Concrete shrinkage parameter testing method for steel-concrete combined bridge deck

Abstract

The invention belongs to the field of concrete shrinkage, and relates to a steel-concrete combined bridge deck concrete shrinkage parameter testing method which comprises the following steps: S1, manufacturing an equal-proportion test model according to a to-be-built steel-concrete combined bridge deck; s2, actually measured strain force of each strain force measuring point and actually measured displacement of each deflection measuring point in the test model are collected in real time; s3, obtaining the theoretical strain force of each strain force measuring point and the theoretical displacement of each deflection measuring point in the test model; s4, obtaining an actual measurement shrinkage equivalent cooling coefficient based on the actual measurement strain force of each strain force measuring point and the actual measurement displacement of each deflection measuring point in the test model, and the theoretical strain force of each strain force measuring point and the theoretical displacement of each deflection measuring point; and S5, inputting the actually measured shrinkage equivalent cooling coefficient and the concrete shrinkage hyperbolic power function into an Origin model for fitting to obtain a concrete shrinkage coefficient equation parameter and a fitting shrinkage equivalent cooling coefficient curve. The problem that the concrete shrinkage parameter testing result of an existing steel-concrete combined bridge deck is not accurate is solved.

Description

Technical Field

[0001] The invention relates to the field of concrete shrinkage, and particularly discloses a method for testing shrinkage parameters of steel-concrete composite bridge deck concrete. Background Art

[0002] Concrete shrinkage is a characteristic of concrete materials and varies with factors such as the material's origin, mix ratio, and ambient temperature and humidity. Concrete shrinkage causes concrete components to shorten and deform. Of course, when deformation is constrained, forces and deformations will be generated. In steel-concrete composite structures, concrete shrinkage will cause self-stress in the components of the steel-concrete composite structure, driving forces and deformations in the steel structure. In the construction of long-span bridges, concrete shrinkage is affected by steel components and statically indeterminate structures, resulting in significant complex forces and deformations, which increase with increasing span. Complex forces and deformations will affect the safety and durability of the bridge. Therefore, it is very necessary to conduct shrinkage tests on long-span bridges with steel-concrete composite structures. Based on the shrinkage test results, relevant technical measures can be taken to control complex forces and deformations, thereby improving the safety and durability of the bridge.

[0003] Existing concrete shrinkage tests primarily rely on indoor standard specimens combined with deformation testing. This presents the following challenges: 1. The small size of standard specimens results in large errors in testing even small shrinkage and deformations, leading to inaccurate test results. 2. Indoor standard specimen testing fails to account for the effects of environmental temperature and humidity fluctuations, sunlight, and wind on concrete shrinkage, leading to inaccurate test results. 3. Existing concrete shrinkage tests are limited to measuring the shrinkage of standard concrete and are not suitable for testing concrete shrinkage in reinforced concrete composite structures. The accuracy of test results directly impacts the control precision of bridge construction deformation, and thus the safety and durability of bridges. Therefore, an efficient steel-concrete composite bridge deck shrinkage test that can reflect real-world conditions is needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for testing shrinkage parameters of steel-concrete composite bridge deck concrete, so as to solve the problem of inaccurate test results of shrinkage parameters of existing steel-concrete composite bridge deck concrete.

[0005] The specific scheme of the present invention is as follows:

[0006] A method for testing shrinkage parameters of steel-concrete composite bridge deck concrete comprises the following steps:

[0007] S1. Make a scaled test model based on the steel-concrete composite bridge deck to be built;

[0008] S2, real-time acquisition of the measured strain force at each strain force measurement point and the measured displacement at each disturbance measurement point in the test model;

[0009] S3. Perform finite element analysis on the test model under various cooling modes using the ANSYS finite element model to obtain the theoretical strain of each strain measurement point and the theoretical displacement of each disturbance measurement point in the test model;

[0010] S4. Obtaining a measured shrinkage equivalent temperature drop coefficient based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model and the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point;

[0011] S5. Input the measured shrinkage equivalent temperature drop coefficient and the concrete shrinkage hyperbolic power function into the Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent temperature drop coefficient curve.

[0012] In some embodiments, the test model comprises:

[0013] The pedestal and two cantilevers are symmetrically arranged on both sides of the pedestal to form a double cantilever. The pedestal includes multiple steel bars and pedestal concrete. The double cantilever includes a double cantilever steel structure and concrete. The double cantilever steel structure includes a steel bridge deck, two side-by-side longitudinal ribs and multiple ordinary steel bars. The longitudinal ribs are arranged on the steel bridge deck, and the ordinary steel bars pass through the longitudinal ribs.

