 test models.

[0044] In the cantilever sections of the steel bridge deck 3 and concrete surface of the C40 and C50 test models, root sections and mid-span sections were selected respectively. Three measuring points were set at each section, namely one strain measuring point at each symmetrical position on the left and right sides of each section and one strain measuring point at the center of each section. In the ordinary steel reinforcement, root sections were selected, and two strain measuring points were set at each section, namely one strain measuring point at each symmetrical position on the left and right sides of each section. In the cantilever section of the steel-concrete composite bridge deck, cantilever end sections and mid-span sections were selected, and one deflection measuring point was set at each section.

[0045] S2. Real-time acquisition of the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the test model; Three days after the C40 and C50 test models were poured, the measured strain force at each strain measurement point and the measured displacement at each deflection measurement point in the C40 and C50 test models were collected in real time through the data collection system, and the monitoring was carried out regularly for more than 180 days a day.

[0046] S3. Using the ANSYS finite element model, finite element analysis was performed on the test model under various cooling modes to obtain the theoretical strain force and displacement of each strain force measurement point in the test model. Based on the C40 and C50 experimental models, C40 and C50 spatial solid finite element models were constructed using ANSYS finite element modeling. Finite element analysis was performed on the C40 and C50 spatial solid finite element models under three cooling modes: uniform cooling of concrete by 10℃, inverted triangular cooling of concrete by 10℃, and trapezoidal cooling of concrete by 10℃. The simulated strain force and simulated displacement of each strain measurement point in both models were obtained under each cooling mode. The measured strain force and measured displacement of each strain measurement point in both the C40 and C50 experimental models were then compared with those of the C40 spatial solid finite element model. The simulated strain force and simulated displacement of each strain force measurement point in the C40 and C50 spatial solid finite element models under various cooling modes were compared to obtain the shrinkage equivalent cooling modes of the C40 and C50 spatial solid finite element models, respectively. The simulated strain force and simulated displacement of each strain force measurement point in the C40 and C50 spatial solid finite element models under the shrinkage equivalent cooling modes were used as the theoretical strain force and theoretical displacement of each strain force measurement point in the C40 and C50 experimental models, respectively.

[0047] S4. Based on the measured strain force and measured displacement of each strain force measuring point in the experimental model, the measured shrinkage equivalent cooling coefficient is obtained by comparing it with the theoretical strain force and theoretical displacement of each strain force measuring point.

[0048] Based on the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the C40 and C50 test models, the average measured strain values ​​at the root of the first cantilever, the mid-span of the first cantilever, the root of the second cantilever, and the mid-span of the second cantilever in the C40 and C50 test models are obtained. Based on the theoretical strain force at each strain force measuring point and the theoretical displacement at each deflection measuring point in the C40 and C50 test models, the average theoretical strain values ​​at the root of the first cantilever, the mid-span of the first cantilever, the root of the second cantilever, and the mid-span of the second cantilever in the C40 and C50 test models are obtained. These average measured strain values ​​are then compared with the average measured strain values ​​at the root of the first cantilever, the mid-span of the first cantilever, the root of the second cantilever, and the mid-span of the second cantilever in the C40 and C50 test models. The average theoretical strain of the first cantilever at mid-span, the average theoretical strain of the second cantilever at root, and the average theoretical strain of the second cantilever at mid-span will be calculated by ratio to obtain the equivalent cooling coefficients for shrinkage at the root and mid-span of the first cantilever in the C40 test model, i.e., the C40 equivalent cooling coefficients. Similarly, the equivalent cooling coefficients for shrinkage at the root and mid-span of the first cantilever, the second cantilever at root, and the second cantilever at mid-span in the C50 test model, i.e., the C50 equivalent cooling coefficients, are shown in Tables 1 and 2. Here, 1-root represents the equivalent cooling coefficient for shrinkage at the root of the first cantilever, 1-mid-span represents the equivalent cooling coefficient for shrinkage at mid-span of the first cantilever, 2-root represents the equivalent cooling coefficient for shrinkage at the root of the second cantilever, and 2-mid-span represents the equivalent cooling coefficient for shrinkage at mid-span of the second cantilever. Table 1. C40 Shrinkage Equivalent Cooling Coefficient

