Concrete creep test method considering severe plateau environment

Abstract

The invention discloses a concrete creep test method considering a plateau severe environment, which comprises the following steps: preparing a concrete member in the plateau severe environment, and embedding and installing test equipment; pre-stress is applied to the concrete member in a grading mode, and the load value of the applied pre-stress is calculated according to the number of the steel strands installed in the test piece and the area of the single steel strand; acquiring stress parameter change data of the concrete creep model by adopting an automatic acquisition device; a climate testing device is installed in the severe plateau environment to test meteorological parameters such as wind speed, temperature, humidity, ultraviolet coefficient, altitude and oxygen content; the structural stress and meteorological parameters are applied to the analysis model, and the concrete creep performance considering the severe plateau environment is obtained. According to the method, the creep performance of the concrete in the severe plateau environment can be obtained, and technical support is provided for obtaining the creep characteristics of the prestressed concrete structure.

Description

Technical Field

[0001] The invention relates to the field of material testing, and in particular to a concrete creep testing method taking into account the harsh plateau environment. Background Art

[0002] In the natural environment, when concrete is subjected to external pressure, due to its own material structural characteristics, the strain and deformation will increase under the condition of constant stress, which is called creep. Concrete material itself has the characteristics of high compressive strength and poor tensile performance, which makes it easy to have structural cracks during the stress process of the structure, thereby reducing the service life of the structure. In existing concrete structures, it is necessary to apply prestress to improve the stress performance and crack resistance of the concrete structure.

[0003] Concrete structures will produce significant creep under the action of prestressing. The creep of concrete has an important influence on its structural stress and deformation, and is an important factor affecting prestressed concrete structures. As the scope of infrastructure construction in my country gradually expands, the application scope of prestressed concrete structures is also gradually increasing. The creep performance of concrete in the harsh environment of the plateau remains to be studied.

[0004] There is a need for a concrete creep performance testing method that can take into account the harsh environment of the plateau. The method can be used to test the creep performance of concrete in the harsh environment of the plateau, analyze the mechanical properties of concrete in the harsh environment of the plateau, and provide support for the design and application of prestressed concrete structures in this environment. Summary of the invention

[0005] The present invention aims to solve the problem that concrete structures in the prior art will produce significant creep phenomenon under the action of prestressing. The creep of concrete has an important influence on the stress and deformation of its structure and is an important factor affecting prestressed concrete structures. As the scope of infrastructure construction in my country gradually increases, the application scope of prestressed concrete structures also gradually increases. The creep performance of concrete in the harsh environment of the plateau is still a problem to be studied. A concrete creep test method taking into account the harsh environment of the plateau is provided to solve the above problem.

[0006] The present invention provides a concrete creep test method considering the harsh plateau environment, comprising the following steps:

[0007] S1. Prepare concrete components in the harsh plateau environment and install test equipment inside;

[0008] S2. Prestress concrete components in stages. The prestress load value is calculated based on the number of steel strands installed in the specimen and the area of ​​a single steel strand. The calculation formula is as follows:

[0009] F p =f p ×np ×A p ;

[0010] where f p is the stress value applied to the steel strand, n p is the number of steel strands in the model, A p is the cross-sectional area of ​​a single steel strand;

[0011] S3, using an automatic data collection device to obtain the stress parameter change data of the concrete creep model;

[0012] S4. Install climate testing equipment in the harsh environment of the plateau to test meteorological parameters such as wind speed, temperature, humidity, UV coefficient, altitude, and oxygen content;

[0013] S5. Apply structural forces and meteorological parameters to the analysis model to obtain the creep performance of concrete considering the harsh plateau environment.

[0014] The present invention discloses a concrete creep test method taking into account the harsh plateau environment. As a preferred embodiment, the concrete component includes a specimen concrete block, a steel strand, a pair of anchor plates, a pair of spiral bars, a plurality of stirrups, four longitudinal bars, four steel chord strain gauges and a pressure sensor. The specimen concrete block is a rectangular cross-section column. The steel strand axially penetrates the specimen concrete block and is anchored at both ends of the specimen concrete block by anchor plates and spiral bars. Stirrups are arranged in parallel along the vertical axis in the specimen concrete block. The steel strand passes through the inner hole of the stirrups. The stirrups are rectangular frames. The shapes and sizes of the stirrups are equal and the edges are parallel to the edges of the specimen concrete block. The axial projections of the stirrups coincide with each other. The longitudinal bars are arranged on the inner sides of the four corners of the stirrups and buried in the specimen concrete block. The steel chord strain gauges are arranged in the axial middle of the specimen concrete block and are equidistant from the two nearest longitudinal bars. The pressure sensor is arranged at one end of the specimen concrete block.

