Method for determining the bond strength of high-temperature after steel-reinforced concrete

Abstract

The application provides a method for determining the bonding strength of steel bar-concrete after high temperature, comprising: obtaining the mechanical parameters of concrete after high temperature, which include the elastic modulus, tensile strength and ultimate tensile strain of concrete after high temperature; determining the three-section tensile constitutive model of concrete after high temperature according to the mechanical parameters of concrete after high temperature; solving the radius of the concrete cracking area corresponding to the maximum radial stress based on the three-section tensile constitutive model according to the thick-walled cylinder model and the dispersion crack assumption; obtaining the maximum radial stress of the concrete cover on the steel bar after high temperature according to the radius of the concrete cracking area corresponding to the maximum radial stress; and determining the bonding strength of steel bar-concrete after high temperature according to the relationship between the bonding strength of steel bar-concrete and the maximum radial stress. The application can effectively simulate the bonding strength of steel bar-concrete after high temperature, and the prediction result is accurate and practical.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reinforced concrete bond strength calculation method, in particular to a method for determining the bond strength of reinforced concrete after high temperature. BACKGROUND

[0002] Fire is one of the most frequent disasters of building structures during their service period. A large number of engineering cases show that the reinforced concrete structure can still retain a certain residual bearing capacity after fire and can continue to be put into use under reasonable design conditions, thereby avoiding economic and resource waste. Studies have shown that after being subjected to high temperature within 500℃, the mechanical properties of steel bars can be partially restored, however, the interfacial bond performance of reinforced concrete will be significantly deteriorated, which seriously affects the cooperative force of steel bars and concrete. Under this background, how to consider the interfacial bond performance of reinforced concrete after high temperature has become a difficult problem in the current design of reinforced concrete structures after fire.

[0003] At present, the determination method of the bond strength of reinforced concrete at normal temperature has been systematically studied and a relatively mature design method has been formed. However, for the interfacial performance of reinforced concrete after high temperature, the existing researches are mostly based on interface pull-out tests, and the empirical expressions of the bond strength of reinforced concrete after high temperature are obtained through data fitting. Although these empirical formulas are simple in form, they are highly related to the test conditions, and the influence of the steel bar diameter, concrete strength and other design parameters cannot be considered, so their application in actual engineering is limited. SUMMARY

[0004] In view of the defects in the prior art, the purpose of the present application is to provide a method for determining the bond strength of reinforced concrete after high temperature.

[0005] According to one aspect of the present application, a method for determining the bond strength of reinforced concrete after high temperature is provided, which comprises:

[0006] obtaining the mechanical parameters of concrete after high temperature, wherein the mechanical parameters of concrete after high temperature include the elastic modulus, tensile strength and ultimate tensile strain of concrete after high temperature;

[0007] determining a three-section tensile constitutive model of concrete after high temperature according to the mechanical parameters of concrete after high temperature;

[0008] solving the radius of the concrete cracking area corresponding to the maximum radial stress according to the three-section tensile constitutive model based on the thick-walled cylinder model and the dispersion crack assumption;

[0009] solving the maximum radial stress of the concrete cover on the steel bar after high temperature according to the radius of the concrete cracking area corresponding to the maximum radial stress;

[0010] Based on the relationship between the bond strength of steel-concrete and the maximum radial stress, the bond strength of steel-concrete after high temperature is obtained.

[0011] Furthermore, the acquisition of the mechanical parameters of the concrete after high temperature includes:

[0012] The tensile elastic modulus E of concrete after high temperature t,T Compared with the tensile elastic modulus E of concrete at room temperature t,0 The relational expression is:

[0013]

[0014] Where T represents the maximum temperature experienced by the concrete; 20℃ <T≤800℃;

[0015] Concrete tensile strength f after high temperature t,T The tensile strength f of concrete at room temperature t,0 The relational expression is:

[0016]

[0017] Where T represents the maximum temperature experienced by the concrete; 20℃ <T≤800℃;

[0018] Ultimate tensile strain ε of concrete after high temperature ct,T The expression is:

[0019]

[0020] Furthermore, the determination of the three-segment tension constitutive model of the high-temperature concrete, wherein: the three-segment tension constitutive model of the high-temperature concrete is as follows:

[0021] σ t,T(r =E t,T ·ε t,T(r ;ε t,T(r ≤ε ct,T ;

[0022]

[0023]

[0024] Where, σ t,T (r) represents the circumferential stress of the concrete at radius r after high temperature, ε t,T (r) represents the circumferential strain of the concrete at radius r after high temperature, β is the softening coefficient of the concrete, and ε 1,T ε represents the tensile strain corresponding to the slope change point in the three-segment tensile constitutive model of concrete. u,T This represents the tensile strain at the point where the stress is 0 in the three-segment tensile constitutive model of concrete.

