Grease injection bolt-shearing force connecting pair

Abstract

The utility model relates to a grease injection bolt-shearing force connecting pair which comprises a bolt and a nut, the nut is arranged on a bolt rod of the bolt in a sleeved mode, the head portion, embedded in a bridge deck pavement layer, of the bolt is provided with a variable cross-section bolt head, and the variable cross-section bolt head is provided with a variable cross section with the two ends large and the middle small. A grease injection hole is formed in the top of the head, embedded in the bridge deck pavement layer, of the bolt, and resin is injected through the grease injection hole. Compared with the prior art, continuous structure splicing is achieved, and reliable shearing force transmission between interfaces is also achieved.

Description

Technical Field

[0001] This utility model belongs to the field of structural fastener technology and relates to a grease-injected bolt-shear connection pair. Background Technology

[0002] Precast orthotropic steel bridge deck systems have been widely used in bridge engineering due to their advantages such as high load-bearing capacity, lightweight characteristics, and ease of construction. However, this system is prone to fatigue damage under long-term traffic wheel loads (Abdelbaset H, Cheng B, Tian L, et al. Enhancing fatigue resistance of rib-to-floorbeam welded connections in orthotropic steel bridge decks by using uhpc layer: An experimental study[J]. Structures, 2022, 36: 153-167; Pedrosa B, Correia J, Rebelo C, et al. Fatigue experimental characterization of preloaded injection bolts in a metallic bridge strengthening scenario[J]. Engineering Structures, 2021, 234: 11-2005.). Frequent maintenance and repair not only significantly increase the total life cycle cost but also cause continuous disruption to traffic operations. Constructing a steel-ultra-high performance concrete (UHPC) composite bridge deck structure using an ultra-high performance concrete (UHPC) pavement layer can effectively improve the local stiffness and durability of the bridge deck, meeting the combined requirements of modern bridge engineering for structural performance and service life, and possessing significant technical and economic value. In this composite system, the shear force transfer mechanism between the steel bridge deck and the UHPC pavement layer is the core element to ensure the full realization of the composite effect.

[0003] Currently, steel-ultra-high performance concrete composite bridge decks mostly use welded shear connectors, such as short-head stud connectors, steel profile connectors, perforated plate connectors, welded steel mesh, and pre-bent steel bars (Li Shuyuan. Research on the pull-out performance of welded steel mesh connectors for steel-ultra-thin UHPC composite bridge decks [D]. Changsha: Hunan University, 2018.). Their mechanical properties and fatigue performance have been verified in experiments and new bridge construction practice (Gan Y. Research on the interfacial shear resistance of welded structure of the composite deck system composed of orthotropic deck and ultra-thin uhpc layer [D]. Changsha: Hunan University, 2018; Liao Z. Flexural test and finite element simulation of steel-uhpc composite [D]. Changsha: Hunan University, 2018; Tian Q, Du X. Short stud push-out test study of high performance concrete composite pavement [J]. Bridge). Construction, 2016, 46(001):40-46. These shear keys are fixed to the surface of the steel beam and embedded in the concrete slab through welding, leading to technical bottlenecks such as complex processes and construction difficulties for component replacement and structural demolition during service life. Furthermore, in the joint area of ​​the assembled orthotropic steel bridge deck, on the one hand, the densely packed bolt holes prevent the addition of the aforementioned verified welded shear connectors; on the other hand, the splicing cover plate further reduces the thickness of the ultra-high performance concrete pavement layer in the area, imposing even more stringent requirements on the height of the shear keys.

[0004] Compared to traditional welded shear connectors, the use of detachable pre-tightened bolt shear connectors in steel-precast ultra-high performance concrete composite beam structures not only significantly improves the reversible construction characteristics and material recycling potential of the structure, but also synergistically leverages the mechanical properties of the bolts and the ultra-high performance of the ultra-high performance concrete material. As a current mainstream solution, pre-tightened bolt shear connectors provide shear capacity through the interfacial friction generated by the extended bolt structure and pre-tightening force. Its shear capacity is mainly controlled by parameters such as bolt diameter, concrete material strength, and elastic modulus. Theoretical analysis shows that its shear strength is approximately 50% of its tensile strength. However, experimental studies and numerical simulations show (Rowe M, Bradford MA. Partial shear interaction in deconstructable steel-concrete composite beams with bolted shear connectors[M]. Partial Shear Interaction in Deconstructable Steel-Concrete Composite Beams with Bolted Shear Connectors, 2013; Pavlovic M, Markovic Z, Veljkovic M, et al. Bolted shear connectors vs. Headed studsbehaviour in push-out tests[J]. Journal of Constructional Steel Research, 2013, 88: 134-149.) that when the interfacial friction effect is insufficient, the steel-concrete composite interface will experience non-negligible relative slippage, which poses a serious threat to the stress performance of stiffness-sensitive steel-ultra-high performance concrete composite bridge deck systems. Furthermore, as previously mentioned, in orthotropic steel bridge deck systems using bolted splice joints, the dense arrangement of connecting bolts in the joint area limits the space available for adding traditional shear connectors.

