CN111608418B

CN111608418B - A kind of FRP bar with embedded anchoring device and application method thereof

Info

Publication number: CN111608418B
Application number: CN202010455944.3A
Authority: CN
Inventors: 张世顺; 柯研; 朱宏平; 余涛
Original assignee: Huazhong University of Science and Technology; Hong Kong Polytechnic University HKPU
Current assignee: Huazhong University of Science and Technology; Hong Kong Polytechnic University HKPU
Priority date: 2020-05-26
Filing date: 2020-05-26
Publication date: 2021-08-03
Anticipated expiration: 2040-05-26
Also published as: CN111608418A

Abstract

The invention belongs to the technical field of reinforcement of reinforced concrete structures, and discloses an FRP bar with a novel embedded anchoring device and an application method thereof. Both ends of the FRP rib are provided with a new type of embedded anchoring device, which is made of FRP fiber cloth. The front end of the FRP fiber cloth is crimped to form a sleeve, and the sleeve and the end of the FRP rib are bonded. The rear end is twisted into a bundle, and a fixed rope is used to wrap and shape to form an anchor, and the sleeve and the anchor form an included angle θ. After the FRP bar with the anchoring device is embedded into the reinforced concrete beam to be reinforced, the anchoring device can effectively prevent the end of the FRP bar from peeling and damage during the stress process of the beam, thereby improving the flexural bearing capacity of the reinforced concrete beam to be reinforced. The invention also discloses an application method of the above-mentioned FRP reinforcement with a novel embedded anchoring device in a concrete beam. Through the present invention, the utilization rate of the FRP material can be improved, and the engineering cost can be reduced.

Description

FRP (fiber reinforced plastic) rib with embedded anchoring device and application method thereof

Technical Field

The invention belongs to the technical field related to reinforced concrete structure reinforcement, and particularly relates to an FRP rib with a novel embedded anchoring device and an application method thereof.

Background

In recent years, FRP (Fiber-Reinforced Polymer, Fiber-Reinforced composite) has been widely used for reinforcing concrete structures and other structures due to its advantages of corrosion resistance, light weight, high strength, and convenience in construction. At present, two methods, namely an external attaching method and an embedding method, are mainly used for reinforcing the reinforced concrete structure by FRP. Wherein the embedding method has kept the advantages such as high strength, high efficiency, corrosion resistance of outer FRP reinforcement technique, still has a prominent advantage: the embedded FRP can achieve much higher effective stress than the externally attached FRP. In addition, the insert method is superior to the outer attachment method in impact resistance, durability, fire resistance, and ease of construction.

Even if the embedded FRP has a high bonding efficiency with the concrete structure, peeling damage (peeling of a concrete protective layer or peeling of an FRP-concrete interface) still occurs in the embedded FRP bending-resistant reinforced concrete beam, which becomes an important factor that restricts further improvement of the reinforcing efficiency of the embedded FRP rib bending-resistant reinforced concrete beam.

In order to prevent the reduction of the bearing capacity of the embedded FRP bar anti-bending reinforced concrete beam caused by the peeling damage of the end part, a plurality of expert and scholars at home and abroad research different end part anchoring methods, wherein the external FRP U-shaped hoop is the most common. However, some experimental studies have shown that, in the embedded FRP bar buckling-reinforced concrete beam system, although the end FRP U-shaped hoop can successfully suppress the peeling failure of the concrete cover layer, the failure mode is easily converted into the peeling failure of the end FRP bar (i.e., "pulling out" from the concrete cover layer). This is mainly because in the embedded reinforcement system, the FRP bars embedded in the reinforced concrete beam cannot be directly connected to the FRP U-shaped hoops attached to the outside, but are connected through the concrete protective layer, so that the concrete protective layer with relatively low strength becomes a fragile part, and the FRP bars are likely to be "pulled out" from the concrete protective layer. At this moment, the increase of the usage amount of the FRP U-shaped hoops to the bearing capacity of the reinforcing beam is limited, and the reinforcing cost can be obviously increased. Therefore, the invention develops a novel embedded end anchoring device for anti-bending reinforcement of a reinforced concrete beam based on embedded FRP bars.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides the FRP bar with the novel embedded anchoring device and the application method thereof, and the anchoring device and the FRP bar are tightly combined and embedded into the reinforced concrete beam through the structural design of the anchoring device of the key component, so that the end part of the FRP bar is prevented from being stripped and damaged, and the bending resistance bearing capacity of the reinforced concrete beam is improved.

