CN114673305B - Longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) confined concrete-filled steel tube column with buffer cushion and construction method thereof - Google Patents
Longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) confined concrete-filled steel tube column with buffer cushion and construction method thereof Download PDFInfo
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- CN114673305B CN114673305B CN202210463910.8A CN202210463910A CN114673305B CN 114673305 B CN114673305 B CN 114673305B CN 202210463910 A CN202210463910 A CN 202210463910A CN 114673305 B CN114673305 B CN 114673305B
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/30—Columns; Pillars; Struts
- E04C3/36—Columns; Pillars; Struts of materials not covered by groups E04C3/32 or E04C3/34; of a combination of two or more materials
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
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Abstract
The invention discloses a longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) restrained concrete-filled steel tube column with a cushion layer and a construction method thereof, wherein the longitudinal and transverse CFRP restrained concrete-filled steel tube column comprises a concrete-filled steel tube column (1), the cushion layer (2) is fixed on the periphery of the concrete-filled steel tube column (1), a plurality of layers of CFRP (carbon fiber reinforced plastics) cloth are fixed outside the cushion layer (2), and the CFRP comprises an inner longitudinal CFRP cloth (3) and an outer transverse CFRP cloth (4). According to the invention, reliable force transmission is carried out between the steel pipe concrete and the carbon fiber layer through the foam cushion layer, the working range of the plastic hinge area is enlarged, the working time of the carbon fiber is delayed, and the interaction between the steel pipe and the core concrete is fully exerted; the addition of the longitudinal fibers improves the integral restraint effect of the carbon fibers, prevents the carbon fibers from being damaged between layers too early, and has the advantages of clear stress of the components, simple structure and convenient construction.
Description
Technical Field
The invention belongs to the field of civil engineering, and particularly relates to a longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) confined concrete-filled steel tube column with a cushion layer and a construction method thereof.
Background
The steel pipe concrete is a combined structure form of filling concrete into a steel pipe, fully considers the interaction effect of the concrete and steel, has the advantages of high bearing capacity, good ductility, excellent earthquake resistance, convenient construction and the like, and is applied to civil engineering more than one hundred years ago. The CFRP constraint concrete filled steel tube considers that effective constraint is applied to dangerous areas of the members, and the deformation of the steel tube is limited, so that the mechanical property of the steel tube is improved. The adoption of the fiber reinforced composite material, particularly the carbon fiber material (CFRP), can not only delay or limit the local buckling of the steel pipe, but also enhance the constraint capacity on the core concrete together with the steel pipe, and improve the stress performance of the member.
Under the load action of the existing CFRP (carbon fiber reinforced plastics) constraint concrete-filled steel tube column, the hoop stress of carbon fibers always exists in the loading process and is continuously increased along with the increase of loading displacement. The steel yield parts of the steel pipe are distributed in the plastic hinge area and the upper area of the plastic hinge area, and local buckling is formed at the junction position of the plastic hinge constraint area and the non-constraint area along with the continuous development of stress. In the loading process, the hoop stress of the carbon fibers is continuously increased, so that the interlayer damage of the single-layer carbon fibers is caused too early, and the constraint effect of the single-layer carbon fibers cannot be fully exerted.
Disclosure of Invention
In order to solve the problems, the invention discloses a longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) confined concrete-filled steel tube column with a cushion layer and a method. According to the invention, reliable force transmission is carried out between the steel pipe concrete and the carbon fiber layer through the foam cushion layer, the working range of the plastic hinge area is enlarged, the working time of the carbon fiber is delayed, and the interaction between the steel pipe and the core concrete is fully exerted; the longitudinal fibers are added, the integral restraint effect of the carbon fibers is improved, the carbon fibers are prevented from being damaged between layers too early, the stress of the component is clear, the structure is simple, and construction is convenient.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the utility model provides a set up two-way CFRP restraint steel core concrete column of moving about freely and quickly of cushion course, includes steel core concrete column (1), and steel core concrete column (1) periphery is fixed with cushion course (2), and cushion course (2) external fixation has a plurality of layers of CFRP cloth, CFRP includes inboard vertical CFRP cloth (3) and the horizontal CFRP cloth (4) in the outside.
In a further improvement, the cuff index of CFRP is determined by the following equation:
in the formula: sigma t -CFRP tensile strength;
σ c -core concrete compressive strength;
σ 0 -unrestrained concrete compressive strength;
d, the diameter of the cross section of the core concrete;
r-radius of cross section of core concrete;
k is the lateral constraint coefficient;
k-CFRP transverse tensile strength exertion coefficient;
A t -CFRP cross-sectional area;
A c -core concrete cross-sectional area;
ξ t -cuff index of CFRP;
n is the number of the transverse CFRP cloth layers, and n is between 0 and 4;
t, the thickness of each layer of CFRP cloth;
in the stress process, the circumferential restraining force of the CFRP is mainly provided by the transverse fiber cloth, and the longitudinal fiber cloth mainly plays a role in connecting the fiber yarns to avoid monofilament damage of the fiber yarns, so that the longitudinal carbon fibers cannot participate in restraining stress in the circumferential direction.