[0005] Grease-injected bolt connections are a type of slip-free connection for steel structures. By filling the gap between the bolt and the hole wall with structural resin adhesive, slip-free connection is achieved.Compared with ordinary bolts, resin-injected bolts also have better static mechanical properties (Chen J, Wang W, Ding FX, et al. Behavior of an advanced bolted shear connector in prefabricated steel-concrete composite beams[J]. Materials, 2019, 12(18): 2958; Correia JAF d O, Pedrosa BAS, Raposo PC, et al. Fatigue strength evaluation of resin-injected bolted connections using statistical analysis[J]. Engineering, 2017: 795-805; Gresnigt AM, Paschen GM. Injection bolts to repair old bridges; procedures of the Proceedings of AISC National Steel Construction Conference, F, 2000[C]; Gresnigt AMN, Stark JWB J. Design of bolted connections with injection bolts[J]. Connections in Steel StructuresIII, 1996:77-87; Pedrosa B, Correia J, Rebelo C, et al. Fatigue experimental characterization of preloaded injection bolts in a metallic bridgestrengthening scenario [J]. Engineering Structures, 2021, 234: 112005.) and the ability to withstand short-term overload (Gresnigt AM, Paschen G M. Injection bolts to repair old bridges; proceedings of the Proceedings of AISC National Steel Construction Conference, F, 2000[C]).The stiffness and load-bearing strength of these bolted connections are closely related to the resin properties (Shao X, Yi D, Huang Z, et al. Basic performance of the composite deck system composed of orthotropic steel deck and ultrathin rpc layer[J]. Journal of Bridge Engineering, 2013, 18(5): 417-428; Shi Z, Zhou Y, Sun Z, et al. Fatigue performance of orthotropic steel decks in a wide steel-box girder[J]. Journal of Constructional Steel Research, 2022, 190: 107-109.). Currently, RenGel SW404+HY 2404 two-component resin is the recommended solution by most scholars (Kolstein H, Li J, Koper A, et al. Behaviour of double shear connections with injection bolts[J]. Steel Construction-design and Research, 2017, 10(4): 287-294; Pedrosa B, Buecking L, Veljkovic M. Steel-reinforced resin for bolted shear connectors: Confined behavior under quasi-static cyclic loading[J]. Engineering Structures, 2022, 256: 114023.) and design guidelines (Steelwork ECF C. European recommendations for bolted connections: Instructural steelwork[M]. 1985.).In addition, it has small tolerances for bolt hole size, making it particularly suitable for the reinforcement of existing bridges (Steelwork ECF C. European recommendations for bolted connections: Instructural steelwork [M]. 1985; Liu Zhaoji. Application of grease-injected bolts in bridge engineering [J]. Steel Structure, 2006, 21(2): 51-54.). However, considering only grease injection into the bolt holes to reduce the relative slippage of the composite section, it is impossible to achieve the shear key function. Its application in the joint area of ​​steel bridge deck will also weaken the connection between it and ultra-high performance concrete.

[0006] Patent CN219827418U discloses a torque-shear bolt, comprising an end cap, a connecting rod, a threaded rod, and a star head connected in sequence. The threaded rod has threads, and a nut is threaded onto the threaded rod. The star head has a first guide portion at its bottom, and the threaded rod has a second guide portion at its bottom. Although this patent improves bolt installation efficiency by providing a star head, first guide portion, and second guide portion at the end of the threaded rod, and by using a special wrench, this patent can only be used as a connecting part for steel components and cannot be used as a shear key in composite structures. Under large loads, relative slippage will occur at the composite interface due to the gap between the bolt and the bolt hole.

[0007] Patent CN203248492U discloses a grease-injected one-way bolt, consisting of a nut, a threaded rod, a neck washer, a rubber washer, a sleeve, and a tapered nut. The nut, neck washer, and rubber washer have grease injection channels to facilitate the injection of grease into the one-way bolt to fill the gaps between the sleeve and the threaded rod, as well as between the sleeve and the bolt hole wall. While this patent addresses the issues of low preload and bolt slippage within the bolt hole by injecting grease between the threaded rod and the bolt hole, it still only serves as a bolted connection for steel structures and does not function as a shear key in composite structures. Utility Model Content

[0008] The purpose of this invention is to overcome at least one of the defects in the prior art and provide a grease-injected bolt-shear connection pair. This invention achieves both continuous structural splicing and reliable shear force transfer between interfaces.

[0009] The objective of this utility model can be achieved through the following technical solutions:

[0010] One of the technical solutions of this utility model is to provide a grease-injected bolt-shear connection pair, which includes a bolt and a nut. The nut is fitted onto the bolt shank, and the head of the bolt embedded in the bridge deck pavement layer adopts a variable cross-section bolt head.

[0011] The variable cross-section bolt head adopts a variable cross-section design with large ends and small middle. After the ultra-high performance concrete has been poured and cured to a certain strength, the extended variable cross-section bolt head increases the contact area with the concrete during longitudinal and transverse shear resistance, and better applies the mechanical properties of the concrete pavement layer to the steel bridge deck.

[0012] Meanwhile, when the bridge deck is bent, the mechanical interlocking force of the variable cross-section bolt head on the ultra-high performance concrete layer can restrain the separation of the vertical pavement layer and the steel bridge deck, preventing the bolt from detaching from the concrete layer.

[0013] The head of the bolt embedded in the bridge deck pavement has a grease injection hole at the top, which facilitates resin injection through the grease injection hole after the bolt is tightened.

