CN113738150A - Method for improving bending strength of existing reinforced concrete beam - Google Patents

Method for improving bending strength of existing reinforced concrete beam Download PDF

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Publication number
CN113738150A
CN113738150A CN202111079502.4A CN202111079502A CN113738150A CN 113738150 A CN113738150 A CN 113738150A CN 202111079502 A CN202111079502 A CN 202111079502A CN 113738150 A CN113738150 A CN 113738150A
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CN
China
Prior art keywords
reinforced concrete
concrete beam
uhpc
composite board
bending strength
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Withdrawn
Application number
CN202111079502.4A
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Chinese (zh)
Inventor
杨家林
王国林
张宇轩
杨冀锟
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Shanghai Institute of Technology
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Shanghai Institute of Technology
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Publication date
Application filed by Shanghai Institute of Technology filed Critical Shanghai Institute of Technology
Priority to CN202111079502.4A priority Critical patent/CN113738150A/en
Publication of CN113738150A publication Critical patent/CN113738150A/en
Withdrawn legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
    • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
    • E04C2/04—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres
    • E04C2/06—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of concrete or other stone-like material; of asbestos cement; of cement and other mineral fibres reinforced
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E04G23/0244—Increasing or restoring the load-bearing capacity of building construction elements of beams at places of holes, e.g. drilled in them

Abstract

The invention provides a method for improving the bending strength of an existing reinforced concrete beam, and relates to the technical field of civil engineering structure reinforcement, wherein the method comprises the following steps: step 1, manufacturing a UHPC composite board; and 2, mounting the UHPC composite board at the bottom of the reinforced concrete beam. The invention improves the bending resistance bearing capacity and the durability of the reinforced concrete beam, shortens the construction period, reduces the interference to the surrounding environment, reduces the later maintenance cost and has beneficial technical effects.

