CN221193030U - Reinforced concrete beam reinforcing structure equipped with steel wire mesh ultra-high performance concrete - Google Patents

Abstract

The utility model relates to a reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete, comprising a reinforced concrete beam, the bottom surface of which is provided with a groove layer and coated with a structural adhesive layer; bolts are respectively fixed at both ends of the bottom surface of the reinforced concrete beam, and a wire mesh fixedly connected to the lower part of the bolt is provided; the bottom surface of the reinforced concrete beam is also provided with UHPC which is cast into one piece with the reinforced concrete beam and wraps the bolt and the wire mesh. The reinforcement structure helps to effectively prevent the main cracks in the reinforced beam from causing brittle failure, and improves the utilization rate of UHPC and the ductility of the reinforced beam.

Description

A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete

Technical Field

The utility model relates to a reinforced concrete beam reinforcement structure configured with steel wire mesh ultra-high performance concrete.

Background technique

In recent years, with the development of urban construction and the increase in people's commuting needs, bridge traffic has increased rapidly. A large number of bridges in service have been designed with economically reasonable solutions, and the bearing capacity is limited. This causes the bearing performance to deteriorate during use. How to improve the bearing capacity through reinforcement to meet operational requirements has become an urgent problem that needs to be solved for the current bridge structures in service. Ultra-high Performance Concrete (UHPC) has ultra-high strength, high toughness, high durability, and high crack resistance, so UHPC is used to reinforce bridges. Studies have shown that although the use of UHPC to reinforce beams has increased the bearing capacity of the beams, due to the excessive stiffness of the beams after reinforcement, brittle failure of a single crack at the bottom of the beam occurs and develops rapidly.

[Wu Bin. Research on Material Performance and Stress Characteristics of RPC Reinforced Concrete Simply Supported Beam Bridge [D]. Jilin Jianzhu University, 2020] Two ordinary reinforced concrete beams were designed and manufactured, and one of them was partially reinforced with pure UHPC. Result analysis: Compared with ordinary concrete beams, simply using UHPC to reinforce the beam body has no obvious help in improving the bearing capacity of the beam, but only improves its stiffness, and the beam body suffers brittle failure during loading.

[Li Xingliang. Finite Element Analysis of Flexural Performance of Damaged RC Beams Reinforced with UHPC [J]. Highway Engineering, 2021, 46(04): 98-103+162] steel bars are placed in the UHPC reinforcement layer to improve the tensile toughness of the reinforcement layer. The test shows that the use of reinforced UHPC to reinforce ordinary reinforced concrete beams can effectively improve the flexural performance of the test beams and greatly improve their flexural bearing capacity. The higher the reinforcement ratio, the better the flexural performance, and the failure mode is ductile failure.

[Zhang Yang, Huang Songling, Liu Yingfeng, Shao Xudong. Experimental study on the flexural performance of RC beams reinforced with prestressed UHPC [J]. Journal of Hunan University (Natural Science Edition), 2022, 49(03): 23-3] et al. proposed a prestressed UHPC reinforcement technology and designed an experimental comparative analysis of the reinforcement effects of prestressed UHPC and conventional reinforced UHPC. The results showed that the test beams all showed traditional bending failure, among which the reinforcement efficiency of the prestressed UHPC layer was significantly higher than that of the conventional reinforced UHPC layer. The prestressed UHPC reinforcement layer improved the structural stress state and further inhibited the formation and development of cracks; in addition, the better tensile performance of the prestressed UHPC reinforcement layer made the flexural stiffness and ultimate bearing capacity of the RC beam more significantly improved.

However, when cracks appear in the reinforcement layer of UHPC reinforced reinforced concrete beams, they will quickly develop along a certain crack to form a single main crack, causing brittle failure of the beam body, and the crack-resistance effect of the steel fiber in UHPC cannot be exerted, resulting in a significant reduction in ductility. The configuration of steel bars and prestressed tendons in the UHPC reinforcement layer places high demands on the reinforcement layer. If the reinforcement layer is too thin, it cannot effectively protect the steel bars and prestressed tendons, and the configuration of prestressed tendons greatly increases the difficulty of construction.