[0015] The concrete creep test method considering the harsh plateau environment described in the present invention is, as a preferred embodiment, step S1 specifically comprises:

[0016] S11. Apply release oil on the inner surface of the model steel mold;

[0017] S12, judging whether it is necessary to consider ordinary steel bars, if yes, tying the steel cage and placing it in the steel mold and then proceeding to step S13, otherwise proceeding to step S13;

[0018] S13. Install anchor plates and spiral reinforcement at the model end;

[0019] S14. Install a concrete strain test device in the mid-span area of ​​the model;

[0020] S15, pouring concrete in the formwork and curing the concrete;

[0021] S16. Complete the preparation of concrete components.

[0022] The concrete creep test method considering the harsh plateau environment described in the present invention is, as a preferred embodiment, step S2 specifically comprises:

[0023] S21. Install a steel strand force measuring device at the end of the member;

[0024] S22, the anchoring system is installed at the end of the component, one end of which is the fixed end and the other end is the tensioning end of the steel strand;

[0025] S23. The steel strands are tensioned by graded tension loading. The model components are subjected to compressive stress. The stress magnitude is based on the load value borne by the measured prestressed structure and is recommended to be less than 50% of the concrete strength grade.

[0026] The concrete creep test method considering the harsh plateau environment described in the present invention is, as a preferred embodiment, an analysis model includes a judgment module and a parameter analysis module, the parameter analysis module receives the judgment result in the judgment module, and performs data analysis based on the environmental parameters corresponding to the judgment result as environmental conditions;

[0027] The judgment module is used to judge whether the current environmental conditions are suitable for the harsh plateau environment. The judgment principle is to judge whether the temperature difference between day and night exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the annual solar radiation exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the maximum score and the maximum humidity exceed the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it is judged as a non-harsh plateau environment.

[0028] The analysis module is used for the correspondence analysis between concrete creep performance and environmental parameters in the harsh plateau environment. The specific analysis of concrete creep performance is as follows:

[0029] Based on the cross-sectional dimensions of concrete and steel pipe components, the mid-span section is used as the analysis section;

[0030] According to the steel strand load of the check section, the concrete stress of the check section is calculated by the following formula;

[0031] σ c =F P / A c

[0032] Among them, σc is the initial stress of concrete; Fp is the load of steel strand; Ac is the cross-sectional area of ​​concrete member;

[0033] According to the steel strand load of the check section, the stress of the steel pipe of the check section is calculated by the following formula;

[0034] σ s =FP / A s

[0035] Among them, σs is the initial stress of the steel pipe; Fp is the load of the steel strand; As is the cross-sectional area of ​​the steel pipe component;

[0036] After a certain time T, and after plateau environmental testing and judgment, the concrete stress value σcT(f) under the harsh plateau environment is obtained;

[0037] After a certain time T, and after plateau environmental testing and judgment, the stress value σsT(f) of the steel pipe under the harsh plateau environment is obtained;

[0038] After a certain time T, considering the harsh environment of the plateau and removing the relaxation effect of the steel strand, the creep performance of concrete εc is obtained by the following formula:

[0039] εc=(σcT(f)-σc-σsT(f)*As / Ac) / Ec

[0040] Where Ec is the elastic modulus of concrete.

[0041] The present invention discloses a concrete creep test method that takes into account the harsh plateau environment. As a preferred method, the analysis module establishes a corresponding numerical matrix of environmental parameters and concrete creep performance based on historical data, generates a corresponding relationship between theoretical concrete creep performance and environmental parameters based on the numerical matrix, forms a relationship point cloud between environmental parameters and concrete creep performance based on the historical corresponding relationship, performs linear regression based on the relationship point cloud to obtain a predicted value of the corresponding relationship between theoretical concrete creep performance and environmental parameters, wherein the environmental parameters use ambient temperature, humidity, wind speed, and ultraviolet coefficient as relationship values ​​to obtain a corresponding theoretical predicted concrete elastic modulus, and the analysis module obtains the concrete elastic modulus based on the actual plateau environment test and judgment values, and changes the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus to the regression curve of the actual environmental parameters and the actual concrete elastic modulus, and uses its change equation as a change equation for other environmental influencing factors to adjust the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus to derive the theoretical concrete elastic modulus value.