[0014] As a preferred technical solution, the length of the variable cross-section bolt head can be adjusted according to the thickness of the pavement layer required for the specific project, and should meet the pouring thickness requirements of the ultra-high performance concrete pavement layer of the steel bridge deck.

[0015] Furthermore, several grease injection holes are arranged parallel to the axis of the bolt rod; providing multiple grease injection holes can improve grease injection efficiency and prevent the gap between the bolt rod and the bolt hole of the bridge deck from being filled with grease; the direction of the grease injection holes is parallel to the axis of the bolt rod, that is, the vertical direction of gravity, which is conducive to resin flow and injection, and also facilitates manufacturing.

[0016] Furthermore, the grease injection hole has a channel that penetrates the variable cross-section bolt head, and the bottom opening of the grease injection hole is located at the bolt shank.

[0017] The grease injection hole penetrates the head of the bolt, and the bottom opening of the grease injection hole is connected to the gap between the bolt shank and the bolt hole on the bridge deck, ensuring that the resin is directly injected into the target area.

[0018] The grease injection hole is extended slightly to the bolt rod to ensure that the cross-sectional area of ​​the bottom opening of the grease injection hole is not less than the cross-sectional area of ​​the hole, thus ensuring smooth resin flow.

[0019] Furthermore, the distance from the farthest end of the grease injection hole to the axis of the bolt shank is greater than the radius of the bolt shank and the minimum radius of the variable cross-section bolt head, while the distance from the nearest end to the axis of the bolt shank is less than the radius of the bolt shank and the minimum radius of the variable cross-section bolt head.

[0020] The diameter of the injection hole is limited by the diameter of the injection needle and the fluidity of the resin, and can be further limited to be greater than the distance between the bolt rod and the bolt hole of the bridge deck.

[0021] The bottom opening of the grease injection hole must be connected to the gap between the bolt rod and the bolt hole on the bridge deck in order to allow the resin to be injected into the target area. Therefore, the grease injection hole is partially inside the outer periphery of the bolt rod and partially outside.

[0022] As an alternative technical solution, if the distance between the bolt rod and the bolt hole on the bridge deck is large enough, and the distance between the grease injection hole and the axis of the bolt rod is greater than the radius of the bolt rod and the minimum radius of the variable cross-section bolt head, then all of them can be located outside the outer periphery of the bolt rod.

[0023] Furthermore, the top of the variable cross-section bolt head is provided with a groove, the top opening of the grease injection hole is located on the lower surface of the groove, and the distance between the outer periphery of the groove and the axis of the bolt is greater than the distance between the grease injection hole and the axis of the bolt.

[0024] The groove design increases the contact area between the variable cross-section bolt head and the pavement layer, thereby improving friction and ensuring that the variable cross-section bolt head can be better fixed in place when subjected to shear force, making it less prone to slipping or loosening, stably transmitting loads, and improving the connection strength and stability of the overall structure.

[0025] At the same time, the presence of grooves also helps to disperse the stress borne by the variable cross-section bolt head, avoid local stress concentration, thereby extending the service life of the bolt and improving its load-bearing capacity.

[0026] Furthermore, the bolt rod has an external thread at its tail end extending from the bottom of the bridge deck, and the bolt rod engages with the nut through the matching of the external thread and the internal thread of the nut.

[0027] Furthermore, the bolt's tail end extending from the bottom of the bridge deck is provided with a star-shaped head. This star-shaped head is used in the bolt tightening process. When using manual or automatic bolt tightening equipment, the star-shaped head is broken off, which can ensure precise torque control for tightening each bolt.

[0028] As a preferred technical solution, the nut is screwed onto the tail of the bolt shank, and the size of the nut is the same as the size of the washer.

[0029] Furthermore, a washer is fitted on the bolt rod between the bottom of the bridge deck and the nut.

[0030] Furthermore, a gap should be left between the bolt rod and the bolt hole on the bridge deck. Resin injected through the grease injection hole fills the duct of the grease injection hole and the gap between the bolt rod and the bolt hole on the bridge deck. The injection space of the resin ends at the washer.

[0031] Furthermore, an venting groove is provided on the upper surface of the gasket to ensure that air can escape during grease injection.

[0032] As a preferred technical solution, the diameter of the bolt rod is 22mm, and the height of the variable cross-section bolt head is 30mm.

[0033] As a preferred technical solution, the upper part of the variable cross-section bolt head is a round block with an outer rounded corner transition. The diameter of the round block is 36mm, the height is 10mm, and the transition radius is 2mm.

[0034] As a preferred technical solution, the groove at the top of the variable cross-section bolt head has a diameter of 28mm and a depth of 3mm.

[0035] As a preferred technical solution, the diameter of the grease injection hole is 3mm, the depth is 29mm, and the axis coincides with the outer periphery of the bolt rod, that is, the distance from the axis of the bolt rod is 22mm.

[0036] As a preferred technical solution, the lower part of the variable cross-section bolt head is a round block with an outer rounded corner transition. The diameter of the round block is 41mm, the height is 6mm, and the transition radius is 1.25mm.

[0037] As a preferred technical solution, the lower part of the variable cross-section bolt head is integrally transitioned to the inner rounded corner of the bolt shank, with a transition radius of 1.2mm.