Description

Method for improving bending strength of existing reinforced concrete beam
Technical Field
The invention relates to the technical field of civil engineering structure reinforcement, in particular to a method for improving the bending strength of an existing reinforced concrete beam.
Background
A Reinforced Concrete (RC) frame structure is one of the most common structural forms in the field of civil engineering. The RC beam is an important bearing and force transmission component in the building, and the reduction of the bending bearing capacity of the RC beam seriously affects the safety and normal use of the building. During the service period, adverse factors such as regional seismic intensity adjustment, building function change, external load increase and material performance degradation can be encountered, so that the bearing capacity of the RC beam is reduced or the requirement of regional seismic intensity adjustment is not met.
At present, the main methods for the anti-bending reinforcement of the RC beam are an external attachment method (steel plates, FRP sheets and the like) and a cast-in-place beam height increasing method. The outer pasting method can effectively improve the bearing capacity of the RC beam, but the steel plate has the defects of easy corrosion, high later maintenance cost, easy end peeling of FRP in the later loading period, poor high-temperature stability of structural adhesive and the like. The construction period of the cast-in-place beam-increasing method is long, and the influence on the surrounding environment is large. Therefore, there is a need for a green, efficient and cost effective method of reinforcing RC beams against bending.
Therefore, the invention provides a method for improving the bending strength of the existing reinforced concrete beam, and aims to solve the problems in the prior art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for improving the bending strength of the existing reinforced concrete beam.
The invention provides a method for improving the bending strength of an existing reinforced concrete beam, which comprises the following steps:
step 1, manufacturing a UHPC composite board;
and 2, mounting the UHPC composite board at the bottom of the reinforced concrete beam.
In the invention, UHPC refers to ultra-high performance concrete, UHPC board refers to ultra-high performance concrete board, and UHPC composite board refers to ultra-high performance concrete board provided with reinforcing ribs.
Further, the step 1 specifically includes: and manufacturing a UHPC plate, and configuring reinforcing ribs in the UHPC plate to manufacture the UHPC composite plate.
Preferably, the compressive strength of the UHPC plate material is not lower than 120MPa, the content of the steel fiber is 2% -3%, the length of the steel fiber is 10-20mm, and the diameter of the steel fiber is 0.1-0.25 mm.
The content of steel fibers refers to volume ratio.
Preferably, the reinforcing bar is a ribbed bar.
Further, the step 1 specifically includes: determining the shape, size and thickness of the UHPC composite board and the distribution of the reinforcing ribs according to the size, reinforcing ribs and stress conditions of the reinforced concrete beam to be reinforced; then, a template is manufactured, and the mixed UHPC material is injected into the template for molding and curing.
Preferably, the UHPC composite board is rectangular, the thickness of the UHPC composite board is 50-100mm, and the length and the width of the UHPC composite board are consistent with those of the reinforced concrete beam; the diameter of the reinforcing rib is 12-25mm, the reinforcing rib is arranged in the middle of a single layer along the thickness direction of the UHPC composite board, and the distance along the width direction of the UHPC composite board is not less than 30 mm; when the reinforcing ribs are arranged in the UHPC composite board, the thickness of the side protective layer is not less than 20mm, and the thickness of the end protective layer is not less than 20 mm.
The shape of the UHPC composite board is consistent with the ground shape of the reinforced concrete beam, the shape of the manufactured UHPC composite board is generally rectangular according to the shape of the reinforced concrete beam, and the thickness of the UHPC composite board is finally determined according to the calculation result of the bearing capacity.
The number of the reinforcing ribs is determined according to the bearing capacity calculation result, the reinforcing ribs are arranged along the length direction of the reinforced concrete beam, and the length of the reinforcing ribs is matched with the length of the reinforced concrete beam; when the reinforcing ribs are arranged in the UHPC plate, the thickness of the side surface protective layer of the reinforcing rib at the outermost side is not less than 20mm, and the thickness of the end protective layer of the reinforcing rib is not less than 20 mm.