[0014] In some embodiments, making a scaled test model includes:

[0015] Installing a formwork for the test model, and pouring pedestal concrete onto a plurality of steel bars of the pedestal in the formwork to form a pedestal;

[0016] The double-cantilever steel structure is placed on a pedestal and concrete is poured into the double-cantilever steel structure to form a test model.

[0017] In some embodiments, making a scaled test model includes:

[0018] After the test model is separated from the template, paint is applied to both ends of the test model.

[0019] In some embodiments, making a scaled test model includes:

[0020] Multiple strain measurement points are set up on the root section and mid-span section of the steel bridge deck and concrete surface;

[0021] Set up multiple strain measurement points on the root section of ordinary steel bars;

[0022] A deflection measuring point is set on the end section and mid-span section of the cantilever respectively.

[0023] In some embodiments, the measured strain force of each strain force measurement point is collected in real time by multiple resistance strain gauges of the data collection system, and the measured displacement of each disturbance measurement point is collected in real time by multiple electromechanical dial indicators.

[0024] In some embodiments, step S3 includes:

[0025] Based on the test model, a spatial solid finite element model is constructed using the ANSYS finite element model;

[0026] Finite element analysis of the spatial entity finite element model is performed under various cooling modes to obtain the simulated strain force of each strain force measurement point and the simulated displacement of each disturbance measurement point of the spatial entity finite element model under various cooling modes;

[0027] The measured strains at each strain measurement point and the measured displacements at each disturbance measurement point in the collected test model are compared with the simulated strains at each strain measurement point and the simulated displacements at each disturbance measurement point in the spatial solid finite element model under various cooling modes. The cooling mode with the smallest difference between the simulated strains at each strain measurement point and the simulated displacements at each disturbance measurement point in the spatial solid finite element model and the measured strains at each strain measurement point and the measured displacements at each disturbance measurement point in the test model is selected as the shrinkage equivalent cooling mode.

[0028] The simulated strain of each strain measuring point and the simulated displacement of each disturbance measuring point in the spatial solid finite element model under the shrinkage equivalent cooling mode are used as the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model.

[0029] In some embodiments, the multiple cooling modes include:

[0030] The concrete overall uniform cooling mode is 10℃, the concrete inverted triangle cooling mode is 10℃, and the concrete trapezoidal cooling mode is 10℃.

[0031] In some embodiments, step S4 includes:

[0032] Based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model, 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 are obtained;

[0033] According to the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model, the theoretical strain average value of the first cantilever root, the theoretical strain average value of the first cantilever mid-span, the theoretical strain average value of the second cantilever root and the theoretical strain average value of the second cantilever mid-span in the test model are obtained;

[0034] 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 are respectively calculated 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 to obtain the equivalent cooling coefficient of contraction of the root of the first cantilever, the equivalent cooling coefficient of contraction of the mid-span of the first cantilever, the equivalent cooling coefficient of contraction of the root of the second cantilever and the equivalent cooling coefficient of contraction of the mid-span of the second cantilever in the test model;

[0035] The average value of the shrinkage equivalent temperature cooling coefficient at the root of the first cantilever, the shrinkage equivalent temperature cooling coefficient at the mid-span of the first cantilever, the shrinkage equivalent temperature cooling coefficient at the root of the second cantilever, and the shrinkage equivalent temperature cooling coefficient at the mid-span of the second cantilever is taken as the measured shrinkage equivalent temperature cooling coefficient.

[0036] In some embodiments, the formula for the concrete shrinkage hyperbolic power function is:

[0037]

[0038] Among them, ε cs (t) is the concrete shrinkage coefficient at a certain time t, A and B are parameters of the concrete shrinkage coefficient equation, and t is time.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] The present invention uses a full-scale test model of a double-cantilever structure to measure the actual strain of each strain measuring point and the actual displacement of each disturbance measuring point under natural environmental conditions, and performs finite element analysis on the test model under multiple cooling modes using an ANSYS finite element model to obtain the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model. Based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model and the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point, the measured shrinkage equivalent cooling coefficient is obtained. The measured shrinkage equivalent cooling coefficient and the concrete shrinkage hyperbolic power function are input into an Origin model for fitting to obtain concrete shrinkage coefficient equation parameters and a fitted shrinkage equivalent cooling coefficient curve, thereby improving the validity and accuracy of the concrete shrinkage coefficient equation parameters of a steel-concrete composite bridge deck, thereby improving the safety and durability of the bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart of a method for testing shrinkage parameters of steel-concrete composite bridge deck concrete in Example 1 of the present invention.

