CN116296906A

CN116296906A - Drop hammer impact test device for bridge FRP inhaul cable

Info

Publication number: CN116296906A
Application number: CN202310364104.XA
Authority: CN
Inventors: 许国文; 刘晓刚; 王安妮; 亓立刚; 杨燕; 马明磊; 张宏涛; 葛杰; 杨朔; 冯明扬
Original assignee: University of Science and Technology Beijing USTB; China Construction Eighth Engineering Division Co Ltd
Current assignee: University of Science and Technology Beijing USTB; China Construction Eighth Engineering Division Co Ltd
Priority date: 2023-04-06
Filing date: 2023-04-06
Publication date: 2023-06-23

Abstract

The invention discloses a drop hammer impact test device for a bridge FRP inhaul cable, which adopts a full-automatic system to control the whole test process, and is convenient and efficient. In addition, the bridge FRP inhaul cable can be impacted under various working conditions such as different spans, pretensions and inclination angles, in-situ bending resistance and tensile residual performance test after the impact of the FRP inhaul cable can be realized, adverse effects of the disassembling inhaul cable on the accuracy of test results are avoided, a researcher can grasp the impact failure mechanism of the FRP inhaul cable at multiple angles, and theoretical guidance is provided for practical engineering industrialization application. The invention solves the problem that the FRP inhaul cable impact resistance test under the combined working conditions of different spans, pretension, inclination angles and the like cannot be realized in the prior art.

Description

Drop hammer impact test device for bridge FRP inhaul cable

Technical Field

The invention relates to the technical field of building construction, in particular to a drop hammer impact test device for a bridge FRP inhaul cable.

Background

The parallel steel wire rope and the steel strand rope are the most main inhaul cable application forms in the bridge of the cable bearing system at present, and the excellent mechanical property of the parallel steel wire rope and the steel strand rope enables the bridge structure to develop towards the gentle direction of the large span in recent years. The cable is used as the main stress member of the cable bearing system bridge, and the cable corrosion caused by various factors such as environment can produce serious safety results on the bridge structure.

The fiber reinforced composite material (fiber reinforced polymer, FRP for short) has the advantages of light weight, high strength, good durability, excellent fatigue resistance and the like, can replace traditional steel, and the prepared inhaul cable is applied to bridge structures, so that the durability of the structures can be improved, and the spans and bearing capacity of the structures can be improved.

With the increasing of the conservation quantity of motor vehicles in China, the traffic operation demands are also higher and higher. The bridge guy cable can not be influenced by impact load such as vehicles in the actual operation process, and when the impact load exceeds the self resistance of the guy cable, the guy cable is extremely easy to break, and the bridge structure is seriously collapsed. And the FRP rope with orthotropic characteristic is more easy to generate the phenomenon under the impact load. Therefore, a great number of tests and theoretical analysis are necessary to be carried out before engineering application to explore the transverse stress performance and the residual performance of the bridge inhaul cable. The prior art has no device for testing the shock resistance of the FRP rope under the combined working conditions of different spans, pretension, inclination angles and the like.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

Disclosure of Invention

In order to overcome the defects existing in the prior art, a drop hammer impact test device for the FRP inhaul cable of the bridge is provided at present, so that the problem that the impact resistance test of the FRP inhaul cable under the combined working conditions of different spans, pretension, inclination angles and the like is not realized in the prior art is solved.

In order to achieve the above object, the present invention provides a drop hammer impact test device for a bridge FRP cable, comprising:

the base is provided with a top plate through a plurality of upright posts, and a guide rod is arranged between the top plate and the base;

the two abutment blocks are oppositely arranged, the abutment blocks are adjustably arranged on the base in position, and the abutment blocks are reversibly provided with supporting plates for installing stay cable anchorage devices;

the hammering assembly comprises a sliding block, a hammer body and a lifting device, wherein the sliding block is provided with a guide hole, the guide rod movably penetrates through the guide hole, the lifting device is connected with the sliding block through a chain, the sliding block is adsorbed to the hammer body through electromagnetism, and the hammer body is arranged between two abutment blocks;

the anti-rebound piece is used for electromagnetically absorbing the hammer body, is detachably arranged on the base and is arranged below the hammer body, and the base is provided with a distance sensor for collecting a distance value between the hammer body and the anti-rebound piece;

and the controller is connected with the lifting device, the distance sensor and the rebound prevention piece.