[0038] As a preferred technical solution, the middle part of the variable cross-section bolt head is a transition section.

[0039] As a preferred technical solution, the upper part of the transition section has a height of 3mm, and the upper part of the transition section is tangentially connected to the upper inner arc of the variable cross-section bolt head, with a transition radius of 3mm.

[0040] As a preferred technical solution, the lower part of the transition section has a height of 9.5mm, and the lower part of the transition section is integrally transitioned with the lower inner arc of the variable cross-section bolt head, with a transition radius of 9.5mm.

[0041] As a preferred technical solution, the middle part of the transition section is a circular block with a diameter of 22mm and a height of 1.5mm, and the middle part of the transition section is seamlessly connected to the upper and lower parts.

[0042] One of the technical solutions of this utility model is to provide a grease injection-shear connection method, which uses the aforementioned connection pair to perform continuous rotational structural splicing and shear force transmission, including the following steps:

[0043] S1. Bolt tightening process.

[0044] When tightening bolts, bolt fastening can be divided into two modes: mechanized operation and manual operation, depending on the tightening method. Mechanized fastening is suitable for scenarios with sufficient construction space and batch operations, and has the advantages of high efficiency and low labor intensity. Manual fastening is used in special parts where the space of the components is limited and mechanical equipment cannot be used. It is only suitable for small-scale construction.

[0045] S1.1 Mechanized fastening solution,

[0046] The mechanized fastening operation is carried out by using an electric torque shear wrench. The spline head is broken by rotating the nut in the opposite direction. The mechanized fastening of a single connection pair takes 10 to 20 seconds. The specific operation procedure is as follows: the spline head is clamped by the electric torque shear wrench, and the reverse torque is applied to the nut until the spline head is cut off.

[0047] S1.2, Manual tightening process and related tools,

[0048] For a few connection pairs that cannot be automatically tightened due to structural limitations, manual tightening can be used, and a matching tightening tool kit has been designed. The tool kit consists of a wrench, a hollow steel pipe, and two steel bars with holes at the ends. The size of the holes at the ends of the steel bars corresponds to the star head and the nut, respectively.

[0049] The manual tightening process consists of three stages. First, a wrench is used for initial fixing. Then, two matching steel rods are used for tightening until the spline head breaks and the connection reaches the designed preload. One steel rod fixes the spline head, and the other steel rod fixes the nut. If tightening is difficult, a hollow steel pipe can be added to the outside of the steel rods. The manual tightening process is completed by two people. One person is responsible for fixing the spline head, and the other person is responsible for rotating the nut until the spline head breaks and the rotation stops.

[0050] S2, Grease injection process

[0051] After the bolts are tightened, resin injection is required to fill the gap between the bolts and the hole wall;

[0052] Resin used The resin is a two-component mixture of SW404 and HY 2404, with a weight ratio of SW404 to HY2404 of 100:(5-15). After thorough mixing, a blue resin material is formed, which reaches the designed strength after a curing period of 24-30 hours. The mixing process varies depending on the dosage; small doses are thoroughly mixed using a stirring spoon, while large doses require specialized mixing equipment. After proper mixing, the resin can be injected using a manual syringe or a pressure dispensing gun.

[0053] Before injection, the venting grooves on the gaskets should be sealed with sealant. The injection should be carried out in an alternating manner, with each connection point injection time being 2-8 minutes and the total injection time being 5-15 minutes. The injection is considered complete when resin overflows from the injection hole. After injection, it should be kept at room temperature for 24-30 hours to cure. Key operational points include eliminating air bubbles during the injection process, maintaining a uniform and slow speed, and ensuring the injection density.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) This utility model innovatively proposes to combine the advantages of pre-tightened bolt shear connectors and grease-injected bolt shear connectors to design and develop a new type of grease-injected bolt-shear connector. At the bolted joint of the steel bridge deck, it can be used as a steel structure bolt connector to realize the structural splicing continuity, and it can also be used as a shear key to realize reliable shear force transfer between the steel-ultra-high performance concrete interface. This solves the problem that shear keys cannot be welded in the bridge deck joint area, and helps to break through the bottleneck of ultra-high performance concrete pavement layer reinforcement in spliced ​​orthotropic steel bridge deck system;

[0056] (2) Based on the existing bridge project, this utility model combines the actual engineering needs and data to carry out the design research of a new type of grease injection bolt-shear connection pair, and proposes a complete installation process matching the connection pair. At the same time, it solves the problem of relative movement between the bolt and the bolt hole under dynamic load. Attached Figure Description

[0057] Figure 1 This is a front view of the grease-injection bolt-shear connection assembly in an embodiment of this utility model.

[0058] Figure 2 This is a front view of the bolt in an embodiment of the present utility model;

[0059] Figure 3 This is a top view of the bolt in an embodiment of the present invention;

[0060] Figure 4 This is a front view of the nut in an embodiment of the present invention;

[0061] Figure 5 This is a top view of the nut in an embodiment of the present invention;

[0062] Figure 6 This is a front view structural diagram of the gasket in an embodiment of this utility model;

[0063] Figure 7 This is a top view of the gasket in an embodiment of the present invention;

[0064] Figure 8This is a schematic diagram of the installation of the grease-injected bolt-shear connection on the bridge deck in an embodiment of this utility model.