[0025] Further, the expression of ε 1,T and ε u,T are respectively:

[0026]

[0027]

[0028] wherein h c is the crack length characteristic value, G f,T is the post-high-temperature concrete fracture energy.

[0029] Further, the solving of the radius of the concrete cracking area corresponding to the maximum radial stress comprises:

[0030] According to the thick-walled cylinder model and the dispersion crack hypothesis, the concrete protective layer is divided into a cracked interior and an uncracked exterior, and the radius R i,T of the concrete cracking area corresponding to the maximum radial stress is calculated. cr The calculation equation of R i,T is:

[0031]

[0032] wherein p c,T is the post-high-temperature concrete protective layer radial stress on the steel bar, R i,T is the cracking limit radius, R b is the steel bar radius, R c is the minimum thickness from the steel bar center to the outside of the concrete; and I is the resultant force of the circumferential tensile stress of the cracking area concrete.

[0033] Further, the segmented expression of I is:

[0034]

[0035]

[0036] wherein I a and I b take values as:

[0037]

[0038]

[0039] wherein ε t,T (R b ) represents the circumferential strain of the post-high-temperature concrete at the steel bar and concrete interface; and the expression of ε t,T (R b ) is:

[0040]

[0041] wherein R 1,T represents the radius corresponding to the strain of the concrete after high temperature as ε 1,T u,T represents the radius corresponding to the strain of the concrete after high temperature as ε u,T 1,T and R u,T The expression of R c,T and R max is:

[0042]

[0043]

[0044] Further, the maximum radial stress of the concrete cover on the steel bar after high temperature is obtained, comprising:

[0045] According to , the maximum radial stress p T,max of the concrete cover on the steel bar after high temperature can be solved.

[0046] Further, the bond strength of the steel bar-concrete after high temperature is obtained according to the relationship between the bond strength and the maximum radial stress, comprising:

[0047] According to the load transfer relationship of the steel bar-concrete, the expression of the bond strength τ sv is:

[0048]

[0049] wherein, is the angle between the concrete failure surface and the longitudinal axis of the steel bar obtained by the pull-out test, and f is the friction coefficient between the cracked and intact concrete.

[0050] Further, after the bond strength of the steel bar-concrete after high temperature is obtained, it further comprises: according to the enhancement effect of the stirrup on the bond strength of the steel bar-concrete after high temperature, the bond strength of the steel bar-concrete after high temperature is corrected.

[0051] Further, the bond strength of the steel bar-concrete after high temperature is corrected according to the enhancement effect of the stirrup on the bond strength of the steel bar-concrete after high temperature, comprising: introducing the enhancement coefficient K T,max of the stirrup, considering the bond strength τ SV after the enhancement of the stirrup. The expression is:

[0052]

[0053] wherein ρ sv is the reinforcement ratio of the stirrup, d sv is the diameter of the stirrup, and Ssv The hoop spacing is provided.

[0054] Compared with the prior art, the embodiment of the present application has at least one of the following beneficial effects:

[0055] The method for determining the high-temperature post-reinforced concrete bonding strength provided by the present application can consider the influence of design parameters such as the strength of the reinforced concrete, and the prediction result is accurate, and the application range is wider in actual engineering.

[0056] The method for determining the high-temperature post-reinforced concrete bonding strength provided by the present application is obtained based on a thick-walled cylinder model, a dispersion crack assumption and the constitutive relationship of the reinforced concrete after high temperature, and simultaneously considers the influence of factors such as the diameter and shape of the reinforced concrete, the thickness of the concrete protective layer and the change of the constitutive relationship of the concrete after high temperature, can effectively predict the high-temperature post-reinforced concrete bonding strength, has good precision, the prediction result is accurate, and the practicality is strong, and the deficiencies of the prior art are improved, and strong technical support can be provided for the analysis of the mechanical behavior of the high-temperature post-reinforced concrete structure. BRIEF DESCRIPTION OF DRAWINGS

[0057] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the attached drawings:

[0058] Figure 1 FIG. 1 is a flowchart of a method for determining the high-temperature post-reinforced concrete bonding strength according to an embodiment of the present application;

