A new type of GFRP tube-concrete sandwich composite pipe column and a preparation method thereof

Abstract

This invention discloses a novel composite column consisting of a GFRP pipe-concrete-sandwich composite pipe and its preparation method, specifically relating to the field of building engineering technology. The column comprises an outer GFRP pipe, a sandwich composite pipe, and ECC concrete. The ECC concrete exhibits excellent mechanical properties and high ductility under tensile and shear loads, effectively enhancing the seismic resistance of the component. The sandwich composite pipe, composed of high-performance grouting material and thin-walled steel pipe, possesses outstanding compressive strength, providing axial force and working with the GFRP pipe to constrain the lateral deformation of the concrete. The ECC concrete also possesses good ductility and crack resistance, further enhancing the overall structural toughness. Integrating the advantages of ECC concrete, the sandwich composite pipe, and the GFRP pipe, its seismic performance is significantly superior to traditional components. Its synergistic effect of compressive strength, constraint, and ductility allows it to maintain stable performance even in corrosive environments with high salinity and humidity, effectively solving the corrosion problem of steel-concrete composite components.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a novel composite column of GFRP pipe-concrete-sandwich composite pipe and its preparation method. Background Technology

[0002] Due to the influence of complex geographical environments and frequent geological disasters, modern engineering structures are developing towards diversification, intelligence, and lightweighting. Against this backdrop, there is an urgent need to develop a new type of engineering structural system that combines long service life with strong disaster resistance to adapt to increasingly stringent operating environments and safety requirements. Fiber-reinforced polymer (FRP) composites, due to their lightweight, high strength, and excellent corrosion resistance, have become important materials for structural innovation. Combining them with ordinary building materials can form complementary composite structural systems. As a type of FRP, GFRP has lower costs and better corrosion resistance, and has been applied in many fields. Improving existing structures based on GFRP pipes has significantly enhanced their performance, leading to the development of a new composite structure of GFRP pipe-concrete-steel pipe (DSTC). This structural form exhibits significant advantages in both mechanical properties and durability.

[0003] Although the DSTC structure has demonstrated good overall performance, actual stress analysis shows that its internal steel pipes often experience severe localized deformation failure rather than overall instability. This characteristic reflects that the load-bearing capacity of the steel pipe material is not fully utilized, resulting in material waste and low structural efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a novel composite column of GFRP pipe-concrete-sandwich composite pipe and its preparation method, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a novel composite column of GFRP pipe-concrete-laminated composite pipe, comprising an outer GFRP pipe, a laminated composite pipe, and ECC concrete filled between the inner sides of the GFRP pipe and the laminated composite pipe; The sandwich composite pipe, ECC concrete, and GFRP pipe are arranged coaxially from the inside to the outside. The sandwich composite pipe is made of a double-layer thin-walled steel pipe and a high-performance grout injected into the sandwich of the double-layer thin-walled steel pipe. The double-layer thin-walled steel pipe is specifically Q235 low carbon steel, and the single layer thickness is 3mm. The GFRP tube is a pultruded glass fiber tube; The ECC concrete includes ECC made of polyvinyl alcohol fiber, with a fiber length of 12 mm, a tensile strength of 1830 MPa, an initial modulus of 40 GPa, and an equivalent diameter of 15.3 μm.

[0006] Preferably, the ECC concrete further includes coarse aggregate, fine aggregate, cement, and admixtures.

[0007] Preferably, the coarse aggregate of the concrete is a continuous graded aggregate with a particle size of 5-10mm; the fine aggregate is natural river sand with a fineness modulus of 2.8; the cement is 42.5 ordinary Portland cement; the admixture is a high-performance compound polycarboxylate admixture; and the high-performance grouting material is C40 high-strength grouting material.

[0008] A method for preparing a novel composite column consisting of GFRP pipe, concrete, and sandwiched pipe is described below: S1. Pre-treatment: Inspection of the appearance and dimensions of GFRP pipes and thin-walled steel pipes; S2. Clamping: Assemble and fix the GFRP pipe and the inner and outer thin-walled steel pipes for preparing the sandwich composite pipe onto the wooden template, ensuring that the axes are aligned. S3. Inject the prepared high-performance grout between the two steel pipes and wait for it to set. S4. Pour the prepared ECC concrete between the GFRP pipe and the sandwich composite pipe.

[0009] Preferred options also include: S5. After the cast specimen has been covered with a film for 24 hours of curing, the formwork is removed. S6. The specimens were cured for 28 days under standard conditions of temperature 20±2℃ and humidity ≥95%.