Further, the two opposite sides of the abutment are respectively provided with an ear plate, the ear plates are provided with two strip-shaped holes, at least one strip-shaped hole is arc-shaped, the supporting plate is arranged between the two ear plates, the two opposite sides of the supporting plate are respectively provided with an inserting rod, the inserting rods movably penetrate through the strip-shaped holes and extend to the outer sides of the ear plates, and the inserting rods are provided with locking pieces for locking the ear plates.

Further, limiting plates are formed on opposite sides of the supporting plates on the two abutment, and through holes for the FRP inhaul cables to penetrate are formed in the limiting plates.

Further, the slider and the rebound prevention member are respectively provided with an electromagnetic member.

Further, the base is provided with a reinforcing beam, and the abutment is adjustably arranged at two opposite ends of the reinforcing beam.

Further, the reinforcing beam and the base are provided with through holes, the rebound prevention piece is detachably arranged on the reinforcing beam to shield the through holes, the base is laid on a foundation, the foundation is provided with accommodating holes, the accommodating holes are aligned to the through holes, and a loading head for testing bending resistance residual performance of the FRP inhaul cable is arranged in the accommodating holes in a lifting manner.

Further, a bedplate is arranged in the accommodating hole in a lifting manner, a loading jack is vertically arranged on the bedplate, and the loading head is arranged on the loading jack.

Further, a containing frame for the FRP inhaul cable to penetrate is arranged at the top of the loading jack, and the loading head is arranged at the upper part of a frame opening of the containing frame.

The invention provides a construction method of a drop hammer impact test device for a bridge FRP inhaul cable, which comprises the following steps:

two ends of an FRP inhaul cable to be tested are respectively arranged on the supporting plates of the two piers through anchors;

the positions of the two piers on the base and the overturning angle of the supporting plate are adjusted, so that the FRP inhaul cable is arranged at the preset position of the base in a preset inclination angle;

starting a lifting device through a controller to enable a hammer body to be suspended above an FRP inhaul cable to be tested;

the sliding block is powered off, so that the hammer body falls down to impact the FRP inhaul cable to be tested, and the distance sensor collects the distance value between the hammer body and the rebound prevention piece;

the controller starts the rebound prevention piece based on the distance value, so that the hammer body is adsorbed to the rebound prevention piece electromagnetically when approaching to the base, and the hammer body is prevented from rebounding secondarily.

The drop hammer impact test device for the bridge FRP inhaul cable has the beneficial effects that the drop hammer impact test device for the bridge FRP inhaul cable has the advantages that the whole test process is controlled by adopting a full-automatic system, and convenience and high efficiency are realized. In addition, the device can not only impact the bridge inhaul cable under various working conditions such as different spans, pretensions and inclination angles, but also test the in-situ bending resistance and tensile residual performance of the inhaul cable after impact, prevent the inhaul cable from being disassembled after impact so as to influence the accuracy of test results, facilitate researchers to master the impact failure mechanism of the inhaul cable at multiple angles, and provide theoretical guidance for practical engineering industrialization application.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the following drawings, in which:

fig. 1 is a schematic structural diagram of a drop hammer impact test device for a bridge FRP cable according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of an internal structure of a drop hammer impact test device for a bridge FRP cable according to an embodiment of the present invention.

Fig. 3 is an internal structure elevation view of a drop hammer impact test device for a bridge FRP cable according to an embodiment of the present invention.

Fig. 4 is a schematic view illustrating inclination angle adjustment of the FRP cable according to an embodiment of the present invention.

Fig. 5 is a schematic view showing the adjustment of the installation position of the FRP cable according to the embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a usage state of a loading head according to an embodiment of the present invention.

Fig. 7 is a schematic structural view of a loading head according to a first form of the embodiment of the present invention.

Fig. 8 is a schematic structural view of a loading head according to a second form of embodiment of the present invention.

