A cross-shaped steel-fiber composite prestressed local reinforcing block structure

Abstract

The present application relates to a kind of cross steel-fiber composite prestressed local reinforcing block structures, for the constraint reinforcement of concrete main body local area, the prestressed local reinforcing block structure includes: several prestressed tendons;Cross steel member between several prestressed tendons;Micro-expansion concrete is poured in the inside and outside of the prestressed tendon and cross steel member;And fiber composite material is wound in the outside of the micro-expansion concrete.Compared with the prior art, the present application comprehensively applies cross steel member and fiber composite material, significantly improves the compressive strength and overall performance of the concrete in compression zone, simplifies the construction process, is suitable for prefabrication and assembly, can significantly speed up construction progress, provides effective solutions for the stability and safety of prestressed structure.

Description

Technical Field

[0001] This invention relates to the field of prefabricated bridge technology, and in particular to a prestressed local reinforcing block structure of cross-shaped steel-fiber composite material. Background Technology

[0002] Prestressed technology plays a crucial role in bridge engineering, with its applications becoming increasingly widespread and mature. Over time, this technology has been widely used in projects such as long-span prestressed beams and slope reinforcement to ensure project quality and safety. Compared to non-prestressed structures, modern prestressed structures possess advantages such as high crack resistance, impermeability, high stiffness, high strength, superior load-bearing performance, excellent durability, lightweight and aesthetic appeal, economy, material conservation, and energy conservation.

[0003] Prestressed technology has been used in practice for over half a century. Due to its advantages such as high structural safety, high stiffness, material saving, light weight, and superior crack resistance, prestressed concrete has seen rapid development in research and application, with its application scope continuously expanding and its quantity gradually increasing. However, traditional prestressed anchor blocks use a method of restraint around reinforcing bars, which has limited restraint capacity, leading to frequent cracking or spalling of the concrete in the stress zone under the anchor.

[0004] Recent studies have shown that in spiral reinforced concrete structures, when the strain reaches the ultimate strain of plain concrete, the member is prone to splitting failure, and the stirrups often fail to reach their yield strength, thus failing to fully exert their restraining effect and resulting in poor restraint. In traditional reinforcement measures, the stress of indirect reinforcement under local loads is usually kept within a small range. Multiple experimental studies have shown that within a moderate range of indirect reinforcement ratios, the local compressive strength increases with the increase of the reinforcement ratio. However, when the reinforcement ratio is too high, the stress of the indirect reinforcement may fail to reach the yield strength, thus failing to fully exert its effect and reducing the load-bearing capacity of the structure. Under local pressure loads, the stress distribution under anchors is quite complex. The "concentric, symmetrical, effective area" principle is usually used to simplify the stress distribution under anchors to consider the case of eccentric local pressure and multiple anchors acting simultaneously. However, when multiple anchors act simultaneously, the stress distribution under anchors becomes more complex, and relevant experimental data are relatively limited. The commonly used method is to calculate the base area according to the non-overlapping principle and then estimate the local compressive strength based on the calculation method for a single anchor. However, current domestic and international standards have not yet provided a clear calculation method. While spiral reinforcement significantly affects the load-bearing capacity of a local model, it determines the load-bearing capacity of that model at structural failure, and also significantly influences the displacement of the anchor head. Spiral reinforcement can effectively increase the displacement of the anchor head at structural failure, thereby significantly improving the compressive strength of concrete. However, during the stress process, spiral reinforcement is in the elastic deformation stage. When the ultimate load is reached, the spiral reinforcement yields, losing its restraining effect on the concrete. This causes the concrete to no longer be in a triaxial compressive state, and is subsequently rapidly crushed, causing the anchor head to lose its load-bearing capacity.

[0005] Patent publication number CN217711380U discloses a cross-shaped steel frame-fiber woven mesh reinforced fiber concrete octagonal column. The C-shaped steel is rotated to form a closed cross-shaped steel frame. A fiber woven mesh is provided on the outer surface of the closed cross-shaped steel frame, and the fiber woven mesh constrains the outer edge of the steel frame. Fiber concrete, which is an ultra-high toughness cement-based composite material, is poured on both the inner and outer sides of the closed cross-shaped steel frame. However, this method uses C-shaped steel rotated to form a closed cross-shaped steel frame and then wraps it with a fiber woven mesh to form an octagon. The fiber woven mesh has a uniform thickness and does not form uneven contact with the external concrete, thus failing to provide anchoring. Furthermore, this concrete octagonal column structure is inconvenient to construct. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a prestressed local reinforcement block structure of cross-shaped steel-fiber composite material. Through the combined effect of the built-in cross-shaped steel and the externally wound fiber composite material, the confinement effect, crack resistance, and load-bearing capacity of concrete can be improved, providing a more reliable solution for the development of modern prestressed structures.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] In one aspect, the present invention provides a prestressed local reinforcement block structure of cross-shaped steel-fiber composite material for constraining and reinforcing local areas of a concrete matrix, the prestressed local reinforcement block structure comprising:

