Calculation method of thermal stress of reinforced concrete based on steel bar load distribution

Abstract

A method for calculating the temperature stress of reinforced concrete based on steel bar distribution, the method comprising: constructing a numerical simulation model of reinforced concrete; taking reinforced concrete as a homogeneous body and obtaining the comprehensive elastic modulus of reinforced concrete; calculating the comprehensive temperature stress of reinforced concrete based on the comprehensive elastic modulus and using the numerical simulation model; distributing the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress and temperature change of concrete; obtaining the temperature change during the actual pouring of reinforced concrete, and obtaining the temperature stress value of concrete based on the temperature change and the corresponding relationship. The present invention accurately analyzes and calculates the temperature stress value of concrete in reinforced concrete, and then more reasonable temperature control measures can be formulated to prevent early or late cracks in concrete.

Description

Technical Field

[0001] The invention relates to the technical field of reinforced concrete construction, and in particular to a method for calculating reinforced concrete temperature stress based on steel bar load distribution. Background Art

[0002] Reinforced concrete is one of the main structures of buildings such as high-speed bridge piers and ship locks. Due to the temperature characteristics of concrete materials themselves and the difference in linear expansion coefficients between concrete and steel bars, such as Figure 2 As shown in the figure, during the early construction process, concrete A and steel bar B will produce uneven steel bar temperature drop deformation F1 and concrete temperature drop deformation F2. This uneven deformation makes it very easy for the concrete to produce tensile stress exceeding the limit value, resulting in early or late concrete cracks.

[0003] At present, the calculation of temperature stress of reinforced concrete is mainly completed through numerical simulation. Due to the limitations of finite element models, the influence of steel bars is often ignored in the calculation process, resulting in large differences in the calculation of concrete temperature stress and unreasonable temperature control measures. This makes it very easy for some reinforced concrete to have early or late cracks (or the temperature control standards are too strict, increasing the cost of temperature control measures), affecting the safety and stability of the overall structure and the economy of construction. Summary of the invention

[0004] In order to solve the above problems in the prior art, that is, to solve the technical problem of inaccurate calculation of early or late temperature stress of reinforced concrete, a method for calculating temperature stress of reinforced concrete based on steel bar distribution is provided, the method comprising:

[0005] Constructing a numerical simulation model of the reinforced concrete;

[0006] Taking the reinforced concrete as a homogeneous body and obtaining a comprehensive elastic modulus of the reinforced concrete;

[0007] Calculating the comprehensive temperature stress of the reinforced concrete based on the comprehensive elastic modulus and using a numerical simulation model;

[0008] Distributing the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress of concrete and the temperature change;

[0009] The temperature change during the actual pouring of reinforced concrete is obtained, and the temperature stress value of the concrete is obtained according to the temperature change and the corresponding relationship.

[0010] Preferably, the step of "taking the reinforced concrete as a homogeneous body and obtaining the comprehensive elastic modulus of the reinforced concrete" comprises:

[0011] Obtaining the elastic modulus of concrete and the elastic modulus of steel bars at different ages and the reinforcement ratio of the steel bars and concrete;

[0012] The elastic modulus of concrete and steel bars of different ages are weighted and summed based on the reinforcement ratio to obtain the comprehensive elastic modulus.

[0013] Preferably, the step of “weighting and summing the concrete elastic modulus and the steel bar elastic modulus based on the reinforcement ratio to obtain the comprehensive elastic modulus” includes:

[0014] The comprehensive elastic modulus E(t) is obtained by the following formula:

[0015] E(t)=E c (t)·(1-n)+E s ·n

[0016] Among them, n is the reinforcement ratio, E c (t) is the elastic modulus of concrete at different ages, E s The elastic modulus of the steel bar.

[0017] Preferably, the step of "distributing the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress of concrete and the temperature change" comprises:

[0018] The corresponding relationship between the temperature stress and temperature change of concrete is obtained by the following formula:

[0019]

[0020] Among them, σ c is the temperature stress of concrete, A is the total area of ​​reinforced concrete, σ is the comprehensive temperature stress of reinforced concrete, A s is the area of ​​the steel bar, E c is the elastic modulus of concrete, A c is the area of ​​the steel bar, ΔT is the temperature change, α s is the linear expansion coefficient of the steel bar, α c is the linear expansion coefficient of concrete.

[0021] The advantages of the present invention are:

[0022] The reinforced concrete temperature stress calculation method based on steel bar load sharing provided by the present invention comprehensively considers the influence of steel bars on reinforced concrete, accurately analyzes and calculates the temperature stress value of concrete in reinforced concrete, and then more reasonable temperature control measures can be formulated according to the concrete temperature stress value to prevent early or late cracks in concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the main steps of the reinforced concrete temperature stress calculation method based on steel bar loading distribution of the present invention.

[0024] Figure 2 This is a schematic diagram of the deformation of early reinforced concrete with temperature drop. DETAILED DESCRIPTION

[0025] See attached Figure 1 , Figure 1 The main steps of a method for calculating the temperature stress of reinforced concrete based on steel bar distribution are exemplified. As shown in Figure 1, the method for calculating the temperature stress of reinforced concrete based on steel bar distribution provided in this embodiment includes:

[0026] Step S1: constructing a numerical simulation model of reinforced concrete. Specifically, the numerical simulation model is constructed according to the geometric structure of reinforced concrete.