Further, the step 2 specifically includes: and adhering the UHPC composite board to the bottom surface of the reinforced concrete beam by using a structural adhesive, and mechanically anchoring the UHPC composite board and the reinforced concrete beam by using a split bolt and a U-shaped hoop.
Preferably, the structural binder is a UHPC material blend.
Further, the step 2 specifically includes: detecting the position of a steel bar in the reinforced concrete beam, determining the position for installing the split bolt on the side surface of the reinforced concrete beam, drilling, and cleaning by using an air pump; then, cleaning the bottom surface of the reinforced concrete beam, coating a layer of structural adhesive with the thickness of 5-6mm, and adhering the UHPC composite board; and finally, mechanically anchoring the UHPC composite board by using the U-shaped hoop and the split bolts.
The nut is tightly attached to the UHPC plate by the pretightening force of the split bolt and nut.
Preferably, the distance between each group of U-shaped hoops and the split bolts is not more than 500mm, the width of each U-shaped hoop is 50mm, and the diameter of each split bolt is 14 mm; the span of the U-shaped hoop and the length of the split bolt are matched with the width of the reinforced concrete beam.
The span of the U-shaped hoop and the length of the split bolt are determined according to the width of the reinforced concrete beam, and the span of the U-shaped hoop refers to the distance between two arms of the U-shaped hoop; the U-shaped hoop and the split bolt need to be subjected to rust prevention treatment before use.
Compared with the prior art, the invention has the following beneficial effects:
1. compared with the reinforcing method of externally-attached steel plates and FRP, the method for improving the bending strength of the existing reinforced concrete beam, which is provided by the invention, has the advantages that the bending strength of the reinforced concrete beam can be effectively improved, the durability is improved, and the later maintenance cost is reduced.
2. The method for improving the bending strength of the existing reinforced concrete beam adopts a prefabrication and assembly mode, and has the advantages of short construction period, small environmental interference and wide application range compared with a cast-in-place method.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is an overall schematic view of a UHPC composite board reinforcing a reinforced concrete beam according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a UHPC composite panel provided by an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a reinforcing bar in a UHPC composite board according to an embodiment of the invention;
FIG. 4 is a schematic structural diagram of a split bolt and a U-shaped hoop anchored UHPC composite plate according to an embodiment of the invention;
fig. 5 is a schematic structural view of a U-shaped hoop according to an embodiment of the present invention.
In the figure:
1-a reinforced concrete beam;
2-UHPC composite board;
3-reinforcing ribs;
4-split bolts;
5-U-shaped hoop.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1, which is a schematic view of the overall effect of the UHPC composite board of the present invention in overall bending resistance reinforcement of a reinforced concrete beam, the UHPC composite board 2 is adhered to the bottom of the reinforced concrete beam 1, and the UHPC composite board 2 and the reinforced concrete beam 1 are mechanically anchored by a U-shaped hoop 5 and a tie bolt 4 at the side of the reinforced concrete beam 1.
As shown in fig. 2 and 3, the UHPC composite board 2 is a rectangular board, the reinforcing rib 3 is disposed inside the UHPC composite board 2 along the longitudinal direction, and the reinforcing rib 3 is disposed centrally in a single layer along the thickness direction of the UHPC composite board 2. The thickness direction means a direction in which the side surface of the reinforced concrete beam 1 points to the UHPC composite panel 2.
UHPC refers to ultra-high performance concrete, UHPC panels refer to ultra-high performance concrete panels, and UHPC composite panels are ultra-high performance concrete panels with reinforcing ribs.
As shown in fig. 5, the U-shaped hoop 5 has bolt holes for mounting the split bolts 4, which are provided on both side arms of the U-shaped hoop 5.
A side view of the reinforced concrete beam 1, the UHPC composite panel 2, the reinforcing bars 3, the split bolts 4, and the U-shaped hoops 5 after assembly is shown in fig. 4.
The invention provides a method for improving the bending strength of an existing reinforced concrete beam, which comprises the following steps:
step 1, manufacturing a UHPC composite board 2;
and 2, mounting the UHPC composite plate 2 at the bottom of the reinforced concrete beam 1.
The step 1 specifically comprises the following steps: and (3) manufacturing a UHPC plate, and arranging reinforcing ribs 3 in the UHPC plate to manufacture a UHPC composite plate 2.
In the embodiment, the compressive strength of the UHPC plate material is not lower than 120MPa, the content of the steel fiber is 2-3%, the fiber length is 10-20mm, and the fiber diameter is 0.1-0.25 mm. The reinforcing bar 3 may be a ribbed bar.
