A low Poisson's ratio elastomer, a seamless expansion joint and its construction process

Abstract

This invention relates to the field of bridge expansion joint engineering technology, and particularly to a low Poisson's ratio elastomer, a seamless expansion device, and a construction process. The low Poisson's ratio elastomer, calculated by weight fraction, comprises 70%–80% negative Poisson's ratio units and 20%–30% high-toughness resin binder. Testing shows that the low Poisson's ratio elastomer has a Poisson's ratio of 0–0.01, a hardness of 60–70 IRHD, a tensile modulus of elasticity ≤2 MPa, and a tensile bond strength with steel plate ≥2.5 MPa. This invention uses negative Poisson's ratio units mixed with high-toughness resin binder to form the low Poisson's ratio elastomer, achieving a low Poisson's ratio in the resin elastomer material for expansion joints. This solves the problem of surface flatness changes caused by the unchanged volume of the resin elastomer under tension and compression. At the same width, the low Poisson's ratio elastomer can accommodate greater expansion and contraction deformation.

Description

Technical Field

[0001] This invention relates to the field of bridge expansion joint engineering technology, and in particular to a low Poisson's ratio elastomer, a seamless expansion device, and a construction process. Background Technology

[0002] Expansion joints are an important structure of bridges, not only related to the structural safety of the bridge and effectively buffering the compression or tension between structures caused by bridge deformation or vibration, but also an important guarantee for road traffic safety.

[0003] Existing resin-based seamless bridge expansion joint technology is limited by the material's Poisson's ratio properties. The resin elastomer does not significantly change volume during deformation. Therefore, under horizontal compression from the bridge, the resin elastomer tends to bulge vertically, and under horizontal tension, it tends to indent vertically. Its surface smoothness varies considerably with temperature, increasing driving bumps and noise, and affecting driving comfort. Furthermore, the sides of the resin elastomer are mostly fixed to the angle steel; under heavy traffic and temperature changes, the bonding interface is prone to cracking, leading to angle steel corrosion and reducing the device's lifespan.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a low Poisson's ratio elastomer, a seamless expansion joint and construction process, which aims to improve the impact resistance and load-bearing performance of the resin seamless expansion joint, and reduce the change in flatness to reduce driving noise and improve driving comfort.

[0006] To achieve the above objectives, the present invention provides a low Poisson's ratio elastomer, comprising, by weight fraction: 70% to 80% negative Poisson's ratio units and 20% to 30% high-toughness resin binder.

[0007] Furthermore, the low Poisson's ratio elastomer has a Poisson's ratio of 0 to 0.01, a hardness of 60 to 70 IRHD, a tensile modulus of elasticity of ≤2 MPa, and a tensile bond strength with steel plate of ≥2.5 MPa.

[0008] It should be explained that the Poisson's ratio of the low Poisson's ratio elastomer provided in this disclosure is 0 to 0.01. When subjected to impact and compression by vehicle tires, the low Poisson's ratio elastomer exhibits a negative Poisson's ratio effect at the crushed part of the marking, which can effectively absorb impact vibration. At the same time, the vertical deformation is smaller, resulting in lower driving noise and higher driving comfort.

[0009] Furthermore, the negative Poisson's ratio unit is a concave hexagonal rubber elastomer, which is made by melting EPDM rubber granules at high temperature, injecting them into a concave quadrilateral mold under high pressure, and then cutting them with a V-shaped cutter.

[0010] The low Poisson's ratio elastomer provided in this disclosure contains an internally concave hexagonal rubber elastomer. When the temperature drops in winter, the bridge concrete shrinks, and the ultra-low Poisson's ratio resin elastomer is stretched horizontally. Vertically, the elastic resin contracts while the negative Poisson's ratio units expand. Ultimately, the ultra-low Poisson's ratio resin elastomer maintains a constant vertical height or slightly concave, reducing changes in the surface flatness of the expansion joint in winter. When the temperature rises in summer, the bridge concrete expands, and the ultra-low Poisson's ratio resin elastomer is compressed horizontally. Vertically, the elastic resin expands while the negative Poisson's ratio units compress. Ultimately, the ultra-low Poisson's ratio resin elastomer maintains a constant vertical height or slightly convex, reducing changes in the surface flatness of the expansion joint under high summer temperatures.