[0059] Figure 2 FIG. 2 is a schematic diagram of a three-section tensile constitutive model of the high-temperature post-concrete according to an embodiment of the present application;

[0060] Figure 3 FIG. 3 is a schematic diagram of a thick-walled cylinder model and its stress analysis according to an embodiment of the present application;

[0061] Figure 4 FIG. 4 is a comparison diagram of the calculation result of the bonding strength and the measured value according to an embodiment of the present application. DETAILED DESCRIPTION

[0062] The present application will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0063] The method for determining the high-temperature post-reinforced concrete bonding strength provided by the embodiment of the present application refers to Figure 1 The method comprises the following steps:

[0064] S1, obtaining a high-temperature post-concrete mechanical parameter, the high-temperature post-concrete mechanical parameter including an elastic modulus, a tensile strength and a limit tensile strain of the high-temperature post-concrete;

[0065] S2, determining a three-section tensile constitutive model of the high-temperature post-concrete according to the high-temperature post-concrete mechanical parameter;

[0066] S3, solving a concrete cracking area radius corresponding to a maximum radial stress according to a thick-walled cylinder model and a dispersion crack assumption based on the three-section tensile constitutive model;

[0067] S4, solving a maximum radial stress of a high-temperature post-concrete protective layer on a steel bar according to the concrete cracking area radius corresponding to the maximum radial stress;

[0068] S5, obtaining a high-temperature post-steel bar-concrete bonding strength according to a relationship between the steel bar-concrete bonding strength and the maximum radial stress.

[0069] In some embodiments, in step S1, the high-temperature post-concrete tensile elastic modulus E t,T and a relationship expression of the high-temperature post-concrete tensile elastic modulus E t,0 at normal temperature is:

[0070]

[0071] wherein T is a maximum temperature experienced by the concrete; 20℃ < T≤ 800℃;

[0072] A relationship expression of the high-temperature post-concrete tensile strength f t,T and a relationship expression of the high-temperature post-concrete tensile strength f t,0 at normal temperature is:

[0073]

[0074] wherein T is a maximum temperature experienced by the concrete; 20℃ < T≤ 800℃;

[0075] A relationship expression of the high-temperature post-concrete limit tensile strain ε ct,T is:

[0076]

[0077] In some embodiments, in step S2, from a microcosmic aspect, the concrete cannot bear tensile force after cracking, but since the steel bar in the steel bar concrete structure is in tension, and not all sections in the concrete have cracks, the concrete can still bear part of the tensile force in the average sense even in the case of cracks. Figure 2A three-segment constitutive model derived based on the dispersed crack assumption is shown. Because this model is segmented, it can more accurately describe the behavior of concrete under different stress levels. According to the formula recommended by the International Association for Structural Concrete (IASC) Model Code 2010, the three-segment tension constitutive model of concrete after high temperature is as follows:

[0078] σ t,T (r)=E t,T ·ε t,T (r); ε t,T (r)≤ε ct,T ;

[0079]

[0080]

[0081] The three expressions above correspond to different line segments in the constitutive model. Where σ t,T (r) represents the circumferential stress of the concrete at radius r after high temperature, ε t,T (r) represents the circumferential strain of the concrete at radius r after high temperature, and β is the softening coefficient of the concrete. The value of β is determined based on specific experiments, for example, it can be 0.15; ε 1,T ε represents the tensile strain corresponding to the slope change point in the three-segment tensile constitutive model of concrete. u,T This represents the tensile strain at the point where the stress is 0 in the three-segment tensile constitutive model of concrete.

[0082] In some implementations, ε 1,T and ε u,T The expressions are as follows:

[0083]

[0084]

[0085] Among them, h c h is the characteristic value of crack length. c The value of G is determined based on the specific experiment; for example, it can be 0.1m. f,T The fracture energy of concrete after high temperature is approximately considered to be G. f,T The value should not change with temperature; the value recommended in the International Association for Structural Concrete Model Code 2010 standard can be used.