Specifically, step 1 further comprises: determining the shape, size and thickness of the UHPC composite board 2 and the distribution of the reinforcing ribs 3 according to the size, reinforcing ribs and stress conditions of the reinforced concrete beam 1 to be reinforced; then, a template is manufactured, and the mixed UHPC material is injected into the template for molding and curing. A UHPC composite panel 2 is thus obtained.
The thickness of the UHPC composite board 2 is 50-100mm, and the diameter of the reinforcing rib 3 is 12-25 mm; the reinforcing ribs 3 are arranged in the middle of a single layer along the thickness direction of the UHPC composite board 2, and the distance along the width direction of the UHPC composite board 2 is not less than 30 mm.
According to the shape of the reinforced concrete beam 1, the manufactured UHPC composite board 2 is generally rectangular, the length and the width of the UHPC composite board 2 are consistent with those of the reinforced concrete beam 1, and the thickness of the UHPC composite board 2 is finally determined according to a bearing capacity calculation result.
The number of the reinforcing ribs 3 is determined according to the bearing capacity calculation result, the reinforcing ribs 3 are arranged along the length direction of the reinforced concrete beam 1, and the length of the reinforcing ribs 3 is matched with the length of the reinforced concrete beam 1; when the reinforcing ribs 3 are arranged in the UHPC board, the thickness of the side surface protective layer of the reinforcing rib 3 at the outermost side is not less than 20mm, and the thickness of the protective layer at the end part of the reinforcing rib 3 is not less than 20 mm.
The step 2 specifically comprises the following steps: the UHPC composite board 2 is adhered to the bottom surface of the reinforced concrete beam 1 by using a structural adhesive, and then the UHPC composite board 2 and the reinforced concrete beam 1 are mechanically anchored by using a tension bolt 4 and a U-shaped hoop 5.
In this embodiment, the structural binder may be a UHPC material blend.
Specifically, step 2 further comprises: detecting the position of a steel bar in the reinforced concrete beam 1, determining the position of a split bolt 4 on the side surface of the reinforced concrete beam 1, drilling, and cleaning by using an air pump; then, cleaning the bottom surface of the reinforced concrete beam 1, coating a layer of structural adhesive with the thickness of 5-6mm, and adhering the UHPC composite board 2; finally, the UHPC composite panel 2 is mechanically anchored using U-shaped hoops 5 and split bolts 4. The nut is tightly attached to the UHPC composite board 2 by the pretightening force of the nut of the split bolt 4.
The distance between each group of U-shaped hoops 5 and the split bolts 4 in the length direction of the reinforced concrete beam 1 is not more than 500mm, in the embodiment, the width of the U-shaped hoops 5 is 50mm, and the diameter of the split bolts 4 is 14 mm. The span of the U-shaped hoop 5 and the length of the split bolt 4 are determined according to the width of the reinforced concrete beam 1, and the U-shaped hoop 5 and the split bolt 4 need to be subjected to rust prevention treatment before use.
Example 1
The invention particularly discloses an implementation mode for improving the bending strength of an existing reinforced concrete beam.
The reinforced concrete beam 1 has length × height × width dimensions of 4000mm × 500mm × 250 mm.
The length, width and thickness of the UHPC composite board 2 are 4000mm, 250mm and 40mm, the steel fiber content of the UHPC board is 2 percent, the length of the steel fiber is 10mm, and the diameter of the steel fiber is 0.15 mm. The reinforcing ribs 3 in the UHPC plate are arranged along the length direction of the reinforced concrete beam 1 and are configured to be 12mm @50mm (namely the diameter is 12mm, the distance is 50mm), the thickness of the side surface protective layer is 20mm, and the thickness of the end protective layer is 20 mm.
Before the UHPC composite board 2 is installed, drilling holes in opposite directions at corresponding positions of the reinforced concrete beam 1, and cleaning the holes by using an air pump; then, the surface of the reinforced concrete beam 1 is washed by a high-pressure water gun to remove scum and dust.
And adhering a UHPC composite board 2 to the bottom surface of the reinforced concrete beam 1. And uniformly smearing a layer of UHPC material stirring material with the thickness of 5mm on the bottom surface along the whole length of the reinforced concrete beam 1, pasting the UHPC composite board 2, and uniformly extruding redundant slurry to enable the slurry to be smooth. Then, assembling the split bolt 4 and the U-shaped hoop 5, wherein the nut is tightly attached to the UHPC plate by the nut pretightening force of the split bolt 4, the installation is completed as shown in figure 1, and the cross-sectional structure is shown in figure 4.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (10)

