A method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity

Abstract

This invention discloses a method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity. The method enhances the anchorage bearing capacity of the main reinforcement bars within the joint by adding a brick wing wall and a reinforced concrete end column to the inner side of the existing structural column, thereby improving the overall integrity of the concrete frame. The brick wing wall is constructed using red bricks and cement mortar within the rectangular space formed by the end column and the existing beams and columns of the building wall. The standard brick masonry method is adopted, and mortar is used to fill the gaps between bricks and between bricks and the surrounding structure. The end column is constructed through drilling, rebar installation, welding of the rebar to the main reinforcement bars of the structural column, stirrup binding, concrete formwork fabrication, concrete pouring, and curing. This method solves the problems of existing seismic reinforcement technologies for concrete beam-column joints, such as technical complexity and high cost, and the lack of a specific reinforcement method for beam-column joints with insufficient anchorage bearing capacity.

Description

Technical Field

[0001] This invention belongs to the field of seismic resistance of building structures and relates to a method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity. Background Technology

[0002] Earthquakes are one of the greatest threats to building structural safety. In developing countries, numerous cases have been observed where earthquakes of relatively low intensity caused severe damage to buildings, and even instances of buildings collapsing under only vertical loads. This indicates that the structural performance of existing buildings in developing countries is far from satisfactory. Investigations have revealed that many existing and even newly constructed reinforced concrete buildings, both domestically and internationally, do not meet seismic resistance requirements. Analysis suggests the following main reasons: some buildings were designed according to outdated codes; buildings were constructed without professional design, relying instead on the owner's experience; construction workers lacked basic seismic knowledge, and inadequate construction management led to construction not strictly adhering to the design, such as insufficient or absent reinforcement in complex joint areas.

[0003] The beam-column joints of reinforced concrete frame structures are critical areas for ensuring the structure's horizontal bearing capacity and seismic resistance. If the main reinforcement bars of the beams have insufficient anchorage bearing capacity within the joints, the bars will be pulled out of the joints under seismic loads, resulting in anchorage failure and a lack of structural integrity in the building.

[0004] For existing building structures lacking overall integrity, seismic reinforcement is a better option than direct demolition. Existing reinforcement technologies for concrete beam-column joints, both domestically and internationally, suffer from drawbacks such as technical complexity and high cost, and no reinforcement methods have been found for joints with insufficient anchorage bearing capacity. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a reinforcement method that improves the anchorage bearing capacity of the main reinforcement of the beam within the edge node by adding brick masonry wing walls and reinforced concrete wall end columns to the inner side of the existing structural columns, thereby enhancing the overall integrity of the concrete frame. This method solves the problems of existing seismic reinforcement technologies for concrete beam-column joints, such as technical complexity and high cost, and the lack of a reinforcement method for beam-column joints with insufficient anchorage bearing capacity.

[0006] This invention is achieved through the following technical solution:

[0007] A method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity includes,

[0008] S1, Select concrete frame buildings with insufficient anchorage bearing capacity for concrete beam-column joints;

[0009] S2, by adding brick walls and end columns, reinforces the concrete beam-column joints of the concrete frame building with insufficient anchorage bearing capacity.

[0010] Preferably, in S1, the method for determining the concrete beam-column joint with insufficient anchorage bearing capacity is as follows:

[0011] To determine whether the anchorage bearing capacity of the main reinforcement of a beam in a concrete frame building is sufficient, the minimum value of the anchorage length l of the main reinforcement is calculated using formula (1). min If the actual anchorage length l a Less than l min If the anchorage bearing capacity of the main reinforcement is insufficient, then it is determined that the main reinforcement is not strong enough.

[0012]

[0013] In the formula: ζ a α is the anchorage length correction factor, taken according to relevant specifications; α is the shape factor of the anchorage reinforcement, 0.16 for plain round bars and 0.14 for ribbed bars; f y f is the design value of the tensile strength of the reinforcing steel. t d is the design value of the axial tensile strength of concrete; d is the diameter of the anchoring steel bar.

[0014] Preferably, the specific process of S2 is as follows:

[0015] For beam-column edge nodes of concrete frame buildings with insufficient anchorage bearing capacity, brick masonry wing walls and reinforced concrete wall end columns are added inside the structural columns connected to the beam-column edge nodes to reinforce the beam-column edge nodes.

[0016] Preferably, the brick wall is made of red bricks and cement mortar, and the wall end column is made of concrete, rebar, rebar adhesive, main reinforcement and stirrups.

[0017] Preferably, the dimensions of the brick wall should meet the following requirements:

[0018] l w ≥l min -l a ;

[0019] In the formula: l w l is the length of the brick wall; min The minimum value of the anchorage length of the main reinforcement of the aforementioned beam, l a The actual anchorage length of the main reinforcement bars of the beam.