[0042] Figure 2 This is a front view of the test model in Example 1 of the present invention.

[0043] Figure 3 This is a top view of the test model in Example 1 of the present invention.

[0044] Figure 4 These are the measured shrinkage equivalent temperature reduction coefficient curve of C40 and the fitted shrinkage equivalent temperature reduction coefficient curve of C40 in Example 2 of the present invention.

[0045] Figure 5 These are the C50 measured shrinkage equivalent temperature reduction coefficient curve and the C50 fitted shrinkage equivalent temperature reduction coefficient curve in Example 2 of the present invention.

[0046] Reference numerals: 1-base, 2-cantilever, 3-steel bridge deck, 4-longitudinal rib, 5-ordinary steel bar, 6-concrete, t-time, ε cs -Concrete shrinkage coefficient. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0048] Example 1

[0049] A test method for shrinkage parameters of steel-concrete composite bridge deck concrete, such as Figure 1 As shown, the following steps are included:

[0050] S1. Make a scaled test model based on the steel-concrete composite bridge deck to be built;

[0051] First, a test model of a double-cantilever structure is designed based on the steel-concrete composite bridge deck to be built. A pedestal 1 is provided in the middle of the test model to support the cantilevers 2 symmetrical on both sides.

[0052] like Figure 2 and Figure 3As shown, the test model includes a pedestal 1, on which a double-cantilever steel structure including a first cantilever and a second cantilever is arranged. The double-cantilever steel structure includes a steel bridge deck 3, two side-by-side longitudinal ribs 4 and a plurality of ordinary steel bars 5. The longitudinal ribs 4 are arranged on the steel bridge deck, and the plurality of ordinary steel bars 5 pass through the longitudinal ribs 4. The pedestal 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 laminate tubes. The steel bridge deck 3 and ordinary steel bars 5 in the test model are made of the same material as the actually constructed steel-concrete composite bridge deck. The concrete 6 is made of 2 to 3 types of the actually constructed steel-concrete composite bridge deck mix ratio test for comparative testing, and 1 to 3 test models are set up for comparative testing for each concrete mix ratio. The pedestal 1 includes a plurality of steel bars, and the plurality of steel bars of the pedestal are cast into the pedestal 1 by pedestal concrete. The pedestal concrete uses concrete 6 of grade not less than C40 and is set on a hardened site with a stable foundation.

[0053] The test models serve as control groups through the dual cantilever structure to ensure the accuracy of the experimental data and the overall self-balance of the test model.

[0054] The pedestal height ranges from 40cm to 100cm, and the pedestal width ranges from 40cm to 80cm, providing testing space for the test model and ensuring good long-term stability. The test model's double-cantilever steel structure thickness, longitudinal rib opening size and spacing, and concrete deck thickness are identical to those of the actual steel-concrete composite bridge deck. The test model width corresponds to the steel-concrete composite bridge deck width corresponding to two to four longitudinal ribs, and the test model width ranges from 0.6m to 1.5m. The test model's cantilever length is the preferred maximum length required for the cantilever steel structure to bear the weight of the concrete and the weight of the cantilever steel structure without exceeding its yield strength. This allows the test model to experience greater deformation and stress under concrete shrinkage, which helps reduce the impact of test data errors. The cantilever length typically ranges from 2m to 4m.

[0055] Secondly, the test model is cast and the measuring points are set.

[0056] The casting process for the test model includes: tying multiple steel bars for the pedestal, installing the test model formwork, positioning the tied pedestal steel bars in the corresponding positions within the formwork, and pouring pedestal concrete into the steel bars to form the pedestal 1. A double-cantilever steel structure is placed on the pedestal, and concrete 6 is poured 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 a support, with the wet weight of the concrete borne by the double-cantilever steel structure, without the need for supports. After casting, cantilever 2 supports the weight of the double-cantilever steel structure and the concrete. The concrete surface of the test model is cured according to the curing methods used for actual steel-concrete composite bridge decks. After the test model is removed from the formwork, its sides are painted to prevent water loss and shrinkage, simulating the continuity of the side of a steel-concrete composite bridge deck. During the casting process, the weight of the double-cantilever steel structure is first borne by the pedestal 1, followed by the weight of the poured concrete, ensuring that the concrete 6 is essentially stress-free.