[0011] Furthermore, the negative Poisson's ratio unit has a Poisson's ratio of -0.1 to -0.05, a particle size of 16 to 30 mesh, and a moisture content of ≤1%.

[0012] Furthermore, the high-toughness resin binder is prepared by mixing component A and component B in a 1:1 ratio. Calculated by mass parts, component A includes 50-65 parts of polyether polyol, 1-7 parts of calcium oxide, 30-50 parts of diethanolamine, and 1-5 parts of defoamer. Component B includes 50-70 parts of isocyanate, 5-10 parts of bisphenol A epoxy resin, 1-4 parts of 1,4-butanediol, and 2-5 parts of organometallic catalyst.

[0013] Furthermore, the preparation method of the high-toughness resin binder includes the following steps:

[0014] S1: Dehydrate the polyether polyol, and place the dehydrated polyether polyol, calcium oxide, diethanolamine and defoamer into a mixing container according to the designed ratio and stir for 30 minutes.

[0015] S2: According to the designed ratio, place isocyanate, bisphenol A epoxy resin, butanediol and organometallic catalyst into a stirring container and stir for 30 minutes.

[0016] S3: When in use, mix the A component mixture obtained from S1, the B component mixture obtained from S2, and the negative Poisson's ratio unit, and then pour them into the pit.

[0017] This disclosure also provides a seamless expansion joint device, installed above the expansion joint between adjacent box girders. An asphalt concrete pavement layer is provided above the box girder, comprising: two side formworks, a comb-tooth pad, two external angle steels, several dowel bars, and a low Poisson's ratio elastomer. The box girder, along with the asphalt concrete pavement layer, has trenches excavated on both sides of the expansion joint. The upper portion of the pre-embedded reinforcing bars located inside the box girder is exposed in the trenches. The two side formworks are vertically and symmetrically arranged above both sides of the expansion joint. The comb-tooth pad is horizontally laid above the side formworks. The end is fixedly connected to the pre-embedded reinforcing bar by the first shear nail. The two external angle steels are respectively located on both sides of the comb tooth pad. An adjustment base plate is provided at the bottom of the external angle steel. The adjustment base plate is fixed to the pre-embedded reinforcing bar by anchor bolts and the second shear nail. The external angle steel, the adjustment base plate and the comb tooth pad form a casting groove. Multiple through holes are provided on the opposite end faces of the external angle steel. The force transmission rod is fixed in the through holes. The low Poisson's ratio elastomer is cast in the casting groove. Cement concrete is also cast between the side formwork and the side wall of the pit.

[0018] Furthermore, the force transmission rod includes a threaded steel pipe and a flexible sleeve. One end of the flexible sleeve is closed and the other end is open. A spring in a compressed state is installed inside the flexible sleeve. The open end of the flexible sleeve is sleeved on the threaded steel pipe and partially overlaps with it. The overlapping part of the flexible sleeve and the threaded steel pipe passes through the through hole of the angle steel and is held in place by fixing rings located on both sides of the angle steel. The flexible sleeve is located in the casting groove.

[0019] This disclosure can use a traditional metal rod as a force transmission rod, such as inserting a whole metal rod through the through hole of an angle steel. However, on the one hand, the connection strength between the metal material and the low Poisson's ratio elastomer is low, and separation is easy to occur. On the other hand, the volume of the metal material remains almost unchanged with seasonal changes, so it cannot deform in tandem with the negative Poisson's ratio elastomer. Therefore, this disclosure specifically provides a new force transmission rod. The part of the force transmission rod inserted into the cement concrete is a threaded steel pipe, while the part inserted into the low Poisson's ratio elastomer is a flexible sleeve. The flexible sleeve is formed inside the low Poisson's ratio elastomer. The flexible sleeve is preferably made of polyurethane, which has elasticity. Through the combination of the flexible sleeve and the built-in spring, it can deform in tandem with the negative Poisson's ratio elastomer to absorb interface stress and avoid interface cracking.

[0020] Furthermore, a limiting rod is provided at the end of the threaded steel pipe that contacts the flexible sleeve, and the spring portion is sleeved on the limiting rod.

[0021] Furthermore, the embedded steel bar has an inverted U-shaped structure, including a top horizontal section and vertical sections connecting the two ends of the horizontal section.

[0022] Furthermore, longitudinal reinforcing bars are fixed between the pre-embedded reinforcing bars, and the axis of the longitudinal reinforcing bars is parallel to the length direction of the expansion joint.