[0020] Preferably, the thickness and height of the wall end column are the same as those of the brick wall, and the upper and lower parts of the wall end column are closely connected to the building beam and the floor slab, respectively. The thickness of the brick wall is 240mm, and the length of the wall end column is 150mm.

[0021] Preferably, the fabrication process of the wall end column is as follows: after drilling and cleaning the building beams and floor slabs, rebar is installed using rebar anchoring adhesive, with the anchoring rebar located inside the main rebar of the beam; then the main rebar of the wall end column is lapped and welded to the anchoring rebar with a length of not less than 10d; then the stirrups are tied, concrete formwork is made, and concrete is poured to obtain the wall end column.

[0022] Preferably, the drilling diameter is d+4mm and the depth is not less than 10d, where d is the diameter of the rebar; the rebar adhesive used is modified epoxy rebar adhesive.

[0023] Preferably, the number of rebars is 4, and the exposed lengths of the 4 rebars are 15d, 20d, 25d, and 30d, respectively, where d is the diameter of the rebar.

[0024] Preferably, the concrete poured for the wall end column is cured for at least 7 days before the next step of brick masonry wing wall construction is carried out.

[0025] Preferably, the brick wall is built in the rectangular space formed between the end column and the building wall, and a 240mm thick wing wall is built using red bricks and cement mortar. The brick wall is built using the standard brick wall construction method. The gaps between bricks and between bricks and the surrounding structure are filled with mortar, and the thickness of the mortar is 10mm. No tie bars are set between the brick wall and the surrounding reinforced concrete structure.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] This invention proposes a method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity. This method enhances the anchorage bearing capacity of the main reinforcement bars within the joint by adding a brick wing wall and a reinforced concrete end column to the inner side of the existing structural column, thereby improving the overall integrity of the concrete frame. The brick wing wall is constructed using red bricks and cement mortar within the rectangular space formed by the end column and the existing beams and columns of the building wall. The standard brick masonry method is employed, with mortar filling the gaps between bricks and between bricks and the surrounding structure. The end column is constructed through drilling, rebar installation, welding of the rebar to the main reinforcement bars of the structural column, stirrup binding, concrete formwork fabrication, concrete pouring, and curing. This method addresses the shortcomings of existing seismic reinforcement techniques for concrete beam-column joints, such as technical complexity and high cost, and the lack of a specific reinforcement method for beam-column joints with insufficient anchorage bearing capacity.

[0028] Furthermore, the reinforcement method of the present invention provides a novel reinforcement method and specific structural form for reinforced concrete frame structures that lack structural integrity. The reinforcement method is simple and easy to construct, the reinforcement materials are readily available, and the reinforcement cost is low.

[0029] Furthermore, after rebar installation, allow it to stand for at least 24 hours to prevent the adhesive from being disturbed and affecting its strength.

[0030] Furthermore, during welding, necessary measures should be taken to cool down the root of the rebar to prevent the adhesive from deteriorating due to high temperatures. Attached Figure Description

[0031] Figure 1 The structure is a reinforced concrete frame with insufficient integrity. (a) is a structural diagram of the reinforced concrete frame; (b) is a structural diagram of the reinforcement in the beams and columns connected to the edge nodes; (c) is a structural diagram of the main reinforcement of the middle beam without hooks in the nodes; (d) is a structural diagram of the anchorage failure of the reinforced concrete frame.

[0032] Figure 2 It is a reinforced concrete frame structure with insufficient integrity; (a) is a plan view of the reinforcement method of adding brick wing walls and reinforced concrete wall end columns; (b) is a three-dimensional view of the reinforcement method of adding brick wing walls and reinforced concrete wall end columns.

[0033] Figure 3 These are the dimensions of the brick wall and the end column in the embodiment;

[0034] Figure 4 This is a schematic diagram showing the location of the rebar anchoring for the wall end column;

[0035] Figure 5 This is a schematic diagram showing the exposed length of the rebar.

[0036] Figure 6 This is a schematic diagram showing the connection between the rebar and the main reinforcement of the wall end column;

[0037] Figure 7 This is a schematic diagram of a reinforced concrete wall end column;

[0038] Figure 8 This is a schematic diagram of brick wall construction;

[0039] In the diagram: 1. Beam, 2. Column, 3. Floor slab, 4. Brick wall, 5. End column of the wall. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] The technical solution of the present invention is as follows:

[0044] (1) Select concrete frame buildings with insufficient anchorage bearing capacity at selected nodes.

[0045] (2) The reinforcement is carried out by adding brick wing walls and reinforced concrete end columns to the inside of the existing structural columns.

[0046] (3) Select the type of reinforcement material.

[0047] (4) Set the dimensions of the brick wing wall and the end column.

[0048] (5) Construct wall end columns.

[0049] (6) Building brick walls.