Detailed Description

The present application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be noted that, for convenience of description, only the portions related to the invention are shown in the drawings.

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Referring to fig. 1 to 8, the present invention provides a drop hammer impact test device for a bridge FRP cable, comprising: base 1, two pier 2, hammering subassembly, rebound prevention piece 4, controller.

In this embodiment, the base is a high-quality steel plate base. The base 1 is erected with a top plate 11 by a plurality of columns 12. A guide rod 13 is installed between the top plate 11 and the base 1. The top plate and the base are respectively rectangular. The number of the upright posts is four. Four stand columns are rectangular. The upper end of the upright post is connected with the top plate through a flange. The lower end of the upright post is connected with the base through a flange. The two ends of the guide rod are connected with threaded holes of the top plate and the base through threads. After the guide rod is installed, the two ends of the guide rod are in a tensioning state.

The two abutment 2 are arranged opposite to each other. The two abutment 2 are respectively and adjustably mounted on the base 1. Abutment 2 is reversibly fitted with a support plate 21. The support plate 21 is used for mounting the stay 6 anchor.

As a preferred embodiment, the base 1 is provided with reinforcing beams 14. Abutment 2 is adjustably mounted to opposite ends of reinforcing beam 14.

In this embodiment, the stiffening beams are double T-beams. The reinforcing beam is provided with a plurality of first positioning holes. The first positioning holes are arranged at intervals along the length direction of the reinforcing beam. The abutment is provided with a plurality of second positioning holes. The second positioning hole is aligned with the first positioning hole and is connected by a bolt.

Referring to fig. 5, the second positioning holes are aligned to the first positioning holes at different positions, so as to adjust the position of the abutment on the reinforcing beam.

As a preferred embodiment, the abutment 2 is formed with an ear plate 22 on each of opposite sides. The ear plate 22 is provided with two strip-shaped holes. At least one of the strip-shaped holes is arc-shaped. The support plate 21 is disposed between the two ear plates 22. Opposite sides of the support plate 21 are formed with insert bars 211, respectively. The inserting rod 211 is movably inserted through the strip-shaped hole and extends to the outer side of the ear plate 22. The insert bar 211 is fitted with a locking member for locking the lug plate 22.

In this embodiment, a circular hole and a strip-shaped hole are formed in the lug plate of one abutment, the inner diameter of the circular hole is adapted to the outer diameter of the inserted link, so that the inserted link can only rotate in the circular hole, the intrados of the lug plate strip-shaped hole of the abutment faces the circular hole, and two arc-shaped strip-shaped holes are respectively formed in the lug plate of the other abutment. The three arc-shaped strip-shaped holes are all obtained by taking the circular hole as the center of a circle.

The outermost strip-shaped holes, i.e. the strip-shaped holes of the longest length, are marked with angle values beside them. The strip-shaped hole near the center of the circle is used as the innermost strip-shaped hole, and the length of the strip-shaped hole gradually increases from the innermost strip-shaped hole to the outermost strip-shaped hole. Referring to fig. 4, the impact resistance test of the FRP cable under different inclination angles can be performed by adjusting and setting the turning angles of the two support plates.

As a preferred embodiment, the two abutment 2 are formed with a limiting plate 212 on opposite sides of the support plate 21. The limiting plate 212 is provided with a perforation for the FRP stay rope 6 to pass through. Depending on the limiting plate, pretension can be applied to the FRP inhaul cable by adopting a pretension device or in-situ tensile residual performance test can be carried out.

FRP guy cable is fixed in the bearing plate through the ground tackle, specifically, installs in the both sides of the perforation of limiting plate through pretension nut or jack, force sensor etc. through pretension nut or jack can realize exerting pretension to the guy cable, and the size of force is through force sensor measurement record. After the related operation is finished, the impact resistance performance of the inhaul cable under different pretensions can be tested. In addition, after the impact test is finished, secondary torque is applied to the pre-tightening nut or secondary tension is applied to the pre-tightening nut by adopting a jack, so that the tensile residual performance of the FRP inhaul cable after impact can be tested.