[0009] If the stress tendons are interfered with;

[0010] A cross-shaped steel member located between several prestressed tendons;

[0011] Micro-expansion concrete poured inside and outside the prestressed tendons and cross-shaped steel members;

[0012] And the fiber composite material wrapped around the outside of the micro-expansion concrete.

[0013] Furthermore, the prestressing tendons are arranged symmetrically in a square, and the center-to-center distance between adjacent prestressing tendons is 3 / 2 to 7 times the diameter of the prestressing tendon.

[0014] Furthermore, the center-to-center spacing between adjacent prestressing tendons is 3 to 6 times the diameter of the prestressing tendon.

[0015] Furthermore, the prestressing tendon has a hole on its outer side for the prestressing tendon to pass through, and a pad at its end for the prestressing force of the prestressing tendon to diffuse within the cross-sectional area; the ratio of prestressing tendon diameter to hole diameter to pad diameter is 1:(8 / 5~2):(16 / 5~4).

[0016] The holes are pre-set during the pre-fabrication of the prestressed local reinforcement block structure to allow the prestressing tendons to pass through. The prestressing tendons are tensioned on the construction site, and the prestressing tendons and pads are anchored in the micro-expansion concrete of the pressure area, transferring the pre-applied pressure to the micro-expansion concrete, thereby providing pre-compression stress, preventing the micro-expansion concrete from cracking, and improving material utilization efficiency.

[0017] Furthermore, the cross-shaped steel components are manufactured by cold bending, hot rolling, or welding, and are prefabricated in the factory.

[0018] Furthermore, the cross-shaped steel member is arranged in a crisscross pattern at the geometric center of the four prestressing tendons and extends into the spaces between adjacent prestressing tendons.

[0019] Furthermore, the cross-shaped steel member has a cross-sectional length that is 3 to 15 times the diameter of the prestressing tendon, and a cross-shaped steel member has a cross-sectional width that is 1 / 50 to 1 / 10 of its length.

[0020] Furthermore, the cross-shaped steel member has a cross-sectional length that is 3 to 5 times the diameter of the prestressed tendon, and a cross-sectional width that is 1 / 15 to 1 / 10 of its length.

[0021] During prestressing, due to the Poisson effect, the cruciform steel member exhibits a significant expansion effect in the transverse direction, thereby compressing the micro-expansion concrete in the compression area. This compression results in strong transverse constraint on the micro-expansion concrete, generating substantial transverse compressive stress. Simultaneously, the cross-section of the cruciform steel member possesses significant shear capacity in both principal axis directions, effectively improving the stiffness of the reinforced area in those directions. Therefore, it also significantly enhances fatigue resistance under live loads.

[0022] Furthermore, the cross-section of the micro-expansion concrete is circular, with a diameter 3 to 75 times that of the prestressing tendon.

[0023] Furthermore, the diameter of the micro-expansion concrete is 10 to 20 times the diameter of the prestressing tendon.

[0024] The micro-expansion concrete is the core area concrete. Under pre-stress, the micro-expansion concrete exhibits a tendency to expand outwards laterally. However, due to the expansion of the internal cruciform steel components and the constraint of the external fiber composite material, the lateral expansion of the micro-expansion concrete is strongly hindered. This combined effect results in the micro-expansion concrete exhibiting a three-phase compressive stress state, significantly improving its load-bearing capacity. The micro-expansion concrete used is a conventional material in this field and can be selected according to actual construction conditions and requirements. Suitable models include C35P8, C35P6, and C35 micro-expansion concrete.

[0025] Furthermore, the fiber composite material is wound around the outside of the micro-expansion concrete, and the surface has an uneven structure. The thickness of the concave portion is 1 / 25 to 2 / 5 of the diameter of the prestressing tendon, and the difference between the thickness of the convex portion and the concave portion is 1 / 4 to 1 times the thickness of the concave portion. The winding distance between the concave portion and the convex portion is 1 to 5 times the diameter of the prestressing tendon.