[0057] The measurement point setting includes: selecting the root section and the mid-span section on the steel bridge deck and the concrete surface in the cantilever of the steel-concrete composite bridge deck, setting 2 to 4 strain measurement points at the left and right symmetrical positions of each section, and setting 1 strain measurement point in the middle position of each section; selecting the root section on the ordinary steel bar, setting 2 to 4 strain measurement points on it, setting strain measurement points on the concrete surface, the steel bridge deck and the ordinary steel bar to measure the upper surface strain of the steel-concrete composite bridge deck, the upper surface strain of the steel bridge deck and the ordinary steel bar respectively. All measurement points use single-point compensation to form a half-bridge test to eliminate the influence of factors such as ambient temperature changes; selecting the cantilever end section and the mid-span section in the cantilever of the steel-concrete composite bridge deck, and setting 1 deflection measurement point on each section.

[0058] Strain measurement points are used to measure strain, and strain measurement focuses on the local stress distribution of the material; disturbance measurement points are used to measure displacement, and disturbance measurement focuses on the overall deformation of the structure, such as the bending deformation of beams and plates.

[0059] S2, real-time acquisition of the measured strain force at each strain force measurement point and the measured displacement at each disturbance measurement point in the test model;

[0060] The data collection system collects the measured strains and displacements at each strain measurement point and disturbance measurement point in real time. Three days after the cast of the test model, strains and displacements at each strain measurement point and disturbance measurement point are measured, with daily monitoring for at least 180 days.

[0061] The data collection system includes multiple resistive strain gauges, fiber optic sensors, multiple electromechanical dial indicators, a static data acquisition instrument, sensor connection wires, an intelligent socket, and a computer. Resistive strain gauges are placed at each strain measurement point on the test model, and electromechanical dial indicators are placed at each deflection measurement point. The fiber optic sensors connect to the resistive strain gauges and electromechanical dial indicators via sensor connection wires, collecting data from these gauges and transmitting this data to the static data acquisition instrument. The static data acquisition instrument receives the data collected by the fiber optic sensors and transfers it to the computer for storage. The intelligent socket remotely controls the computer's power supply, enabling remote control of the computer system, remote control software, and data testing software at fixed times daily. This allows for daily remote control of the computer to collect and archive data from each measurement point. Collecting data from each measurement point through the data collection system facilitates remote data collection, improving work flexibility and efficiency. After the test model is installed outdoors, a test chamber is installed nearby to provide shelter from wind and rain for the data collection system.

[0062] Resistive strain gauge is a sensor based on strain effect, which is usually used for surface stress analysis of civil structures, such as bridge surface stress analysis and building surface stress analysis.

[0063] The electromechanical dial indicator is a precision measuring tool that combines mechanical transmission and electronic technology. It is mainly used to detect small dimensional changes and shape and position errors of workpieces.

[0064] S3. Perform finite element analysis on the test model under various cooling modes using the ANSYS finite element model to obtain the theoretical strain of each strain measurement point and the theoretical displacement of each disturbance measurement point in the test model;

[0065] Based on the experimental model, a refined spatial solid finite element model was constructed using the ANSYS finite element model. The spatial solid finite element model was used to analyze the stress and deformation patterns caused by concrete shrinkage under various cooling modes. Specifically, the spatial solid finite element model was analyzed under various cooling modes to obtain simulated strains at each strain measurement point and simulated displacements at each disturbance measurement point. The various cooling modes include: a 10°C uniform cooling mode for the entire concrete, a 10°C inverted triangle cooling mode for concrete, and a 10°C trapezoidal cooling mode for concrete. The 10°C inverted triangle cooling mode achieves maximum cooling at the concrete surface, with the cooling decreasing linearly through the thickness to 0°C at the steel plate. The trapezoidal cooling mode achieves maximum cooling at the concrete surface, with relatively low, but not 0°C, temperatures at the steel plate, such as 2.5°C, 5.0°C, or 7.5°C. The measured strains of each strain measuring point and the measured displacements of each disturbance measuring point in the test models of different ages were sorted out, and the simulated strains of each strain measuring point and the simulated displacements of each disturbance measuring point in the spatial entity finite element model under various cooling modes were compared. The cooling mode with the smallest difference between the simulated strains of each strain measuring point and the simulated displacements of each disturbance measuring point in the spatial entity finite element model and the measured strains of each strain measuring point and the measured displacements of each disturbance measuring point in the test model was selected as the shrinkage equivalent cooling mode, and the simulated strains of each strain measuring point and the simulated displacements of each disturbance measuring point in the spatial entity finite element model under the shrinkage equivalent cooling mode were used as the theoretical strains of each strain measuring point and the theoretical displacements of each disturbance measuring point in the test model.