[0050] A further preferred embodiment is a concrete frame with insufficient node anchorage bearing capacity, such as... Figure 1 As shown. Figure 1 (a) is a reinforced concrete frame structure, and the area inside the dashed circle is the beam-column edge node; Figure 1 (b) Reinforcement of the edge node and the beams and columns connected thereto, as shown in the figure. Usually, the main reinforcement of the beam is bent into a 90° hook inside the node to prevent the main reinforcement from being pulled out of the node and causing anchorage failure. Figure 1 (c) The main reinforcement bars of the beam have no hooks within the joint, and due to the small cross-sectional dimensions of the column, the anchorage length l is limited. a The beam is relatively small, resulting in low anchorage bearing capacity. Under earthquakes and other loads, the beam ends are subjected to bending moment M. Under this bending moment, the main reinforcement on one side of the beam is under tension. Due to insufficient anchorage bearing capacity, the main reinforcement is pulled out of the joint before yielding, leading to anchorage failure. Figure 1 As shown in (d), this leads to the frame structure losing its integrity and collapsing. Design codes require "strong nodes, weak members," and do not allow the aforementioned failure modes in structures. [The last sentence appears to be incomplete and possibly refers to a specific failure mode or mechanism.] Figure 1 (d) The concrete frame with anchorage failure is defined as a concrete frame with insufficient joint anchorage bearing capacity. The method for determining whether the anchorage bearing capacity of the main reinforcement of the beam is sufficient is as follows: First, use formula (1) to calculate the minimum value l of the anchorage length of the main reinforcement of the beam. min If the actual anchorage length l a Less than l min If the anchorage bearing capacity of the main reinforcement is insufficient, then it is determined that the anchorage bearing capacity is inadequate. In the formula, ζ aα is the anchorage length correction factor, taken according to relevant specifications; α is the shape factor of the anchorage reinforcement, 0.16 for plain round bars and 0.14 for ribbed bars; f y f is the design value of the tensile strength of the reinforcing steel. t d is the design value of the axial tensile strength of concrete; d is the diameter of the anchoring steel bar.

[0051]

[0052] A further preferred embodiment is the method of adding brick wing walls and reinforced concrete end columns to the inner side of existing structural columns, as follows: Figure 2 As shown. For beam-column joints with insufficient anchorage bearing capacity, a brick wall 4 and a wall-end column 5 are added inside the column 2 connected to the joint to reinforce the joint and prevent anchorage failure. Figure 2 As shown in (a). Figure 2 (b) A three-dimensional diagram of the reinforcement method of adding brick wing walls and reinforced concrete wall end columns.

[0053] Further optimization involves selecting appropriate reinforcement materials that meet the reinforcement requirements. Specifically, this includes red bricks and cement mortar for the brick wing walls, and concrete, rebar, rebar adhesive, main reinforcement bars, and stirrups for the wall end columns. The red bricks are 240mm×115mm×53mm standard-sized sintered bricks with a strength of MU15 or higher. The mortar is M20 or higher cement mortar. The concrete for the wall end columns is ordinary concrete with a strength grade of C30 or higher. The rebar and main reinforcement bars have the same diameter, using HRB400 grade ribbed steel bars with a diameter of 14mm or higher. The stirrups are steel bars with a diameter of 8mm or higher. The rebar adhesive is a modified epoxy-based rebar adhesive.

[0054] In a further preferred embodiment, the dimensions of the brick wing wall and the end column are determined to be the dimensions of the components that can meet the reinforcement requirements. For example... Figure 3 As shown, the thickness of the brick wing wall is 240mm, which is the length of a standard sintered red brick; the length of the brick wall is l. w Determined according to Formula 2, where l min l a These are the minimum anchorage length of the main reinforcement bars of the aforementioned beam and the actual anchorage length of the main reinforcement bars of the beam; the height of the brick masonry wing wall is the net height of the floor, that is, it is arranged along the entire length of the column; the length of the wall end column is 150mm, the thickness is the same as the brick wall, i.e., 240mm, the height is the same as the brick masonry wing wall, and it is closely connected to beam 1 and floor slab 3 at the top and bottom.

[0055] l w ≥l min -l a (2)

[0056] In a further preferred embodiment, the fabrication of the wall end column involves constructing and curing a reinforced concrete wall end column at a predetermined location. The fabrication of the wall end column includes: drilling, rebar installation, welding the rebar to the main reinforcement of the structural column, stirrup tying, concrete formwork fabrication, concrete pouring, and curing. A hammer drill is used to drill holes with a diameter of d + 4 mm and a depth of not less than 10d, where d is the diameter of the rebar to be installed. After drilling and cleaning, modified epoxy-based rebar adhesive is used for installation, with four rebars installed. The rebars should be located inside the main reinforcement of the beam. Figure 4 As shown; the exposed lengths of the four rebars are all different, namely 15d, 20d, 25d, and 30d, respectively. Figure 5 As shown; after rebar installation, allow it to stand for at least 24 hours to avoid disturbing the adhesive and affecting its strength. The main reinforcement bars of the wall end column should be lapped and welded to the installed rebars with a length not less than 10d. Figure 6 As shown. During welding, necessary measures should be taken to cool the base of the rebar to prevent high temperatures from deteriorating the adhesive. Then, the stirrups are tied, concrete formwork is fabricated, and concrete is poured. The concrete should be cured for at least 7 days before proceeding to the next step of masonry construction. Figure 7 This is a schematic diagram of a reinforced concrete wall end column.

