Method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns

Abstract

This invention discloses a method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns, including: determining the volume replacement rate α of waste rubber particles on steel slag in steel slag concrete; and measuring the compressive strength f of steel slag concrete. co steel pipe yield strength f y The cross-sectional area A of the steel pipe s and the cross-sectional area A of the core concrete c The method for determining the bearing capacity of steel-slag and rubber-mixed fine aggregate steel-concrete composite columns is proposed in this invention. It comprehensively considers the influence of various factors on the bearing capacity of these columns, enabling a more accurate determination. This method is simple, easy to implement, and has significant practical engineering application value.

Description

Technical Field

[0001] This invention relates to a method for determining the bearing capacity of a concrete column, specifically a method for determining the bearing capacity of a steel slag and rubber mixed fine aggregate steel pipe concrete column, belonging to the field of bridge and culvert engineering technology. Background Technology

[0002] Preparing fine aggregate concrete by mixing waste rubber tire particles with steel slag is an effective measure for treating waste rubber tires and steel slag. This method not only allows for the recycling of steel slag and waste rubber tires but also reduces the extraction of natural river sand resources, thus benefiting environmental protection.

[0003] When steel slag in steel slag-rubber mixed fine aggregate concrete is exposed to air, it generates oxidation products such as iron oxide, causing the concrete to crack. Therefore, using the sealed, moisture-proof environment of steel pipes to fill the steel slag-rubber mixed fine aggregate concrete not only avoids cracking caused by the later hydration expansion of the steel slag but also improves the mechanical properties of the steel pipes. However, existing theories mainly focus on ordinary steel pipe concrete, and theoretical research on steel slag-rubber mixed fine aggregate steel pipe concrete columns has not yet been found. In order to promote the application of steel slag-rubber mixed fine aggregate steel pipe concrete structures in engineering structures, it is necessary to study its load-bearing capacity. Summary of the Invention

[0004] To address the problem that existing theories on steel-concrete composite tubes are not applicable to the calculation of the bearing capacity of steel-concrete composite tube columns made of steel slag and rubber mixed fine aggregates, this paper proposes a method for determining the bearing capacity of such columns, aiming to accurately determine their bearing capacity.

[0005] This invention is implemented as follows:

[0006] A method for determining the bearing capacity of a steel slag and rubber mixed fine aggregate steel tube concrete column includes the following steps:

[0007] S1, Determine the volume replacement rate of waste rubber particles for steel slag in steel slag concrete. ;

[0008] S2, measuring the compressive strength of steel slag concrete. ;

[0009] S3, measuring the yield strength of the steel pipe ;

[0010] S4, Measure the cross-sectional area A of the steel tube in the steel-concrete composite steel tube column made of steel slag and rubber mixed fine aggregate. s and the cross-sectional area A of the core concrete cThe cross-sectional area of ​​the steel pipe refers only to the area of ​​the steel pipe cross-section material, excluding the area of ​​the concrete inside the steel pipe.

[0011] S5, calculate the clamping coefficient ξ of the steel pipe. The basic form of the calculation formula is:

[0012]

[0013] S6, based on the cross-sectional area of ​​the steel pipe in each specimen. A s and yield strength The compressive strength of steel slag concrete With cross-sectional area A c Calculate the clamping coefficient of the steel pipe. ξ value.

[0014] S7. Axial loading tests were conducted on steel slag and rubber mixed fine aggregate steel tube concrete columns using a pressure machine to obtain the test values ​​of the bearing capacity of each specimen, and the basic form of the bearing capacity calculation formula was determined as follows:

[0015]

[0016] In the formula, β1-β4 are the coefficients that need to be determined;

[0017] S8, based on the cross-sectional area of ​​the steel pipe in each specimen. A s and hoop coefficient ξ Cross-sectional area of ​​core steel slag and rubber concrete A c and compressive strength By using regression analysis with differential evolution method, the values ​​of coefficients β1-β4 were obtained, thus determining the calculation formula for the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns:

[0018]

[0019] Compared with the prior art, the present invention has at least the following outstanding advantages:

[0020] The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns proposed in this invention comprehensively considers the influence of steel tube hoop coefficient, steel tube wall thickness, steel slag concrete compressive strength, rubber replacement rate, and steel slag and rubber mixed fine aggregate concrete on the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns. This method can more accurately determine the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns. The method is simple, easy to implement, and has significant practical engineering application value. Attached Figure Description

[0021] Figure 1This is a calculation process for the bearing capacity of a steel slag and rubber mixed fine aggregate steel tube concrete column according to an embodiment of the present invention;

[0022] Figure 2 This is a comparison chart of the calculated and experimental results of the load-bearing capacity of various specimens according to an embodiment of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] To fully explain the technical solution of the present invention, the following preparatory work is required first, including:

[0025] 1. Determine the main performance indicators of the materials related to this embodiment.