[0066] S4. Obtaining a measured shrinkage equivalent temperature drop coefficient based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model and the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point;

[0067] Based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model, the average measured strain of the root and mid-span of the two cantilevers is calculated respectively to obtain the average measured strain of the root of the first cantilever, the average measured strain of the mid-span of the first cantilever, the average measured strain of the root of the second cantilever and the average measured strain of the mid-span of the second cantilever in the test model; based on the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model, the average theoretical strain of the root and mid-span of the two cantilevers is calculated respectively to obtain the average theoretical strain of the root of the first cantilever, the average theoretical strain of the mid-span of the first cantilever, the average theoretical strain of the root of the second cantilever and the average theoretical strain of the mid-span of the second cantilever in the test model; the average measured strain of the root of the first cantilever, the average measured strain of the mid-span of the first cantilever, the average measured strain of the root of the second cantilever and the average theoretical strain of the mid-span of the second cantilever are calculated respectively. The average value of the measured strain at the root and the average value of the measured strain at the mid-span of the second cantilever are respectively ratioed with the average value of the theoretical strain at the root of the first cantilever, the average value of the theoretical strain at the mid-span of the first cantilever, the average value of the theoretical strain at the root of the second cantilever and the average value of the theoretical strain at the mid-span of the second cantilever to obtain the equivalent cooling coefficient of contraction at the root of the first cantilever, the equivalent cooling coefficient of contraction at the mid-span of the first cantilever, the equivalent cooling coefficient of contraction at the root of the second cantilever and the equivalent cooling coefficient of contraction at the mid-span of the second cantilever in the test model. The average value of the equivalent cooling coefficient of contraction at the root of the first cantilever, the equivalent cooling coefficient of contraction at the mid-span of the first cantilever, the equivalent cooling coefficient of contraction at the root of the second cantilever and the equivalent cooling coefficient of contraction at the mid-span of the second cantilever is taken as the measured equivalent cooling coefficient of contraction, and the measured equivalent cooling coefficient of contraction is used to generate a curve of the measured equivalent cooling coefficient of contraction as the time passes.

[0068] S5. Input the measured shrinkage equivalent temperature drop coefficient and the concrete shrinkage hyperbolic power function into the Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent temperature drop coefficient curve.

[0069] The measured shrinkage equivalent temperature cooling coefficient and the concrete shrinkage hyperbolic power function are input into the Origin model for fitting to obtain the parameters of the concrete shrinkage coefficient equation. The parameters of the concrete shrinkage coefficient equation are substituted into the concrete shrinkage hyperbolic power function to obtain the fitting value of the shrinkage equivalent temperature cooling coefficient. The fitting value of the shrinkage equivalent temperature cooling coefficient changes with time to generate a fitted shrinkage equivalent temperature cooling coefficient curve.

[0070] The formula for the hyperbolic power function of concrete shrinkage is:

[0071]

[0072] Among them, ε cs (t) is the concrete shrinkage coefficient at a certain time t, A and B are parameters of the concrete shrinkage coefficient equation, and t is time.

[0073] The Origin model is a scientific drawing and data analysis software developed by OriginLab. It has functions such as statistics, signal processing, curve fitting and peak analysis, and has powerful data import and various graphic output formats.

[0074] The measured strains at each strain measuring point and the measured displacements at each disturbance measuring point of a full-scale test model of a double-cantilever structure under natural environmental conditions were analyzed. Finite element analysis of the test model was performed under multiple cooling modes using the ANSYS finite element model to obtain the theoretical strains at each strain measuring point and the theoretical displacements at each disturbance measuring point in the test model. The measured shrinkage equivalent cooling coefficient was obtained based on the measured strains at each strain measuring point and the measured displacements at each disturbance measuring point in the test model and the theoretical strains at each strain measuring point and the theoretical displacements at each disturbance measuring point. The measured shrinkage equivalent cooling coefficient and the concrete shrinkage hyperbolic power function were input into the Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent cooling coefficient curve. This improves the validity and accuracy of the concrete shrinkage coefficient equation parameters of steel-concrete composite bridge decks, thereby improving the safety and durability of bridges.

[0075] Example 2

[0076] A specific embodiment of a method for testing shrinkage parameters of steel-concrete composite bridge deck concrete includes the following steps:

[0077] S1. Make a scaled test model based on a steel-concrete composite bridge deck;

[0078] The spacing between the stiffening ribs in some parts of a steel-concrete composite bridge deck is 40 cm. The two stiffening ribs and the range 20 cm outward from the stiffening ribs on both sides are selected. The pedestal width is designed to be 80 cm, the pedestal height is 86 cm, the cantilever length on both sides of the pedestal is 240 cm, the total length of the test model is 560 cm, and it is a steel-concrete composite bridge deck with double PBL plates.