[0023] This disclosure also provides a construction process for a seamless expansion joint, comprising the following steps:

[0024] S1: Cut and remove the asphalt concrete pavement and box girder, and clean out the embedded steel bars and bridge expansion joints. For those without embedded steel bars, steel bars need to be installed at equal intervals.

[0025] S2: Lay two side templates, weld and fix the side templates directly above the bridge expansion joint, and spray foam adhesive to seal the overlap between the side templates and the expansion joint.

[0026] S3: Place the comb-tooth pad above the side formwork, and initially fix the first shear nail at the bottom of the comb-tooth pad to the pre-embedded steel bar by binding.

[0027] S4: After measuring and determining the position of the anchor bolts, the design height, distance from the edge, and angle of the anchor bolts are determined. They are then fixed to the pre-embedded steel bars by welding. The adjustment base plate is inserted into the screw of the anchor bolt. The other side is initially fixed by binding the second shear nail at the bottom to the pre-embedded steel bars. The position of the adjustment base plate is adjusted until the design position is reached. Then, the second shear nail is welded to the pre-embedded steel bars.

[0028] S5: Weld the two ends of the comb tooth pad to the adjusting base plate, then weld the side template to the bottom surface of the comb tooth pad, spray foam adhesive at the weld, release the binding of the first shear nail at the bottom of the comb tooth pad to the pre-embedded steel bar, and fix it by welding;

[0029] S6: Place the external angle steel on the adjusting base plate and fix it with the nuts of the anchor bolts. Then insert the force transmission rod into the reserved hole of the external angle steel and fix it to the external angle steel with the fixing ring. At this time, the casting trough is formed.

[0030] S7: Pour cement concrete into the gap between the external angle steel and the asphalt concrete pavement layer. After the concrete has cured to 90% of its design strength, begin the next step of construction.

[0031] S8: Mix the negative Poisson's ratio unit and the high-toughness resin binder evenly according to the ratio to form a low Poisson's ratio resin mixture, and pour it directly into the pouring trench until it is level with the height of the asphalt concrete pavement layers on both sides. Smooth the uneven areas a second time, and after curing, form a low Poisson's ratio elastomer.

[0032] S9: Traffic will resume after 24 hours of rest and recuperation.

[0033] The beneficial effects of this invention are as follows:

[0034] (1) The resin elastomer achieves an ultra-low Poisson's ratio through the negative Poisson's ratio unit, which improves the deformation capacity by 25% and can be used for bridge expansion joints with a deformation of up to 200mm.

[0035] (2) High driving comfort. Depending on the different ratios, it can approach the lower limit of Poisson's ratio, effectively reducing the influence of different seasonal temperatures on the surface smoothness of the resin elastomer. The elastomer can achieve a negative Poisson's ratio locally, effectively absorbing the impact force of the vehicle and reducing the deformation of the elastomer when the vehicle rolls over it. It reduces noise by 10~15dB compared to traditional seamless resin expansion joints.

[0036] (3) Effectively improves the load-bearing capacity of resin elastomers. Under the same vertical deformation conditions, the dynamic stability is greater than 44,000 times / mm, and the load-bearing capacity is increased by about 50%, which can adapt to traffic environment under heavy load conditions.

[0037] (4) Strong interface bonding ability. By using the force transmission rod, the interface connection is strengthened, and the vehicle impact load is transferred to the cement concrete in the anchorage area, thus solving the problem of cracking at the interface between the angle steel and the cement concrete.

[0038] (5) High construction efficiency: single-layer angle steel is used and no other stabilizing elements are set up to realize the full-thickness direct injection process of resin elastomer. No layered paving is required, and the construction efficiency is increased by more than 20%.

[0039] (6) Convenient maintenance and repair: the ultra-low Poisson's ratio resin elastomer can be directly cut and excavated, and after filling with similar materials and curing, it can be opened to traffic. It can achieve local filling and lane-level repair, and maintenance is convenient and inexpensive. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the negative Poisson's ratio unit in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the seamless telescopic device in an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the force transmission rod in an embodiment of the present invention.

