CN114232478A

CN114232478A - Efficient dehumidification method for main cable of suspension bridge

Info

Publication number: CN114232478A
Application number: CN202111039953.5A
Authority: CN
Inventors: 魏建东; 黄毅; 宁轩; 管曼羽; 宋粉丽
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2022-03-25
Anticipated expiration: 2041-09-06
Also published as: CN114232478B

Abstract

The main cable steel wire bundle is kept with the galvanized steel band tied up when the cable tightening machine is in a full circle, and the wire winding machine is not needed during construction, and the surface of the main cable steel wire bundle is not wound with wires and is directly wrapped by the plastic pipe section. The plastic pipe section is made of hot-melt plastic, the plastic pipe section is an integrated sheet before installation, the two sides are only required to be in hot-melt sealing connection during installation, and the two ends are in sealing connection with the protective cover of the cable clamp or the cable saddle. The bottom in the plastic pipe section is provided with a cavity which is beneficial to the flow of dry gas. The lower end of the bottom of the plastic pipe section is provided with an exhaust hole, and the high end of the bottom is provided with an air inlet hole. The main cable is dehumidified at night by the law that the enclosed moisture in the sleeve is 'day-rising night-sinking'. The flow resistance of the dry gas is small, the load of the equipment is small, the energy consumption is low, the existing cable clamp does not need to be transformed, the maintenance cost is reduced, and the construction step of a conventional main cable is reduced.

Description

Efficient dehumidification method for main cable of suspension bridge

Technical Field

The invention relates to corrosion prevention of main cable steel wires of a suspension bridge in bridge engineering, in particular to an efficient dehumidification method of the main cable of the suspension bridge.

Background

The main cable is one of the most important stressed members of the suspension bridge, called "lifelines", which are exposed to the atmospheric environment for a long time and are subject to corrosion in various adverse environments. Meanwhile, the service life of the suspension bridge is directly influenced by the service life of the main cable as the main cable is an irreplaceable component.

In a conventional main cable protection system, a layer of protective putty, such as red lead or zinc powder paste, is coated on the surface of a main cable, and then the main cable is wrapped with a round galvanized mild steel wire, and then the outer surface of the wrapped steel wire is subjected to anticorrosive coating. The traditional main cable protection system actually achieves the purpose of corrosion prevention by sealing and wrapping the outer layer of the main cable to prevent water from invading the inner part of the main cable. The vast majority of suspension bridges built in the last century have adopted this main cable protection system. However, the results of recent foreign research and research indicate that the protective effect of the protective system is not ideal. Such conventional main cable protection measures have been observed and researched for a long time at home and abroad make internal disorder or usurp, for example, when a main cable steel wire of a bridge of a gargle user is opened and inspected in japan, the main cable surface is seriously corroded for ten years, the corrosion mainly occurs on the side surface and the bottom of the main cable, and the protection effect is not good. Water exists in the main cable, when the main cable protection system is finished, only a small part of water in the main cable is removed, and the steel wire of the main cable is rusted by the water retained in the main cable; due to the deterioration of the putty layer and the coating layer material, the paint on the surface of the winding wire is affected by severe external environments such as ultraviolet rays, the putty can be directly contacted with the external environment after aging and cracking, in addition, a corrosive environment is slowly formed by water gathered in the main cable, the physical and chemical properties of the putty are affected by a series of factors such as air, water, temperature change and the like, and finally, the phenomena of crack, oxidative deterioration and even pulverization are caused, so that the protective effect of the putty is lost. After the paint layer on the upper surface of the main cable is cracked, the water cannot be prevented from permeating into the main cable.

Researches show that water which is remained in the main cable and is difficult to discharge evaporates at high temperature in the daytime, is gathered at the upper part, condenses at low temperature at night, sinks to the bottom, and repeats the process, so that the water is the main reason for rusting the surface and the bottom of the steel wire bundle. The steel wires in the middle of the main cable are basically not rusted. In addition, simulation experiments show that the steel wire can not be rusted as long as the relative humidity of the side, top and bottom of the main cable is controlled to be below 60%.

The research of a main cable dehumidification system is carried out from the nineties of the last century in japan, and dry air is sent into a main cable to reduce air humidity in the main cable, thereby preventing corrosion of a steel wire of the main cable. The moistening bridge introduces a main cable dehumidification system into the domestic main cable protection of the large-span suspension bridge for the first time. Dehumidification equipment is generally arranged on two positions with larger space on the cross beam of the main tower or inside the stiffening beam. Meanwhile, the air feeder, the cooling equipment and the control and monitoring system are installed together, the special cable clamps for air supply and exhaust are arranged in a certain length range of the main cable, dry air is fed from the air supply cable clamps, wet air is exhausted from the exhaust cable clamps, and monitoring and control adjusting equipment is arranged at the cable clamp positions.