[0065] Explanation of markings in the diagram:

[0066] 1—Bolt, 101—Grease injection hole, 1011—Resin, 102—Variable cross-section bolt head, 103—Bolt shank, 104—External thread, 105—Plum head, 2—Nut, 3—Washer, 301—Ventilation groove. Detailed Implementation

[0067] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0068] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In addition, the terms "first," "second," "third," etc., used to describe a common object only indicate different instances of the same object, and are not intended to imply that the objects described in this way must be in a given order, whether temporally, spatially, sequentially, or in any other way.

[0069] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0070] Example:

[0071] A type of grease-injected bolt-shear connection pair, such as Figures 1 to 3 , Figure 8 As shown, it includes bolt 1 and nut 2. Nut 2 is fitted onto the bolt shank 103 of bolt 1. The head of bolt 1 embedded in the bridge deck pavement is a variable cross-section bolt head 102.

[0072] The variable cross-section bolt head 102 adopts a variable cross-section design with large ends and small middle. After the ultra-high performance concrete is poured and cured to a certain strength, the extended variable cross-section bolt head 102 increases the contact area with the concrete during longitudinal and transverse shear resistance, and better applies the mechanical properties of the concrete pavement layer to the steel bridge deck.

[0073] Meanwhile, when the bridge deck is bent, the mechanical interlocking force of the variable cross-section bolt head 102 on the ultra-high performance concrete layer can restrain the separation of the vertical pavement layer and the steel bridge deck, preventing the bolt 1 from detaching from the concrete layer.

[0074] The head of bolt 1 embedded in the bridge deck pavement has a grease injection hole 101 at the top, which facilitates the injection of resin 1011 through the grease injection hole 101 after the bolt is tightened.

[0075] The length of the variable cross-section bolt head 102 can be adjusted according to the thickness of the pavement layer required for the specific project, and should meet the pouring thickness requirements of the ultra-high performance concrete pavement layer of the steel bridge deck.

[0076] Several grease injection holes 101 are arranged parallel to the axis of the bolt rod 103, and in this embodiment, a pair is preferred;

[0077] Setting multiple grease injection holes 101 can improve grease injection efficiency and prevent incomplete grease injection in the gap between the bolt rod 103 and the bolt hole of the bridge deck;

[0078] The direction of the grease injection hole 101 is parallel to the axis of the bolt rod 103, that is, the vertical direction of gravity, which is conducive to the flow and injection of resin 1011 and also facilitates manufacturing.

[0079] The grease injection hole 101 passes through the variable cross-section bolt head 102, and the bottom opening of the grease injection hole 101 is located at the bolt shank 103.

[0080] The grease injection hole 101 penetrates the head of the bolt 1. The bottom opening of the grease injection hole 101 is connected to the gap between the bolt shank 103 and the bolt hole of the bridge deck, ensuring that the resin 1011 is directly injected into the target area.

[0081] The channel of the grease injection hole 101 is slightly extended to the bolt rod 103 in order to ensure that the cross-sectional area of ​​the bottom opening of the grease injection hole 101 is not less than the cross-sectional area of ​​the channel, so as to ensure that the resin 1011 flows smoothly.

[0082] The furthest end of the grease injection hole 101 from the axis of the bolt shank 103 is farther from the axis of the bolt shank 103 than the radius of the bolt shank 103 and the minimum radius of the variable cross-section bolt head 102, while the closest end is farther from the axis of the bolt shank 103 than the radius of the bolt shank 103 and the minimum radius of the variable cross-section bolt head 102.

[0083] The diameter of the grease injection hole 101 is limited by the diameter of the injection needle and the fluidity of the resin 1011. In the embodiment, it is further limited to being greater than the distance between the bolt rod 103 and the bolt hole of the bridge deck.

[0084] The bottom opening of the grease injection hole 101 must be connected to the gap between the bolt rod 103 and the bolt hole of the bridge deck in order to allow the resin 1011 to be injected into the target area. Therefore, the grease injection hole 101 is partially inside the outer periphery of the bolt rod 103 and partially outside.

[0085] Alternatively, if the distance between the bolt rod 103 and the bolt hole on the bridge deck is large enough, and the distance between the channel of the grease injection hole 101 and the axis of the bolt rod 103 is greater than the radius of the bolt rod 103 and the minimum radius of the variable cross-section bolt head 102, then all of them can be located outside the outer periphery of the bolt rod 103.

[0086] The top of the variable cross-section bolt head 102 is provided with a groove, and the top opening of the grease injection hole 101 is located on the lower surface of the groove. The distance between the outer periphery of the groove and the axis of the bolt shank 103 is greater than the distance between the channel of the grease injection hole 101 and the axis of the bolt shank 103.

[0087] The groove design can increase the contact area between the variable cross-section bolt head 102 and the pavement layer, thereby improving the friction and ensuring that the variable cross-section bolt head 102 can be better fixed in place when subjected to shear force, making it less prone to slipping or loosening, stably transmitting load, and improving the connection strength and stability of the overall structure.

[0088] The groove design also helps to disperse the stress borne by the variable cross-section bolt head 102, avoid local stress concentration, thereby extending the service life of bolt 1 and improving its load-bearing capacity;

[0089] The bolt rod 103 is provided with an external thread 104 at the end that extends out of the bottom of the bridge deck. The bolt rod 103 is matched with the internal thread of the nut 2 through the external thread 104.

