An adaptive seismic toughness bearing

Abstract

The present invention discloses an adaptive seismic toughness bearing, comprising an upper bearing plate, a lower bearing plate, an elastic seat arranged between the upper bearing plate and the lower bearing plate, and four energy-absorbing components, wherein the four energy-absorbing components are arranged around the elastic seat; the energy-absorbing components comprise two columns, an upper beam and a lower beam, wherein the two columns, the upper beam and the lower beam form a quadrilateral frame, wherein the columns, the upper beam and the lower beam are all hinged; an energy-absorbing hinge is installed in the quadrilateral frame formed by the columns, the upper beam and the lower beam, wherein the energy-absorbing hinge is hinged to the upper beam and the lower beam. The present invention adopts the design concept of functional separation, wherein the elastic seat is mainly subjected to stress under the action of conventional loads, while the deformation and energy consumption required during earthquakes are borne by the energy-absorbing components, and the stress-bearing structure is more clearly defined, and has better energy-absorbing performance to consume the energy generated by earthquakes, and can produce greater elastic deformation to adapt to the deformation requirements required by multiple earthquakes; at the same time, the present invention is easy to replace after being damaged.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge shock absorption, and in particular relates to an adaptive seismic toughness bearing. Background Art

[0002] The existing seismic isolation bearings mainly include three types: rubber type, sliding type and composite type.

[0003] Rubber seismic isolation bearings are made of multiple layers of steel plates and rubber alternately stacked together. The steel plates are used as stiffening materials for rubber bearings, which change the characteristic of the low vertical stiffness of the rubber body, so that it can reduce horizontal earthquake effects and withstand large vertical loads. Since rubber, as an elastic body, has insufficient energy absorption, lead cores are usually added to the bearings. Lead-core rubber seismic isolation bearings can not only bear the vertical load of the entire superstructure and extend the structural period, but also provide a certain amount of damping, so that the seismic force of the lower structure (piers and abutments) is redistributed, and the displacement of the seismic isolation layer will not be large, which has a good seismic isolation effect. At the same time, lead-core rubber seismic isolation bearings have a certain initial horizontal stiffness, which can withstand the effects of loads and braking loads.

[0004] Sliding isolation bearings are made by setting sliding materials in the isolation layer, such as low-friction materials such as graphite, sand, and talcum powder, so that the foundation can only transmit limited seismic force to the upper structure, thus protecting the upper structure. Its dynamic characteristics are that the natural vibration period of the entire system is the same as the structural period before sliding. Once sliding, the stiffness of the isolation layer becomes very small, and the natural vibration period of the entire system becomes very large. Therefore, in theory, sliding isolation can avoid the resonance effect caused by most seismic waves. In addition, the friction of the isolation layer does work, which can consume the vibration energy of the structure, increase the structural damping, and reduce the seismic response of the structure.

[0005] Composite seismic isolation bearings may produce uncontrollable displacements during a major earthquake because the sliding friction bearings themselves do not have the ability to self-reset; while laminated rubber bearings have the ability to self-reset, but the damping is limited and they have no advantage in dissipating earthquake energy. Currently used composite seismic isolation bearings include the parallel use of rubber bearings and sliding bearings, the parallel use of rubber bearings and dampers, and composite seismic isolation devices that have both elastic horizontal restoring force and damping.

[0006] The above three common vibration isolation bearings all have certain defects. For example, rubber bearings are easily affected by temperature changes, air temperature changes, air oxidation, etc., which may cause rubber aging. Rubber is also prone to deformation under normal loads, and ordinary rubber bearings have no vibration isolation capabilities. The manufacturing process of vibration isolation rubber bearings is complicated, the cost is relatively high, and the damping is limited and the energy consumption is small. The production and manufacturing of composite vibration isolation bearings is complicated, especially the installation of dampers is complicated and the cost is very high. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides an adaptive seismic toughness bearing to solve the technical problems of the existing seismic isolation bearings being complex to manufacture and having limited rubber damping and low energy consumption.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0009] A self-adaptive seismic toughness bearing comprises an upper bearing plate, a lower bearing plate, and an elastic seat and four energy-absorbing components arranged between the upper bearing plate and the lower bearing plate, wherein the four energy-absorbing components are arranged around the elastic seat; the energy-absorbing components comprise two columns, an upper cross beam and a lower cross beam, wherein the two columns, the upper cross beam and the lower cross beam form a quadrilateral frame, and the columns are hinged to the upper cross beam and the lower cross beam; an energy-absorbing hinge is installed in the quadrilateral frame formed by the columns, the upper cross beam and the lower cross beam, and the energy-absorbing hinge is hinged to the upper cross beam and the lower cross beam.