Utility Model Content

The utility model aims to provide a reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete, which helps to effectively prevent the main cracks in the reinforced beam from occurring brittle failure, thereby improving the utilization rate of UHPC and the ductility of the reinforced beam.

The technical solution of the utility model is: a reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete, comprising a reinforced concrete beam, wherein the bottom surface of the reinforced concrete beam is provided with a groove layer and is coated with a structural adhesive layer; bolts are respectively fixed at both ends of the bottom surface of the reinforced concrete beam, and a wire mesh fixedly connected to the lower part of the bolt is provided; the bottom surface of the reinforced concrete beam is also provided with UHPC which is cast into one piece with the reinforced concrete beam and wraps the bolts and the wire mesh.

Furthermore, the groove layer is composed of a plurality of grooves formed by cutting the bottom surface of the reinforced concrete beam with a diamond grinding wheel.

Furthermore, the depth and length of the grooves are 5 mm×20 mm, and the center distance between two adjacent grooves is 55 mm.

Furthermore, blind holes penetrating the structural adhesive layer and the groove layer are respectively arranged at both ends of the bottom surface of the reinforced concrete beam, and the bolts are fixedly connected to the reinforced concrete beam via the anchoring adhesive arranged in the blind holes.

Furthermore, the steel wire mesh is flattened and tightened and then welded or tied to the bolts for fixation.

Furthermore, the number of layers of the steel mesh is 1, and the diameter of the steel wires of the steel mesh is greater than 4 mm.

Furthermore, the structural adhesive is SiKa32LP structural adhesive.

Furthermore, the UHPC has a thickness of 20 mm to 45 mm.

Compared with the prior art, the utility model has the following advantages: the reinforcement structure places the wire mesh in the UHPC reinforcement layer, which enhances the toughness of the reinforcement layer, slows down the degradation of the cross-sectional stiffness, promotes the full development and uniform distribution of cracks, prevents brittle failure, and thus improves the ductility and bearing capacity of the reinforced beam, effectively prevents the main cracks in the reinforced beam from causing brittle failure, and improves the utilization rate of UHPC and the ductility of the reinforced beam. Compared with steel bars and prestressed tendons, the wire mesh reduces the difficulty of construction, reduces the thickness of the UHPC reinforcement layer and the deadweight of the structure, is more economical, and its protective layer is easier to meet. It can be used to reinforce existing reinforced concrete beams.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the structure of the utility model;

Fig. 2 is a schematic cross-sectional view of the utility model;

Figure 3 is a load-displacement curve diagram of different reinforcement methods;

Figure 4 is a comparison of peak loads for the same wire mesh diameter and number of layers;

Figure 5 is a comparison of peak loads at different reinforcement layer thicknesses;

In the figure: 1- reinforced concrete beam 2- wire mesh 3- studs 4- UHPC 5- structural adhesive 6- grooved layer.

Detailed ways

In order to make the above features and advantages of the present invention more understandable, embodiments are given below with reference to the accompanying drawings for detailed description, but the present invention is not limited thereto.

Refer to Figure 1 and Figure 2

A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete comprises a reinforced concrete beam (original beam) 1, the bottom surface of the reinforced concrete beam is provided with a groove layer 6 and is coated with a structural adhesive layer 5, the structural adhesive is SiKa32LP structural adhesive; bolts 3 are fixed to both ends of the bottom surface of the reinforced concrete beam, and a wire mesh 2 is provided which is fixedly connected to the lower part of the bolt, and the wire mesh is welded or tied to the bolt after being flattened and tightened; the bottom surface of the reinforced concrete beam is also provided with UHPC 4 which is cast into one piece with the reinforced concrete beam and wraps the bolt and the wire mesh inside to form a reinforcement layer, and the thickness of the UHPC is 20 mm to 45 mm. The UHPC is sprayed on the bottom surface of the reinforced concrete beam and cured for 28 days in a natural environment to ensure the strength.