[0044] Reference numerals: 1. Box girder; 2. Asphalt concrete pavement layer; 3. Side formwork; 4. Comb tooth pad; 5. External angle steel; 6. Dowel bar; 7. Low Poisson's ratio elastomer; 8. Embedded steel bar; 9. First shear nail; 10. Adjustable base plate; 11. Anchor bolt; 12. Second shear nail; 13. Cement concrete; 14. Threaded steel pipe; 15. Flexible sleeve; 16. Spring; 17. Fixing ring; 18. Limiting rod; 19. Longitudinal steel bar. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] Example 1

[0049] as follows Figures 1-3As shown, this embodiment provides a seamless expansion joint device using a low Poisson's ratio resin elastomer. The device includes: two side templates 3, comb-tooth pads 4, two external angle steels 5, several force transmission rods 6, a low Poisson's ratio elastomer 7, and longitudinal reinforcing bars 19. The entire device is installed above the expansion joint between adjacent box girders 1. The box girders 1, along with the asphalt concrete pavement layer 2, require trenches to be dug on both sides of the expansion joint for installing and fixing the device. Specifically, the upper part of the pre-embedded reinforcing bars 8 located inside the box girders 1 is exposed in the trenches. The two side templates 3 are vertically and symmetrically arranged above both sides of the expansion joint, and the comb-tooth pads 4 are laid horizontally. Above the side formwork 3, the two ends of the comb pad 4 are fixedly connected to the pre-embedded steel bars 8 by the first shear nails 9. Two external angle steels 5 are located on both sides of the comb pad 4. An adjustment base plate 10 is provided at the bottom of the external angle steel 5. The adjustment base plate 10 is fixed to the pre-embedded steel bars 8 by the anchor bolts 11 and the second shear nails 12. The external angle steel 5, the adjustment base plate and the comb pad 4 form a casting groove. Multiple through holes are provided on the opposite end faces of the external angle steel 5. The force transmission rod 6 is fixed in the through holes. The low Poisson's ratio elastomer 7 is poured in the casting groove. Cement concrete 13 is also poured between the side formwork 3 and the side wall of the pit.

[0050] 8 pre-embedded steel bars Figure 2 As can be seen, its structure is an inverted U-shape, including a top horizontal section and vertical sections connecting the two ends of the horizontal section. The pre-embedded steel bars 8 are formed by continuous bending of a single steel bar, which is a common structural component on construction sites. In order to strengthen and fix the pre-embedded steel bars 8, longitudinal steel bars 19 are fixed between the pre-embedded steel bars 8. The axis of the longitudinal steel bars 19 is parallel to the length direction of the expansion joint.

[0051] Specifically, the force transmission rod 6 used in this embodiment is as follows: Figure 3 As shown, the force transmission rod 6 includes a threaded steel pipe 14 and a flexible sleeve 15. One end of the flexible sleeve 15 is closed and the other end is open. A spring 16 in a compressed state is installed inside the flexible sleeve 15. The open end of the flexible sleeve 15 is sleeved on the threaded steel pipe 14 and partially overlaps it. The overlapping part of the flexible sleeve 15 and the threaded steel pipe 14 passes through the through hole of the angle steel and is locked by the fixing rings 17 located on both sides of the angle steel. The flexible sleeve 15 is located in the casting groove.

[0052] Specifically, the preparation method of the low Poisson's ratio elastomer 7 used in this embodiment includes the following steps:

[0053] S1: Weigh 60 parts of polyether polyol according to the weight ratio and dehydrate it. Then, according to the design ratio, put the dehydrated polyether polyol, 4 parts of calcium oxide, 40 parts of diethanolamine and 2 parts of defoamer into a mixing container and stir for 30 minutes.

[0054] S2: According to the design ratio, 60 parts isocyanate, 8 parts bisphenol A epoxy resin, 3 parts butanediol and 4 parts organometallic catalyst are placed in a stirring container and stirred for 30 minutes.

[0055] S3: When in use, the A component mixture obtained from S1 and the B component mixture obtained from S2 are mixed to obtain a blend. The blend and the negative Poisson's ratio unit are mixed at a weight ratio of 25:75 and then poured into the pit.

[0056] It should be noted that the construction process of the seamless expansion joint provided in this embodiment includes the following steps:

[0057] S1: Cut and remove the asphalt concrete pavement layer 2 and box girder 1, and clean out the embedded steel bars 8 and bridge expansion joints. For those without embedded steel bars 8, steel bars need to be installed at equal intervals.