[0010] Furthermore, the energy-absorbing component is connected to the upper support plate and the lower support plate by bolts.

[0011] Furthermore, four mounting holes are respectively provided on the four corners of the upper support plate and the lower support plate.

[0012] Furthermore, the elastic seat is made of rubber, and the energy-absorbing component is made of high-strength steel or aluminum alloy.

[0013] Furthermore, the energy-absorbing hinge comprises a plurality of cross-lapped support rods, each of which has a circular hole at its center and all of the circular holes are penetrated by a pin, and the angles between adjacent support rods are equal; the support rods are hinged to the upper beam and the lower beam; the line connecting the hinge points of all support rods and the upper beam coincides with a diagonal line of the upper beam, and the line connecting the hinge points of all support rods and the upper beam coincides with a diagonal line of the lower beam.

[0014] Furthermore, there are at least three support rods.

[0015] Furthermore, the energy-absorbing hinged component includes a plurality of support rods and an hourglass-shaped plate, and a plurality of protruding anchoring ends are divergently arranged on the upper and lower end surfaces of the hourglass-shaped plate, each protruding anchoring end is hinged to the upper crossbeam or the lower crossbeam through a support rod, and the angles between adjacent support rods are equal; the support rod and the protruding anchoring end are fixedly connected by bolts; the line formed by the hinge points of the support rod and the upper crossbeam is consistent with the length direction of the upper crossbeam, and the line formed by the hinge points of the support rod and the upper crossbeam is consistent with the length direction of the upper crossbeam.

[0016] Furthermore, there are at least three support rods installed on the upper end surface of the hourglass-shaped plate, and the number of support rods installed on the lower end surface is the same as that on the upper end surface.

[0017] Furthermore, the energy-absorbing hinge comprises a plurality of support rods and an hourglass-shaped plate, wherein the upper and lower ends of the hourglass-shaped plate are respectively provided with a plurality of insertion grooves divergently, and mounting holes are provided at the ends of the insertion grooves, and a support rod is respectively inserted into each insertion groove and fixed to the mounting hole by bolts, and the angles between adjacent support rods are equal; the other end of the support rod is hinged to the upper crossbeam or the lower crossbeam; the line formed by the hinge points of the support rod and the upper crossbeam is consistent with the length direction of the upper crossbeam, and the line formed by the hinge points of the support rod and the upper crossbeam is consistent with the length direction of the upper crossbeam.

[0018] Furthermore, the upper crossbeam and the support rod, as well as the lower crossbeam and the support rod are hinged via a rotating device, wherein the rotating device comprises a U-shaped fixing seat and a rotating shaft installed therein, wherein the end of the support rod is installed in the U-shaped fixing seat via the rotating shaft, and the rotating shaft of the rotating device is parallel to the length direction of the upper crossbeam.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses the design concept of functional separation. Under the action of conventional loads, the elastic seat is mainly stressed, while the deformation and energy consumption required during an earthquake are borne by the energy-consuming component. The force-bearing structure is more clear, has better energy-consuming performance to consume the energy generated by the earthquake, and can produce greater elastic deformation to adapt to the deformation requirements required by frequent earthquakes. The specific analysis is as follows:

[0021] (1) When the earthquake is relatively small, the energy-absorbing component is subjected to the horizontal earthquake force as a whole. At this time, the support rod undergoes elastic buckling. After buckling, the overall stiffness of the energy-absorbing component decreases sharply, and the flexibility increases. The energy-absorbing component is combined with the elastic seat to play a limiting role under the action of small earthquakes, and the whole is in the elastic stage, with good self-reset ability.

