CN108824830B - Reinforcing device for steel column bolt node and design method thereof - Google Patents

Abstract

The invention discloses a reinforcing device at a steel column bolt joint, which comprises two reinforcing steel plates with U-shaped sections, wherein the reinforcing steel plates are welded at the splicing positions of steel column flanges in a bilateral symmetry mode, steel columns are I-shaped steel, and the reinforcing steel plates and the steel columns form a closed box body. Fiber concrete can be poured in the box-shaped body, and reinforcing steel bars are arranged in the area, close to the I-shaped steel, in the box body. The invention overcomes the defect that the bolt splicing node has uneven bolt side and can not be welded with a steel plate for reinforcement, ensures that the node has good energy consumption performance, meets the requirement of bearing capacity and simplifies the node construction. According to a large amount of data and curve characteristics, the invention establishes a fiber concrete stress-strain curve equation. According to the stress-strain curves of the fiber concrete and the steel, whether the reinforcement requirements are met or not is checked by utilizing a fiber section method.

Description

Reinforcing device for steel column bolt node and design method thereof

Technical Field

The invention relates to the technical field of building structure engineering, in particular to a reinforcing device for a steel column bolt node and a design method thereof.

Background

At present, in the construction process of buildings, a steel column is generally reinforced by adopting a method of adhering a steel plate, and if the section bearing capacity is insufficient, the steel plate can be welded on the flange of the steel column through a perforation plug to achieve the effect of reinforcement. But at the splicing position of the steel column flange, the surface of the steel column flange is uneven due to the existence of the bolts, and a steel plate cannot be adhered, so that the reinforcement of the joint becomes difficult.

Because the reinforcement of the steel column node region not only needs to meet the strength requirement, but also needs to have certain energy consumption performance, if the mode of direct welding reinforcement is adopted in the bolt node region, the ductility of the node is deteriorated, and the requirement of practical application cannot be met.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a reinforcing device for a steel column bolt node.

Another object of the present invention is to provide a design method for implementing the reinforcing device at the steel column bolt node, which can calculate the strength of the reinforcing device in the design stage, so that the reinforcing device meets the reinforcing requirement.

The purpose of the invention is realized by the following technical scheme: the utility model provides a reinforcing apparatus of steel column bolt node, includes two blocks of cross-sections and becomes the reinforcement steel sheet of "U" font, and bilateral symmetry welds the concatenation department at the steel column edge of a wing, and the steel column is I shaped steel, consolidates steel sheet and steel column and forms a closed box. Through setting up two reinforcing steel plates to overcome and to carry out the defect of consolidating through the welding steel sheet.

Preferably, fiber concrete is poured into the closed box body. Thereby improving the seismic performance of the box-shaped body.

Furthermore, the fiber concrete is steel fiber concrete. The concrete has better crack resistance.

Preferably, reinforcing steel bars are arranged in the closed box body close to the I-shaped steel. Used for improving the section bending-resistant bearing capacity of the box-shaped body.

A design method for realizing the reinforcing device at the node of the steel column bolt comprises the following steps:

(1) acquiring a stress-strain curve of the current fiber concrete;

(2) setting the number of steel bars, and obtaining a stress-strain curve of the current steel;

(3) according to the thickness of the steel plate, the configuration amount of the steel bars and the geometric dimension information of the fiber concrete, a fiber section method is utilized, and the two curves are combined to obtain a theoretical P-M correlation curve, wherein P represents axial force, and M represents bending moment;

(4) checking whether the current design meets the reinforcement requirement, if not, changing the number of the steel bars, and executing the step (3) again until the reinforcement requirement is met, thereby completing the design.

Preferably, in step (1), the stress-strain curve equation of the current fiber concrete is as follows:

x and y represent the strain and stress of the fiber concrete, respectively, a₁The following method was used to determine:

in the softening stage of the stress-strain curve, x reaches xi of peak strain_eWhen the residual strength is doubled, the steel fiber concrete only has residual strength which is f of the peak strength_rMultiple, i.e. x ═ xi_eWhen y is equal to f_rSolve for c₂The following formula:

in the formula, E₀,E_cThe elastic modulus and secant modulus of the fiber concrete are respectively.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. according to the invention, the reinforced steel plates are welded at the splicing positions of the steel column flanges in a bilateral symmetry manner, so that the bearing capacity of the section can be improved.

2. The invention provides that when the bearing capacity provided by the reinforced steel plate cannot meet the bending resistance of the main shaft, the bearing capacity can be further reinforced by additionally arranging the reinforcing steel bars.

3. The reinforced steel plate and the steel column form a closed box body, and steel fiber concrete can be poured into the closed box body to further improve the energy consumption performance.

4. The invention can obtain the required design of the reinforcing device by utilizing the stress-strain curve of the fiber concrete and the stress-strain curve of the steel in advance, and simplifies the structure design method.