[0079] Two identical test models, the C40 and C50, were cast using C40 and C50 steel fiber concrete, respectively. C40 steel fiber concrete is a composite material composed of a certain amount of short, fine steel fibers mixed into ordinary concrete, with a standard compressive strength of 40 MPa. C50 steel fiber concrete is a novel multiphase composite material composed of randomly distributed short steel fibers mixed into ordinary concrete, with a standard compressive strength of 50 MPa. The C40 and C50 test models were placed outdoors on site, the concrete surface covered with plastic sheeting, and watered for curing. After being removed from the formwork, waterproof paint was applied to the sides of the C40 and C50 test models, respectively, to prevent water loss and shrinkage, simulating the continuity of the sides of the C40 and C50 test models.

[0080] The root section and mid-span section were selected from the steel bridge deck 3 and the concrete surface in the cantilever of the C40 test model and the C50 test model, respectively. Three measuring points were set on each section, that is, one strain measuring point was set at the left and right symmetrical positions of each section, and one strain measuring point was set at the center of each section. The root section was selected on the ordinary steel bar, and two strain measuring points were set on each section, that is, one strain measuring point was set at the left and right symmetrical positions of each section. The cantilever end section and mid-span section were selected from the cantilever of the steel-concrete composite bridge deck, and one deflection measuring point was set on each section.

[0081] S2, real-time acquisition of the measured strain force at each strain force measurement point and the measured displacement at each disturbance measurement point in the test model;

[0082] Three days after the casting of the C40 test model and the C50 test model, the measured strain at each strain measurement point and the measured displacement at each disturbance measurement point in the C40 test model and the C50 test model were collected in real time through the data collection system, and monitored regularly every day for more than 180 days.

[0083] S3. Perform finite element analysis on the test model under various cooling modes using the ANSYS finite element model to obtain the theoretical strain and displacement of each strain measurement point in the test model;

[0084] Based on the C40 test model and the C50 test model, the C40 spatial solid finite element model and the C50 spatial solid finite element model were constructed respectively by ANSYS finite element model. The C40 spatial solid finite element model and the C50 spatial solid finite element model were subjected to finite element analysis in the concrete overall uniform cooling mode of 10℃, the concrete inverted triangle cooling mode of 10℃ and the concrete trapezoidal cooling mode of 10℃, respectively. The simulated strain force of each strain measurement point and the simulated displacement of each disturbance measurement point of the C40 spatial solid finite element model and the C50 spatial solid finite element model under each cooling mode were obtained; the measured strain force of each strain measurement point and the measured displacement of each disturbance measurement point in the C40 test model and the C50 test model were compared with the C40 spatial solid finite element model. The simulated strain force of each strain measurement point and the simulated displacement of each disturbance measurement point of the C40 test model and C50 test model under each cooling mode were compared to obtain the shrinkage equivalent cooling modes of the C40 space solid finite element model and the C50 space solid finite element model respectively; the simulated strain force of each strain measurement point and the simulated displacement of each disturbance measurement point of the C40 space solid finite element model and the C50 space solid finite element model under the shrinkage equivalent cooling mode were used as the theoretical strain force of each strain measurement point and the theoretical displacement of each disturbance measurement point in the C40 test model and the C50 test model respectively.

[0085] S4. Based on the measured strain force of each strain force measuring point and the measured displacement of each disturbance measuring point in the test model, the measured shrinkage equivalent temperature reduction coefficient is obtained by comparing them with the theoretical strain force of each strain force measuring point and the theoretical displacement of each disturbance measuring point.