The air supply pressure is generally not more than 3kPa, and the protective measures for damaging the outer layer are prevented. Under this pressure, the drying gas is transported along the gaps between the wires of the main cable for a maximum distance of about 200 m. This requires the installation of a plurality of dedicated air feed and exhaust clamps along the main cable to feed air to the main cable in stages. Because the steel wire space of main push-towing rope is narrow and small, the gas flow resistance is big, so that the full-bridge needs many sets of dehumidification equipment, and power consumption is many, and the expense is high.

In order to reduce the resistance experienced by the gas passing transversely or longitudinally through the main cable, there have recently been some new main cable dehumidification schemes. In the design scheme of the Longtan Yangtze river bridge, a dehumidifying structure in the patent application named as 'a cable air supply pipeline' (with the application number of CN202011075887.2) is adopted, the dehumidifying structure is a system for introducing dry air into the dehumidifying structure, and an air supply pipe made of a high-strength spring and a corrugated pipe is arranged at the center of the section of a main cable, so that the resistance for conveying the dry air is favorably reduced. However, the high-strength spring and the corresponding corrugated pipe are specially manufactured, and an air supply pipe formed by the high-strength spring and the corresponding corrugated pipe is circular and different from a regular hexagon of a main cable strand, so that the arrangement of the cable strands is influenced in construction; the main cable squeezing effect is influenced during cabling; the cable clamp is not beneficial to clamping the main cable and is not beneficial to preventing the main cable from skidding. In the design of the Zhang Rugao river-crossing channel main channel bridge with the main span 2300m, 1 longitudinal ventilation pipe is arranged at the center of a main cable, and the dehumidifying structure in the patent application named as 'a BIM-based suspension bridge main cable dehumidifying and drying system' (with the application number of CN202021156589.1) and 'a main cable dehumidifying and corrosion preventing device' (with the application number of CN202011588740.3) is adopted, 4 longitudinal ventilation pipes are arranged on the outer layer of the main cable, and dry air is firstly sent to an annular pipeline surrounding the main cable by an external air supply pipeline and then is sent to 4 longitudinal air supply pipes on the outer layer of the main cable. The method still has the problems of the central pipeline, and the 4 peripheral longitudinal pipelines are not beneficial to the rounding of the main cable steel wire bundles and the fastening of the cable clamp.

Therefore, the current situation needs to be changed urgently, and an efficient main cable dehumidification method is found, so that the consumption of dehumidification equipment is reduced, the power consumption is reduced, and the maintenance cost of the bridge during operation is reduced.

Disclosure of Invention

In order to solve the problems of low efficiency and complex construction of the existing suspension bridge dehumidification system, the application provides an efficient suspension bridge main cable dehumidification method.

In order to achieve the purpose, the invention adopts the following technical scheme:

a high-efficiency dehumidification method for a main cable of a suspension bridge is characterized in that a steel wire bundle of each cable section of the main cable separated by a saddle and a cable clamp is sleeved with a plastic pipe section, a bottom cavity is formed between the bottom of the steel wire bundle and the plastic pipe section, and dry air is fed into the bottom cavity to discharge moisture out of the main cable; the method comprises the following construction steps:

s1, erecting the steel wire bundles of the main cable according to a conventional method, performing cable tightening operation by using a cable tightening machine, rounding the steel wire bundles, and bundling the steel wire bundles by using a galvanized steel strip;

s2, installing a cable clamp and a suspender and installing a protective cover of a saddle;

s3, for each cable section, hermetically connecting two side edges of a corresponding rectangular plastic sheet, wrapping the corresponding cable section to form a plastic pipe section, and hermetically connecting two ends of the plastic pipe section to the corresponding cable clamp or the protective cover of the saddle; the plastic pipe section is provided with air holes at the bottoms of the high end and the low end; an air supply pipe arranged on the main cable;

s4, mounting a girder to finish bridge construction;

and S5, taking the bottom cavity in each plastic pipe section as a dehumidification section, monitoring the humidity of each dehumidification section at night, and feeding dry air into the corresponding dehumidification section through the air feeding pipe to discharge the moisture in the dehumidification section after the humidity exceeds a preset limit value.