[0058] S2: Lay two side templates 3, weld and fix the side templates 3 directly above the bridge expansion joint, and spray foam adhesive to seal the overlap between the side templates 3 and the expansion joint.

[0059] S3: Place the comb plate 4 above the side template 3, and initially fix the first shear nail 9 at the bottom of the comb plate 4 to the pre-embedded steel bar 8 by binding.

[0060] S4: After measuring and determining the position of the anchor bolt 11, the design height, distance from the edge and angle of the anchor bolt 11 are determined. Then, it is fixed to the pre-embedded steel bar 8 by welding. The adjusting base plate 10 is inserted into the screw of the anchor bolt 11. The other side is initially tied and fixed by the bottom second shear nail 12 and the pre-embedded steel bar 8. After adjusting the position of the adjusting base plate 10 until the design position is reached, the second shear nail 12 is welded to the pre-embedded steel bar 8.

[0061] S5: Weld the two ends of the comb pad 4 to the adjusting base plate 10, then weld the side template 3 to the bottom surface of the comb pad 4, spray foam adhesive at the weld, release the binding of the first shear nail 9 at the bottom of the comb pad 4 to the pre-embedded steel bar 8, and fix it by welding.

[0062] S6: Place the external angle steel 5 on the adjusting base plate 10 and fix it with the nuts of the anchor bolts 11. Then insert the force transmission rod 6 into the reserved hole of the external angle steel 5 and fix it on the external angle steel 5 with the fixing ring 17. At this time, a casting trough is formed.

[0063] S7: Pour cement concrete 13 into the gap between the external angle steel 5 and the asphalt concrete pavement layer 2. After the concrete has cured to 90% of its design strength, begin the next step of construction.

[0064] S8: Mix the negative Poisson's ratio unit and the high-toughness resin binder evenly according to the ratio to form a low Poisson's ratio resin mixture, and pour it directly into the pouring trench until it is level with the height of the asphalt concrete pavement layers on both sides. Smooth the uneven areas a second time, and after curing, form a low Poisson's ratio elastomer 7.

[0065] S9: Traffic will resume after 24 hours of rest and recuperation.

[0066] The performance test results after construction are as follows:

[0067]

[0068] The test results above show that the seamless telescopic device provided in this embodiment has low noise after traffic starts. Under the same vertical deformation conditions, the dynamic stability is greater than 44,000 times / mm, the load-bearing capacity is increased by about 50%, it can adapt to traffic environment under heavy load conditions, and the overall interface bonding strength is high and the service life is long.

[0069] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low Poisson's ratio elastomer characterized in that, According to the weight fraction, including: 70%~80% negative Poisson's ratio unit and 20%~30% high toughness resin binder; The high toughness resin binder is prepared by mixing A component and B component, according to the mass fraction, the A component includes polyether polyol 50~65 parts, calcium oxide 1~7 parts, diethanolamine 30~50 parts and defoaming agent 1~5 parts, and the B component includes isocyanate 50~70 parts, bisphenol A type epoxy resin 5~10 parts, 1,4-butanediol 1~4 parts and organic metal catalyst 2~5 parts.

2. The low Poisson ratio elastomer of claim 1, wherein, The low Poisson's ratio elastomer has a Poisson's ratio of 0~0.01, a hardness of 60~70 IRHD, an elastic modulus of ≤2 MPa, and a bonding tensile strength with a steel plate of ≥2.5 MPa.

3. The low Poisson ratio elastomer of claim 1, wherein, The negative Poisson's ratio unit is a concave hexahedral rubber elastomer, which is prepared by melting EPDM rubber particles at high temperature and then injecting into a concave quadrilateral mold at high pressure, and then cutting by a V-shaped cutter.

4. The low Poisson ratio elastomer of claim 1, wherein, The preparation method of the high toughness resin binder comprises the following steps: S1: Dehydrate the polyether polyol, and place the dehydrated polyether polyol, calcium oxide, diethanolamine and defoaming agent in a stirring container according to the designed ratio and stir for 30 min; S2: Place isocyanate, bisphenol A type epoxy resin, 1,4-butanediol and organic metal catalyst in a stirring container according to the designed ratio and stir for 30 min; S3: When used, mix the A component mixture obtained in S1 and the B component mixture obtained in S2 with the negative Poisson's ratio unit and then pour into a pit.