[0010] The technical effects and advantages of this invention are as follows: 1. The novel composite column consists of a GFRP outer tube, a sandwiched composite tube, and ECC concrete. ECC concrete exhibits excellent mechanical properties and high ductility under tensile and shear loads, effectively improving the seismic resistance of the component. The sandwiched composite tube is composed of high-performance grouting material and thin-walled steel pipe, possessing outstanding compressive strength, providing axial force, and working together with the GFRP tube to constrain the lateral deformation of the concrete. ECC concrete also possesses good ductility and crack resistance, further enhancing the overall toughness of the structure.

[0011] 2. It can effectively solve problems such as the optimized configuration of the cross-section of the new composite column and the improvement of the performance of the sandwich concrete, thereby improving material utilization and construction convenience. The application of sandwich composite pipes makes the adjustment of the stress rationality of the composite column cross-section more controllable.

[0012] 3. The novel composite column integrates the advantages of ECC concrete, sandwich composite pipe, and GFRP pipe, exhibiting significantly superior seismic performance compared to traditional components. Its synergistic effect of compressive strength, confinement, and ductility allows it to maintain stable performance even in corrosive environments with high salinity and humidity, effectively solving the corrosion problem of steel-concrete composite components. Systematic research on this structure will drive innovation in civil engineering and expand its application prospects in the construction industry. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of Example 1 of the present invention; Figure 2 This is a cross-sectional view of the overall structure of Example 1 of the present invention; Figure 3 This is a top view of the structure of Example 1 of the present invention; Figure 4 This is a schematic diagram of the structure of Example 2 of the present invention; Figure 5 This is a cross-sectional view of the overall structure of Example 2 of the present invention; Figure 6 This is a top view of the structure of Example 2 of the present invention.

[0014] In the diagram: 1. GFRP pipe; 2. ECC concrete; 3. Thin-walled steel pipe; 4. High-performance grouting material. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention provides, for example Figures 1-6 The present invention relates to a novel GFRP pipe-concrete-sandwich composite pipe combined column and its preparation method, with reference to... Figures 1-6 This embodiment discloses a novel composite column consisting of a GFRP pipe-concrete-sandwich composite pipe, including a GFRP outer pipe 1, an inner sandwich composite pipe, and ECC concrete 2 filling the space between the GFRP pipe 1 and the inner side of the sandwich composite pipe. The sandwich composite pipe is composed of a thin-walled steel pipe 3, a high-performance grouting material 4, and a thin-walled steel pipe 3. The sandwich composite pipe, ECC concrete 2, and GFRP pipe 1 are arranged coaxially from the inside to the outside.

[0017] The scheme was further optimized by using GFRP pipe 1 as the outer pipe of the composite column structure.

[0018] GFRP has a thermal expansion coefficient close to that of concrete, which provides a basis for constructing a new composite structure of GFRP pipe-concrete-sandwich composite pipe. GFRP pipe 1 can replace formwork, saving costs, speeding up construction, and facilitating industrialized construction. GFRP pipe 1 has good corrosion resistance and can be used in structures exposed, easily corroded, and in special adverse environments, making it more suitable for areas subject to harsh environmental erosion.

[0019] The scheme has been further optimized, and the sandwich composite pipe is composed of thin-walled steel pipe 3, high-performance grouting material 4, and thin-walled steel pipe 3.

[0020] The sandwich composite pipe adopts a structure of double-layer thin-walled steel pipe sandwiching high-performance grouting material. This retains the compressive and restraining capacity of the steel pipe while promoting full yielding of the steel pipe through uniform force transmission by the grouting material, thus avoiding local buckling. This design effectively overcomes the problem of underutilization of steel pipe in DSTC, improves the overall bearing capacity and ductility of the composite column, and maximizes the utilization of material properties.

[0021] Further optimization of the scheme: GFRP pipe 1 is a pultruded glass fiber pipe.

[0022] To further optimize the scheme, ECC concrete 2 was poured between GFRP pipe 1 and the sandwich composite pipe.

[0023] Further optimization of the scheme: the ECC in ECC concrete 2 uses polyvinyl alcohol fiber (PVA), with a fiber length of 12mm, tensile strength of 1830MPa, initial modulus of 40GPa, and equivalent diameter of 15.3μm.