[0086] Based on the measured strain of each strain measurement point and the measured displacement of each disturbance measurement point in the C40 test model and the C50 test model, the average measured strain of the root of the first cantilever, the average measured strain of the mid-span of the first cantilever, the average measured strain of the root of the second cantilever and the average measured strain of the mid-span of the second cantilever in the C40 test model and the C50 test model are obtained respectively. According to the theoretical strain of each strain measurement point and the theoretical displacement of each disturbance measurement point in the C40 test model and the C50 test model, the average theoretical strain of the root of the first cantilever, the average theoretical strain of the mid-span of the first cantilever, the average theoretical strain of the root of the second cantilever and the average theoretical strain of the mid-span of the second cantilever in the C40 test model and the C50 test model are obtained respectively. The average measured strain of the root of the first cantilever, the average measured strain of the mid-span of the first cantilever, the average measured strain of the root of the second cantilever and the average measured strain of the mid-span of the second cantilever in the C40 test model and the C50 test model are respectively compared with the average measured strain of the root of the first cantilever The average theoretical strain of the first cantilever, the average theoretical strain of the mid-span of the first cantilever, the average theoretical strain of the root of the second cantilever and the average theoretical strain of the mid-span of the second cantilever will be ratio-calculated to obtain the equivalent temperature drop coefficient of the first cantilever root, the equivalent temperature drop coefficient of the first cantilever mid-span, the equivalent temperature drop coefficient of the second cantilever root and the equivalent temperature drop coefficient of the second cantilever mid-span in the C40 test model, namely, the C40 equivalent temperature drop coefficient; the equivalent temperature drop coefficient of the first cantilever root, the equivalent temperature drop coefficient of the first cantilever mid-span, the equivalent temperature drop coefficient of the second cantilever root and the equivalent temperature drop coefficient of the second cantilever mid-span in the C50 test model, namely, the C50 equivalent temperature drop coefficient, as shown in Tables 1 and 2, where 1-root is the equivalent temperature drop coefficient of the first cantilever root, 1-midspan is the equivalent temperature drop coefficient of the first cantilever mid-span, 2-root is the equivalent temperature drop coefficient of the second cantilever root and 2-midspan is the equivalent temperature drop coefficient of the second cantilever mid-span:

[0087] Table 1C40 shrinkage equivalent temperature reduction coefficient

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] Table 2C50 shrinkage equivalent temperature reduction coefficient

[0094]

[0095]

[0096]

[0097]

[0098] The average values ​​of the shrinkage equivalent cooling coefficient at the root of the first cantilever, the shrinkage equivalent cooling coefficient at the mid-span of the first cantilever, the shrinkage equivalent cooling coefficient at the root of the second cantilever, and the shrinkage equivalent cooling coefficient at the mid-span of the second cantilever in the C40 test model and the average values ​​of the shrinkage equivalent cooling coefficient at the root of the first cantilever, the shrinkage equivalent cooling coefficient at the mid-span of the first cantilever, the shrinkage equivalent cooling coefficient at the root of the second cantilever, and the shrinkage equivalent cooling coefficient at the mid-span of the second cantilever in the C50 test model are respectively used as the measured shrinkage equivalent cooling coefficient of C40 and the measured shrinkage equivalent cooling coefficient of C50. The measured shrinkage equivalent cooling coefficient of C40 and the measured shrinkage equivalent cooling coefficient of C50 change with time to generate the measured shrinkage equivalent cooling coefficient curve of C40 and the measured shrinkage equivalent cooling coefficient curve of C50, as shown in FIG. Figure 4 and Figure 5 shown.

[0099] S5. Input the measured shrinkage equivalent temperature drop coefficient and the concrete shrinkage hyperbolic power function into the Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent temperature drop coefficient curve.

[0100] The C40 measured shrinkage equivalent cooling coefficient, the C50 measured shrinkage equivalent cooling coefficient and the concrete shrinkage hyperbolic power function were input into the Origin model to fit the C40 concrete shrinkage coefficient equation parameters and the C50 concrete shrinkage coefficient equation parameters, as shown in Tables 3 and 4.

[0101] Table 3 Parameters of the C40 concrete shrinkage coefficient equation

[0102]

[0103] Table 4 Parameters of C50 concrete shrinkage coefficient equation

[0104]

[0105] Substitute the parameters of the C40 concrete shrinkage coefficient equation into the concrete shrinkage hyperbolic power function to obtain the C40 shrinkage equivalent cooling coefficient fitting value. The C40 shrinkage equivalent cooling coefficient fitting value changes with time to generate the C40 fitting shrinkage equivalent cooling coefficient curve, as shown in Figure 4 As shown, the expression of C40 fitting shrinkage equivalent temperature reduction coefficient curve is:

[0106]

[0107] Substitute the parameters of the C50 concrete shrinkage coefficient equation into the concrete shrinkage hyperbolic power function to obtain the C50 shrinkage equivalent cooling coefficient fitting value. The C50 shrinkage equivalent cooling coefficient fitting value changes with time to generate the C50 fitting shrinkage equivalent cooling coefficient curve, as shown in Figure 5 As shown, the expression of C50 fitting shrinkage equivalent temperature reduction coefficient curve is:

[0108]

[0109] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for testing shrinkage parameters of steel-concrete composite bridge deck concrete, characterized in that: The following steps are involved: S1. Make a scaled 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 measurement point and the measured displacement at each disturbance measurement point in the test model; S3. Perform finite element analysis on the test model under various cooling modes using the ANSYS finite element model to obtain the theoretical strain of each strain measurement point and the theoretical displacement of each disturbance measurement point in the test model; S4. Obtaining a measured shrinkage equivalent temperature drop coefficient based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model and the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point; S5. Input the measured shrinkage equivalent temperature drop coefficient and the concrete shrinkage hyperbolic power function into the Origin model for fitting to obtain the concrete shrinkage coefficient equation parameters and the fitted shrinkage equivalent temperature drop coefficient curve.

2. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that: The test model includes: a pedestal and two cantilevers, the two cantilevers are symmetrically arranged on both sides of the pedestal to form a double cantilever, the pedestal includes multiple steel bars and pedestal concrete, the double cantilever includes a double cantilever steel structure and concrete, the double cantilever steel structure includes a steel bridge deck, two side-by-side longitudinal ribs and multiple ordinary steel bars, the longitudinal ribs are arranged on the steel bridge deck, and the ordinary steel bars pass through the longitudinal ribs.

3. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 2, characterized in that: The method of making a proportional test model comprises: Installing a formwork for the test model, and pouring pedestal concrete onto a plurality of steel bars of the pedestal in the formwork to form a pedestal; The double-cantilever steel structure is placed on a pedestal and concrete is poured into the double-cantilever steel structure to form a test model.

4. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 3, characterized in that: The method of making the test model of equal proportion comprises: after the test model is separated from the template, painting the two end surfaces of the test model.

5. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 2, characterized in that: The method of making a proportional test model comprises: Multiple strain measurement points are set up on the root section and mid-span section of the steel bridge deck and concrete surface; Set up multiple strain measurement points on the root section of ordinary steel bars; A deflection measuring point is set on the end section and mid-span section of the cantilever respectively.

6. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that: The measured strain force of each strain force measuring point is collected in real time by multiple resistance strain gauges of the data collection system, and the measured displacement of each disturbance measuring point is collected in real time by multiple electromechanical dial indicators.

7. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 2, characterized in that: Step S3 includes: Based on the test model, a spatial solid finite element model is constructed using the ANSYS finite element model; Finite element analysis was performed on the spatial entity finite element model under various cooling modes to obtain the simulated strain force at each strain force measurement point and the simulated displacement at each disturbance measurement point of the spatial entity finite element model under various cooling modes. The measured strains at each strain measurement point and the measured displacements at each disturbance measurement point in the collected test model are compared with the simulated strains at each strain measurement point and the simulated displacements at each disturbance measurement point in the spatial solid finite element model under various cooling modes. The cooling mode with the smallest difference between the simulated strains at each strain measurement point and the simulated displacements at each disturbance measurement point in the spatial solid finite element model and the measured strains at each strain measurement point and the measured displacements at each disturbance measurement point in the test model is selected as the shrinkage equivalent cooling mode. The simulated strain of each strain measuring point and the simulated displacement of each disturbance measuring point in the spatial solid finite element model under the shrinkage equivalent cooling mode are used as the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model.

8. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 2, characterized in that: The multiple cooling modes include: a concrete overall uniform cooling mode of 10°C, a concrete inverted triangle cooling mode of 10°C, and a concrete trapezoidal cooling mode of 10°C.

9. The method for testing shrinkage parameters of steel-concrete composite bridge deck concrete according to claim 1, characterized in that: Step S4 includes: Based on the measured strain of each strain measuring point and the measured displacement of each disturbance measuring point in the test model, 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 are obtained; According to the theoretical strain of each strain measuring point and the theoretical displacement of each disturbance measuring point in the test model, the theoretical strain average value of the first cantilever root, the theoretical strain average value of the first cantilever mid-span, the theoretical strain average value of the second cantilever root and the theoretical strain average value of the second cantilever mid-span in the test model are obtained; 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 are respectively calculated 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 to obtain the equivalent cooling coefficient of contraction of the root of the first cantilever, the equivalent cooling coefficient of contraction of the mid-span of the first cantilever, the equivalent cooling coefficient of contraction of the root of the second cantilever and the equivalent cooling coefficient of contraction of the mid-span of the second cantilever in the test model; The average value of the shrinkage equivalent temperature cooling coefficient at the root of the first cantilever, the shrinkage equivalent temperature cooling coefficient at the mid-span of the first cantilever, the shrinkage equivalent temperature cooling coefficient at the root of the second cantilever, and the shrinkage equivalent temperature cooling coefficient at the mid-span of the second cantilever is taken as the measured shrinkage equivalent temperature cooling coefficient.

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

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