[0086] In some implementations, in step S3, based on the thick-walled cylindrical model and the dispersed crack assumption, the concrete cover is divided into a cracked interior and an uncracked exterior. The cracked concrete is located inside, and the uncracked concrete is located outside. For the uncracked exterior area, the concrete is analyzed using elastic theory. For the cracked interior area, a three-segment tension constitutive model derived from the dispersed crack assumption is used, and the circumferential stress is solved based on the stress-strain relationship of the concrete derived elastically. Based on the stress balance relationship, the elastic deformation compatibility assumption, and the constitutive relationship, the radial pressure on the reinforcing steel can be obtained. (Refer to...) Figure 3 The radius R of the concrete cracking zone corresponding to the maximum radial stress i,T cr The calculation equation is as follows:

[0087]

[0088] Where, p c,T It is the radial stress R exerted by the concrete cover on the reinforcing steel after high temperature. i,T R is the crack boundary radius. b R is the radius of the reinforcing bar. c I represents the minimum thickness from the center of the reinforcing bar to the outer edge of the concrete; Figure 3 σ t，T The integral over the radius of the cracked region represents the resultant force of the circumferential tensile stress in the concrete within the cracked region. Since the constitutive relation of concrete is piecewise, I also needs to be calculated piecewise.

[0089] In some implementations, the piecewise expression for I is:

[0090]

[0091]

[0092] Among them, I a with I b The possible values ​​are:

[0093]

[0094]

[0095] Where ε t,T (R b The expression () represents the circumferential strain of the concrete at the interface between the steel reinforcement and the concrete (radius Rb) after high temperature. Using the strain compatibility relationship based on elastic theory, a conservative calculation result can be obtained, and its expression is:

[0096]

[0097] The distribution of stress in the concrete in the cracking zone is determined by a three-section constitutive model, where R 1,T represents the radius corresponding to the strain of the concrete after high temperature being ε 1,T R u,T represents the radius corresponding to the strain of the concrete after high temperature being ε u,T R T and R u,T are expressed as:

[0098]

[0099]

[0100] In some embodiments, in step S4, according to the maximum radial stress p c,T max of the concrete cover on the steel bar after high temperature can be solved.

[0101] In some embodiments, in step S5, according to the load transfer relationship of the steel bar-concrete, the expression of the bond strength τ T,max is obtained:

[0102]

[0103] wherein, is the angle between the concrete failure surface and the longitudinal axis of the steel bar obtained by the pull-out test; f is the friction coefficient between the cracked and intact concrete, the value of f can be determined according to the test, and after summarizing the test in the summary part, the value of should be in the range of 10°-40°, for example, it can be taken as 22°; f can be taken as 0.6.

[0104] In some embodiments, for the reinforced concrete slab and the pull-out test specimen, generally no stirrup is provided, so the enhancement effect of the stirrup does not need to be considered, but when the stirrup is configured, for example, the reinforced concrete beam and column generally should be provided with the stirrup, so the enhancement effect of the stirrup needs to be considered. Therefore, after the bond strength of the steel bar-concrete after high temperature is obtained, step S6 is further included: according to the enhancement effect of the stirrup on the bond strength of the steel bar-concrete after high temperature, the bond strength of the steel bar-concrete after high temperature is corrected. Considering the enhancement effect of the stirrup, the accuracy of the calculation of the bond strength can be improved.

[0105] In some embodiments, in step S6, the enhancement coefficient K sv of the stirrup is introduced, and the bond strength τ T,max SV after the enhancement of the stirrup is considered, and the expression is:

[0106]

[0107] wherein p sv is the reinforcement ratio of the stirrup, d sv is the diameter of the stirrup, S sv is the spacing of the stirrup. Considering the favorable effect of the stirrup on the bond strength of the steel-reinforced concrete, the bond strength obtained in the above step S5 can be increased, thereby improving the accuracy of the calculation of the bond strength. SV

[0108] In order to better illustrate the technical effects of the above embodiments of the present application, the document "Temperature effects on the bond behavior between deformed steel reinforcing bars and hybrid fiber-reinforced strain hardening cementitious composite" is taken as a comparative example, and the same test parameters as in the document "Temperature effects on the bond behavior between deformed steel reinforcing bars and hybrid fiber-reinforced strain hardening cementitious composite" are used, and the calculation method of the bond strength in the above embodiments is used for calculation.

[0109] In this embodiment, the test parameters are: T = 200C°, ΔT = 180C°, E t,0 = 3.84x10 4 MPa, f t,0 = 4.06MPa.