[0024] ECC is a strain-hardening fiber-reinforced cementitious composite material. Its core value lies in its superior tensile and shear ductility imparted through a multi-crack mechanism. Leveraging the excellent axial deformation compatibility of ECC and the high tensile strength of GFRP reinforcement, this composite column achieves significant improvements in ductility and hysteretic energy dissipation capacity, thus exhibiting superior seismic performance under strong earthquakes. Furthermore, the excellent crack resistance of ECC effectively inhibits crack propagation and delays damage evolution, enabling it to adapt to complex stress states and ensuring the composite column maintains high structural toughness and stability under disaster conditions.

[0025] Further optimization of the scheme: the thin-walled steel pipe 3 is a seamless steel pipe made of Q235 low carbon steel with a thickness of 3mm.

[0026] Further optimization of the scheme: Compared with other schemes, the present invention preferably uses Q235 low-carbon steel because the stress mechanism of this composite column belongs to a multi-nested constraint system. Under axial load, the outer GFRP pipe, the middle sandwich composite pipe, and the core grouting material share the stress. The yield strength (235MPa) of Q235 steel is moderate compared with ordinary steel, and its elastic modulus forms a good stiffness gradient match with the GFRP pipe and ECC material. If steel with excessive strength is used, the yield strain of the steel pipe will be small, which will cause it to buckle locally before the GFRP pipe can fully exert its tensile performance, destroying the constraint effect of the outer GFRP on the inside; while Q235 steel has good plastic deformation capacity and can yield when the structure is close to failure, transferring the load to the outer GFRP pipe, thereby realizing a secondary stress defense line and significantly improving the ultimate deformation capacity and ductility of the composite column.

[0027] Further optimization of the scheme: Compared with other schemes, this invention preferably uses a thin-walled steel pipe with a wall thickness of 3mm. This thickness is based on a balance between local stability and constraint efficiency. When the wall thickness is less than 2mm, the steel pipe is prone to local buckling due to lateral pressure when pouring high-performance grout, resulting in an irregular cross-section and failing to provide effective lateral constraint to the core concrete. When the wall thickness is greater than 5mm, the steel pipe changes from a "constraint member" to a "main load-bearing member." Although the strength is improved, the structural self-weight is significantly increased, and an overly rigid steel pipe will inhibit the stress development of the GFRP pipe, leading to material waste. Experiments and simulations show that a 3mm wall thickness, while ensuring the geometric stability of the steel pipe itself, can maximize the "triaxial stress" effect of the core grout, enabling the composite column to achieve the optimal axial compression ratio while maintaining lightweight design. The optimized solution uses high-performance grouting material 4, which is C40 high-strength grouting material; the coarse aggregate of the concrete is 5-10mm continuous graded aggregate stone, the fine aggregate is natural river sand with a fineness modulus of 2.8, the cement is 42.5 ordinary Portland cement, and the admixture is high-performance compound polycarboxylate admixture.

[0028] Further optimization of the scheme involves using 5-10mm continuously graded coarse aggregate in the concrete. This ensures both the dense filling performance of the grout in the thin-walled composite section and provides the necessary rigid framework and interfacial mechanical interlocking force. This avoids insufficient stiffness and shrinkage cracking due to excessively fine aggregate, or incomplete compaction, weakened interfaces, and localized stress concentration due to excessively large aggregate, thus ensuring the overall load-bearing performance and long-term durability of the composite column. The advantages of this selection are illustrated in the table below. Specific potential problems are shown in Table 1.

[0029] Table 1 Problems arising from mismatched aggregate particle size selection Particle size selection <5mm >10mm question The coarse aggregate skeleton function disappears Lack of concrete compaction Increased risk of localized instability in steel pipes This leads to local buckling of the steel pipe. Shrinkage and cracking occur due to increased wind direction. Uneven distribution of constraint stress Specifically, a method for preparing a novel composite column consisting of GFRP pipe-concrete-sandwiched pipe includes: S1, GFRP pipe 1, thin-walled steel pipe 3: Inspection of pipe appearance and dimensions; Based on the actual engineering structure requirements, the cross-sectional areas of GFRP pipe 1 and thin-walled steel pipe 3 should be selected with full consideration of load-bearing and bending performance. The strength of the ECC concrete can be reasonably set according to design needs to ensure that the entire GFRP pipe-concrete-sandwich composite pipe column meets the design requirements in terms of load-bearing capacity and seismic performance, thus ensuring the safety and reliability of the project.