[0057] A further preferred embodiment is that the brick wall is a 240mm thick wing wall constructed using red bricks and cement mortar within the rectangular space formed by the wall end column and the existing beams and columns of the building wall structure. The wall is constructed using standard brick masonry methods, with mortar filling the gaps between bricks and between bricks and the surrounding structure. The mortar thickness is 10mm. No tie bars are installed between the brick wall and the surrounding reinforced concrete structure. Figure 8 As shown.

[0058] The reinforcement method of this invention provides a novel reinforcement method and specific structural form for reinforced concrete frame structures that lack structural integrity. The reinforcement method is simple and easy to construct, the reinforcement materials are readily available, and the reinforcement cost is low.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity, characterized in that, include, S1, Select concrete frame buildings with insufficient anchorage bearing capacity for concrete beam-column joints; S2, by adding brick walls and end columns, reinforces the concrete beam-column joints of the concrete frame building with insufficient anchorage bearing capacity; In S1, the method for determining the insufficient anchorage bearing capacity of concrete beam-column joints is as follows: To determine whether the anchorage bearing capacity of the main reinforcement of the beam in a concrete frame building is sufficient, the minimum value of the anchorage length of the main reinforcement is calculated using formula (1). l min If the actual anchorage length l a Less than l min If the anchorage bearing capacity of the main reinforcement is insufficient, then it is determined that the main reinforcement is not strong enough. ； （1） In the formula: This is the anchorage length correction factor, which is taken according to relevant specifications; The shape factor for anchoring reinforcement is 0.16 for plain round steel bars and 0.14 for ribbed steel bars; f y This is the design value for the tensile strength of the reinforcing steel. f t This is the design value for the axial tensile strength of concrete; d The diameter of the anchoring steel bar; The specific process of S2 is as follows: For beam-column edge nodes of concrete frame buildings with insufficient anchorage bearing capacity, brick masonry wing walls and reinforced concrete wall end columns are added inside the structural columns connected to the beam-column edge nodes to reinforce the beam-column edge nodes. The dimensions of the brick wall should meet the following requirements: ； In the formula: l w The length of the brick wall; l min This refers to the minimum value of the anchorage length of the main reinforcement bars in the aforementioned beam. l a The actual anchorage length of the main reinforcement bars in the beam; The specific process of fabricating the wall end column is as follows: after drilling and cleaning the building beams and floor slabs, use anchoring adhesive to anchor the rebars, with the anchoring rebars located inside the main reinforcement of the beams; then overlap and weld the main reinforcement of the wall end column with the anchoring rebars at a length of not less than 10d; then tie the stirrups, make the concrete formwork, and pour the concrete to obtain the wall end column.

2. The method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity according to claim 1, characterized in that, The brick wall is made of red bricks and cement mortar, and the wall end column is made of concrete, rebar, rebar adhesive, main reinforcement and stirrups.

3. The method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity according to claim 1, characterized in that, The thickness and height of the wall end column are the same as those of the brick wall. The upper and lower parts of the wall end column are closely connected to the building beam and the floor slab, respectively. The thickness of the brick wall is 240mm, and the length of the wall end column is 150mm.

4. The method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity according to claim 1, characterized in that, The drilling diameter is d+4mm, and the depth is not less than 10d, where d is the diameter of the rebar; the rebar adhesive used is modified epoxy rebar adhesive.

5. The method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity according to claim 1, characterized in that, The number of rebars is 4, and the exposed lengths of the 4 rebars are 15d, 20d, 25d and 30d respectively, where d is the diameter of the rebar; the concrete poured for the wall end column shall be cured for at least 7 days before the next step of brick masonry wing wall construction is carried out.

6. The method for reinforcing concrete beam-column joints with insufficient anchorage bearing capacity according to claim 1, characterized in that, The brick wall is built in the rectangular space formed between the end column and the building wall, and is constructed with red bricks and cement mortar to form a 240mm thick wing wall. The brick wall is built using the standard brick wall construction method. The gaps between bricks and between bricks and the surrounding structure are filled with mortar, which is 10mm thick. No tie bars are installed between the brick wall and the surrounding reinforced concrete structure.

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