[0042] The beneficial effects of the present invention are as follows:

[0043] This technical solution is aimed at testing the creep performance of concrete in harsh plateau environments, taking into account the impact of environmental factors on physical properties. A mathematical relationship model is established between ambient temperature, humidity, wind speed, UV coefficient and concrete creep performance in harsh plateau environments to achieve the detection of the physical properties of concrete creep performance. At the same time, the theoretical data and actual test values ​​are associated to avoid data distortion caused by the large number of small influencing factors stacking. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of a concrete creep test method considering the harsh plateau environment;

[0045] Figure 2 A schematic diagram of a concrete component showing a concrete creep test method considering the harsh plateau environment;

[0046] Figure 3 Schematic diagram of a thick-walled steel pipe component using a concrete creep test method that takes into account the harsh plateau environment. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] Example 1

[0049] like Figure 1 As shown, a concrete creep test method considering the harsh plateau environment includes the following steps:

[0050] S1. Prepare concrete components in the harsh plateau environment and install test equipment inside;

[0051] S2. Prestress concrete components in stages. The prestress load value is calculated based on the number of steel strands installed in the specimen and the area of ​​a single steel strand. The calculation formula is as follows:

[0052] F p =f p ×n p ×A p ;

[0053] where f p is the stress value applied to the steel strand, n p is the number of steel strands in the model, A p is the cross-sectional area of ​​a single steel strand;

[0054] S3, using an automatic data collection device to obtain the stress parameter change data of the concrete creep model;

[0055] S4. Install climate testing equipment in the harsh environment of the plateau to test meteorological parameters such as wind speed, temperature, humidity, UV coefficient, altitude, and oxygen content;

[0056] S5. Apply structural forces and meteorological parameters to the analysis model to obtain the creep performance of concrete considering the harsh plateau environment.

[0057] like Figure 2As shown, the concrete component includes a specimen concrete block, a steel strand, a pair of anchor plates, a pair of spiral bars, a number of stirrups, four longitudinal bars, four steel string strain gauges and a pressure sensor. The specimen concrete block is a rectangular cross-section column. The steel strand runs through the specimen concrete block along the axial direction and is anchored at both ends of the specimen concrete block through the anchor plates and spiral bars. Stirrups are arranged parallel to the vertical axis in the specimen concrete block. The steel strand passes through the inner hole of the stirrup. The stirrup is a rectangular frame. The shapes and sizes of the stirrups are equal and the side lines are parallel to the side lines of the specimen concrete block. The axial projections of the stirrups coincide with each other. The longitudinal bars are arranged on the inner sides of the four corners of the stirrups and buried in the specimen concrete block. The steel string strain gauge is arranged in the axial middle of the specimen concrete block and is equidistant from the two nearest longitudinal bars. The pressure sensor is arranged at one end of the specimen concrete block.

[0058] Step S1 specifically includes:

[0059] S11. Apply release oil on the inner surface of the model steel mold;

[0060] S12, judging whether it is necessary to consider ordinary steel bars, if yes, tying the steel cage and placing it in the steel mold and then proceeding to step S13, otherwise proceeding to step S13;

[0061] S13. Install anchor plates and spiral reinforcement at the model end;

[0062] S14. Install a concrete strain test device in the mid-span area of ​​the model;

[0063] S15, pouring concrete in the formwork and curing the concrete;

[0064] S16. Complete the preparation of concrete components.

[0065] Step S2 specifically includes:

[0066] S21. Install a steel strand force measuring device at the end of the member;

[0067] S22, the anchoring system is installed at the end of the component, one end of which is the fixed end and the other end is the tensioning end of the steel strand;

[0068] S23. The steel strands are tensioned by graded tension loading. The model components are subjected to compressive stress. The stress magnitude is based on the load value borne by the measured prestressed structure and is recommended to be less than 50% of the concrete strength grade.

[0069] The analysis model includes a judgment module and a parameter analysis module. The parameter analysis module receives the judgment result in the judgment module and performs data analysis based on the environmental parameters corresponding to the judgment result as environmental conditions.

[0070] The judgment module is used to judge whether the current environmental conditions are suitable for the harsh plateau environment. The judgment principle is to judge whether the temperature difference between day and night exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the annual solar radiation exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the maximum score and the maximum humidity exceed the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it is judged as a non-harsh plateau environment.