To achieve the above objects, according to one aspect of the present invention, there is provided an FRP bar with a novel embedded anchoring device, the FRP bar being provided with anchoring devices at both ends thereof, wherein,

the anchoring device is made of FRP fiber cloth, the front end of the FRP fiber cloth is curled to form a sleeve, the rear end of the FRP fiber cloth is twisted into a bundle shape and is wound and shaped by a fixing rope to form an anchor, and an included angle theta is formed between the sleeve and the anchor;

and after the FRP bars with the novel embedded anchoring device are embedded into the reinforced concrete beam to be reinforced, the anchoring device avoids the peeling damage of the end parts of the FRP bars in the stress process of the beam, and further improves the bending resistance bearing capacity of the reinforced concrete beam to be reinforced.

Further preferably, the FRP ribs and the anchoring devices are made of one of carbon fiber reinforced polymer, glass fiber reinforced polymer, aramid fiber reinforced polymer, and basalt fiber reinforced polymer.

Further preferably, when the sleeve is sleeved at the two ends of the FRP rib, the sleeve and the FRP rib are connected by an adhesive.

Further preferably, the adhesive is preferably an engineering structural adhesive.

Further preferably, the included angle θ ranges from 45 ° to 90 °.

Further preferably, the bonding force between the sleeve and the FRP ribs is in direct proportion to the length of the sleeve, the sleeve does not change after reaching a critical value, and the length of the sleeve is set according to the critical value of the bonding force after being subjected to a plurality of drawing tests; the bonding force between the anchor bolts and the reinforced concrete beam to be reinforced is in direct proportion to the length of the anchor bolts, the anchor bolts do not change after reaching a critical value, and the length of the anchor bolts is set according to the critical value of the bonding force after being subjected to multiple drawing tests.

Further preferably, the length of the sleeve is preferably 3-5 times of the section perimeter of the FRP rib, and the length of the anchor is preferably 1/2 of the height of the reinforced concrete beam to be reinforced.

According to another aspect of the present invention, there is provided an application method of the FRP bar with the novel embedded anchoring device, the application method comprising the following steps:

(a) selecting materials required by an FRP rib and anchoring devices arranged at two ends of the FRP rib, coating a binder on bonding areas at two ends of the FRP rib, and coating the FRP fiber cloth saturated with the binder on two ends of the FRP rib coated with the binder to form a sleeve;

(b) twisting the tail end of the FRP fiber cloth into a bundle shape, and spirally binding and fixing the FRP fiber cloth by adopting a fixing rope to form an anchor nail, so as to obtain an FRP rib with an anchoring device at the end part;

(c) grooving and drilling at the bottom of the reinforced concrete beam to be reinforced to form a groove and a mounting hole, inserting the anchor into the mounting hole, and embedding the FRP bar into the groove, so that the FRP bar with the anchoring device arranged at the end part is embedded into the reinforced concrete beam to be reinforced.

Generally, compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. compared with the traditional FRP U-shaped hoop, the anchoring device in the FRP rib with the novel embedded anchoring device has better anchoring effect, durability, fire resistance and impact resistance, the FRP rib adopting the novel embedded anchoring device can effectively delay or avoid the peeling and damage of the end part of the FRP rib, so that the bearing capacity, the ductility and the durability of a reinforcing beam are improved, and according to the test result, the bending resistance bearing capacity of the FRP rib reinforcing beam with the novel embedded anchoring device can be further improved by 20-30% compared with that of a common FRP rib reinforcing beam;

2. compared with the externally-adhered FRP U-shaped hoop, the novel embedded anchoring device can effectively improve the utilization rate of an FRP material, and the material cost can be reduced by 40-60%;

3. the embedded anchoring device integrally adopts soft FRP fiber cloth, and the anchoring angle of the anchoring device can be flexibly selected, so that the FRP rib with the novel embedded anchoring device provided by the invention has wider application occasions.

Drawings

FIG. 1 is a schematic structural view of one end of an FRP tendon with a novel embedded anchoring device constructed in accordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic flow chart of the preparation of FRP tendon with novel embedded anchoring device constructed according to the preferred embodiment of the invention;

fig. 3 is a schematic view illustrating an overall installation procedure of embedding FRP bars with a novel embedded anchoring device into a reinforced concrete beam, constructed according to a preferred embodiment of the present invention;

FIG. 4 is a schematic illustration of a double shear pull test constructed in accordance with a preferred embodiment of the present invention to determine the effective bond length L1 of the sleeve over the FRP ribs;

fig. 5 is a schematic illustration of a single shear pull test constructed in accordance with a preferred embodiment of the present invention to determine the effective anchor length L2 for anchor anchoring into concrete.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1-sleeve, 2-anchor, 3-adhesive, 4-FRP rib and 5-fixing rope.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The two ends of the FRP rib with the novel embedded anchoring device are provided with the anchoring devices.