[0027] Step S2: Take reinforced concrete as a homogeneous body and obtain the comprehensive elastic modulus of reinforced concrete. Specifically, obtain the elastic modulus of concrete at different ages, the elastic modulus of steel bars, and the reinforcement ratio of reinforced concrete; weight and sum the elastic modulus of concrete at different ages and the elastic modulus of steel bars based on the reinforcement ratio to obtain the comprehensive elastic modulus.

[0028] Specifically, the comprehensive elastic modulus E(t) can be obtained according to the method shown in formula (1):

[0029] E(t)=E c (t)·(1-n)+E s ·n (1)

[0030] Among them, n is the reinforcement ratio, E c (t) is the elastic modulus of concrete at different ages, E s Elastic modulus of steel bars. It should be noted that before calculating the comprehensive elastic modulus, key parameters of reinforced concrete are also required, including development history, concrete expansion coefficient, and steel expansion coefficient. The linear expansion coefficient of steel bars is usually 12 to 18 (10-6), and the linear expansion coefficient of concrete is 0-10 (10-6).

[0031] Step S3: Calculate the comprehensive temperature stress of reinforced concrete based on the comprehensive elastic modulus and using the numerical simulation model. Specifically, assign the comprehensive elastic modulus to the numerical simulation model and calculate the comprehensive temperature stress of reinforced concrete.

[0032] Step S4: Distribute the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress of concrete and the temperature change.

[0033] Specifically, the calculated comprehensive temperature stress is the stress borne by the steel bar and concrete together, and the temperature stress of the concrete needs to be calculated by dividing the load between the steel bar and concrete. Therefore, the corresponding relationship between the temperature stress of the concrete and the temperature change can be obtained according to the method shown in formula (2):

[0034]

[0035] Among them, σ c is the temperature stress of concrete, A is the total area of ​​reinforced concrete, σ is the comprehensive temperature stress of reinforced concrete, E s is the elastic modulus of the steel bar, A s is the area of ​​the steel bar, E c is the elastic modulus of concrete, A c is the area of ​​the steel bar, ΔT is the temperature change, α s is the linear expansion coefficient of the steel bar, α c is the linear expansion coefficient of concrete. is the comprehensive temperature stress of concrete, It is the self-restrained stress of concrete due to temperature changes.

[0036] In addition, the temperature stress of the steel bar load can also be calculated according to the method shown in formula (3):

[0037]

[0038] in, is the comprehensive temperature stress borne by the steel bars, It is the self-restrained stress borne by the steel bars due to temperature changes.

[0039] Step S5: Obtain the temperature change during the actual pouring of reinforced concrete, and obtain the temperature stress value of the concrete according to the temperature change and the corresponding relationship. Specifically, obtain the temperature change during the actual pouring of reinforced concrete, substitute the temperature change as the temperature change ΔT into formula (2), and the temperature stress value of the concrete can be obtained.

[0040] In summary, the reinforced concrete temperature stress calculation method based on steel bar load sharing provided by the present invention comprehensively considers the influence of steel bars on reinforced concrete, accurately analyzes and calculates the temperature stress value of concrete in reinforced concrete, and then more reasonable temperature control measures can be formulated according to the concrete temperature stress value to prevent early or late cracks in concrete.

[0041] The above are preferred embodiments of the present invention and the technical principles used therein. For those skilled in the art, any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, are within the scope of protection of the present invention.

Claims

1. A method for calculating the temperature stress of reinforced concrete based on steel bar load distribution, characterized in that: The method comprises: Constructing a numerical simulation model of the reinforced concrete; Taking the reinforced concrete as a homogeneous body and obtaining a comprehensive elastic modulus of the reinforced concrete; Calculating the comprehensive temperature stress of the reinforced concrete based on the comprehensive elastic modulus and using a numerical simulation model; Distributing the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress of concrete and the temperature change; Obtaining the temperature change during the actual pouring of reinforced concrete, and obtaining the temperature stress value of the concrete according to the temperature change and the corresponding relationship; The step of "taking the reinforced concrete as a homogeneous body and obtaining the comprehensive elastic modulus of the reinforced concrete" comprises: Obtaining the elastic modulus of concrete and the elastic modulus of steel bars at different ages and the reinforcement ratio of the steel bars and concrete; Based on the reinforcement ratio, weighted and summed the elastic modulus of concrete and steel bars of different ages to obtain the comprehensive elastic modulus; The step of "weighting and summing the concrete elastic modulus and the steel elastic modulus based on the reinforcement ratio to obtain the comprehensive elastic modulus" includes: The comprehensive elastic modulus E(t) is obtained by the following formula: E(t)=E c (t)·(1-n)+E s ·n Among them, n is the reinforcement ratio, E c (t) is the elastic modulus of concrete at different ages, E s The elastic modulus of the steel bar; The step of "distributing the comprehensive temperature stress to obtain the corresponding relationship between the temperature stress of concrete and the temperature change" includes: The corresponding relationship between the temperature stress and temperature change of concrete is obtained by the following formula: Among them, σ c is the temperature stress of concrete, A is the total area of ​​reinforced concrete, σ is the comprehensive temperature stress of reinforced concrete, A s is the area of ​​the steel bar, E c is the elastic modulus of concrete, A c is the area of ​​the steel bar, ΔT is the temperature change, α s is the linear expansion coefficient of the steel bar, α c is the linear expansion coefficient of concrete.

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