WO2019033789A1

WO2019033789A1 - Permanent magnet-based tuned mass damper device for deterioration control of bridge expansion joint

Info

Publication number: WO2019033789A1
Application number: PCT/CN2018/084943
Authority: WO
Inventors: 王浩; 张一鸣; 茅建校; 郑文智
Original assignee: 东南大学
Priority date: 2017-08-15
Filing date: 2018-04-27
Publication date: 2019-02-21
Also published as: CN107354867B; CN107354867A

Abstract

A permanent magnet-based tuned mass damper device for deterioration control of a bridge expansion joint, the device comprising a mass block (1), permanent magnets (5) arranged on inner and outer sides of the mass block (1) and coated with a graphene coating, an inner copper plate (4), an outer copper plate (3), and a number of springs (2, 6, 7). The inner copper plate (4) and outer copper plate (3) have fixed positions. The mass block (1) is suspended from an upper fixing plate (9) of the device via the spring II (6). Horizontal vibration of a box girder causes the mass block (1) to swing, and the inner copper plate (4) intercepts field lines of an induced magnetic field generated by the permanent magnet (5) on the inner side of the mass block (1). Vertical vibration of the box girder causes the mass block (1) to move vertically, the outer copper plate (3) intercepts field lines of an induced magnetic field generated by the permanent magnet (5) on the outer side, and the vibration energy is dissipated by means of resistance heat generation of the copper plate. The device has a simple structure and is convenient to install, avoids the leakage problem of conventional viscous liquid dampers, significantly increases service life of dampers, and improves damping efficiency of the device. In addition, the damper device can control both horizontal and vertical displacement of a girder end, thus greatly reducing the probability of a corner of the girder end distorting or damaging an expansion gap, and controlling the start and progress of a deterioration process of an expansion gap.

Description

Permanent magnet type tuned mass damping device for disease control of bridge expansion joint

Technical field

The invention relates to the field of vibration control of civil engineering, in particular to a permanent magnet type tuned mass damping device for disease control of bridge expansion joints.

Background technique

The expansion joint is an important part of the bridge structure, and its function is to enable the bridge to freely expand and contract under the action of temperature change, driving and wind without generating binding force. Due to the direct bearing of repeated vehicle loads and long-term exposure to the atmosphere, the use environment is harsh, making the expansion joint the weakest part of the bridge structure, and the service life is far less than the design value, which directly leads to a large amount of maintenance and replacement costs.

According to US statistics, the average life span of bridge expansion joints is 10 to 15 years, which is much lower than the design life of the bridge itself. During the 8 years of the opening of the Tomei Expressway in Japan, the average number of repairs of expansion joints was 1.6 times/seam. With the vigorous development of China's transportation industry, the number and scale of bridge construction and the increasing traffic volume make the damage of the expansion joint more prominent. According to the survey data in 1990, the bridge management departments of 13 cities including the Beijing Highway Administration Office and the Tianjin Bridge Management Office investigated 556 bridges under the jurisdiction, of which 271 were destroyed by the expansion joint device. Investigate 48.7% of the total number of bridges. Once the bridge expansion joint is damaged, it not only directly affects traffic safety and driving comfort, but also affects the stress of the superstructure and reduces the service life of the bridge.

Exploring the cause of the expansion joint damage is of great significance for the early prevention and discovery of the damage of the expansion joint and the extension of the service life of the expansion joint. The research shows that the cumulative displacement of the box girder is the main reason for the expansion of the expansion joint. The temperature deformation only accounts for a small part of the overall displacement, and the wind and vehicle load cause the small rapid vibration of the box girder to cause the fatigue failure of the support beam. Therefore, measures must be taken to reduce the vibration of the box girder. The existing measures are mainly to install a viscous damper inside the box girder and a tuned mass damper (TMD) to reduce the structure's response under vibration. The viscous damper reduces vibration by consuming vibration energy. Since the damper is filled with liquid, the internal stiffness is almost zero, so the vibration frequency of the original structure is not changed, and the force and displacement hysteresis curve is elliptical for the controlled structure, but There is a problem of oil leakage and difficulty in curing, which affects the vibration damping effect. The TMD consists of a mass, a spring and a damping system. When the main structure generates vibration under external excitation, the system vibrates together. The inertial force generated by the motion of the system reacts to the inertial force of the main structure to make it opposite to the direction of the excitation force. The reaction values of the main structure are reduced to achieve the purpose of controlling the vibration of the main structure. Existing small TMD damping elements are generally rubber materials, and large TMDs use oil dampers, but both dampers have problems with rubber aging and oil leakage and fatigue.