[0022] (2) When the earthquake vibration increases, the function of the bearing of the present invention changes from seismic isolation to shock absorption. As the earthquake vibration continues to increase, the energy-absorbing component eventually enters the plastic energy-absorbing stage. This hourglass-shaped flexural component can not only yield before the elastic seat and consume earthquake energy, but also prevent the ordinary bearing from moving out of control, causing damage to the bridge block and even the harm of falling beams, thereby achieving the effect of damage control.

[0023] (3) Energy-absorbing components can be easily replaced after an earthquake, greatly reducing costs.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of an adaptive seismic toughness bearing according to an embodiment of the present invention.

[0026] Figure 2 It is a front cross-sectional view of the adaptive seismic toughness bearing according to an embodiment of the present invention.

[0027] Figure 3 It is a front structural schematic diagram of the internal oblique rod cross-arranged energy-absorbing component of Example 1.

[0028] Figure 4 It is a three-dimensional diagram of the internal oblique rod cross-arranged energy-absorbing component of Example 1.

[0029] Figure 5 It is a schematic structural diagram of the energy-absorbing component of Example 2 based on the hourglass-shaped plate connection of the extended anchoring end.

[0030] Figure 6 Schematic diagram of the structure of the hourglass-shaped plate of Example 2.

[0031] Figure 7 It is a front structural schematic diagram of the energy-absorbing component connected by the hourglass-shaped plate with the embedded anchor end according to Example 3.

[0032] Figure 8 Schematic diagram of the structure of the hourglass-shaped plate of Example 3.

[0033] Fig. 9 It is a mechanical model established for the energy-absorbing components of the seismic isolation bearings of Examples 1, 2, and 3.

[0034] Fig.10 It is a schematic diagram of the finite element simulation of the stress on energy-absorbing components under earthquake action.

[0035] Fig.11 It is the force-displacement curve of the energy-absorbing component in case A.

[0036] Fig.12 It is the force-displacement curve of the energy-absorbing component in case B.

[0037] The symbols in the figure represent:

[0038] 1-upper support plate, 2-lower support plate, 3-elastic seat, 4-energy dissipation member; 5-upper crossbeam, 6-lower crossbeam, 7-column, 8-support rod, 9-bolt, 10-pin, 11-hourglass-shaped plate, 12-extended anchor end, 13-embedded anchor end, 14-rotating device, 15-mounting hole;

[0039] The specific contents of the present invention are further explained in detail below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0040] The specific implementation methods of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0041] In the present invention, unless otherwise specified, directional words such as "upper" and "lower" are usually defined based on the drawings of the corresponding figures, and "inside" and "outside" refer to the inside and outside of the corresponding component outline.

[0042] like Figure 1 , Figure 2 As shown, this embodiment provides an adaptive seismic toughness bearing, including an upper bearing plate 1, a lower bearing plate 2, an elastic seat 3 and four energy-absorbing components 4 arranged between the upper bearing plate 1 and the lower bearing plate 2, and the four energy-absorbing components 4 are arranged around the elastic seat 3.

[0043] Preferably, the energy absorbing member 4 is connected to the upper support plate 1 and the lower support plate 2 by bolts.

[0044] In addition, four mounting holes 15 are respectively provided on the four corners of the upper support plate 1 and the lower support plate 2; the embedded parts embedded in the bridge, the cap beam and the pier are connected to the upper support plate 1 and the lower support plate 2 through the mounting holes 15, so that the support of the present invention can be fixedly connected to the bridge, the cap beam and the pier.

[0045] Specifically, the elastic seat 3 is made of rubber, and the energy dissipation component 4 is made of high-strength steel or aluminum alloy or other materials with good ductility. The specific material is selected according to actual needs. High-strength steel has high yield strength and ultimate tensile strength. Aluminum alloy has the advantages of light weight, high strength, corrosion resistance, and good plasticity.

[0046] Specifically, the energy dissipation component 4 includes two columns 7, an upper cross beam 5 and a lower cross beam 6, wherein the two columns 7, the upper cross beam 5 and the lower cross beam 6 form a quadrilateral frame, and the columns 7 are hinged to the upper cross beam 5 and the lower cross beam 6. An energy dissipation hinge is installed in the quadrilateral frame formed by the columns 7, the upper cross beam 5 and the lower cross beam 6, and the energy dissipation hinge is hinged to the upper cross beam 5 and the lower cross beam 6. The energy dissipation hinge is in an hourglass shape.