[0090] The dimensions of the external thread 104 shall conform to the requirements of GB / T 196 for coarse ordinary threads. The thread tolerance zone of bolt 1 shall conform to 6g (GB / T 197), and the thread tolerance zone of nut 2 shall conform to 6H (GB / T 197).

[0091] Bolt 1 has a sprite head 105 at the end extending from the bottom of the bridge deck. The sprite head 105 is used for the bolt 1 tightening process. When using manual or automatic bolt tightening equipment, the sprite head 105 is broken off, which can ensure precise torque control for tightening each bolt 1.

[0092] like Figure 4 and Figure 5As shown, nut 2 is screwed onto the tail of bolt shank 103, and the size of nut 2 is the same as that of washer 3;

[0093] The mechanical performance design requirement for nut 2 is a nominal stress cross-sectional area of ​​303 mm². 2 To ensure a load-bearing capacity of 315kN, the performance grade of nut 2 should meet 10H, and the corresponding hardness design range is Vickers hardness 222HV30~304HV30 (Rockwell hardness 98HRB~32HRC).

[0094] like Figure 6 and Figure 7 As shown, a washer 3 is fitted on the bolt rod 103 between the bottom of the bridge deck and the nut 2;

[0095] According to GB / T 669 standard, the hardness design range of gasket 3 is Vickers hardness 329HV30~436HV30 (Rockwell hardness 35HRC~45HRC) to meet the high hardness requirements and effectively prevent plastic deformation during use.

[0096] There should be a gap between the bolt rod 103 and the bolt hole on the bridge deck. The resin 1011 injected through the grease injection hole 101 fills the channel of the grease injection hole 101 and the gap between the bolt rod 103 and the bolt hole on the bridge deck. The injection space of the resin 1011 ends at the washer 3.

[0097] An venting groove 301 is provided on the upper surface of the gasket 3 to ensure that air can escape during grease injection;

[0098] The surface quality of bolt 1 and nut 2 must meet the relevant requirements of GB / T 5779.1 or GB / T 5779.2; the surface of washer 3 must be free from cracks, burrs, loose rust, dents and scratches that may affect its use, so as to ensure the overall appearance quality and performance of the connection pair.

[0099] The dimensions and geometric tolerances of bolt 1, nut 2 and washer 3 shall comply with the relevant provisions of Class C products in GB / T 3103.1 or GB / T 3103.3 to ensure that the machining accuracy meets the actual application requirements;

[0100] It is recommended to use hot-dip galvanizing to treat bolt 1, nut 2 and washer 3 to improve the durability of the connection in corrosive environments. Provided that the usage requirements are met, the manufacturer may also choose other suitable surface treatment processes according to its own conditions after consultation.

[0101] The specified parameters for bolt 1, nut 2 and washer 3 are shown in Table 1.

[0102] Table 1 specifies the parameters for bolts 1, nuts 2, and washers 3.

[0103] category Performance level Material Standard Number Specification bolt 10.9S ML20MnTiB steel GB / T 6478 M22 Nut 10H 45 steel GB / T 699 M22 washer 35HRC~45HRC 45 steel GB / T 699

[0104] At bolted joints, the thickness of the ultra-high performance concrete thin-layer pavement is further reduced by the connecting cover plate, with a thickness range generally between 45 and 55 mm. M22 high-strength bolts are a commonly used bolt specification in steel structures. Based on this, a new type of connection pair with a 30mm variable cross-section bolt head and a height of 102 is specifically designed. The main design references include: "High-strength Torque-Shear Bolt Connection Pairs for Steel Structures" (GB / T 3632-2008), "High-strength Large Hexagonal Head Bolts for Steel Structures" (GB / T 1228-2006), "High-strength Large Hexagonal Nuts for Steel Structures" (GB / T1229-2006), "High-strength Washers for Steel Structures" (GB / T 1230-2006), and "Technical Conditions for High-strength Large Hexagonal Head Bolts, Large Hexagonal Nuts, and Washers for Steel Structures" (GB / T 1231-2006).

[0105] In this embodiment, the diameter of the bolt rod 103 is 22mm;

[0106] The upper part of the variable cross-section bolt head 102 is a round block with an outer rounded corner transition. The diameter of the round block is 36mm, the height is 10mm, and the transition radius is 2mm.

[0107] The groove on the top of the variable cross-section bolt head 102 has a diameter of 28mm and a depth of 3mm;

[0108] The diameter of the grease injection hole 101 is 3mm, the depth is 29mm, and the axis coincides with the outer periphery of the bolt rod 103, that is, the distance from the axis of the bolt rod 103 is 22mm.

[0109] The lower part of the variable cross-section bolt head 102 is a round block with an outer rounded corner transition. The diameter of the round block is 41mm, the height is 6mm, and the transition radius is 1.25mm.

[0110] The lower part of the variable cross-section bolt head 102 is integrally transitioned to the inner rounded corner of the bolt shank 103, with a transition radius of 1.2mm;

[0111] The middle section of the variable cross-section bolt head 102 is a transition section.

[0112] The upper part of the transition section has a height of 3mm, and the upper part of the transition section is tangentially connected to the upper inner arc of the variable cross-section bolt head 102, with a transition radius of 3mm.