Graphene has excellent electrical, thermal and mechanical properties and can be applied to almost all fields. In recent years, the preparation method of graphene has been continuously improved to produce large-area, low-cost, high-quality graphene. Based on the excellent properties of graphene, it will likely become the core material for high speed transistors, high sensitivity sensors and composite materials. Graphene has strong chemical inertness and stability, long service life and good stability. The preparation of a graphene film on the copper surface can improve the corrosion resistance of copper and increase the electrical and thermal conductivity.

When the non-magnetic conductor is in a time-varying magnetic field or in the magnetic field, the magnetic flux changes, and according to Faraday's law of electromagnetic induction, an induced electromotive force is generated in the conductor, thereby forming a vortex-like current, that is, an eddy current. According to the principle of eddy current, a series of eddy current dampers for civil engineering are developed, such as CN201010022003 permanent magnet eddy current tuned mass damper and CN201310080464 pendulum eddy current tuned mass damper device.

For the vulnerability of the expansion joint, although the viscous damper is generally used for vibration reduction, the effect of reducing the transverse and vertical vibration of the expansion joint is not good, and the problem of oil leakage and rubber aging is still inevitable. The vibration damping device using the eddy current principle has the advantages of no friction and no leakage, but there is still no damping device specifically for reducing vibration in all directions of the expansion joint, so how to effectively use the eddy current principle to reduce the vibration of the expansion joint is A topic of great research value.

Summary of the invention

Technical problem: In order to solve the premature failure of the expansion joint caused by the small and rapid vibration of the expansion joint caused by wind and vehicle load, a permanent magnet type tuned mass damping device for the control of bridge expansion joint disease is invented to overcome the existing viscous damping. The shortcomings of the device can cut the magnetic induction line in different directions, thereby effectively reducing the vibration of the joint expansion joint in all directions, and greatly reducing the distortion probability of the expansion joint caused by the corner end angle of the beam.

Technical Solution: The permanent magnet type tunable mass damping device for the bridge expansion joint disease control of the present invention comprises the upper fixed plate welded to the top plate of the end of the box beam connected with the expansion joint, and the lower fixed plate welded with the bottom of the box girder; The inner and outer mounted permanent magnets are integrally formed with the mass, and are hinged to the upper fixing plate by springs; the inner copper plate is connected to the upper fixing plate via the spring in the steel sleeve, and is located inside the mass block, and the top of the steel sleeve is bolted to the upper fixing plate; the outer copper plate The magnet is fixed to the upper and lower fixing plates, and one end of the bottom spring is fixed to the lower fixing plate, and the other end is fixed to the curved plate.

In order to prevent the vertical vibration of the mass, the inner copper plate is in contact with the permanent magnet in the vertical direction, and the steel sleeve is opened at the level of the lower edge of the top plate of the mass, and the horizontal limiting short plate is connected with the spring at the opening. When the mass shifts downward, the mass drives the lower limit plate of the lower edge to move downward together, so that the spring is elongated and the inner copper plate is displaced downward. The formula of the frequency of the pendulum TMD:

It can be known from equation (1) that the frequency of the pendulum TMD is determined by the pendulum length. Therefore, the TMD frequency can be brought to the design value by adjusting the stiffness of the spring, and the damper performance is optimized.

The outer surface of the copper plate is covered with a graphene coating to make full use of the good electrical conductivity and thermal conductivity of the graphene material and the corrosion resistance. The outer portion of the steel sleeve is coated with an epoxy resin to prevent corrosion, and the permanent magnet is a neodymium iron boron material. The material with the largest magnetic energy product.

When the permanent magnet is arranged, the top plate of the mass block and the inner permanent magnet of the bottom plate are arranged opposite each other, the magnetic grade is N, S level, and the magnetic induction intensity of the copper plate on the same row reaches the maximum when the magnetic level of the adjacent permanent magnet is opposite. For the best.