[0047] The energy-absorbing hinge is an energy-absorbing component whose function is to consume most of the pressure of the load during vibration such as earthquakes. Together with the hinge between the column 7 and the upper beam 5 and the lower beam 6, it constitutes the energy-absorbing system of the energy-absorbing component 4, and together realizes the seismic reduction and isolation effect during vibration such as earthquakes. The energy-absorbing hinge can be set in a variety of structural forms, and the present invention provides the following preferred methods.

[0048] Embodiment 1:

[0049] like Figure 3 , Figure 4As shown, in this embodiment, an energy dissipation hinge is provided, comprising a plurality of cross-lapped support rods 8, each of which has a circular hole at its center and all of which are penetrated by a pin 10, and the angles between adjacent support rods 8 are equal, so that an hourglass-shaped energy dissipation hinge is obtained; the support rods 8 are hinged to the upper crossbeam 5 and the lower crossbeam 6. Figure 4 As shown, a line connecting the hinge points of all support rods 8 and the upper crossbeam 5 coincides with a diagonal line of the upper crossbeam 5 , and a line connecting the hinge points of all support rods 8 and the upper crossbeam 6 coincides with a diagonal line of the lower crossbeam 6 .

[0050] In the above technical solution, the upper crossbeam 5 and the lower crossbeam 6 are used to constrain each internally hinged support rod 8 within the plane where the support rod 8 is located, so as to prevent it from being displaced out of the plane.

[0051] Preferably, there are at least three support rods 8. According to tests, the number of support rods 8 is 11, which has the best vibration reduction and isolation effect.

[0052] Embodiment 2:

[0053] like Figure 5 , Figure 6 As shown, another energy dissipation hinge is provided in this embodiment, including a plurality of support rods 8 and an hourglass-shaped plate 11, as shown in FIG. Figure 6 As shown, multiple outward-extending anchoring ends 12 are respectively arranged on the upper and lower end faces of the hourglass-shaped plate 11 in a divergent manner, each outward-extending anchoring end 12 is respectively hinged to the upper crossbeam 5 or the lower crossbeam 6 through a support rod 8, and the angles between adjacent support rods 8 are equal; the support rod 8 and the outward-extending anchoring ends 12 are fixedly connected by bolts 9; the line formed by the hinge points of the support rod 8 and the upper crossbeam 5 is consistent with the length direction of the upper crossbeam 5, and the line formed by the hinge points of the support rod 8 and the upper crossbeam 6 is consistent with the length direction of the upper crossbeam 5. Preferably, there are at least three support rods 8 installed on the upper end face of the hourglass-shaped plate 11, and the number of support rods 8 installed on the lower end face is the same as that on the upper end face.

[0054] Embodiment 3:

[0055] like Figure 7 , Figure 8 As shown, another energy dissipation hinge is provided in this embodiment, including a plurality of support rods 8 and an hourglass-shaped plate 11, as shown in FIG. Figure 6As shown, the upper and lower ends of the hourglass-shaped plate 11 are respectively provided with a plurality of insertion slots divergently, and mounting holes are provided at the ends of the insertion slots, and a support rod 8 is respectively inserted into each insertion slot and fixed to the mounting hole by bolts 9, and the angles between adjacent support rods 8 are equal; the other end of the support rod 8 is hinged to the upper crossbeam 5 or the lower crossbeam 6; the line formed by the hinge point of the support rod 8 and the upper crossbeam 5 is consistent with the length direction of the upper crossbeam 5, and the line formed by the hinge point of the support rod 8 and the upper crossbeam 6 is consistent with the length direction of the upper crossbeam 5. Preferably, there are at least three support rods 8 installed on the upper end surface of the hourglass-shaped plate 11, and the number of support rods 8 installed on the lower end surface is the same as that on the upper end surface.