5. A seamless expansion joint disposed over an expansion joint between adjacent box girders, said box girders having an asphaltic concrete deck disposed thereon, wherein: It comprises: Two side formworks, a comb tooth pad plate, two external angle steels, a plurality of force transmission rods and the low Poisson's ratio elastomer according to any one of claims 1~4, a pit is dug on both sides of the expansion joint of the box girder together with the asphalt concrete paving layer, the upper part of the embedded steel in the box girder is exposed in the pit, the two side formworks are vertically and symmetrically arranged above both sides of the expansion joint, the comb tooth pad plate is horizontally laid above the side formworks, the comb tooth pad plate is fixedly connected with the embedded steel through first shear nails at both ends, the two external angle steels are respectively located at both sides of the comb tooth pad plate, the bottom of the external angle steel is provided with an adjusting bottom plate, the adjusting bottom plate is fixed on the embedded steel through anchor bolts and second shear nails, a pouring groove is formed between the external angle steel, the adjusting bottom plate and the comb tooth pad plate, a plurality of through holes are arranged on the opposite end faces of the external angle steel, the force transmission rods are fixed in the through holes, the low Poisson's ratio elastomer is poured in the pouring groove, and cement concrete is also poured between the side formworks and the pit side wall.

6. The seamless expansion joint of claim 5, wherein, The force transmission rod comprises a threaded steel pipe and a flexible sleeve, one end of the flexible sleeve is closed and the other end is open, a spring in a compressed state is arranged in the flexible sleeve, the open end of the flexible sleeve is sleeved on the threaded steel pipe and partially overlaps, the overlapping part of the flexible sleeve and the threaded steel pipe is arranged in the through hole of the angle steel and clamped by the fixing ring located on both sides of the angle steel, and the flexible sleeve is located in the pouring groove.

7. The seamless expansion joint of claim 6, wherein, The embedded steel bar is in an inverted U-shaped structure, comprising a top horizontal section and vertical sections connected to both ends of the horizontal section.

8. The seamless expansion joint of claim 7, wherein, Longitudinal steel bars are fixed between the embedded steel bars, and the axis of the longitudinal steel bars is parallel to the length direction of the expansion joint.

9. A process for the construction of seamless expansion joints according to any one of claims 5 to 8, characterized in that, The method comprises the following steps: S1: cutting and chiseling the asphalt concrete paving layer and the box girder, cleaning out the embedded steel bars and the bridge expansion joint, and for those without embedded steel bars, planting steel bars at equal intervals; S2: laying two side formworks, which are welded and fixed directly above the bridge expansion joint, and spraying foam glue at the overlapping parts of the side formworks and the expansion joint for sealing; S3: placing the comb tooth pad plate above the side formwork, and preliminarily fixing the first shear pins at the bottom of the comb tooth pad plate to the embedded steel bars through binding; S4: measuring and determining the position of the anchor bolt, determining the design height, distance from the edge and angle of the anchor bolt, and then fixing the anchor bolt to the embedded steel bar through welding, putting the adjusting base plate into the screw rod of the anchor bolt, preliminarily binding and fixing the other side through the second shear pins at the bottom and the embedded steel bars, adjusting the position of the adjusting base plate until the designed position is reached, and then welding the second shear pins to the embedded steel bars; S5: welding the two ends of the comb tooth pad plate to the adjusting base plate, then welding the side formwork to the bottom surface of the comb tooth pad plate, spraying foam glue at the weld, removing the binding of the first shear pins at the bottom of the comb tooth pad plate to the embedded steel bars, and fixing through welding; S6: placing the external angle steel on the adjusting base plate and fixing it through the nut of the anchor bolt, then putting the load transmission rod into the reserved hole of the external angle steel and fixing it to the external angle steel through the fixing ring, thus forming a pouring groove; S7: pouring cement concrete from the gap between the external angle steel and the asphalt concrete paving layer, and after the concrete is cured to 90% of the designed strength, starting the next step of construction; S8: uniformly mixing the negative Poisson's ratio unit and the high-toughness resin binder according to the proportion to form a low Poisson's ratio resin mixture, directly pouring it into the pouring groove, pouring it to the same height as the two sides of the asphalt concrete paving layer, and secondly smoothing the uneven parts, and forming a low Poisson's ratio elastomer after curing; S9: opening the traffic after 24 hours of curing.

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