In the specific engineering application, in order to increase the magnetic flux and the cutting efficiency to a greater extent, the permanent magnet can be added to the outside of the top of the mass, and a copper plate is fixed on the upper fixing plate at the upper part of the mass.

When the load such as wind and vehicle causes the expansion joint to produce small and rapid vibration, the mass in the box girder will oscillate, the inner copper plate cuts the magnetic induction line generated by the permanent magnet inside the mass, and the permanent magnet on the outer side of the outer copper cutting mass is generated. The magnetic induction line generates a corresponding induced electromotive force in the inner and outer copper plates to form an eddy current. When the conductor moves at a velocity v in a uniform magnetic field B, the current density flowing through the conductor is:

J=σ(v×B) (2)

Where σ is the conductivity of the conductor; B is the magnetic induction; J is the eddy current density.

The electromagnetic force that the conductor current receives in the magnetic field is:

Among them, Γ - the volume of the conductor.

It can be seen from the equations (2) and (3) that the damping force is related to the magnetic field and the volume of the conductor cutting magnetic line.

Since the direction of the conductor speed is perpendicular to the magnetic induction, the size of F is:

F=-σδSB ² v (4)

Where δ is the thickness of the conductor; S is the surface area of the conductor.

In the formula (4), the negative sign indicates that the electromagnetic force is opposite to the linear velocity of the cutting magnetic induction, and according to Lenz's law, the eddy current generates a magnetic field opposite to the direction of the original magnetic field. When the copper plate cuts the magnetic induction line, a damping force is formed to prevent the relative motion of the two, which causes the energy to be consumed by the resistance heat effect of the copper plate, and finally reduces the vibration of the expansion joint.

Advantageous Effects: The present invention integrates a permanent magnet and a mass by arranging a permanent magnet inside and outside the mass, and mounting a copper plate inside and outside the mass. When the box beam vibrates horizontally, the mass is oscillated, and the inner copper plate cuts the magnetic induction line generated by the permanent magnet inside the mass; when the box beam vibrates vertically, the mass is vertically displaced, and the outer copper plate is cut outside the mass. The magnetic induction line generated by the magnet is known from the eddy current principle, and the vibration energy is dissipated by the resistance heat effect of the copper plate. In addition, the permanent magnet tuned mass damping device of the invention is simple and flexible to install, and can be respectively arranged according to the transverse bridge direction and the shun bridge direction, thereby simultaneously controlling the displacement of the transverse bridge to the bridge beam end, and greatly reducing the expansion joint caused by the beam end angle. The probability of distortion and damage, control the generation and development of expansion joint disease.

DRAWINGS

Figure 1 is a schematic view showing the structure of the device of the present invention;

Figure 2 is a side cross-sectional view of the device of the present invention;

Figure 3 is a plan view of the mass of the device of the present invention;

Figure 4 is a cross-sectional view taken along line I-I of Figure 3 of the present invention;

Figure 5 is a side view of the steel sleeve of the device of the present invention;

Figure 6 is a cross-sectional view taken along line II-II of Figure 5 of the present invention;

Figure 7 is a side plan view of the outer copper plate of the device of the present invention;

In the figure: 1, mass; 2, spring I; 3, outer copper plate; 4, inner copper plate; 5, permanent magnet; 6, spring II; 7, spring III; 8, steel casing; 9, upper fixing plate; 10, box girder top plate; 11, lower fixed plate; 12, box girder bottom plate; 13, curved plate; 14, limit short plate; 15, magnetic guide.

Detailed ways

A permanent magnet type tuned mass damping device for bridge expansion joint disease control, comprising an upper fixing plate 9 welded to a top plate 10 at an end of a box beam connected to an expansion joint, and a lower fixing plate 11 welded to the box beam bottom plate 12; The inner and outer mounting permanent magnets 5 of the block 1 are integrally formed with the mass block 1 and are hinged to the upper fixing plate 9 by a spring II6; the inner copper plate 4 is connected to the upper fixing plate 9 via the spring III7 in the steel sleeve, and is located inside the mass block 1, the steel sleeve The top of the 8 is bolted to the upper fixing plate 9; the outer copper plate 3 and the magnetizer 15 are fixed to the upper fixing plate 9 and the lower fixing plate 11, and one end of the spring I2 is fixed to the lower fixing plate 11 and the other end is fixed to the curved plate 13.