[0056] From the above, in Example 1, all the support rods 8 are overlapped and are not in the same plane. In Examples 2 and 3, (1) due to the use of the hourglass-shaped plate 11, all the support rods 8 are located in the same plane, making the wall of the energy-absorbing component 4 thin, thereby saving materials. (2) Due to the use of the hourglass-shaped plate 11, the length of the support rods 8 in Examples 2 and 3 is at least halved compared to that in Example 1, which allows for more flexible replacement of damaged support rods 8 and saves more materials. In addition, compared to Example 2, the anchor point of Example 3 is designed from outside the steel plate to inside the steel plate, thereby enhancing the strength of the anchor point.

[0057] Preferably, the upper cross beam 5 and the support rod 8, and the lower cross beam 6 and the support rod 8 are hinged via a rotating device, which includes a U-shaped fixing seat and a rotating shaft installed therein, and the end of the support rod 8 is installed in the U-shaped fixing seat via the rotating shaft, and the rotating shaft of the rotating device is parallel to the length direction of the upper cross beam 5, thereby restraining the support rod 8 from left and right displacement in the plane.

[0058] In order to verify the feasibility and effectiveness of the present invention, the present invention establishes a mechanical model of the energy-absorbing component 4 of the seismic isolation support, such as Fig. 9 The energy-absorbing components 4 obtained from the energy-absorbing hinges in the embodiments 1, 2 and 3 of the present invention are all suitable for this model. In this model:

[0059] Assuming that the energy dissipation component system undergoes a slight deformation, and the angle α between each internal support rod and the horizontal direction remains unchanged, according to material mechanics, the stiffness of a single support rod 8 is:

[0060]

[0061] The overall initial lateral stiffness of the energy-absorbing component 4 is derived according to structural mechanics:

[0062]

[0063] The adjacent support rods 8 have equal included angles to form a symmetrical arrangement, and the number n is greater than 3, then n≥3, and n is an odd number. E, A, α, and L are the elastic modulus, cross-sectional equivalent area, horizontal included angle with the ground, and length of the support rod, respectively.

[0064] As the horizontal thrust continues to increase, when the force reaches the critical buckling load of the first internal support rod, the first internal support rod will buckle and deform, and the stiffness will suddenly decrease until the horizontal thrust reaches the critical buckling load of the second internal support rod. In this process, the sudden drop in stiffness is caused by the buckling of the support rod 8, which can be approximately regarded as the internal support rod stiffness dropping to zero and quitting work. In theory, as the number of support rods 8 removed increases, the overall lateral stiffness of the energy-absorbing component 4 will gradually decrease, as shown in the following formula, and the flexibility of the energy-absorbing component 4 increases.

[0065]

[0066] Among them, P1~P n is the critical elastic buckling load of the support rod 8. The hourglass-shaped member conforms to the design concept of seismic isolation, which requires that the energy-absorbing component 4 yields plastically before the support, and the horizontal plastic yield displacement of the energy-absorbing component 4 is smaller than the horizontal plastic yield displacement of the support.

[0067] The horizontal plastic yield strength of the energy dissipation component is:

[0068] σ R =A1f1cosα1+…+A n f n cosα n

[0069] Among them, f1~f n is the plastic yield strength of the support rod steel. Then the horizontal plastic yield displacement of the energy dissipation component is:

[0070]

[0071] Depend on Fig.10 From the finite element simulation of the force on the support rod 8 in the energy-absorbing component 4 under the action of an earthquake (taking Example 1 as an example), it can be seen that as the earthquake force is loaded, the support rods 8 are destroyed one by one by the energy-absorbing force. During the destruction process, the ductility of the support of the present invention increases, so the adaptability of the present invention can be reflected. Since seismic toughness refers to the recoverability of the structure, the destroyed support rods 8 can also be flexibly replaced in the specific structures of the three embodiments of the present invention, which reflects good seismic toughness.