The hammering assembly comprises a slide 31, a hammer body 32 and a lifting device 33. The slider 31 is provided with a guide hole. The guide rod 13 is movably inserted into the guide hole. The lifting device 33 is connected to the slider 31 by means of a chain. The slider 31 is attracted to the ram 32 by electromagnetic attraction. The hammer 32 is disposed between the two abutments 2.

The lifting device comprises a motor. The motor is connected with the sliding block through a chain and a chain wheel. The sliding block is lifted up and down by the positive and negative rotation of the output shaft of the motor.

The motor adopts the brake motor, can take place the auto-lock under outage or the equipment condition of closing, and the hammer block is not unexpected under the effect of tensile force to drop.

The hammer body is lifted by the chain, and compared with the high-strength steel wire rope, the chain has small elasticity, so that the height measurement is more accurate, the chain has higher strength, and abrasion is not easy to occur.

The hammer body adopts a split design and comprises a main hammer body and an auxiliary hammer body, wherein the main hammer body is connected with the auxiliary hammer body through a high-strength bolt. The auxiliary hammer body is in direct contact with the test piece, so that the auxiliary hammer body is convenient to detach and replace. The hammer body is processed by a high-strength steel plate, has good impact resistance, and can not be broken due to casting defects.

The rebound prevention member 4 is for electromagnetically attracting the hammer 32. The rebound prevention member 4 is detachably mounted to the base 1 and disposed below the hammer 32. The base 1 is mounted with a distance sensor 7 for acquiring a distance value between the hammer 32 and the rebound prevention member 4.

In the present embodiment, the slider 31 and the rebound prevention member 4 are respectively mounted with electromagnetic members. The electromagnetic part generates magnetism or magnetic disappearance through on-off current, and then the falling of the hammer body is realized, and the hammer body after falling is adsorbed by the rebound prevention part.

The distance sensor adopts an infrared sensor. When impact energy is large, the inhaul cable fails to fracture, the hammer body continuously falls under the action of gravity, corresponding position signals are sensed by the infrared sensing equipment when approaching to the base, the electromagnetic part of the rebound prevention part associated with the hammer body is started, the hammer body is clamped, adsorbed and locked through the clamp in an electromagnetic force mode, and therefore secondary damage to the inhaul cable caused by rebound of the hammer body is effectively prevented.

As a preferred embodiment, the reinforcing beam 14 and the base 1 are provided with through holes. The rebound prevention piece 4 is detachably mounted to the reinforcing beam 14 to shield the through hole. The foundation 1 is laid on the foundation. The foundation is provided with a containing hole. The accommodating hole is aligned with the through hole. A loading head 5 for testing bending resistance residual performance of the FRP inhaul cable 6 is arranged in the accommodating hole in a lifting manner.

The in-situ static load system comprises a jacking jack, a bedplate, a force sensor, a loading jack, a loading head and the like, and is positioned in a foundation accommodating hole with a limited area within a certain depth range below the horizontal ground where the base is positioned. Referring to fig. 7 and 8, a platen 51 is installed in the accommodating hole in a liftable manner, a loading jack 52 is vertically installed on the platen 51, and the loading head 5 is installed on the loading jack 52. Specifically, the jacking jacks are vertically arranged in the accommodating holes, the number of the jacking jacks is multiple, the bedplate 51 is arranged on the jacking jacks, and the force sensor pad is arranged between the bedplate 51 and the loading jack 52.

In the present embodiment, the loading heads are of two types, and as shown in fig. 7, the loading heads are of a down-press type; as shown in fig. 8, the loading head is an overhead loading head.

With continued reference to fig. 6 and 7, the top of the loading jack is mounted with a receiving frame 53 through which the FRP cable 6 is threaded. The downward loading head 5 is mounted on the upper part of the frame opening of the accommodating frame.

In the FRP inhaul cable impact test, if the impact energy is smaller, the FRP inhaul cable is not failed and broken at the moment, after the impact is finished, the motor is started to lift the hammer body to the position fixed by the original grabbing and releasing hammer device, and the rebound prevention piece positioned at the top of the reinforcing beam is removed. And then the height of the loading jack and the bedplate of the in-situ static load system can be adjusted by controlling the lifting jack, so that the loading head extends to the upper part of the reinforcing beam. When the FRP inhaul cable shock resistance test is carried out, the loading head is lowered below the horizontal ground where the base is located, and then the rebound prevention piece is arranged on the reinforcing beam to shield the through hole of the reinforcing beam, so that the two tests are not mutually influenced.