[0071] The analysis module is used for the correspondence analysis between concrete creep performance and environmental parameters in the harsh plateau environment. The specific analysis of concrete creep performance is as follows:

[0072] Based on the cross-sectional dimensions of concrete and steel pipe components, the mid-span section is used as the analysis section;

[0073] According to the steel strand load of the check section, the concrete stress of the check section is calculated by the following formula;

[0074] σ c =F P / A c

[0075] Among them, σc is the initial stress of concrete; Fp is the load of steel strand; Ac is the cross-sectional area of ​​concrete member;

[0076] According to the steel strand load of the check section, the stress of the steel pipe of the check section is calculated by the following formula;

[0077] σ s =F P / A s

[0078] Among them, σs is the initial stress of the steel pipe; Fp is the load of the steel strand; As is the cross-sectional area of ​​the steel pipe component;

[0079] After a certain time T, and after plateau environmental testing and judgment, the concrete stress value σcT(f) under the harsh plateau environment is obtained;

[0080] After a certain time T, and after plateau environmental testing and judgment, the stress value σsT(f) of the steel pipe under the harsh plateau environment is obtained;

[0081] After a certain time T, considering the harsh environment of the plateau and removing the relaxation effect of the steel strand, the creep performance of concrete εc is obtained by the following formula:

[0082] εc=(σcT(f)-σc-σsT(f)*As / Ac) / Ec

[0083] Where Ec is the elastic modulus of concrete.

[0084] On the basis of the above technical features, in further use, optionally, the analysis module establishes a corresponding numerical matrix of environmental parameters and concrete creep performance based on historical data, and generates a corresponding relationship between theoretical concrete creep performance and environmental parameters based on the numerical matrix, and forms a relationship point cloud between environmental parameters and concrete creep performance based on the historical corresponding relationship, and performs linear regression based on the relationship point cloud to obtain the predicted numerical value of the corresponding relationship between theoretical concrete creep performance and environmental parameters, wherein the environmental parameters use ambient temperature, humidity, wind speed, and ultraviolet coefficient as relationship numerical values ​​to obtain the corresponding theoretical predicted concrete elastic modulus, the analysis module obtains the concrete elastic modulus based on the actual plateau environment test and judgment values, and changes the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus to the regression curve of the actual environmental parameters and the actual concrete elastic modulus, and uses its change equation as the change equation of other environmental influencing factors to adjust the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus to derive the theoretical concrete elastic modulus value.

[0085] Example 2

[0086] On the basis of Example 1, this example also performs a prestress loss test of thick-walled steel pipes in the process of using an automatic acquisition device to obtain the stress parameter change data of the concrete creep model.

[0087] like Figure 3 As shown in the figure, thick-walled steel pipe components are set in the same harsh plateau environment, and the number, stress and cross-section of steel strands are consistent with the parameters of steel strands in prestressed concrete structures. The prestress loss of steel strands caused by stress relaxation of steel strands is tested in the same harsh plateau environment.

[0088] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A concrete creep performance testing method considering the harsh plateau environment, characterized by: The following steps are involved: S1. Prepare concrete components in the harsh plateau environment and install test equipment inside; S2. Prestress concrete components in stages. The prestress load value is calculated based on the number of steel strands installed in the specimen and the area of ​​a single steel strand. The calculation formula is as follows: F p =f p ×n p ×A p ; where f p is the stress value applied to the steel strand, n p is the number of steel strands in the model, A p is the cross-sectional area of ​​a single steel strand; S3, using an automatic data collection device to obtain the stress parameter change data of the concrete creep model; S4. Install climate testing equipment in the harsh environment of the plateau to test meteorological parameters such as wind speed, temperature, humidity, UV coefficient, altitude, and oxygen content; S5. Apply structural forces and meteorological parameters to the analysis model to obtain the creep performance of concrete considering the harsh plateau environment.

2. A concrete creep test method considering the harsh plateau environment according to claim 1, characterized in that: The concrete component includes a specimen concrete block, a steel strand, a pair of anchor plates, a pair of spiral bars, a number of stirrups, four longitudinal bars, four steel chord strain gauges and a pressure sensor. The specimen concrete block is a rectangular cross-section column. The steel strand axially penetrates the specimen concrete block and is anchored at both ends of the specimen concrete block through the anchor plates and the spiral bars. The stirrups are arranged parallel to the vertical axis in the specimen concrete block. The steel strand passes through the inner hole of the stirrups. The stirrups are rectangular frames. The shapes and sizes of the stirrups are equal and the edges are parallel to the edges of the specimen concrete block. The axial projections of the stirrups coincide with each other. The longitudinal bars are arranged on the inner sides of the four corners of the stirrups and buried in the specimen concrete block. The steel chord strain gauge is arranged in the axial middle of the specimen concrete block and is equidistant from the two nearest longitudinal bars. The pressure sensor is arranged at one end of the specimen concrete block.