[0072] In order to verify the technical effect of the present invention, the present invention conducted the following experiments. The experiment was carried out by taking Example 1 as an example. According to the different cross-sectional radii of the support rods 8, it was divided into two cases. Case A: The cross-sectional radius of the middle rod is 3mm, and there are 7 rods on each side. From the outside to the inside, the cross-sectional radius of the first three rods is 6mm, and the cross-sectional radius of the last four rods is 5.5-3.5mm. Case B: There are 15 support rods 8 in total. The cross-sectional radius of the middle rod is 3.5mm, and there are 7 rods on each side. The cross-sectional radius of these 7 rods gradually decreases from the outside to the inside with a step size of 0.5mm, and is 7-4mm. The cross-sectional radius of the upper beam 5, the lower beam 6 and the column 7 are all 500mm. The 15 support rods 8 are symmetrically arranged. The load-displacement curves of the two schemes are shown as follows. Fig.11 , Fig.12 It can be seen from the figure that both Case A and Case B are better, but because the rod of B is set to be thicker and the initial stiffness is relatively high, it decreases faster during the stiffness degradation process, so the curve is not smooth enough during the stiffness degradation process. Case A is more in line with the curve of the seismic isolation bearing and has better ductility performance.

Claims

1. An adaptive seismic toughness bearing, comprising an upper bearing plate and a lower bearing plate, characterized in that: It also includes an elastic seat and four energy-absorbing components arranged between the upper support plate and the lower support plate, and the four energy-absorbing components are arranged around the elastic seat; the energy-absorbing components include two columns, an upper crossbeam and a lower crossbeam, wherein the two columns, the upper crossbeam and the lower crossbeam form a quadrilateral frame, and the columns are hinged to the upper crossbeam and the lower crossbeam; an energy-absorbing hinge is installed in the quadrilateral frame surrounded by the columns, the upper crossbeam and the lower crossbeam, and the energy-absorbing hinge is hinged to the upper crossbeam and the lower crossbeam; the energy-absorbing components are connected to the upper support plate and the lower support plate by bolts; and four mounting holes are respectively provided at the four corners of the upper support plate and the lower support plate; The energy dissipation hinge is of the first structure: it comprises a plurality of cross-lapped support rods, each of which has a circular hole at its center and all of which are penetrated by a pin, and the angles between adjacent support rods are equal; the support rods are hinged to the upper beam and the lower beam; the line connecting the hinge points of all support rods and the upper beam coincides with a diagonal line of the upper beam, and the line connecting the hinge points of all support rods and the upper beam coincides with a diagonal line of the lower beam; Alternatively, the energy dissipation hinge is of the second structure: comprising a plurality of support rods and an hourglass-shaped plate, wherein a plurality of outward-extending anchoring ends are respectively arranged on the upper and lower end surfaces of the hourglass-shaped plate in a divergent manner, each outward-extending anchoring end is respectively hinged to the upper crossbeam or the lower crossbeam through a support rod, and the angles between adjacent support rods are equal; the support rods and the outward-extending anchoring ends are fixedly connected by bolts; the line formed by the hinge points of the support rods and the upper crossbeam is consistent with the length direction of the upper crossbeam; Alternatively, the energy-absorbing hinge is of the third structure: comprising a plurality of support rods and an hourglass-shaped plate, wherein the upper and lower ends of the hourglass-shaped plate are respectively provided with a plurality of insertion grooves divergently, and mounting holes are provided at the ends of the insertion grooves, and a support rod is inserted into each insertion groove and fixed to the mounting hole by bolts, and the angles between adjacent support rods are equal; the other end of the support rod is hinged to the upper crossbeam or the lower crossbeam; the line connecting the hinge points of the support rod and the upper crossbeam is consistent with the length direction of the upper crossbeam.

2. The adaptive seismic toughness bearing according to claim 1, characterized in that: The elastic seat is made of rubber, and the energy-absorbing component is made of high-strength steel or aluminum alloy.

3. The adaptive seismic toughness bearing according to claim 1, characterized in that: In the first structure, there are at least three support rods.

4. The adaptive seismic toughness bearing according to claim 1, characterized in that: In the second structure, there are at least three support rods installed on the upper end surface of the hourglass-shaped plate, and the number of support rods installed on the lower end surface is the same as that on the upper end surface.

5. The adaptive seismic toughness bearing according to claim 1, characterized in that: The upper crossbeam and the support rod, as well as the lower crossbeam and the support rod are hinged via a rotating device, which includes a U-shaped fixing seat and a rotating shaft installed therein, and the end of the support rod is installed in the U-shaped fixing seat via the rotating shaft, and the rotating shaft of the rotating device is parallel to the length direction of the upper crossbeam.

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