In the in-situ static load system, the top-up type loading head and the bottom-down type loading head can respectively carry out bending resistance residual performance test on the loading of the inhaul cable at the positions of the back impact side and the impacted side of the inhaul cable, and relevant mechanical parameter indexes are exported and recorded by the force sensor.

In this embodiment, the controller is connected to the lifting device 33, the distance sensor 7 and the anti-rebound member 4. The controller is designed by adopting a PLC programmable controller, the electronic touch screen is used for direct operation of a user, and the rotary encoder is used for collecting and controlling the drop height, so that the grabbing hammer, the lifting hammer, the zero position and the impact become a set of full-automatic process.

With continued reference to fig. 1, the drop hammer impact test device for the bridge FRP cable of the present invention further includes an enclosure. The enclosure structure comprises a closed electromagnetic protective door arranged around the impact testing machine. The protection door can be opened towards four directions, so that the test piece can be conveniently fed, and related equipment parts can be conveniently installed and removed. The protective door is provided with the induction equipment, when the protective door is opened, the drop hammer impact test device for the bridge FRP inhaul cable can be self-locked through the controller, and the corresponding equipment cannot be operated, so that the safety of test personnel is ensured.

After the cable test piece to be tested is installed, before the formal test is started, the protective door is closed, the danger caused by splashing of the broken test piece in the test process can be effectively prevented, the induction equipment is installed on the protective door, the test opportunity is self-locked when the test is not completely closed, and meanwhile, the warning lamp starts to flash. After the test is started, the drop hammer starting lamp is lightened, and the sliding block releases the hammer body so as to impact the FRP inhaul cable test piece to be tested. In the impact process, impact force received by a sensor arranged on a cable test piece to be tested and deformation of the test piece are transmitted to a computer through corresponding equipment, so that required indexes such as an impact force-time curve, an impact force-displacement curve and the like are obtained.

The cable length of the FRP inhaul cable test piece to be tested is kept unchanged, the position of the abutment is moved again, and the impact resistance test of the inhaul cable at different impact positions of the hammer body can be realized.

In this embodiment, the cable test piece to be tested is an FRP bar-type cable, an FRP twisted-type cable, or an FRP sheet-type cable, and the corresponding anchor form may be a bond anchor, a clip-type anchor, or a mechanical clip-type anchor.

s1: two ends of the FRP inhaul cable 6 to be tested are respectively arranged on the supporting plates 21 of the two piers 2 through anchors.

S2: the positions of the two piers 2 on the base 1 and the turning angle of the supporting plate 21 are adjusted so that the FRP cable 6 is arranged at a preset position of the base 1 in a preset inclination angle.

S3: the controller opens the lifting device 33 to suspend the hammer 32 above the FRP cable 6 to be tested.

S4: the sliding block 31 is powered off to enable the hammer 32 to fall down to impact the FRP inhaul cable 6 to be tested, and the distance sensor 7 collects the distance value between the hammer 32 and the rebound prevention piece 4.

S5: the controller starts the rebound prevention member 4 based on the distance value, so that the hammer 32 is electromagnetically attracted to the rebound prevention member 4 when approaching to the base 1, and the hammer 32 is prevented from rebounding secondarily.

The FRP cable to be tested possibly encounters the effect of smaller impact energy in the actual operation process, at the moment, macroscopic damage can possibly occur on the surface of the FRP cable to be tested, but the FRP cable to be tested is not completely broken, or macroscopic damage can possibly occur in the inside of the cable. In these cases, although the load can be continued, the residual performance after the cable is impacted needs to be tested. At this time, since the hammer body does not fall down onto the base, after the impact test is completed, the hammer body is first lifted to the original position, and then the rebound preventing member located on the reinforcing beam is detached.