[0026] This embodiment uses steel slag and rubber particles to completely replace the fine aggregate in concrete, thereby preparing steel slag and rubber mixed fine aggregate concrete. The density of the steel slag is 3500 kg / m³. 3 The density of the rubber granules is 1120 kg / m³. 3 The coarse aggregate is natural crushed stone with a particle size of 5-20mm, and the cement is P O.425 ordinary Portland cement. Depending on the mix proportion, the rubber content in steel slag and rubber fine aggregate concrete has three types: 0%, 20%, and 40%, as shown in Table 1. The particle size of both the steel slag and rubber particles is less than 5mm.

[0027] Table 1. Mix proportions of steel slag and rubber fine aggregate concrete ( )

[0028]

[0029] 2. Specimen Design

[0030] Twenty-seven steel-slag and rubber-mixed fine aggregate steel-concrete composite columns, each 450 mm in length and with an inner diameter of 147 mm, were fabricated. The steel used in the columns had a yield strength of 300 MPa. The parameters for variation in the specimens were the steel pipe wall thickness and the rubber volume replacement rate. Three steel pipe wall thicknesses were used: 3 mm, 5 mm, and 7 mm. Three rubber particle volume replacement rates were used: 0%, 20%, and 40%. Three specimens with the same parameters were fabricated, resulting in a total of 27 specimens. The rubber particle volume replacement rate was obtained by replacing the steel slag with an equal volume of rubber particles. Specimen numbers were assigned as follows: rubber replacement rate - steel pipe thickness - specimen number. (See Table 1.) The axial compressive strength of steel slag and rubber concrete; The yield strength of the steel pipe; N exp The bearing capacity test value is given by ξ, where ξ is the coupling coefficient of the steel pipe. Nexp These are the load-bearing capacity test values. N cal This is the calculated value for load-bearing capacity.

[0031] Table 2 Test Data of Steel Tube Slag Concrete Short Columns

[0032]

[0033] Note: Specimen 20%-5-3 was damaged due to improper loading.

[0034] 3. Measurement point layout and loading scheme

[0035] A hydraulic servo press was used to load steel slag and rubber-blended fine aggregate steel-concrete composite columns. The experiment employed simultaneous force-controlled and displacement-controlled loading. Initially, force-controlled loading was used at a rate of 50 kN / min. When the load-displacement curve reached its inflection point, displacement-controlled loading was switched to a rate of 2 mm / min. Loading was stopped when the specimen displacement reached 50 mm or when the specimen failed.

[0036] With the preceding preparatory work completed, the method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns, as described in this embodiment, can be carried out, as shown in the attached figure. Figure 1 As shown, the specific steps include the following:

[0037] S1, Determine the volume replacement rate of waste rubber particles for steel slag in steel slag concrete. ;

[0038] S2, measuring the compressive strength of steel slag concrete. ;

[0039] S3, measuring the yield strength of the steel pipe ;

[0040] S4, Measure the cross-sectional area A of the steel tube in the steel-concrete composite steel tube column made of steel slag and rubber mixed fine aggregate. s and the cross-sectional area A of the core concrete c ;

[0041] S5, calculate the clamping coefficient ξ of the steel pipe. The basic form of the calculation formula is:

[0042]

[0043] S6, based on the cross-sectional area A of the steel pipe in each specimen. s and yield strength The compressive strength of steel slag concrete With cross-sectional area A c The clamping coefficient ξ of the steel pipe is calculated.

[0044] S7. Axial loading tests were conducted on steel slag and rubber mixed fine aggregate steel tube concrete columns using a pressure machine to obtain the test values ​​of the bearing capacity of each specimen, and the basic form of the bearing capacity calculation formula was determined as follows:

[0045]

[0046] In the formula, β1-β4 are the coefficients that need to be determined;

[0047] S8, based on the cross-sectional area As of the steel pipe and the clamping coefficient ξ of each specimen, and the cross-sectional area A of the core steel slag and rubber concrete. c and compressive strength By using regression analysis with differential evolution method, the values ​​of coefficients β1-β4 were obtained, thus determining the calculation formula for the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns:

[0048]

[0049] Based on the cross-sectional area A of the steel tube in the steel-concrete composite column made of steel slag and rubber mixed fine aggregate... s And the confinement coefficient ξ, the cross-sectional area A of the core steel slag and rubber concrete column c and compressive strength Substituting into the above formula, the bearing capacity of the steel slag and rubber mixed fine aggregate steel tube concrete column is calculated. The calculation results are shown in Table 2.