Specifically, as shown in fig. 1, a schematic structural diagram of an end of an FRP rib with a novel embedded anchoring device is shown in fig. 1, the end anchoring device includes a sleeve 1 and an anchor 2 coated on an outer surface of the FRP rib 4, wherein the FRP rib 4 and the sleeve 1 are bonded by an adhesive 3, and a fixing rope 5 is adopted on the anchor 2 for winding and shaping, in this embodiment, the fixing rope 5 is a thin iron wire to prevent the anchor 2 from being scattered, so that the anchor is more easily inserted into a mounting hole on a beam.

Specifically, the sleeve 1 and the anchor stud 2 in the anchoring device of the end portion of the present invention are made of one piece of FRP fiber cloth 6.

Specifically, the FRP material in the anchoring device includes, but is not limited to, one of Carbon Fiber Reinforced Polymer (CFRP), Glass Fiber Reinforced Polymer (GFRP), Aramid Fiber Reinforced Polymer (AFRP), Basalt Fiber Reinforced Polymer (BFRP). Any one of the FRP materials has excellent characteristics of light weight, high strength, durability and corrosion resistance, and it is preferable to select the CFRP material because the CFRP material is more excellent to further enhance the performance of the end portion anchoring device.

Specifically, the cross-sectional form of the FRP rib 4 of the present invention includes, but is not limited to, one of a round rib, a square rib and a batten cross-sectional rib, and the FRP rib 4 of any cross-sectional form can be effectively bonded to the sleeve 1.

Specifically, the angle of sweep of the anchor can be determined by engineering practice, generally between 45 degrees and 90 degrees, but the sweep must be performed before the initial setting of the adhesive, and fig. 3 shows the overall installation process of the FRP bar with embedded anchoring device, and illustrates the sweep angles (45 degrees and 90 degrees) of both anchors.

Specifically, the length of the sleeve 1 is 3-5 times of the perimeter of the section of the FRP rib 4, the effective bonding length is determined by a series of FRP rib-sleeve double shear tests, the length of the anchor 2 is preferably 1/2 of the height of the reinforced concrete beam to be reinforced, and the effective anchoring length is determined by a series of anchor-concrete single shear drawing tests.

Based on the FRP bar with the novel embedded anchoring device, the invention also provides a method for preparing and installing the FRP bar into a reinforced concrete beam, as shown in figure 2, the method comprises the following steps:

s100, uniformly pressing and fully coating the FRP cloth with the width of W and the length of L (L1 + L2) (shown in figure 2) with a binder on two sides by using a roller brush;

s200, polishing the lower surface of the end part of the FRP rib into a circular arc shape to prevent the sleeve from being punctured;

s300, uniformly coating a layer of adhesive on the bonding area at the end part of the FRP rib to ensure that the FRP rib and the sleeve have enough adhesive force, wherein the thickness of the adhesive layer is preferably 1 mm;

s400, winding the FRP cloth saturated with the binder around the FRP rib in the axial direction, forming a sleeve at the end part of the FRP rib, wherein the overlapping length of the sleeve and the FRP rib is L1 (see figure 2);

s500, twisting the part of the FRP cloth with the length of L2 (shown in figure 2) into a bundle shape, winding and binding the bundle into an anchor by using a thin iron wire, and then bending the anchor at a certain angle;

s600, embedding the FRP ribs with the anchoring devices at the end parts into the concrete beam which is drilled and grooved in advance.

Specifically, as shown in fig. 4, when the FRP cloth is wrapped around the end portion of the FRP rib to form the sleeve, the specific determination method of the overlapping length L1 between the sleeve and the FRP rib in step S400 includes:

s401, adopting a double-shear drawing test method to lap the FRP cloth in a wrapping manner on two identical FRP ribs to form a sleeve, paying attention to the fact that the two FRP ribs need to be aligned, and leaving a space of 1-2cm (recommended value, which can be determined according to different conditions) in the middle. In order to control the shearing failure to occur at one designated end, the lapping length of the other end is 5-10cm (recommended value, which can be determined according to different conditions) longer than that of the failure control end, then a drawing test is carried out, and the failure mode and the maximum drawing force are recorded;

s402, gradually increasing the lap joint length of the control damage end until the FRP rib and sleeve peeling damage is converted into sleeve fracture damage or the maximum drawing force is not increased any more in the damage mode, wherein the bonding length at the moment is the effective bonding length L1 of the sleeve and the FRP rib;