The in-situ static load device is positioned on the ground of the containing hole at a certain depth below the horizontal ground where the base is positioned, and the bedplate is lifted by the jack capable of lifting, so that the loading head extends to the upper side of the reinforcing beam to perform bending resistance residual performance test.

The bending resistance residual performances obtained by loading the FRP inhaul cable to be tested after impact on the impact side and the back impact side are different. The loading head shown in fig. 7 can apply downward acting force to the position of the impacted FRP cable at the impacted side until the FRP cable is completely broken and fails, the loading head shown in fig. 8 can apply vertical upward acting force to the position of the impacted FRP cable at the back impact side to perform bending resistance residual performance test, and relevant data are transmitted to a computer through a force sensor to be recorded.

The tensile residual performance of the FRP inhaul cable to be tested after impact also has important guiding significance for evaluating the mechanical performance of the FRP inhaul cable. The tensile residual performance change rule of the FRP inhaul cable to be tested after impact can be recorded to evaluate the mechanical property of the inhaul cable by applying secondary torque to the pre-tightening nut or adopting a jack to carry out secondary tensioning on the FRP inhaul cable until failure.

The foregoing description is only of the preferred embodiments of the present application and is presented as a description of the principles of the technology being utilized. It will be appreciated by persons skilled in the art that the scope of the invention referred to in this application is not limited to the specific combinations of features described above, but it is intended to cover other embodiments in which any combination of features described above or equivalents thereof is possible without departing from the spirit of the invention. Such as the above-described features and technical features having similar functions (but not limited to) disclosed in the present application are replaced with each other.

Claims

1. A drop hammer impact test device for bridge FRP cable, its characterized in that includes:

2. The drop hammer impact test device for the bridge FRP stay cable according to claim 1, wherein ear plates are respectively formed on two opposite sides of the abutment, two strip-shaped holes are formed in the ear plates, at least one strip-shaped hole is arc-shaped, the supporting plate is arranged between the two ear plates, inserting rods are respectively formed on two opposite sides of the supporting plate, the inserting rods movably penetrate through the strip-shaped holes and extend to the outer sides of the ear plates, and locking pieces for locking the ear plates are mounted on the inserting rods.

3. The drop hammer impact test device for the bridge FRP stay cable according to claim 2, wherein limiting plates are formed on opposite sides of the supporting plates on the two pier blocks, and the limiting plates are provided with through holes for the FRP stay cable to pass through.

4. The drop impact test device for a bridge FRP cable according to claim 1, wherein the slider and the rebound prevention member are respectively mounted with an electromagnetic member.

5. The drop impact test apparatus for a bridge FRP cable according to claim 1, wherein the base is formed with a reinforcing beam, and the abutment is position-adjustably installed at opposite ends of the reinforcing beam.

6. The drop hammer impact test device for the bridge FRP stay cable according to claim 5, wherein the reinforcing beam and the base are provided with through holes, the rebound prevention member is detachably mounted on the reinforcing beam so as to shield the through holes, the base is laid on a foundation, the foundation is provided with a containing hole, the containing hole is aligned with the through holes, and a loading head for testing bending resistance residual performance of the FRP stay cable is mounted in the containing hole in a liftable manner.

7. The drop hammer impact test device for the bridge FRP inhaul cable according to claim 6, wherein a bedplate is installed in the accommodating hole in a lifting manner, a loading jack is vertically arranged on the bedplate, and the loading head is installed on the loading jack.

8. The drop hammer impact test device for the bridge FRP inhaul cable according to claim 7, wherein a containing frame for the FRP inhaul cable to pass through is installed at the top of the loading jack, and the loading head is installed at the upper portion of a frame opening of the containing frame.

9. A construction method of the drop impact test device for the bridge FRP cable according to any one of claims 1 to 8, comprising the steps of:

the positions of the two abutment blocks on the base and the overturning angle of the supporting plate are adjusted, so that the FRP inhaul cable is arranged at the preset position of the base in a preset inclination angle;

the sliding block is powered off to enable the hammer body to fall down to impact the FRP inhaul cable to be tested, and the distance sensor collects the distance value between the hammer body and the rebound prevention piece;