Preferably, the material of the plastic pipe section is hot melt plastic.

Preferably, the plastic sheet is composed of two layers, the inner layer is high density polyethylene, and the outer side is high density polyethylene doped with carbon black.

Preferably, the inner surface of the plastic pipe section is coated or adhered with a water-proof film and the outer surface is coated or adhered with an ultraviolet-proof film.

Preferably, the air hole at the high end of the plastic pipe section is an air inlet hole, and the air hole at the low end of the plastic pipe section is an air outlet hole.

Preferably, in step S5, the duration of introducing the dry air into the bottom cavity of the plastic pipe section with excessive humidity is one minute.

Preferably, in step S5, for the cable segments that need to be dehumidified, the cable segment with the highest humidity is selected for the dehumidification operation, and the above steps are repeated.

Preferably, the main cable section on the side of the span or the main cable saddle of the same main cable is connected to the main cable section in the span, and the air holes of a plurality of adjacent plastic pipe sections can be communicated, so that the corresponding bottom cavities are communicated to serve as a dehumidifying large section.

Preferably, the exhaust holes of the dehumidification section and the dehumidification large section are connected by a gas pipe, and in the dehumidification process, if the humidity of the exhausted air is less than the air humidity of the surrounding environment, the air exhausted by the gas pipe is conveyed to a dehumidifier in the dehumidification equipment.

Preferably, the outer surface of the plastic pipe section is provided with a pipe clamp, and the clamped plastic pipe section is fixed on the steel wire bundle.

On the basis of the scheme, a top cavity can be formed between the top of the steel wire bundle and the plastic pipe section, and dry air is fed into the top cavity to enable moisture to be discharged out of the main cable. Considering the corrosion distribution characteristics of the existing main cable, the corrosion at the top is relatively light, so that the scheme of only forming the bottom cavity is more efficient.

The invention has the beneficial effects that:

1. the initial equipment investment of the dehumidification system is reduced. According to the scheme, the cycle ascending and descending rule of the humidity in the main cable at night in the day is skillfully utilized, the cavity is built, the large airflow channel is formed, the airflow circulation resistance is reduced, the power consumption is reduced, the moisture is discharged by keeping the plant to stand for the rabbit, and the purpose of dehumidifying the main cable can be achieved by adopting the dehumidifying equipment with smaller power;

2. the dehumidification system works at night, peak-shifting power utilization is realized, power cost is reduced, and energy is saved, so that operation and maintenance cost is reduced;

3. the scheme is efficient, the dehumidification system is simple, a special air inlet cable clamp, a special air exhaust cable clamp and a corresponding pipeline system are not required to be installed, and the existing cable clamp is not required to be transformed;

4. the plastic pipe section in the scheme is environment-friendly and has various colors; the plastic pipe section is fast to install; the service life is long, maintenance is almost not needed, and ultraviolet ray resistance and severe weather resistance can be realized;

5. during construction, a wire winding machine is not needed, coating of the outer surface of a winding wire in conventional construction is omitted, the construction steps of a conventional main cable are reduced, material and labor input are saved, and the construction period is shortened;

6. according to the characteristic that moisture in the main cable descends at night, the main cable dehumidification system in the scheme simultaneously solves the problem of corrosion prevention of the main cable steel wire in the saddle; considering that the dehumidification efficiency of this scheme is very high, dehumidification equipment has more idle time, can participate in or directly be responsible for the dehumidification task in anchorage and the girder at idle time, practices thrift the dehumidification equipment input of full-bridge.

Drawings

FIG. 1 is a schematic view of a main cable section after cable tightening construction;

FIG. 2 is a schematic view of the plastic pipe section of example 1 after installation;

FIG. 3 is a schematic sectional view A-A;

FIG. 4 is a schematic view of a dual magnet block tube clamp;

FIG. 5 is a schematic view of the plastic sheet of example 1;

FIG. 6 is a schematic view showing the flow of gas when the bottom of the main cable segment is dehumidified in embodiment 1;

FIG. 7 is a schematic view showing the flow of air when the bottom of the main cable segment is dehumidified in embodiment 2;

FIG. 8 is a schematic cross-sectional view of a main cable in example 3;

FIG. 9 is a schematic view of a four-magnet clamp;

FIG. 10 is a schematic view of the plastic sheet of example 3;

FIG. 11 is a schematic view showing the flow of air when the bottom of the main cable segment is dehumidified in embodiment 3;

fig. 12 is a schematic view showing the flow of gas when the top of the main cable segment is dehumidified in embodiment 3.