In this embodiment, the groove layer is composed of a plurality of grooves formed by cutting the bottom surface of the reinforced concrete beam with a diamond grinding wheel. The depth and length of the grooves are 5 mm×20 mm, the center distance between two adjacent grooves is 55 mm, and the surface roughness of the groove layer is 2 mm.

In this embodiment, a number of blind holes are drilled at both ends of the bottom surface of the reinforced concrete beam to pass through the structural adhesive layer and the groove layer. After the blind holes are drilled, they are cleaned and dusted, filled with anchoring glue, and then bolts are inserted into the blind holes to be fixedly connected to the reinforced concrete beam through the anchoring glue.

In this embodiment, the number of layers of the steel mesh is 1, and the diameter of the steel wires of the steel mesh is greater than 4 mm.

In this embodiment, the reinforced concrete beam may be a reinforced concrete T-beam.

Specific embodiment: The cross-sectional dimensions of the specimen component are 90 mm×250 mm, the beam flange width is 100 mm, the flange height is 65 mm, the beam length is l = 2400 mm, the span is l ₀ = 2000 mm, and the thickness of the reinforcement layer is 35 mm. The test materials are C40 concrete for ordinary concrete, UHPC for reinforcement layer, 304 stainless steel with 1 layer, 4 mm diameter, and 30 mm mesh size for wire mesh, 2 HRB400 steel bars with a diameter of 14 mm for the lower tensile reinforcement of the T-beam, 4 HRB400 steel bars with a diameter of 10 mm for the upper compressive longitudinal reinforcement, and HPB300 plain round steel bars with a diameter of 6 mm for the stirrups of the beam body and the stirrups of the upper flange.

The reinforcement process is as follows:

(1) Grooves were made on the concrete surface of the reinforced concrete beam. The NC surface was cut into grooves using a diamond grinding wheel. The groove size was about 5 mm × 20 mm, the center spacing was 55 mm, and the interface roughness was evaluated to be about 2 mm. (2) Blind holes were drilled at both ends of the bottom surface of the reinforced concrete beam. After drilling the blind holes, the holes were cleaned and dusted. After the holes were filled with rebar glue, the bolts were inserted. (3) When the rebar glue solidified, the gravel dust on the beam surface was brushed off with a brush and rinsed with clean water. When there was no obvious water stain on the beam surface, SiKa32LP structural glue was applied on the beam surface. (4) A wire mesh was laid and fixed on the rebar. When fixing, the wire mesh was flattened and tightened. (5) UHPC was sprayed and cured in a natural environment for 28 days.

After curing, the bending performance tests of UHPC reinforced beams and UHPC-wire mesh reinforced beams were carried out, and the failure mode, bearing capacity and ductility of the reinforced beams were analyzed.

Comparing the failure modes of UHPC reinforcement and UHPC-wire mesh reinforcement, the UHPC reinforcement broke along one of the main cracks in the mid-span, and the crack developed rapidly, while other cracks were sparsely distributed, showing brittle failure. However, when the wire mesh was placed in the UHPC reinforcement layer, the cracks in the specimen developed fully, improving the ductility of the reinforced beam, showing a ductile failure mode in which the tensile steel bars yielded, the reinforcement layer did not break, and the concrete in the compression zone was fully crushed. This shows the advantage of configuring wire mesh in the UHPC reinforcement layer.

The load-mid-span displacement curves of UHPC reinforcement and UHPC-wire mesh reinforcement are compared, as shown in Figure 3. After the tensile reinforcement of the UHPC reinforced beam yields, the curve rises briefly and then drops rapidly, and the damage stage is short, because the UHPC reinforcement layer breaks and exits work at this time. However, after the reinforcement yields, the UHPC-wire mesh reinforced beam undergoes a long damage stage until it reaches the ultimate bearing capacity. Because the concrete in the compression zone is fully crushed, the bearing capacity slowly decreases. The maximum bearing capacities of UHPC reinforcement and UHPC-wire mesh reinforcement are 106.8 kN and 167.30 kN, respectively. The bearing capacity of the UHPC reinforced beam is only 4.60% higher than that of the unreinforced beam, while the bearing capacity of the UHPC-wire mesh reinforced beam is increased by 63.86%. The ultimate deflections of UHPC reinforcement and UHPC-wire mesh reinforcement are 19.64 mm and 82.21 mm respectively. When the tensile reinforcement yields, the reinforcement layer of the UHPC reinforced beam breaks brittlely and stops working. However, after the tensile reinforcement yields, the UHPC-wire mesh reinforced beam continues to bear the load. When the deflection reaches 82.21 mm, the compressive concrete is fully crushed and the specimen is destroyed. This also fully demonstrates the superiority of UHPC-wire mesh reinforced reinforced concrete beams.