1. A method for improving the bending strength of an existing reinforced concrete beam is characterized by comprising the following steps:
step 1, manufacturing a UHPC composite board;
and 2, mounting the UHPC composite board at the bottom of the reinforced concrete beam.
2. The method for improving the bending strength of the existing reinforced concrete beam according to claim 1, wherein the step 1 specifically comprises the following steps: and manufacturing a UHPC plate, and configuring reinforcing ribs in the UHPC plate to manufacture the UHPC composite plate.
3. The method for improving the bending strength of the existing reinforced concrete beam according to claim 2, wherein the compressive strength of the UHPC plate material is not lower than 120MPa, the content of the steel fiber is 2% -3%, the length of the steel fiber is 10-20mm, and the diameter of the steel fiber is 0.1-0.25 mm.
4. The method for increasing the bending strength of an existing reinforced concrete beam according to claim 2, wherein the reinforcing bars are ribbed reinforcing bars.
5. The method for improving the bending strength of the existing reinforced concrete beam according to claim 2, wherein the step 1 specifically comprises the following steps: determining the shape, size and thickness of the UHPC composite board and the distribution of the reinforcing ribs according to the size, reinforcing ribs and stress conditions of the reinforced concrete beam to be reinforced; then, a template is manufactured, and the mixed UHPC material is injected into the template for molding and curing.
6. The method for improving the bending strength of the existing reinforced concrete beam according to claim 2, wherein the UHPC composite plate is rectangular in shape, the thickness of the UHPC composite plate is 50-100mm, and the length and the width of the UHPC composite plate are consistent with those of the reinforced concrete beam; the diameter of the reinforcing rib is 12-25mm, the reinforcing rib is arranged in the middle of a single layer along the thickness direction of the UHPC composite board, and the distance along the width direction of the UHPC composite board is not less than 30 mm; when the reinforcing ribs are arranged in the UHPC composite board, the thickness of the side protective layer is not less than 20mm, and the thickness of the end protective layer is not less than 20 mm.
7. The method for improving the bending strength of the existing reinforced concrete beam according to claim 1, wherein the step 2 specifically comprises the following steps: and adhering the UHPC composite board to the bottom surface of the reinforced concrete beam by using a structural adhesive, and mechanically anchoring the UHPC composite board and the reinforced concrete beam by using a split bolt and a U-shaped hoop.
8. The method for increasing the flexural strength of an existing reinforced concrete beam according to claim 7, wherein the structural adhesive is UHPC material blend.
9. The method for improving the bending strength of the existing reinforced concrete beam according to claim 7, wherein the step 2 specifically comprises the following steps: detecting the position of a steel bar in the reinforced concrete beam, determining the position for installing the split bolt on the side surface of the reinforced concrete beam, drilling, and cleaning by using an air pump; then, cleaning the bottom surface of the reinforced concrete beam, coating a layer of structural adhesive with the thickness of 5-6mm, and adhering the UHPC composite board; and finally, mechanically anchoring the UHPC composite board by using the U-shaped hoop and the split bolts.
10. The method for increasing the bending strength of an existing reinforced concrete beam according to claim 7, wherein the interval between each set of the U-shaped hoop and the split bolt is not more than 500mm, the width of the U-shaped hoop is 50mm, and the diameter of the split bolt is 14 mm; the span of the U-shaped hoop and the length of the split bolt are matched with the width of the reinforced concrete beam.
CN202111079502.4A 2021-09-15 2021-09-15 Method for improving bending strength of existing reinforced concrete beam Withdrawn CN113738150A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111079502.4A CN113738150A (en) 2021-09-15 2021-09-15 Method for improving bending strength of existing reinforced concrete beam

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111079502.4A CN113738150A (en) 2021-09-15 2021-09-15 Method for improving bending strength of existing reinforced concrete beam

Publications (1)

Publication Number Publication Date
CN113738150A true CN113738150A (en) 2021-12-03

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220178158A1 (en) * 2020-12-07 2022-06-09 Fuzhou University Device and method for reinforcing round section wood beam by combination of prestressed frp sheet and high strength steel wire rope

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220178158A1 (en) * 2020-12-07 2022-06-09 Fuzhou University Device and method for reinforcing round section wood beam by combination of prestressed frp sheet and high strength steel wire rope
US11674323B2 (en) * 2020-12-07 2023-06-13 Fuzhou University Device and method for reinforcing round section wood beam by combination of prestressed FRP sheet and high strength steel wire rope

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Application publication date: 20211203