Drawings

Fig. 1 is a front view of the present embodiment.

Fig. 2 is a cross-sectional view taken along the plane a-a in fig. 1.

Fig. 3 is a cross-sectional view taken along plane B-B of fig. 1.

Fig. 4a is a schematic structural view of the bolted plate shown as B1 in fig. 3.

Fig. 4B is a schematic structural view of the bolted plate shown as B2 in fig. 3.

Fig. 4c is a schematic structural view of the bolted plate shown as B3 in fig. 3.

Fig. 5 is a graph comparing theoretical and experimental stress-strain curves of the fiber concrete constructed in this example.

Fig. 6 is a schematic cross-sectional view of a fiber unit.

Wherein: 1-fiber concrete; 2-reinforcing steel bars; and 3, reinforcing the steel plate.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.

Example 1

As shown in fig. 1 to 3, the steel column in this embodiment is an i-shaped steel, and the surface of the steel column is provided with the bolt connecting plate shown in fig. 4a, 4b, and 4c, so that the surface is uneven due to the bolts during connection, and thus the steel column cannot be reinforced by welding steel plates by using a conventional method. Therefore, the embodiment provides a reinforcing device for a steel column bolt node, which specifically comprises two reinforcing steel plates 3 with U-shaped cross sections, a poured fiber concrete 1 and an additional steel bar 2. It should be noted that the above-mentioned fiber concrete casting and steel bar addition can be selected according to specific engineering requirements, and are not necessary.

The U-shaped reinforced steel plate can be directly processed and formed in a factory or manufactured on site, and the size of the section is determined according to the strength requirement of section reinforcement. The two reinforcing steel plates with U-shaped sections are welded at the splicing positions of the flanges of the steel columns in a bilateral symmetry mode, and the reinforcing steel plates and the steel columns form a closed box body. The closed box body can also be used as a pouring template of fiber concrete.

If engineering needs, the fiber concrete can be poured in the closed box body, and the fiber concrete can be steel fiber concrete or can be replaced by other fiber concrete with better crack resistance. Under the action of earthquake, the crack propagation caused by concrete cracking generates larger energy dissipation due to the blocking of fibers, so that the concrete has good energy consumption performance.

Similarly, if the bearing capacity provided by the U-shaped steel plate cannot meet the bending resistance of the spindle, the bearing capacity can be adjusted by arranging the steel bars in the area close to the i-shaped steel in the box body, as shown in fig. 3. If the reinforcing steel bar needs to be added, the construction steps of the reinforcing device are as follows: firstly welding a pair of U-shaped steel plates on two sides of the original cross section, then fixing the positions of the steel bars, and finally pouring fiber concrete.

In order to prolong the service life of the device, the outer surface of the closed box body is coated with protective coatings such as antirust coatings, fireproof coatings and the like.

For the reinforcing device for pouring fiber concrete and additionally arranging the reinforcing steel bars, the following design method can be adopted for pre-design, and the steps are as follows:

(1) acquiring a stress-strain curve of the current fiber concrete;

(2) setting the number of steel bars, and obtaining a stress-strain curve of the current steel;

(3) according to the thickness of the steel plate, the configuration amount of the steel bars and the geometric dimension information of the fiber concrete, a fiber section method is utilized, and the two curves are combined to obtain a theoretical P-M correlation curve, wherein P represents axial force, and M represents bending moment;

(4) checking whether the current design meets the reinforcement requirement, if not, changing the number of the steel bars, and executing the step (3) again until the reinforcement requirement is met, thereby completing the design.

In the step (1), the geometric characteristics of the concrete axial compressive stress-strain full curve need to be firstly found out to establish the stress-strain curve equation of the fiber concrete, the concrete compressive stress-strain full curve is expressed by dimensionless coordinates according to the results of a large number of experiments, and the geometric characteristic points of the curve are as follows:

(1) the starting point x is 0, and y is 0;

(2)0≤x＜1，d²y/dx²< 0, i.e., the slope of the rising curve (dy/dx) decreases monotonically and has no inflection point;

(3) when x is 1, y is 1, dy/dx is 0, i.e. single peak;

the dividing point of the ascending and descending segments of the curve. When the stress reaches the peak point, the main crack penetrates through the steel fiber concrete test piece.

(4) When d is²y/dx²When equal to 0, x_DThe descending section has an inflection point (D) if the angle is more than 1;

after passing through the peak point, the transverse deformation rapidly increases, the unstable crack rapidly expands, and the stress reduction rate reaches the maximum value when the point reaches the inflection point.

(5) When d is³y/dx³When equal to 0, x_E> 1, the point of maximum curvature (E) on the descending segment;

the maximum curvature point is the convergence point, after the inflection point is crossed, a plurality of longitudinal cracks are developed and connected to run through the whole test piece to form a plurality of nearly vertical fracture sections, and along with the continuous increase of the width of the fracture sections, the steel fibers crossing the cracks are pulled out, and the steel fiber concrete is disintegrated and damaged.