[0113] The lower part of the transition section has a height of 9.5mm, and the lower part of the transition section seamlessly transitions with the lower inner arc of the variable cross-section bolt head 102, with a transition radius of 9.5mm.

[0114] The middle part of the transition section is a circular block with a diameter of 22mm and a height of 1.5mm. The middle part of the transition section is seamlessly connected to the upper and lower straight sections.

[0115] A grease-injection shear connection method, using the above-mentioned connection pair for structural splicing continuity and shear force transfer, comprises the following steps:

[0116] S1.1 Bolt tightening process,

[0117] When tightening bolt 1, depending on the tightening method, bolt 1 tightening can be divided into two modes: mechanized operation and manual operation. Mechanized tightening is suitable for scenarios with sufficient construction space and batch operation, and has the advantages of high efficiency and low labor intensity. Manual tightening is used in special parts where the space of the component is limited and mechanical equipment cannot be used. It is only suitable for small-scale construction.

[0118] S1.1.1 Mechanized fastening solution,

[0119] The mechanized fastening operation is carried out by using an electric torque shear wrench. The nut 2 is rotated in the opposite direction to break the sponge head 105. The mechanized fastening of a single connection pair takes 15 seconds. The specific operation procedure is as follows: the sponge head 105 is clamped by the electric torque shear wrench, and the reverse torque is applied to the nut 2 simultaneously until the sponge head 105 is cut off.

[0120] S1.1.2 Manual tightening process and related tools

[0121] For a few connection pairs that cannot be automatically tightened due to structural limitations, manual tightening can be used, and a matching tightening tool kit has been designed. The tool kit consists of a wrench, a hollow steel pipe, and two steel bars with holes at the ends. The size of the holes at the ends of the steel bars corresponds to the 105-type star head and the 2-type nut, respectively.

[0122] The manual tightening process consists of three stages. First, a wrench is used for initial fixing. Then, two matching steel rods are used for tightening until the sprite head 105 breaks and the connection reaches the designed preload. One steel rod fixes the sprite head 105, and the other steel rod fixes the nut 2. If tightening is difficult, a hollow steel pipe can be added to the outside of the steel rods. The manual tightening process is completed by two people. One person is responsible for fixing the sprite head 105, and the other person is responsible for rotating the nut 2 until the sprite head 105 breaks and the rotation stops.

[0123] S1.2, Grease injection process,

[0124] After bolt 1 is tightened, resin 1011 needs to be injected to fill the gap between the bolt and the hole wall;

[0125] Resin 1011 selected The resin is a two-component mixture of SW404 and HY 2404, with a weight ratio of 100:10. After thorough mixing, a blue resin material is formed, which reaches its designed strength (density 1.8 g / cm³) after a 24-hour curing period. 2 (Shore D hardness 85-90); the mixing process varies depending on the dosage. Small doses are thoroughly mixed using a stirring spoon, while large doses require specialized mixing equipment; after mixing to the required standard, a manual syringe or pressure dispensing gun can be used for dispensing.

[0126] For manual injection, a dedicated injection needle with a 14 / 15mm orifice and a 38mm length is recommended. Before injection, the venting groove 301 on the gasket 3 should be sealed with sealant. The injection should be carried out in an alternating manner, with each connection pair requiring 2.5 minutes for single-point injection and a total injection time of 5 minutes. The injection is considered complete when resin 1011 overflows from the injection hole 101. After injection, the resin should be kept at 25°C for 24 hours to cure. Key operational points include eliminating air bubbles during the injection process, maintaining a uniform and slow advance, and ensuring the density of the injection.

[0127] The above-mentioned connection pairs are subjected to the following tests or experiments, and then the test or experiment results are analyzed.

[0128] Experimental Example 1:

[0129] Tensile tests were performed on the bolted connections of the above-mentioned connection pairs, and the test was conducted in accordance with the "Mechanical Properties of Fasteners: Bolts, Screws and Studs" (GB / T 3098.1-2010).

[0130] In the embodiment, the tensile strength of the connecting pair meets the specification requirements, satisfying a load of not less than 315kN. The fracture location is concentrated in the unthreaded bolt rod 103, which meets the relevant technical requirements.

[0131] Experimental Example 2:

[0132] The preload axial force of the shear connector was tested on the above-mentioned connection pair to test whether it could meet the relevant requirements of the same grade of high strength bolt. The connection pair was tightened with a torque wrench, and the peak load when the 105-type bolt with a Phillips head broke was recorded.

[0133] In the embodiment, the fracture surface of the connecting pair is located at the root of the 105-type splice head. The ultimate loads of the wedge test are 351.9 kN, 363.0 kN, and 347.4 kN, with an average value of 354.1 kN. This result is higher than the preload limit of the M22 high-strength bolt, proving that the connecting pair can replace the high-strength bolt of the same size and specification to achieve component bolting.