[0026] Furthermore, the thickness of the recessed portion is 2 / 25 to 1 / 5 of the diameter of the prestressing tendon, the difference between the thickness of the protruding portion and the recessed portion is 1 / 3 to 1 / 3 times the thickness of the recessed portion, and the winding distance between the recessed portion and the protruding portion is 3 to 4 times the diameter of the prestressing tendon.

[0027] Furthermore, the fiber composite material is wound at a winding angle of 85 to 90 degrees, stops at the protruding part, and then wound at a winding angle of 90 degrees.

[0028] Furthermore, the fiber composite material includes carbon fiber and glass fiber.

[0029] By winding the prestressed local reinforcing block structure with varying numbers of layers, a concave-convex contact is formed with the external concrete matrix, thereby increasing the contact area and establishing a mechanical connection. The excellent tensile properties of the fiber composite material positively impact the restraint effect, effectively restraining the expansion of the micro-expansion concrete in the internal core area and enhancing its load-bearing capacity. Furthermore, the treated area can be considered as coarse reinforcing steel in the external concrete matrix, contributing to the overall stability of the component. Moreover, its Poisson effect is minimal, preventing significant tensile stress from being generated in the contacting external concrete matrix.

[0030] In another aspect, the present invention also provides a cross-shaped steel-fiber composite concrete structure, which is constrained and reinforced by the above-mentioned cross-shaped steel-fiber composite prestressed local reinforcing block structure, and the concrete structure also includes a concrete body located thereon.

[0031] Furthermore, the prestressed local reinforcing block structure is suitable for use between concrete main structures with prestress between 1000 and 1800 MPa.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The prestressed local reinforcing block structure provided by the present invention has a cross-shaped steel member inside. Under compressive loading, it exhibits significant lateral expansion due to the Poisson effect, thereby compressing the micro-expansion concrete in the compression zone and providing more obvious restraint for the micro-expansion concrete. At the same time, the cross-shaped steel member has a large shear bearing capacity in the two principal axis directions, effectively improving the stiffness of the reinforced area in these two directions, and thus significantly improving the fatigue resistance.

[0034] (2) The embedded cruciform steel member in this invention provides strong bending and shear stiffness in the local area. When prestress is applied, the Poisson effect of steel is significantly greater than that of concrete, causing the cruciform steel member to effectively compress the micro-expansion concrete in the compression zone during lateral expansion, confining it to a triaxial compression state, thereby significantly improving the compressive strength of the core concrete. In this process, the cruciform steel member, as an embedded confinement element, has excellent load-bearing capacity, transferring prestress to the concrete and providing important reinforcement for the structure of prestressed tendons and concrete.

[0035] (3) In addition to the built-in cross-shaped steel component, the prestressed local reinforcement block structure provided by this invention also incorporates fiber composite materials to further enhance the performance of the prestressed local reinforcement block structure. The fiber composite material, through different layers of winding, forms an uneven contact with the micro-expansion concrete, thereby increasing the contact area and forming a mechanical connection. This connection method effectively constrains the expansion of the internal prestressing tendons, providing stronger constraint for the micro-expansion concrete in the compression area, thus significantly improving the constraint effect, crack resistance, and load-bearing capacity of the component, and reinforcing the prestressed structure in a more reliable manner.

[0036] (4) By selecting the type and number of layers of the fiber composite material, the present invention enables the fiber composite material to form an uneven contact with the micro-expansion concrete during winding, thereby increasing the contact area and forming a mechanical connection. Simultaneously, the fiber composite material exhibits excellent tensile strength, effectively constraining the expansion of the internal cross-shaped steel components and prestressing tendons, further improving the overall performance of the prestressed local reinforcement block structure. This dual constraint mechanism allows the core concrete to withstand higher stresses, thereby enhancing its compressive strength.

[0037] (5) The present invention moderately limits the indirect reinforcement ratio or local pressure core area to avoid problems caused by excessive reinforcement, which can improve material utilization efficiency, avoid over-reinforcement problems, and the calculation method is simple. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. However, the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0039] Figure 1 This is a top view of the prestressed local reinforcement block structure shown in Example 1;

[0040] Figure 2 This is a front view of the prestressed local reinforcement block structure shown in Example 1;

[0041] Figure 3 This is a right view of the prestressed local reinforcement block structure shown in Example 1;

[0042] Figure 4 This is an isometric view of the prestressed local reinforcement block structure shown in Example 1;

[0043] Figure 5 This is a right view of the connection between the prestressed local reinforcement block structure and the external concrete shown in Example 1.