In the figure: the device comprises a rope clamp 1, a hanger rod 2, an ear plate 3, a galvanized steel strip 4, a plastic pipe section 5, a double-magnetic-block pipe clamp 6, a four-magnetic-block pipe clamp 7, a bottom air inlet 8, an air outlet 9, a steel wire bundle 10, a top air inlet 11, an arc clamp 12, a bottom cavity 13, a magnet block 14, a plastic sheet 15, a bottom air supply pipe 16, a top air supply pipe 17, a bottom connecting pipe 18, a top connecting pipe 19, a top cavity 20, an electric valve 21 and a communicating pipe 22.

Detailed Description

Example 1

In this example, the case where the bundle of wires of the main cable has a bottom cavity is shown. The dehumidification method in this embodiment includes the following construction steps.

S1, erecting the steel wire bundle of the main cable according to the conventional method, wherein the steel wire bundle is a cable section in the suspension bridge, the left end of the cable section is higher than the right end and is positioned between two adjacent cable clamps 1, the steel wire bundle 10 of the main cable is just finished with cable tightening construction, and the galvanized steel belt 4 is bundled on the steel wire bundle.

And S2, installing the suspension rod 2, wherein the suspension rod 2 is connected with the cable clamp 1 through the lug plate 3. And a protective cover for mounting the main cable saddle and the cable saddle.

S3, installing the plastic pipe section, the schematic diagram after installation is shown in fig. 2, and the schematic diagram of the section of the main cable is shown in fig. 3. The hot-melt plastic selected in the embodiment is Polycarbonate (PC), and the Polycarbonate (PC) is the only transparent product in five engineering plastics, is odorless, nontoxic and transparent, and is beneficial to directly observing the condition of the steel wire bundle 10 during the operation of the bridge. Polycarbonate (PC) material has strong impact resistance, good strength and toughness, strong ultraviolet resistance, good weather resistance, good size stability and forming processing performance of products, and has obvious technical performance advantages compared with inorganic glass used traditionally in the building industry; in addition, it is a flame retardant material. According to the design information of the bridge, a rectangular plastic sheet 15 has been manufactured for each cable segment, and bottom air inlet holes 8 and air outlet holes 9 have been thermally fused on the plastic sheet 15, as shown in fig. 5. Buckling a plastic sheet 15 on the corresponding steel wire bundle 10 of the cable section, carrying out hot melting sealing connection on two side edges, forming a longitudinal bottom cavity 13 at the bottom, and positioning a bottom air inlet hole 8 and an exhaust hole 9 right below the cable section, wherein the exhaust hole 9 is positioned at the right end; the ends of the plastic pipe sections 5 are sealingly connected to the respective cable clamps 1. A temperature and humidity sensor is arranged in the plastic pipe section 5, and a small hole through which a data line passes is sealed. In order to securely fasten the plastic pipe section 5 to the steel wire bundle 10, a double magnet clamp 6 is mounted on the plastic pipe section 5, see fig. 4. The double-magnetic-block pipe clamp 6 is composed of an arc clamp 12 and magnetic blocks 14 at two ends, and is shaped like a rubber earphone. A bottom air supply pipe 16 is installed and connected with the bottom air inlet hole 8 by a bottom connecting pipe 18, see fig. 6; a normally closed electric valve 21 is mounted on the exhaust hole 9.

And S4, mounting a main beam of the bridge to finish bridge construction. The screw on the cable clamp 1 is tensioned again, and the gap between the two halves of the cable clamp 1 is filled with the sealing paste.

And S5, monitoring the relative humidity of the air in each bottom cavity 13 of the full bridge at night when the temperature is low and stable, and starting the dehumidification operation if the relative humidity exceeds 50%. The dehumidification operation is carried out by selecting the bottom cavity 13 with the maximum humidity, and the dehumidification equipment is started to feed dry air into the bottom air feed pipe 16, and simultaneously the electric valve 21 of the cable section is opened for one minute, so that the dehumidification of one cable section is completed. And then, monitoring the relative humidity of the air in each bottom cavity 13 of the full bridge, and judging whether to start the dehumidification operation, and circulating the operation until the relative humidity of the air in each bottom cavity 13 of the full bridge is lower than 50%, namely finishing the full-bridge dehumidification program.