specifically, as shown in fig. 5, when the part of the FRP cloth with the length of L2 is helically twisted into a bundle to form an anchor, the specific determination method of the length of L2 of the anchor in the step S500 includes:

s501, adopting a single-shear drawing test method, lapping one end of FRP cloth on an FRP rib in a wrapping mode to form a sleeve, wherein the lapping length is not less than the effective bonding length L1, screwing the other end of the FRP cloth into a bundle shape, and spirally winding a thin iron wire to form an anchor, wherein the anchor lengths of different samples are different;

s502, drilling a certain number of plain concrete blocks with the same size along the direction vertical to the surface, wherein the drilling depth corresponds to the length of each sample anchor, and the drilling diameter is the diameter of the anchor plus the thickness of a glue layer of 4-6 mm;

s503, pouring structural adhesive into the hole, slowly inserting the anchor, performing a drawing test after the complete coagulation, and when the damage mode is just changed from the pulling-out damage of the anchor from the concrete block to the breaking damage of the FRP material or the drawing force is not increased any more, the bonding length at the moment is the effective anchoring length L2 of the anchor in the concrete.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. An FRP rib with embedded anchoring device, characterized in that, both ends of this FRP rib (4) are provided with embedded anchoring device, wherein,

The material of the anchoring device is FRP fiber cloth, the front end of the FRP fiber cloth is crimped and formed to form a sleeve (1), the rear end of the FRP fiber cloth is twisted into a bundle shape, and a fixed rope (5) is used to wrap and shape, so as to form a sleeve (1). An anchor (2) is formed, and the sleeve (1) and the anchor (2) form an included angle θ;

After the FRP bar with the embedded anchoring device is embedded in the reinforced concrete beam to be reinforced, the anchoring device prevents the end of the FRP bar (4) from being peeled and damaged during the stress process of the beam, thereby improving the resistance of the reinforced concrete beam to be reinforced. Bending capacity.

2. The FRP rib with embedded anchoring device according to claim 1, characterized in that, the materials of the FRP rib (4) and the anchoring device are carbon fiber reinforced polymer, glass fiber reinforced polymer, aramid fiber One of reinforced polymer and basalt fiber reinforced polymer.

3. The FRP rib with embedded anchoring device according to claim 1, characterized in that, when the sleeve (1) is sleeved on both ends of the FRP rib (4), an adhesive (3) ) to realize the connection between the sleeve (1) and the FRP rib (4).

4 . The FRP rib with embedded anchoring device according to claim 3 , wherein the adhesive ( 3 ) is preferably an engineering structural adhesive. 5 .

5 . The FRP rib with embedded anchoring device according to claim 1 , wherein the included angle θ ranges from 45° to 90°. 6 .

6 . The FRP bar with embedded anchoring device according to claim 1 , wherein after the FRP bar is embedded in the reinforced concrete beam to be reinforced, its flexural bearing capacity is increased by 20% to 30%. 7 .

7. The FRP rib with embedded anchoring device according to claim 1, wherein the adhesive force between the sleeve (1) and the FRP rib (4) is the same as that of the sleeve (1) ) is proportional to the length of a The bonding force between the reinforced reinforced concrete beams is proportional to the length of the anchors (2), and will not change after reaching the critical value. threshold value is set.

8 . The FRP rib with embedded anchoring device according to claim 1 , wherein the length of the sleeve ( 1 ) is preferably 3 to 5 times the perimeter of the cross-section of the FRP rib ( 4 ). 9 . The length of the anchor (2) is preferably 1/2 of the height of the reinforced concrete beam to be reinforced.

9. The application method of the FRP rib with embedded anchoring device described in any one of claims 1-8, characterized in that, the application method comprises the following steps:

(a) Select FRP bars and the materials required for the anchoring devices arranged at both ends of the FRP bars, coat the bonding areas at both ends of the FRP bars with adhesive, and wrap the FRP fiber cloth saturated with the adhesive on the Both ends of the FRP rib coated with adhesive form a sleeve;

(b) twisting the ends of the FRP fiber cloth into bundles, and using fixed ropes to be helically tied and fixed to form anchors, so far to obtain FRP bars with anchoring devices at the ends;

(c) Slotting and drilling holes at the bottom of the reinforced concrete beam to be reinforced to form grooves and mounting holes, then inserting the anchors into the mounting holes, and inserting the FRP bars into the grooves, thereby connecting the ends The FRP bars provided with anchoring devices are embedded in the reinforced concrete beams to be reinforced.