[0044] Explanation of markings in the diagram:

[0045] 1-Cross-shaped steel component, 2-Micro-expansion concrete, 3-Fiber composite material, 4-Prestressed tendon, 5-Concrete, 6-Pad, 7-Hole. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0047] Example

[0048] See Figures 1-5 A prestressed local reinforcement block structure of cross-shaped steel-fiber composite material is used to constrain and reinforce local areas of the concrete main body 5. The prestressed local reinforcement block structure includes:

[0049] If the stress tendon 4 is interfered with;

[0050] A cross-shaped steel member 1 located between several prestressed tendons 4;

[0051] Micro-expansion concrete 2 is poured inside and outside the prestressed tendons 4 and the cross-shaped steel member 1;

[0052] And the fiber composite material 3 wrapped around the outside of the micro-expansion concrete 2.

[0053] In this embodiment, the prestressing tendons 4 are symmetrically arranged in a square, each with a cross-sectional diameter of 10 mm and a center-to-center distance of 50 mm between adjacent tendons 4. Each prestressing tendon 4 has a hole 7 on its outer side for passage, the hole 7 having a cross-sectional diameter of 20 mm. At its end, there is a pad 6 with a cross-sectional diameter of 40 mm to diffuse the prestressing force of the tendon 4 across its cross-section. The ratio of the prestressing tendon diameter to the hole 7 diameter to the pad 6 diameter is 1:2:4. The hole 7 is pre-set during the prefabrication of the prestressed local reinforcement block structure for the prestressing tendons 4 to pass through, and the prestressing tendons 4 are tensioned on-site.

[0054] In this embodiment, the cross-shaped steel member 1 is arranged in a crisscross pattern at the geometric center of the four prestressing tendons 4, extending into the spaces between adjacent prestressing tendons 4. The cross-shaped steel member 1 has a cross-sectional length of 100mm and a cross-sectional width of 7.5mm. The cross-shaped steel member 1 is manufactured by welding and is prefabricated in the factory.

[0055] In this embodiment, the cross-section of the micro-expansion concrete 2 is circular with a diameter of 300 mm. The micro-expansion concrete 2 is made of C35P8. Sufficient moisture needs to be maintained during the initial setting and curing processes to ensure the continuous hydration reaction of the cement. In the first few days after pouring, water should be sprayed regularly, covered with damp cloths, or a curing agent should be used to prevent excessive evaporation of surface moisture. In high-temperature environments, shading measures can be taken to avoid direct sunlight exposure. After curing, quality control and testing should be carried out, including: compressive strength testing, flexural strength testing, density measurement, porosity measurement, and visual inspection, until the construction requirements are met.

[0056] In this embodiment, the fiber composite material 3 is wound around the outside of the micro-expansion concrete 2, with a surface featuring an uneven structure. The thickness of the recessed portion is 2 mm, and the difference in thickness between the recessed and raised portions is 1 mm. The winding distance between the recessed and raised portions is 50 mm. The fiber composite material 3 is wound at an 85° winding angle, stopping at the raised portion, and then wound at a 90° winding angle. The fiber composite material 3 includes carbon fiber and glass fiber, and the thickness of a single layer of the fiber composite material is 0.3 mm. By winding with different numbers of layers, the prestressed local reinforcing block structure forms an uneven contact with the external concrete body 5, thereby increasing the contact area and forming a mechanical connection.

[0057] In this embodiment, the method for preparing the prestressed local reinforcing block structure is as follows:

[0058] A1: Determine the position of the prestressing tendons 4 so that they are arranged in a square, and reserve holes 7 according to the position;

[0059] A2: Determine the position of the cross-shaped steel member 1, arrange it at the geometric center of the four prestressing tendons 4, and extend it between the adjacent prestressing tendons 4;

[0060] A3: Pour micro-expansion concrete 2 inside and outside the prestressed tendons 4 and the cross-shaped steel member 1;

[0061] A4: After the pouring is completed, the fiber composite material 3 is wrapped around the outside of the solidified micro-expansion concrete 2, and the prefabricated part of the prestressed reinforcing block structure is completed.

[0062] A5: Tension the prestressing tendon 4 at the hole position 7, and the prestressing reinforcement block structure is completed.