In a further improvement, the cushion layer (2) is adhered and fixed on a potential plastic hinge area of the steel tube concrete column (1).
In a further development, the thickness t of the cushion layer (2) h The D/th is controlled to be not less than 75, the thickness of the cushion layer (2) is 1mm at the minimum, and the elastic modulus of the cushion layer (2) is 0.01Et.
In a further improvement, the cushion layer (2) is a foam cushion layer.
A method for constructing a longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) restrained concrete-filled steel tube column with a cushion layer comprises the following steps:
step one, manufacturing a steel pipe concrete column (1) on a base;
secondly, sticking a cushion layer (2) on a potential plastic hinge area of the concrete-filled steel tubular column (1);
and step three, adhering longitudinal CFRP cloth (3) outside the cushion layer (2), and then adhering transverse CFRP cloth (4) outside the longitudinal CFRP cloth (3).
In the second step, the surface of the steel pipe on the steel pipe concrete column (1) is cleaned to ensure that the adhered surface is sufficiently dry, flat and dustless, and the cushion pad layer (2) is adhered to the working surface of the steel pipe.
The invention has the advantages that:
the integral constraint effect of the carbon fibers is improved, the working range of the plastic hinge area is enlarged, the participation working time of the carbon fibers is prolonged, the interaction of the steel pipe and core concrete is fully exerted, the deformation performance of the component is improved, and the constraint column has better ductility and energy consumption capability.
Moreover, the cushion layer of the invention is convenient to obtain, does not need special technology when being pasted, and is simple and convenient to operate.
Drawings
FIG. 1 is a schematic cross-sectional view of the present invention;
FIG. 2 is a graph of a test column skeleton under two working conditions;
FIG. 3 is a diagram of the energy consumption of the test column under two working conditions.
Detailed Description
The invention is further explained with reference to the drawings and the embodiments.
Examples
The prefabricated steel pipe is processed in a factory, the steel pipe is rolled into a cylinder by a plate rolling machine, the welding design is carried out according to the requirements of the national standard 'design Specification for Steel Structure' (GB 50017-2003), and the straight welded steel pipe is welded by adopting a groove. In order to meet the rigid connection between the steel pipe and the base, four rib plates are welded at the lower end of the steel pipe and punched, so that the steel bars of the base penetrate through the rib plates, and the connection strength is enhanced. The steel plate is welded at the bottom of the steel pipe, so that core concrete can be poured conveniently, and rib plates can be welded conveniently.
Firstly, the base adopts a reinforced concrete structure, so that the rigidity of the base is ensured to avoid damage in the test process, sufficient guarantee is provided in the aspect of reinforcing bars, and the base concrete is poured and tamped on the base.
And then, pouring core concrete inside the steel pipe.
Then, in order to facilitate the test loading, a reinforced concrete column cap is designed on the top of the column. To ensure the rigidity of the column head, reinforcing bars are reinforced like the base. And then pouring concrete, and curing and forming.
And after the concrete-filled steel tube column is formed and maintained, sticking a cushion layer and carbon fiber cloth on the potential plastic hinge area. In the process of pasting the cushion layer, the surface of the steel pipe is cleaned firstly, the pasted surface is ensured to be fully dry, flat and dustless, and the cushion layer is pasted on the working surface. In conjunction with the findings of the prior art, it is suggested that the thickness of the cushion layer be 1mm.
Finally, after epoxy resin is mixed uniformly according to a proportion, the epoxy resin is uniformly smeared on a cushion pad layer by a short hair roller, and longitudinal and transverse bidirectional carbon fiber layers are sequentially pasted on a working surface: the working face is hugged closely to horizontal carbon fiber layer, and horizontal carbon fiber layer is hugged closely to vertical carbon fiber layer to roll repeatedly the roll extrusion carbon cloth surface with the defoaming, make carbon fiber layer and buffer layer combine closely, be unlikely to have the bubble to exist.
By comparison with the test column skeleton curve without cushion, the following differences can be found: before the peak point, the stress performance of the two is basically consistent; after the peak point, the composite column without the cushion layer buckles at the junction of the constrained region and the unconstrained region, and the carbon fiber constraint is not provided at the junction, resulting in reduced ductility and load-bearing capacity of the column, as shown in fig. 2
The comparison of the energy consumption situation of the test column without the cushion mat shows that the test column with the longitudinal fibers is superior to the test column without the longitudinal fibers in the aspect of energy consumption, which shows that the addition of the longitudinal fibers improves the anti-seismic performance of the test piece, namely the ductility. Before breaking, the CFRP satisfies hooke's law, i.e., σ = E ∈ (E is the elastic modulus of CFRP), and when breaking occurs, the CFRP should reach its ultimate strain and ultimate stress, but in reality, it does not reach, i.e., there is a CFRP transverse tensile exertion coefficient k, at which the CFRP stress-strain relationship is σ = E ∈, and the addition of longitudinal fibers increases the exertion coefficient. And the compressive strength of the concrete after CFRP reinforcement meets the following requirements:
in the formula: sigma t -CFRP tensile strength;
σ c -core concrete compressive strength;
σ 0 -unrestrained concrete compressive strength;
d, the diameter of the cross section of the core concrete;
r-radius of cross section of core concrete;
k is the lateral constraint coefficient;
k-CFRP transverse tensile strength exertion coefficient;
A t -CFRP cross-sectional area;
A c -core concrete cross-sectional area;
ξ t -cuff index of CFRP;
n is the number of the transverse CFRP cloth layers, and n is recommended to be between 0 and 4;
t is the thickness of each layer of CFRP cloth.