[0049] Table 2. C50 Shrinkage Equivalent Cooling Coefficient

[0050] The average values ​​of the equivalent cooling coefficients at the root of the first cantilever, the mid-span of the first cantilever, the root of the second cantilever, and the mid-span of the second cantilever in the C40 test model, and the average values ​​of the same values ​​in the C50 test model, are used as the measured equivalent cooling coefficients for C40 and C50, respectively. The measured equivalent cooling coefficients for C40 and C50 are then used to generate curves showing their variation over time. Figure 4 and Figure 5 As shown.

[0051] S5. Input the measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage into the Origin model to obtain the parameters of the concrete shrinkage coefficient equation and the fitted shrinkage equivalent cooling coefficient curve.

[0052] The measured shrinkage equivalent cooling coefficient of C40 concrete, the measured shrinkage equivalent cooling coefficient of C50 concrete, and the hyperbolic power function of concrete shrinkage were input into the Origin model to obtain the equation parameters for the shrinkage coefficient of C40 concrete and the shrinkage coefficient of C50 concrete, respectively, as shown in Tables 3 and 4. Table 3. Equation parameters for shrinkage coefficient of C40 concrete

[0053] Table 4. Equation parameters for shrinkage coefficient of C50 concrete

[0054] Substituting the parameters of the C40 concrete shrinkage coefficient equation into the hyperbolic power function of concrete shrinkage yields the fitted value of the C40 shrinkage equivalent cooling coefficient. The variation of the fitted value of the C40 shrinkage equivalent cooling coefficient with time generates a curve of the C40 fitted shrinkage equivalent cooling coefficient, as shown below. Figure 4 As shown, the expression for the C40 fitted shrinkage equivalent cooling coefficient curve is: , Substituting the parameters of the C50 concrete shrinkage coefficient equation into the hyperbolic power function of concrete shrinkage, we obtain the fitted value of the C50 shrinkage equivalent cooling coefficient. The change of the fitted value of the C50 shrinkage equivalent cooling coefficient over time generates a curve of the C50 fitted shrinkage equivalent cooling coefficient, as shown below. Figure 5 As shown, the expression for the C50 fitted shrinkage equivalent cooling coefficient curve is: . The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 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 testing the shrinkage parameters of concrete in steel-concrete composite bridge decks, characterized in that, Includes the following steps: S1. Construct a scaled-down test model based on the steel-concrete composite bridge deck to be built. The test model includes: a platform and two cantilever arms, which are symmetrically arranged on both sides of the platform to form a double cantilever. The platform includes multiple reinforcing bars and platform concrete. The double cantilever arms include a double cantilever steel structure and concrete. The double cantilever steel structure includes a steel bridge deck, two parallel longitudinal ribs, and multiple ordinary reinforcing bars. The longitudinal ribs are arranged on the steel bridge deck, and the ordinary reinforcing bars pass through the longitudinal ribs. The process of creating a scaled-down test model includes: setting multiple strain force measuring points at the root section and mid-span section of the steel bridge deck and concrete surface, respectively; setting multiple strain force measuring points at the root section of ordinary steel bars; and setting one deflection measuring point at the end section and mid-span section of the cantilever, respectively. S2. Real-time acquisition of the measured strain force at each strain force measuring point and the measured displacement at each deflection measuring point in the test model; S3. Using the ANSYS finite element model, the experimental model was analyzed under various cooling modes to obtain the theoretical strain force at each strain force measurement point and the theoretical displacement at each deflection measurement point in the experimental model. S4. Based on the measured strain force and measured displacement of each strain force measuring point in the test model, and the theoretical strain force and theoretical displacement of each strain force measuring point, obtain the measured shrinkage equivalent cooling coefficient; specifically, this includes: obtaining the average measured strain at the root of the first cantilever, the average measured strain at the mid-span of the first cantilever, the average measured strain at the root of the second cantilever, and the average measured strain at the mid-span of the second cantilever in the test model based on the measured strain force and measured displacement of each strain force measuring point in the test model; The theoretical strain values ​​at the root of the first cantilever, the theoretical strain values ​​at the mid-span of the first cantilever, the theoretical strain values ​​at the root of the second cantilever, and the theoretical strain values ​​at the mid-span of the second cantilever are obtained based on the theoretical strain force at each strain force measuring point and the theoretical displacement at each deflection measuring point in the test model. The measured average strain at the root of the first cantilever, the measured average strain at the mid-span of the first cantilever, the measured average strain at the root of the second cantilever, and the measured average strain at the mid-span of the second cantilever are respectively compared with the theoretical average strain at the root of the first cantilever, the theoretical average strain at the mid-span of the first cantilever, the theoretical average strain at the root of the second cantilever, and the theoretical average strain at the mid-span of the second cantilever to obtain the equivalent cooling coefficient of shrinkage at the root of the first cantilever, the equivalent cooling coefficient of shrinkage at the mid-span of the first cantilever, the equivalent cooling coefficient of shrinkage at the root of the second cantilever, and the equivalent cooling coefficient of shrinkage at the mid-span of the second cantilever in the test model. The average value of the equivalent cooling coefficient of the first cantilever root contraction, the equivalent cooling coefficient of the first cantilever mid-span contraction, the equivalent cooling coefficient of the second cantilever root contraction, and the equivalent cooling coefficient of the second cantilever mid-span contraction is taken as the measured equivalent cooling coefficient of contraction. S5. Input the measured shrinkage equivalent cooling coefficient and the hyperbolic power function of concrete shrinkage into the Origin model to obtain the parameters of the concrete shrinkage coefficient equation and the fitted shrinkage equivalent cooling coefficient curve.

2. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that, The process of creating a scaled-down experimental model includes: The template for installing the test model is used to pour concrete into the multiple steel bars of the platform in the template to form the platform. The double cantilever steel structure was placed on a pedestal, and concrete was poured into the double cantilever steel structure to form a test model.

3. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 2, characterized in that, The process of creating a scaled-down test model includes: after the test model is removed from the template, paint is applied to both ends of the test model.

4. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that: The data collection system uses multiple resistance strain gauges to collect the measured strain force at each strain force measurement point in real time, and multiple electromechanical dial gauges to collect the measured displacement at each deflection measurement point in real time.

5. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that, Step S3 includes: A spatial solid finite element model was constructed based on the experimental model using the ANSYS finite element model. Finite element analysis was performed on the spatial entity finite element model under various cooling modes, and the simulated strain force and simulated displacement of each strain force measurement point and each deflection measurement point of the spatial entity finite element model under various cooling modes were obtained respectively. The measured strain force and measured displacement of each strain force measurement point in the experimental model were compared with the simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model under various cooling modes. The cooling mode with the smallest difference between the simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model and the measured strain force and measured displacement of each strain force measurement point in the experimental model was selected as the shrinkage equivalent cooling mode. The simulated strain force and simulated displacement of each strain force measurement point in the spatial entity finite element model under the shrinkage equivalent cooling mode are used as the theoretical strain force and theoretical displacement of each strain force measurement point in the experimental model.

6. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that, The various cooling modes include: uniform cooling of concrete by 10℃, inverted triangular cooling of concrete by 10℃, and trapezoidal cooling of concrete by 10℃.

7. The method for testing the shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that, The formula for the hyperbolic power function of concrete shrinkage is: ， in, ε cs ( t ) for a certain t The concrete shrinkage coefficient at time t. A and B These are all parameters from the concrete shrinkage coefficient equation. t For time.

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