[0030] Based on actual needs and engineering requirements, the processes related to engineering needs will be determined for those skilled in the art, which will not be elaborated here.

[0031] S2. Assemble and fix the GFRP pipe (1) and the inner and outer thin-walled steel pipes (3) for preparing the sandwich composite pipe onto the wooden template with their axes aligned.

[0032] S3. Inject the prepared high-performance grout (4) between the two steel pipes and wait for it to set.

[0033] S4. Pour the prepared ECC concrete (2) between the GFRP pipe (1) and the sandwich composite pipe.

[0034] S5. After the cast specimen has been covered with a film and cured for 24 hours, the mold is removed.

[0035] S6. The specimens were cured under standard conditions (temperature 20±2℃, humidity ≥95%) for 28 days.

[0036] In this embodiment, GFRP pipe, ECC concrete, and sandwich composite pipe are combined. The use of sandwich composite pipe can reduce local buckling of steel pipe and improve material utilization; ECC gives the structure high ductility and seismic performance; GFRP is corrosion resistant, lightweight and high-strength. The synergistic effect of the three significantly improves the load-bearing capacity, ductility and durability of the composite column, making it particularly suitable for engineering in highly corrosive and seismic zones. Example 2: Refer to Figures 4-6 The only difference between this embodiment and Embodiment 1 is that the GFRP pipe 1 has a circular cross-sectional shape, while the thin-walled steel pipe 3 has a square shape. The square cross-section of the sandwich composite pipe not only facilitates building layout and node connection, improving space utilization, but also improves the interfacial stress performance between the grout and the steel pipe through planar contact. At the same time, the square cross-section provides more flexible parameter optimization space for the multi-pipe composite system, which is conducive to achieving a balance between structural performance and construction convenience.

[0037] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A new type of GFRP tube-concrete sandwich composite pipe combined column, characterized in that: The outer tube is made of GFRP, the sandwich composite tube is made of two thin-walled steel tubes and high-performance grouting material filled in the sandwich of the two thin-walled steel tubes, and the ECC concrete is filled between the inner side of the GFRP tube and the sandwich composite tube. The sandwich composite tube, the ECC concrete and the GFRP tube are coaxially arranged from inside to outside. The sandwich composite tube is made of two thin-walled steel tubes and high-performance grouting material filled in the sandwich of the two thin-walled steel tubes, and the ECC concrete is filled between the inner side of the GFRP tube and the sandwich composite tube. The GFRP tube is a pultrusion type glass fiber tube. The ECC concrete includes ECC, polyvinyl alcohol fiber, the length of the polyvinyl alcohol fiber is 12 mm, the tensile strength is 1830 MPa, the initial modulus is 40 GPa, and the equivalent diameter is 15.3 μm.

2. The new type of GFRP tube-concrete sandwich composite column composite column according to claim 1, characterized in that: The ECC concrete further includes concrete coarse aggregate, fine aggregate, cement and admixture.

3. The new type of GFRP tube-concrete sandwich composite column composite column according to claim 2, characterized in that: The concrete coarse aggregate is continuous grading hornstone with a particle size of 5-10 mm, the fine aggregate is natural river sand with a fineness modulus of 2.8, the cement is 42.5 ordinary portland cement, the admixture is high-performance compound polycarboxylic admixture, and the high-performance grouting material is C40 high-strength grouting material.

4. A method for preparing a new type of GFRP tube-concrete sandwich composite column, for preparing the column according to claim 3, characterized in that: The specific steps are as follows: S1, pretreatment, checking the appearance and size of the GFRP tube and the thin-walled steel tube; S2, clamping, assembling and fixing the GFRP tube and the inner and outer thin-walled steel tubes for preparing the sandwich composite tube on the wood mold plate under the condition that the axial lines are consistent; S3, injecting the prepared high-performance grouting material into the space between the two steel tubes and waiting for the initial setting; S4, pouring the prepared ECC concrete between the GFRP tube and the sandwich composite tube.

5. The method according to claim 4, wherein the GFRP tube-concrete sandwich composite column is prepared by the following steps: (1) preparing a GFRP tube; (2) preparing a concrete tube; (3) preparing a GFRP tube-concrete sandwich composite column by bonding the GFRP tube and the concrete tube. Further comprising: S5, removing the mold after the pouring of the test piece is completed and the test piece is covered and maintained for 24 h; S6, maintaining the test piece under the standard condition of a temperature of 20±2℃ and a humidity of ≥95% until 28 d.

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