As shown in Fig. 1, when the mass 1 is swung, the swing direction is perpendicular to the direction of the paper; as shown in Fig. 2, when the mass 1 is horizontally oscillated, the swing direction is oscillated in the plane, and the mass is swung inside the copper plate 4. The direction is set to a sufficiently large space to prevent the inner copper plate 4 from colliding with the inner wall of the mass 1. By adjusting the stiffness of the spring II6 to control the swing period of the mass 1, the TMD frequency is brought to the design value, and the damper performance is optimized.

The inner copper plate 4 and the outer copper plate 3 are covered with a graphene coating to make full use of the good electrical conductivity and thermal conductivity of the graphene material and the corrosion resistance. The outer portion of the steel sleeve 8 is coated with an epoxy resin to prevent corrosion, and the permanent magnet 5 is a crucible. Iron-boron material, which is the material with the largest magnetic energy product. One end of the spring I2 on the lower fixing plate 11 is fixed to the lower fixing plate 11, and the other end is fixed to the curved plate 13. The vertical distance between the bottom of the mass 1 and the curved plate at rest is set to 3 to 5 mm.

As shown in FIGS. 3 to 4, the top plate of the mass 1 and the inner permanent magnet 5 of the bottom plate are arranged opposite each other, and the magnetic level of the inner facing magnet is opposite to the N and S levels, and the magnetic level of the adjacent permanent magnet 5 in the same row is opposite. The magnetic induction generated on the inner copper plate 4 and the outer copper plate 3 is the largest, so that more energy is consumed by the resistance thermal effect of the copper plate. The number of the same row of permanent magnets 5 is arranged according to the specific situation, but not less than two, the permanent magnets may be added outside the top of the mass block, and a copper plate is added to the upper fixing plate at the upper part of the mass.

As shown in FIGS. 5-7, in order to prevent the vertical vibration of the mass 1 , the inner copper plate 4 is in contact with the permanent magnet 5 in the vertical direction, and the steel sleeve 8 is opened at the level of the lower edge of the top plate of the mass block 1 to open. The limiting short plate 14 is connected to the spring III7 in the horizontal direction. When the mass 1 is displaced downward, the mass 1 drives the lower limit plate 14 of the lower edge to move downward together, so that the spring III7 is elongated and the inner copper plate 4 is displaced downward.

The above description is only a preferred embodiment of the present invention, and those skilled in the art can appropriately change and improve the embodiments according to the disclosure. The present invention is not limited to the specific embodiments described above, and the modifications and improvements are intended to be included within the scope of the appended claims.

Claims

A permanent magnet tuned mass damping device for bridge expansion joint disease control, comprising an upper fixed plate welded to a top plate of an end of a box girder connected with an expansion joint, a lower fixed plate welded to the bottom of the box girder; The permanent magnet is integrally formed with the mass, and is hinged to the upper fixing plate by a spring; the inner copper plate is connected to the upper fixing plate through a spring in the steel sleeve and is located inside the mass block, and the top of the steel sleeve is bolted with the upper fixing plate; the outer copper plate and the guide The magnet is fixed to the upper fixing plate and the lower fixing plate, and one end of the bottom spring is fixed to the lower fixing plate, and the other end is fixed to the curved plate.
The permanent magnet type tuned mass damping device for bridge expansion joint disease control according to claim 1, wherein the copper plate is covered with a graphene coating, the outer portion of the steel sleeve is coated with epoxy resin, and the permanent magnet is 钕Iron boron material.
The permanent magnet type tuned mass damping device for bridge expansion joint disease control according to claim 1, wherein when the permanent magnet is arranged, the magnetic poles of the permanent magnets facing the inner side of the mass block are N and S grades, And the magnetic level of the adjacent permanent magnets in the same row is opposite.
The permanent magnet type tuned mass damping device for the bridge expansion joint disease control according to claim 1, wherein the permanent magnet is added to the outside of the top of the mass block, and the copper plate is fixed on the upper fixed plate at the upper part of the mass.
The permanent magnet type tunable mass damping device for the bridge expansion joint disease control according to claim 1, wherein the steel sleeve is open to the bottom edge of the top plate of the mass block, and the limit short plate is provided at the opening. Connected to the spring in a horizontal direction.