[0110] In step S1, the method for solving the mechanical parameters of the concrete after high temperature is as follows:

[0111] Solving the tensile elastic modulus E t,T of the concrete after high temperature:

[0112]

[0113] Solving the tensile strength f t,T of the concrete after high temperature:

[0114]

[0115] Solving the ultimate tensile strain ε ct,T of the concrete after high temperature:

[0116] ​

[0117] In step 2, the three-stage tensile constitutive model of high-temperature after-concrete is as follows:

[0118] σ t,T (r) = 2.85 x 10 4 ·ε t,T (r) ; ε t,T (r) < 1.13 x 10 -4 ;

[0119]

[0120] 1.13 x 10 -4 <ε t,T (r) < 4.73 x 10 -4 ;

[0121]

[0122] 4.73 x 10 -4 <ε t,T (r) < 3.10 x 10 -3 ;

[0123] In step 3, the following equation is solved to obtain the radius R of the concrete cracking area corresponding to the maximum radial stress i,T cr , where R c = 0.076 m, R b = 0.008 m:

[0124]

[0125] where the piecewise expression of I is as follows:

[0126]

[0127]

[0128]

[0129]

[0130] The values of R 1,T and R u,T and ε t,T (R b ) in the above formula are as follows:

[0131]

[0132]

[0133]

[0134] Substitute the corresponding parameters into the above equation, the R can be solved by using the dichotomy method i,T cr :R i,T cr = 0.0551m.

[0135] In step 4, the maximum radial stress of the concrete on the steel bar after high temperature is solved as follows:

[0136] Substitute R i,T cr = 0.0551m into the following formula, the maximum radial stress p of the concrete cover on the steel bar after high temperature is solved c,T max = 17.18MPa.

[0137]

[0138] In step 5, the expression of the bond strength is as follows:

[0139]

[0140] Using the method in the above embodiment, the bond strength of the steel bar-concrete after high temperature is solved as 22.77MPa.

[0141] It should be noted that since the test referred to in the above embodiment does not configure the stirrup, the calculation considering the enhancement effect of the stirrup in step 6 is omitted here.

[0142] The comparison chart of the predicted value and the measured value of the bond strength of the steel bar-concrete after high temperature is shown in Figure 4 The test parameters and results are given in the literature “Temperature effects on the bond behavior between deformed steel reinforcing bars and hybrid fiber-reinforced strain hardening cementitious composite”, Figure 4The model prediction corresponds to the result calculated by the method in the above embodiment, and the test result corresponds to the result in the literature. By comparing the predicted value and the measured value of the bond strength of the steel bar-concrete after being subjected to high temperatures of 20 DEG C, 100 DEG C, 200 DEG C, 400 DEG C, 600 DEG C and 800 DEG C, it is found that the calculation method in the above embodiment can accurately calculate the bond strength of the steel bar-concrete after being subjected to high temperatures, and the accuracy of the calculation method in the embodiment is proved. It should be noted that although there is a certain deviation between the predicted value and the measured value at 400 DEG C and 600 DEG C, since the discreteness of the concrete material is large and the mechanical behavior after high temperature is difficult to predict, the deviation between the model prediction result and the test result is within an acceptable range, and the consistency between the model prediction result and the test result is high.

[0143] The calculation method of the bond strength of the steel bar-concrete after high temperature provided by the above embodiment is obtained based on the thick-walled cylinder model, the dispersion crack assumption and the constitutive relationship of the steel bar and the concrete after high temperature, and simultaneously considers the influence of factors such as the diameter and shape of the steel bar, the thickness of the concrete protective layer and the change of the constitutive relationship of the concrete after high temperature, can effectively predict the bond strength of the steel bar-concrete after high temperature, has good precision, the prediction result is accurate, has strong practicability, improves the deficiency of the existing calculation method of the bond strength of the steel bar-concrete, and can provide strong technical support for the analysis of the mechanical behavior of the steel bar-concrete structure after high temperature.

[0144] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The above preferred features can be combined for use in the case of not conflicting with each other.