[0134] Experimental Example 3:

[0135] Bridge deck tests were conducted on the aforementioned connection pairs. Based on existing bridge structures, the reliable bolted connection of the steel structure and the reliable combination of the steel-ultra-high performance concrete interface were verified. A full-scale bridge test specimen (2600×2200×727mm) was used to simulate the actual bridge structure. The performance of the grease-injected bolt-shear connector in the steel-ultra-high performance concrete composite structure was studied. Three stages of fatigue loading (20~80 / 140 / 200kN) were applied, and the connection reliability was verified using the equivalent cumulative damage theory. The evolution of key mechanical indicators was dynamically monitored through quasi-static loading. The specific steps are as follows:

[0136] S2.1. The bridge deck adopts a steel-ultra-high performance concrete composite deck + three longitudinal U-ribs + double crossbeams (center distance 2200mm). The connecting pair is set as a transverse bolted joint at the mid-span. The non-joint area uses Φ19×35mm short studs (spacing 320mm). The four-point simply supported boundary conditions are applied. The load is applied at the mid-span (600×200mm range), and the loading point is located directly above the weld of the third bridge deck-U-rib.

[0137] S2.2, Phased loading,

[0138] Phase I, 2 million cycles of 20–80 kN cyclic loading (verified by standards and specifications).

[0139] Stage II, 1 million cycles of 20–140 kN cyclic loading (equivalent damage propagation),

[0140] Phase III, 500,000 cycles of 20-200kN cyclic loading (limit state investigation);

[0141] S2.3. Quasi-static loading is implemented after every 500,000 cycles to track parameters such as displacement and stress, while damage indicators such as crack development and interface slip are observed throughout the process.

[0142] The combined structure using connecting pairs in the embodiment exhibits a significant synergistic effect, and the mechanical properties of the joint area meet the design requirements. After 3.5 million loading cycles, the connecting pairs in the embodiment show no decrease in load-bearing capacity or plastic deformation (Δ). max =0.30mm). In the embodiment, the interface between the ultra-high performance concrete layer and the steel using the connecting joint has no visible cracks / slippage, and the neutral axis is stable at 258mm from the bottom of the U-rib. In the embodiment, the stress range of the ultra-high performance concrete at mid-span using the connecting joint is -4.0 to 1.0 MPa, and the stress distribution uniformity of the steel bridge deck is better than that of traditional structures. The displacement value under design wheel load (0.29 to 0.30 mm) of the connecting joint used in the embodiment is lower than the limits of Chinese / European / American standards.

[0143] The test results of the connection pairs in the embodiment show that:

[0144] (1) Mechanical performance tests of the connection pair show that its main performance meets the requirements of high-strength bolts of the same specifications, and it can be used as a structural component connector to achieve reliable bolting.

[0145] (2) After replacing the original bolted joint high-strength bolts, the structural mechanical properties of the connection pair are good under the design and actual traffic fatigue load, with no obvious stiffness degradation or plastic deformation, and the design limit is met; the steel-ultra-high performance concrete composite interface in the bolted joint area is always reliably connected, verifying the reliability of the connection pair in actual bridge reinforcement engineering.

[0146] The above description of the embodiments is provided to enable those skilled in the art to understand and use the utility model. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present utility model is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present utility model without departing from its scope should be within the protection scope of the present utility model.

Claims

1. A grease-injected bolt-shear connection pair, characterized in that, The connection pair includes a bolt (1) and a nut (2). The nut (2) is fitted onto the bolt shank (103) of the bolt (1). The head of the bolt (1) embedded in the bridge deck pavement is a variable cross-section bolt head (102). The variable cross-section bolt head (102) has a variable cross-section that is large at both ends and small in the middle. The head of the bolt (1) embedded in the bridge deck pavement has a grease injection hole (101) at the top, through which resin (1011) is injected.

2. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, Several grease injection holes (101) are set parallel to the axis of the bolt rod (103).

3. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, The grease injection hole (101) passes through the variable cross-section bolt head (102), and the bottom opening of the grease injection hole (101) is located at the bolt rod (103).

4. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, The furthest end of the grease injection hole (101) from the axis of the bolt rod (103) is farther from the axis of the bolt rod (103) than the radius of the bolt rod (103) and the minimum radius of the variable cross-section bolt head (102), while the closest end is farther from the axis of the bolt rod (103) than the radius of the bolt rod (103) and the minimum radius of the variable cross-section bolt head (102).

5. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, The top of the variable cross-section bolt head (102) is provided with a groove, and the top opening of the grease injection hole (101) is located on the lower surface of the groove. The distance between the outer periphery of the groove and the axis of the bolt rod (103) is greater than the distance between the channel of the grease injection hole (101) and the axis of the bolt rod (103).

6. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, The bolt rod (103) is provided with an external thread (104) at the end extending from the bottom of the bridge deck. The bolt rod (103) is engaged with the nut (2) through the matching of the external thread (104) and the internal thread of the nut (2).

7. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, The bolt (1) has a swivel head (105) at its tail end extending from the bottom of the bridge deck.

8. The grease-injected bolt-shear connection pair according to claim 1, characterized in that, A washer (3) is fitted on the bolt rod (103) between the bottom of the bridge deck and the nut (2).

9. A grease-injected bolt-shear connection according to claim 8, characterized in that, A gap is left between the bolt rod (103) and the bolt hole of the bridge deck. The resin (1011) injected through the grease injection hole (101) fills the channel of the grease injection hole (101) and the gap between the bolt rod (103) and the bolt hole of the bridge deck. The injection space of the resin (1011) ends at the washer (3).

10. A grease-injected bolt-shear connection according to claim 9, characterized in that, The gasket (3) has an exhaust groove (301) on its upper surface.

Images