3. A concrete creep test method considering the harsh plateau environment according to claim 2, characterized in that: The step S1 specifically comprises: S11. Apply release oil on the inner surface of the model steel mold; S12, judging whether it is necessary to consider ordinary steel bars, if yes, tying the steel cage and placing it in the steel mold and then proceeding to step S13, otherwise proceeding to step S13; S13. Install anchor plates and spiral reinforcement at the model end; S14. Install a concrete strain test device in the mid-span area of ​​the model; S15, pouring concrete in the formwork and curing the concrete; S16, completing the preparation of the concrete component.

4. A concrete creep test method considering the harsh plateau environment according to claim 2, characterized in that: The step S2 specifically comprises: S21. Install a steel strand force measuring device at the end of the member; S22, the anchoring system is installed at the end of the component, one end of which is the fixed end and the other end is the tensioning end of the steel strand; S23. The steel strands are tensioned by graded tension loading. The model components are subjected to compressive stress. The stress magnitude is based on the load value borne by the measured prestressed structure and is recommended to be less than 50% of the concrete strength grade.

5. The concrete creep test method considering the harsh plateau environment according to claim 1 is characterized by: The analysis model includes a judgment module and a parameter analysis module, wherein the parameter analysis module receives the judgment result in the judgment module and performs data analysis based on the environmental parameters corresponding to the judgment result as environmental conditions; The judgment module is used to judge whether the current environmental conditions are suitable for the harsh plateau environment. The judgment principle is to judge whether the temperature difference between day and night exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the annual solar radiation exceeds the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it continues to judge whether the maximum score and the maximum humidity exceed the threshold. If so, it is judged as a harsh plateau environment. Otherwise, it is judged as a non-harsh plateau environment. The analysis module is used for the correspondence analysis between the creep performance of concrete and environmental parameters in the harsh plateau environment, wherein the specific analysis of the creep performance of concrete is as follows: Based on the cross-sectional dimensions of concrete and steel pipe components, the mid-span section is used as the analysis section; According to the steel strand load of the check section, the concrete stress of the check section is calculated by the following formula; s c =F P / A c Among them, σc is the initial stress of concrete; Fp is the load of steel strand; Ac is the cross-sectional area of ​​concrete member; According to the steel strand load of the check section, the stress of the steel pipe of the check section is calculated by the following formula; s s =F P / A s Among them, σs is the initial stress of the steel pipe; Fp is the load of the steel strand; As is the cross-sectional area of ​​the steel pipe component; After a certain time T, and after plateau environmental testing and judgment, the concrete stress value σcT(f) under the harsh plateau environment is obtained; After a certain time T, and after plateau environmental testing and judgment, the stress value σsT(f) of the steel pipe under the harsh plateau environment is obtained; After a certain time T, considering the harsh environment of the plateau and removing the relaxation effect of the steel strand, the creep performance of concrete εc is obtained by the following formula: εc=(σcT(f)-σc-σsT(f)*As / Ac) / Ec Where Ec is the elastic modulus of concrete.

6. The concrete creep test method considering the harsh plateau environment according to claim 1 is characterized by: The analysis module establishes a corresponding numerical matrix of environmental parameters and concrete creep performance based on historical data, generates a corresponding relationship between theoretical concrete creep performance and environmental parameters based on the numerical matrix, forms a relationship point cloud between environmental parameters and concrete creep performance based on the historical corresponding relationship, performs linear regression based on the relationship point cloud to obtain a predicted value of the corresponding relationship between theoretical concrete creep performance and environmental parameters, wherein the environmental parameters use ambient temperature, humidity, wind speed, and ultraviolet coefficient as relationship values ​​to obtain a corresponding theoretical predicted concrete elastic modulus, the analysis module obtains the concrete elastic modulus based on actual plateau environmental tests and judgment values, and changes the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus to the regression curve of the actual environmental parameters and the actual concrete elastic modulus, uses its change equation as a change equation for other environmental influencing factors, adjusts the regression curve of the theoretical environmental parameters and the theoretical concrete elastic modulus, and derives the theoretical concrete elastic modulus value.

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