[0063] In this embodiment, the precast portion of the prestressed local reinforcement block structure is prefabricated in the factory. After completion, it is transported to the construction site, and the prestressing tendons 4 are tensioned. The prestressing tendons 4 used are HPB300. To ensure the connection between the prestressed local reinforcement block structure and the concrete main body 5, the connection process can refer to the treatment method of construction joints. Specifically, the cement mortar and loose layer on the surface of the poured concrete are removed, ensuring that the area of ​​fresh concrete exposed is not less than 75%, and then washed clean with water to ensure the firmness of the connection. A layer of cement slurry is brushed on the old concrete surface, and a 30cm thick layer of concrete is laid on the old concrete surface. After solidification, the prestressed local reinforcement block structure is hoisted to the removed position. During the hoisting process of the prestressed local reinforcement block structure, the bending and shear resistance of the prestressed local reinforcement block structure is fully utilized, and the hoisting point positions are reasonably set according to the actual engineering conditions to ensure the stability and safety of the hoisting.

[0064] In this embodiment, the prestress of the concrete main body 5 is 1800 MPa. The prestressing tendons 4 and the concrete 5, together with the prestressed local reinforcement block structure, constitute a "coarse steel bar" anchoring method, namely a cross-shaped steel-fiber composite concrete structure, which effectively improves the overall load-bearing performance. This method is equivalent to adding steel bars with greater stiffness to the overall load-bearing system, thereby enhancing the overall stiffness of the component. At the same time, this also helps to transfer the longitudinal prestress inside the "coarse steel bar" to all parts of the component. Moreover, the construction process of the prestressed local reinforcement block structure is relatively simple, and the entire reinforcement area is suitable for prefabrication and assembly in the factory, thereby significantly shortening the construction cycle and improving construction efficiency.

[0065] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A prestressed local reinforcing block structure of cross-shaped steel-fiber composite material, characterized in that, The prestressed local reinforcement block structure is used to constrain and reinforce a local area of ​​the concrete main body (5), and includes: If the prestressing tendons (4) are interfered with, the prestressing tendons (4) are arranged symmetrically in a square; A cross-shaped steel member (1) is located between several prestressing tendons (4). The cross-shaped steel member (1) is arranged in a cross-shaped manner at the geometric center of the four prestressing tendons (4) and extends into the space between adjacent prestressing tendons (4). The cross-shaped steel member (1) has a cross section length that is 3 to 15 times the cross section diameter of the prestressing tendon (4) and a cross section width that is 1 / 50 to 1 / 10 of the length. Micro-expansion concrete (2) is poured inside and outside the prestressed tendons (4) and the cross-shaped steel members (1). And a fiber composite material (3) wrapped around the outside of the micro-expansion concrete (2), the fiber composite material (3) being wrapped around the outside of the micro-expansion concrete (2) with a concave-convex structure on the surface, the fiber composite material forming a concave-convex contact with the micro-expansion concrete during winding, forming a mechanical connection.

2. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 1, characterized in that, The center-to-center distance between adjacent prestressing tendons (4) is 3 / 2 to 7 times the diameter of the prestressing tendon (4).

3. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 1, characterized in that, The prestressing tendon (4) has a hole (7) on its outer side for the prestressing tendon (4) to pass through, and a pad (6) at its end for the prestressing force of the prestressing tendon (4) to diffuse within the cross-sectional area; the diameter of the prestressing tendon (4): the diameter of the hole (7): the diameter of the pad (6) is 1: (8 / 5~2): (16 / 5~4).

4. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 1, characterized in that, The cross-section of the micro-expansion concrete (2) is circular, and its diameter is 3 to 75 times the diameter of the prestressed tendon (4).

5. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 1, characterized in that, The fiber composite material (3) is wrapped around the outside of the micro-expansion concrete (2), and the surface has a concave-convex structure. The thickness of the concave part is 1 / 25 to 2 / 5 of the diameter of the prestressed tendon (4), and the difference between the thickness of the convex part and the concave part is 1 / 4 to 1 times the thickness of the concave part. The winding distance between the concave part and the convex part is 1 to 5 times the diameter of the prestressed tendon (4).

6. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 5, characterized in that, The fiber composite material (3) is wound at a winding angle of 85~90°, stops at the protruding part, and then wound at a winding angle of 90°.

7. The prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material according to claim 1, characterized in that, The fiber composite material (3) includes carbon fiber and glass fiber.

8. A cross-shaped steel-fiber composite concrete structure, characterized in that, It employs a prestressed local reinforcing block structure of a cross-shaped steel-fiber composite material as described in any one of claims 1 to 7 for constraint reinforcement, and the concrete structure also includes a part located in the concrete body (5).

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