Therefore, the increase of the coefficient k is utilized, so that the compressive strength of the concrete after CFRP reinforcement is increased.
In addition, compared with a comparison column, the longitudinal and transverse bidirectional CFRP test piece with the buffer cushion layer is improved by 10.2% in strength and 6.6% in ductility coefficient. By analyzing the experimental parameters, the strength improvement coefficient k can be obtained p The calculation formula of (a) is as follows:
in the formula: t is t s -the thickness of the steel tube;
n 0 -axial pressure ratio.
And in the degradation stage, the additional transverse constraint enables the degradation of the component to be effectively controlled, and the degradation curve is more stable compared with a comparison column. In the aspect of energy consumption, under the initial loading stage or the small deformation condition, the longitudinal and transverse bidirectional CFRP test piece and the comparison column provided with the buffer cushion layer are under the same-stage circulation, and along with the increase of displacement load (2% lateral displacement rate), the energy consumption coefficient of the restraint test piece is remarkably increased, as shown in fig. 3.
While embodiments of the invention have been disclosed above, it is not limited to the applications set forth in the specification and the embodiments, which are fully applicable to various fields of endeavor for which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (4)
1. A longitudinal and transverse bidirectional CFRP (carbon fiber reinforced plastics) restrained concrete-filled steel tube column provided with a cushion layer is characterized by comprising a concrete-filled steel tube column (1), wherein the cushion layer (2) is fixed on the periphery of the concrete-filled steel tube column (1), a plurality of layers of CFRP cloth are fixed outside the cushion layer (2), and the CFRP comprises an inner longitudinal CFRP cloth (3) and an outer transverse CFRP cloth (4); the cuff index of CFRP is determined by the following equation:
in the formula:
-CFRP tensile strength;
D-core concrete cross-section diameter;
K-a lateral constraint coefficient;
in the stress process, the circumferential constraint force of the CFRP is provided by the transverse fiber cloth, and the longitudinal fiber cloth plays a role in connecting the fiber yarns and avoiding the fiber yarns from being damaged by monofilaments, so that the longitudinal carbon fibers do not participate in constraint stress in the circumferential direction.
2. The column of claim 1, wherein the cushion layer (2) is adhesively fixed to the potential plastic hinge area of the column (1).
3. The longitudinal and transverse bidirectional CFRP confined steel core concrete column with a cushion layer as set forth in claim 1, wherein the thickness of the cushion layer (2) is set
Is controlled at
Not less than 75 mm, and the thickness of the cushion layer (2) is 1mm at the minimum.
4. The longitudinal and transverse both-way CFRP confined concrete filled steel tubular column with a cushion layer according to claim 1, wherein the cushion layer (2) is a foam cushion layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN2022103015253 | 2022-03-25 | ||
| CN202210301525 | 2022-03-25 |
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| CN114673305A CN114673305A (en) | 2022-06-28 |
| CN114673305B true CN114673305B (en) | 2022-11-25 |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201762818U (en) * | 2010-09-16 | 2011-03-16 | 南京林业大学 | FRP-rubber-steel compound pipe concrete structure |
| CN102936941A (en) * | 2012-10-24 | 2013-02-20 | 南京林业大学 | Composite pipe concrete composite structure |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101936852B (en) * | 2010-07-12 | 2012-07-04 | 哈尔滨工业大学深圳研究生院 | Confirming method of axial compression bearing capacity of steel tube-FRP (Fiber Reinforced Plastic)-concrete column as well as application |
| CN202390752U (en) * | 2011-10-13 | 2012-08-22 | 南京市公路建设处 | Fiber-steel composite pipe reinforced concrete pier |
| CN102912936A (en) * | 2012-10-16 | 2013-02-06 | 浙江树人大学 | Method for designing FRP (fiber reinforce plastic) tube-concrete-steel tube combined column |
| CN108316559A (en) * | 2017-01-18 | 2018-07-24 | 湖南大学 | A kind of novel stage construction CFRP restrained concrete superposed column |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201762818U (en) * | 2010-09-16 | 2011-03-16 | 南京林业大学 | FRP-rubber-steel compound pipe concrete structure |
| CN102936941A (en) * | 2012-10-24 | 2013-02-20 | 南京林业大学 | Composite pipe concrete composite structure |
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