(6) When x → ∞, y → 0, dy/dx → 0

After the curve passes the convergence point, the curve develops nearly horizontally and there is residual intensity for a considerable period of time.

(7) All curves x is more than or equal to 0, and y is more than or equal to 1 and more than or equal to 0.

According to the characteristics of the curve, the following equation expression form can be established firstly:

in the formula, x and y respectively represent the strain and stress of the fiber concrete, a₁、a₂、b₂、c₂Are all undetermined parameters.

From the above condition (2), it can be obtained:

solving equation (1.2) yields:

a₂＝a₁-2+c₂，b₂＝1-2c₂

substituting the formula (1.1) to obtain the stress-strain curve equation of the fiber concrete as follows:

the first derivative is calculated from the formula (1.1) to obtain a₁：

In the formula, E₀,E_cThe elastic modulus and secant modulus of the fiber concrete are respectively.

In the softening stage of the stress-strain curve, x reaches xi of peak strain_eWhen the residual strength is doubled, the steel fiber concrete only has residual strength which is f of the peak strength_rMultiple, i.e. x ═ xi_eWhen y is equal to f_rSolve for c₂The following formula:

the stress-strain curve equation of the fiber concrete provided by the embodiment describes the ascending section and the descending section of the stress-strain curve by using only one expression, has simple form and adaptive capacityA strong force, and a₁And c₂Can be deduced by indexes with definite physical significance, and has high practicability. Referring to fig. 5, comparing the equation with data collected in actual experiments, the equation curve established in this embodiment is consistent with the experimental curve to a high degree.

In step (2) of this embodiment, the stress-strain curve of the steel bar is known. Can be directly applied by adopting the data in the prior art.

In the step (3) of this embodiment, a P-M correlation curve is calculated by using a fiber section method according to information such as a preliminarily designed steel plate thickness, a steel bar allocation amount, and a geometric size of fiber concrete. The fiber section method described herein is a fiber model method of section analysis, and the basic principle thereof can be referred to "elastic-plastic time course analysis and engineering application of fiber model-based super-high-rise reinforced concrete structure" published by korea and so on, and "development of concrete hysteretic model of ABAQUS fiber unit" published by lujian and chikun. As shown in fig. 6, it is assumed that the figure shows a section of a fiber unit, the fiber section method is to divide the section into grids, a rectangular grid B in each grid figure is a concrete "fiber", and a black dot a represents a steel fiber. Subsequent calculations can be performed using the characteristics of these fibers. The method has the advantages of: (1) the section of the member is divided into fibers, the position, the section area and the uniaxial constitutive relation of materials of the fibers are defined by users, and the fiber reinforced concrete member can be applied to various section shapes such as profiled columns, steel-concrete combined members and steel tube concrete members. In addition, it is suitable for a single material component part having a complicated cross-sectional shape. (2) It can accurately take into account uniaxial bidirectional axial force and moment coupling. (3) Different fibers with the same section can have different uniaxial constitutive relations, so that more suitable uniaxial constitutive relations of materials can be applied. Such as protective layer concrete and confined concrete.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (2)

1. A reinforcing device at a steel column bolt node is characterized by comprising two reinforcing steel plates with U-shaped sections, wherein the reinforcing steel plates are welded at the splicing positions of steel column flanges in a bilateral symmetry mode, steel columns are I-shaped steel, and the reinforcing steel plates and the steel columns form a closed box body;

pouring fiber concrete in the closed box body;

the fiber concrete is steel fiber concrete;

and reinforcing steel bars are arranged in the area, close to the I-shaped steel, in the closed box body.

2. A design method for realizing the reinforcing device at the node of the steel column bolt in the claim 1, which is characterized by comprising the following steps:

(1) acquiring a stress-strain curve of the current fiber concrete;

(2) setting the number of steel bars, and obtaining a stress-strain curve of the current steel;

(3) according to the thickness of the steel plate, the configuration amount of the steel bars and the geometric dimension information of the fiber concrete, a fiber section method is utilized, and the two curves are combined to obtain a theoretical P-M correlation curve, wherein P represents axial force, and M represents bending moment;

(4) checking whether the current design meets the reinforcement requirement, if not, changing the number of the steel bars, and executing the step (3) again until the reinforcement requirement is met, thereby completing the design;

in the step (1), the stress-strain curve equation of the current fiber concrete is as follows:

x and y represent the strain and stress of the fiber concrete, respectively, a₁The following method was used to determine:

in the softening stage of the stress-strain curve, x reaches xi of peak strain_eWhen the residual strength is doubled, the steel fiber concrete only has residual strength which is f of the peak strength_rMultiple, i.e. x ═ xi_eWhen y is equal to f_rSolve for c₂The following formula:

in the formula, E₀,E_cThe elastic modulus and secant modulus of the fiber concrete are respectively.

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