Claims

1. A method for determining the bond strength of steel reinforcement-concrete after high temperature, characterized in that, include: The mechanical parameters of the concrete after high temperature are obtained, including the elastic modulus, tensile strength and ultimate tensile strain of the concrete after high temperature. Based on the mechanical parameters of the high-temperature concrete, a three-segment tension constitutive model of the high-temperature concrete was determined. Based on the thick-walled cylindrical model and the assumption of diffuse cracks, the radius of the concrete cracking region corresponding to the maximum radial stress is solved based on the three-segment tensile constitutive model. Based on the radius of the concrete cracking area corresponding to the maximum radial stress, the maximum radial stress of the concrete cover on the reinforcing steel after high temperature is calculated. Based on the relationship between the bond strength of steel-concrete and the maximum radial stress, the bond strength of steel-concrete after high temperature is obtained; The three-segment tension constitutive model of the high-temperature concrete is determined as follows: s t,T (r)=E t,T ·e t,T (r);e t,T (r)≤ε ct,T ; Where, σ t,T (r) represents the circumferential stress of the concrete at radius r after high temperature, ε t,T (r) represents the circumferential strain of the concrete at radius r after high temperature, β is the softening coefficient of the concrete, and ε 1,T ε represents the tensile strain corresponding to the slope change point in the three-segment tensile constitutive model of concrete. u,T E represents the tensile strain at the point where the stress is zero in the three-segment tensile constitutive model of concrete. t,T ε is the tensile elastic modulus of concrete after high temperature. ct,T f is the ultimate tensile strain of concrete after high temperature. t,T The tensile strength of the concrete after high temperature, where T is the maximum temperature experienced by the concrete; The calculation of the radius of the concrete cracking region corresponding to the maximum radial stress includes: Based on the thick-walled cylindrical model and the assumption of diffuse cracking, the concrete cover is divided into a cracked interior and an uncracked exterior. The radius R of the cracked concrete region corresponding to the maximum radial stress is... i,T cr The calculation equation is as follows: Where, p c,T It is the radial stress R exerted by the concrete cover on the reinforcing steel after high temperature. i,T R is the crack boundary radius. b R is the radius of the reinforcing bar. c I represents the minimum thickness from the center of the reinforcing bar to the outer side of the concrete; I represents the resultant force of the circumferential tensile stress in the concrete of the cracked area.

2. The method for determining the bond strength of steel-concrete after high temperature as described in claim 1, characterized in that, The method for obtaining the mechanical parameters of concrete after high temperature includes: The tensile elastic modulus E of concrete after high temperature t,T Compared with the tensile elastic modulus E of concrete at room temperature t,0 The relational expression is: Among them: 20℃ <T≤800℃; Concrete tensile strength f after high temperature t,T The tensile strength f of concrete at room temperature t,0 The relational expression is: Among them: 20℃ <T≤800℃; Ultimate tensile strain ε of concrete after high temperature ct,T The expression is:

3. The method for determining the bond strength of steel reinforcement-concrete after high temperature as described in claim 1, characterized in that, ε 1,T and ε u,T The expressions are as follows: Among them, h c G is the characteristic value of crack length. f,T This refers to the fracture energy of concrete after high temperature.

4. The method for determining the bond strength of steel-concrete reinforcement after high temperature as described in claim 1, characterized in that, The piecewise expression for I is: Among them, I a with I b The possible values ​​are: Where ε t,T (R b ε represents the circumferential strain of the concrete at the interface between the reinforcing steel and the concrete after high temperature; t,T (R b The expression for ) is: Among them, R 1,T The strain of concrete after high temperature is expressed as ε. 1,T The corresponding radius, R 1,T The expression is:

5. The method for determining the bond strength of steel-concrete reinforcement after high temperature as described in claim 4, characterized in that, The determination of the maximum radial stress of the concrete cover on the reinforcing steel after high temperature includes: according to The maximum radial stress p exerted by the concrete cover on the reinforcing steel after high temperature can then be calculated. c,T max .

6. The method for determining the bond strength of steel-concrete reinforcement after high temperature as described in claim 5, characterized in that, The method of obtaining the bond strength of steel-concrete after high temperature based on the relationship between the bond strength of steel-concrete and the maximum radial stress includes: Based on the load transfer relationship between steel reinforcement and concrete, the bond strength τ is obtained. T The expression for max: in, denoted as , where is the angle between the concrete failure surface obtained from the pull-out test and the longitudinal axis of the reinforcing bar, and f is the coefficient of friction between the cracked and intact concrete.

7. The method for determining the bond strength of steel-concrete reinforcement after high temperature as described in claim 6, characterized in that, After determining the bond strength of steel-concrete after high temperature, the method further includes: correcting the bond strength of steel-concrete after high temperature based on the enhancing effect of stirrups on the bond strength of steel-concrete after high temperature.

8. The method for determining the bond strength of steel reinforcement-concrete after high temperature as described in claim 7, characterized in that, The modification of the bond strength of steel-concrete after high temperature based on the enhancing effect of stirrups on the bond strength of steel-concrete after high temperature includes: introducing a reinforcing factor K for the stirrups. sv Considering the bond strength τ after stirrup reinforcement T,max SV The expression is: Where, ρ sv Let d be the reinforcement ratio of the stirrups. sv S is the diameter of the stirrup. sv This refers to the spacing between the stirrups.

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