Because the normally closed electric valve 21 is adopted in the embodiment, the exhaust holes 9 are closed but not communicated in a normal state, when a certain rope segment is dehumidified, after the corresponding electric valve 21 is opened, most of the dry air in the bottom air supply pipe 16 flows in the direction in fig. 6 except a small amount of dry air entering the adjacent rope segment, and moisture in the bottom cavity 13 is taken away. Although it seems that only a small part of moisture in the main cable is taken away every day, the dehumidification operation is carried out every day, and the air in the main cable continuously flows along with the change of air temperature and the like, so that the air humidity in the main cable can be quickly maintained at a low level, the steel wires of the main cable are protected, and the main cable is not corroded.

Example 2

This embodiment is a modification of embodiment 1, see fig. 7. In order to accelerate the dehumidification progress, the main cables or the main cables saddle at the side of the span are communicated with the bottom cavities 13 of the adjacent cable sections of the main cables in the span to form a dehumidification large section. The concrete operation is that the communicating pipe 22 is used for connecting the bottom air inlet hole 8 and the air outlet hole 9 of the adjacent cable section in the dehumidification large section. Accordingly, the time for introducing the drying air during the dehumidifying operation can be properly prolonged to three minutes.

Example 3

This embodiment is a modified form of embodiment 1, with the addition of a cavity at the top of the main cable, see fig. 11 and 12. A schematic cross-sectional view of the main cable is shown in fig. 8, the main cable having a bottom cavity 13 and a top cavity 20. In order to securely fix the plastic pipe section 5 to the steel wire bundle 10, a four-magnet pipe clamp 7 is mounted on the plastic pipe section 5, see fig. 9. The four-magnet pipe clamp 7 is composed of an arc clamp 12 and four magnet blocks 14. The plastic sheet is schematically shown in FIG. 10. To improve dehumidification efficiency, except for the operation of dehumidifying the bottom cavity 13 at night, the operation of dehumidifying the top cavity 20 of the full bridge at noon in the daytime is added. The top connection pipe 19 connects the top air feed pipe 17 and the top air intake hole 11. When the top cavity 20 is dehumidified, dry air enters the top cavity 20 from the top air supply pipe 17, and since a large gap exists between the plastic pipe section 5 and the steel wire bundle 10 near the cable clamp 1, air flow is discharged from the lower normally closed air discharge hole 9.

Claims

1. A high-efficiency dehumidification method for a main cable of a suspension bridge is characterized in that a steel wire bundle of each cable section of the main cable separated by a saddle and a cable clamp is sleeved with a plastic pipe section, a bottom cavity is formed between the bottom of the steel wire bundle and the plastic pipe section, and dry air is fed into the bottom cavity to discharge moisture out of the main cable; the method comprises the following construction steps:

s4, mounting a girder to finish bridge construction;

2. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: the plastic pipe section is made of hot-melt plastic.

3. The efficient dehumidification method for the main cable of the suspension bridge according to claim 2, wherein: the plastic sheet consists of two layers, wherein the inner layer is made of high-density polyethylene, and the outer side is made of high-density polyethylene doped with carbon black.

4. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: the inner surface of the plastic pipe section is coated or stuck with a waterproof film, and the outer surface is coated or stuck with an ultraviolet-proof film.

5. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: the air holes at the high end of the plastic pipe section are air inlet holes, and the air holes at the low end of the plastic pipe section are air outlet holes.

6. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: in step S5, the duration of introducing the dry air into the bottom cavity of the plastic pipe section with the excessive humidity is one minute.

7. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: in step S5, if there are cable segments that need to be dehumidified, the cable segment with the highest humidity is selected for the dehumidification operation, and the process is repeated.

8. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: the main cable section on the side of the same main cable or the main cable saddle is connected to the main cable section in the span, and the air holes of a plurality of adjacent plastic pipe sections on the main cable section can be communicated, so that the corresponding bottom cavities are communicated to be used as a large dehumidifying section.

9. An efficient dehumidification method for a main cable of a suspension bridge according to claim 5 and claim 8, wherein: the dehumidification section is connected with the exhaust holes of the dehumidification section, and in the dehumidification process, if the humidity of the exhausted air is smaller than the air humidity of the surrounding environment, the air exhausted from the gas pipe is conveyed to a dehumidifier in the dehumidification equipment.

10. The efficient dehumidification method for the main cable of the suspension bridge according to claim 1, wherein: and the outer surface of the plastic pipe section is provided with a pipe clamp, and the clamped plastic pipe section is fixed on the steel wire bundle.