According to the test results, as shown in Figure 4, a layer of 4 mm diameter steel mesh is configured in the reinforcement layer. When the tensile steel bars of the reinforced beam yield, the steel mesh can still withstand the tension well and inhibit the development of cracks until the concrete in the compression zone is fully crushed and ductile failure occurs. However, two layers of 3 mm diameter steel mesh are configured in the reinforcement layer. Although the steel mesh reinforcement ratio is the same, the upper and lower layers of steel mesh are unevenly stressed. During the loading process, the lower layer of steel mesh is first pulled and bears a large tensile force. When the cracks in the reinforcement layer widen, the steel mesh in this layer reaches the limit state first and is broken, the bearing capacity drops rapidly, and brittle failure occurs. Therefore, it is recommended that the number of steel mesh layers is 1, and the diameter is 4 mm or above.

According to the finite element analysis, as shown in Figure 5, the thickness of the UHPC-wire mesh reinforcement layer increases from 20 mm to 35 mm, and the ultimate load value increases linearly with the thickness. When the thickness of the reinforcement layer reaches 45 mm, the load value increase decreases slightly. Therefore, the thickness of the reinforcement layer is given to be between 20 mm and 45 mm.

In summary, when using UHPC-wire mesh to reinforce reinforced concrete T-beams, the number of wire mesh layers is 1 and the wire mesh diameter is 4 mm or above, and the thickness of the reinforcement layer is between 20 mm and 45 mm.

If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the fixed connection to each other can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except where it is obviously impossible to use an one-piece molding process).

In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the above utility model include states or shapes that are approximate, similar or close thereto.

Any component provided by the utility model can be assembled from multiple separate components, or can be a separate component manufactured by an integrated molding process.

The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims (8)

1. A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete, comprising a reinforced concrete beam, characterized in that a groove layer is provided on the bottom surface of the reinforced concrete beam and a structural adhesive layer is applied; bolts are respectively fixed at both ends of the bottom surface of the reinforced concrete beam, and a wire mesh fixedly connected to the lower part of the bolt is provided; and a UHPC which is cast into one piece with the reinforced concrete beam and wraps the bolt and the wire mesh is also provided on the bottom surface of the reinforced concrete beam. 2. A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 1, characterized in that the groove layer is composed of a plurality of grooves formed by cutting the bottom surface of the reinforced concrete beam with a diamond grinding wheel. 3. A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 1 or 2, characterized in that the depth and length of the groove are 5 mm×20 mm, and the center distance between two adjacent grooves is 55 mm. 4. According to claim 1, a reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete is characterized in that blind holes passing through the structural adhesive layer and the groove layer are respectively arranged at both ends of the bottom surface of the reinforced concrete beam, and the bolts are fixedly connected to the reinforced concrete beam through the anchor glue arranged in the blind holes. 5. A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 1 or 4, characterized in that the wire mesh is flattened and tightened and then welded or tied to the bolts. 6. A reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 5, characterized in that the number of layers of the wire mesh is 1, and the diameter of the steel wire of the wire mesh is greater than 4 mm. 7. The reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 1, characterized in that the structural adhesive is SiKa32LP structural adhesive. 8. The reinforced concrete beam reinforcement structure configured with wire mesh ultra-high performance concrete according to claim 1, characterized in that the thickness of the UHPC is 20 mm to 45 mm.