[0050] The load-bearing capacity of each specimen was predicted using the above method and compared with the experimental results. For example, the calculated load-bearing capacity of each specimen was compared with the experimental results. Figure 2 As shown. By Figure 2 It can be seen that the calculated and experimental values ​​of the bearing capacity of the steel slag and rubber mixed fine aggregate steel tube concrete column are in good agreement, indicating that the method of the present invention is reliable.

[0051] This embodiment proposes a calculation method for predicting the bearing capacity of steel slag and rubber mixed fine aggregate concrete-tube columns. The calculation method proposed in this invention fills the current gap in the lack of methods for calculating the bearing capacity of steel slag and rubber mixed fine aggregate concrete-tube columns. Furthermore, the model is simple and highly accurate, laying the foundation for the application of steel slag and rubber mixed fine aggregate concrete-tube columns in building structural engineering.

[0052] Although the present invention has been described herein with reference to illustrative embodiments, the above embodiments are merely preferred embodiments of the present invention, and the implementation of the present invention is not limited to the above embodiments. It should be understood that those skilled in the art can devise many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A method for determining the bearing capacity of a steel slag and rubber mixed fine aggregate steel tube concrete column, characterized in that... Specifically, the steps include the following: S1, determine the volume replacement rate α of waste rubber particles for steel slag in steel slag concrete; S2, Measure the compressive strength f of steel slag concrete. co ; S3, Measure the yield strength f of the steel pipe y ; S4, Measure the cross-sectional area A of the steel tube in the steel-concrete composite steel tube column made of steel slag and rubber mixed fine aggregate. s and the cross-sectional area A of the core concrete c ; S5, calculate the clamping coefficient ξ of the steel pipe. The basic form of the calculation formula is: ξ=f y A s / f co A c S6, based on the cross-sectional area A of the steel pipe in each specimen. s and yield strength f y The compressive strength f of steel slag concrete co With cross-sectional area A c Calculate the clamping coefficient ξ of the steel pipe; S7. Axial loading tests were conducted on steel slag and rubber mixed fine aggregate steel tube concrete columns using a pressure machine to obtain the test values ​​of the bearing capacity of each specimen, and the basic form of the bearing capacity calculation formula was determined as follows: In the formula, β1-β4 are the coefficients that need to be determined; S8, based on the cross-sectional area A of the steel pipe in each specimen. s And the confinement coefficient ξ, the cross-sectional area A of the core steel slag and rubber concrete c and compressive strength f co By using regression analysis with differential evolution method, the values ​​of coefficients β1-β4 were obtained, thus determining the calculation formula for the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns: N=(A s +A c )(1.806+0.234ξ)(1-0.522α 0.18 )f co 。 2. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 1, characterized in that: In the concrete, the coarse aggregate is natural crushed stone with a particle size of 5-20mm.

3. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 1, characterized in that: The cement used in the concrete is P O.425 ordinary Portland cement.

4. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 1, 2, or 3, characterized in that: The density of the steel slag is 3500 kg / m³. 3 .

5. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 4, characterized in that: The particle size of the steel slag is less than 5 mm.

6. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 1, 2, or 3, characterized in that: The density of the rubber granules is 1120 kg / m³. 3 .

7. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 6, characterized in that: The size of the rubber particles is less than 5 mm.

8. The method for determining the bearing capacity of steel slag and rubber mixed fine aggregate steel tube concrete columns according to claim 1, characterized in that: In step S7, an axial loading test is conducted on the steel slag and rubber mixed fine aggregate steel tube concrete column using a press. Specifically: A hydraulic servo press was used to load the steel slag and rubber mixed fine aggregate steel tube concrete column. Force-controlled loading and displacement-controlled loading were carried out simultaneously. Force loading was used in the initial stage of loading, with a loading rate of 50 kN / min. When the load-displacement curve of the specimen reached the inflection point, displacement loading was switched to loading rate of 2 mm / min. Loading was stopped when the displacement of the specimen reached 50 mm or the specimen failed.

Images