Method for determining the shear capacity of a composite connector

Abstract

The application discloses a method for determining the shearing bearing capacity of a composite connector, and comprises the following steps: obtaining the structural parameters of the composite connector; according to the stress characteristics of the composite connector, dividing the shearing bearing capacity of the composite connector into end bearing action bearing capacity, concrete tenon action bearing capacity, penetrating steel action bearing capacity and shear stud action bearing capacity; determining the respective calculation parameters based on the push-out test; determining the equivalent connection quantity according to the number and arrangement form of the connecting units of the composite connector, and determining the quantity effect reduction coefficient according to the equivalent connection quantity; and determining the shearing bearing capacity of the steel-lightweight ultra-high performance concrete composite beam connector based on the respective sub-item bearing capacity and the quantity effect reduction coefficient, so as to solve the technical problem of insufficient prediction accuracy of the shearing bearing capacity of the composite connector in the prior art.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, and specifically to a method for determining the shear bearing capacity of composite connectors. Background Technology

[0002] Steel-concrete composite beam structures are widely used in bridge engineering due to their high load-bearing capacity, relatively low structural weight, and high construction efficiency. Shear connectors between the steel beams and concrete slabs are key components for achieving coordinated load-bearing between the two, and their shear capacity directly affects the interface force transmission performance and overall load-bearing performance of the composite structure. Currently, shear connectors mainly include shear stud connectors and perforated steel plate connectors. To further improve the load-bearing capacity of the connectors, existing technologies propose combining shear stud connectors with perforated steel plate connectors to form composite shear connectors, allowing the shear studs, perforated steel plates, concrete tenons, and through-bar reinforcement to jointly participate in load-bearing.

[0003] With the development of lightweight and high-performance bridge structures, lightweight ultra-high performance concrete (UHVPC) is increasingly being applied to steel-concrete composite beam structures. Due to the high compressive strength, low self-weight, and steel fiber bridging capabilities of UHVPC, traditional methods for calculating the shear capacity of composite shear connectors based on ordinary concrete test data cannot accurately reflect the influence of the UHVPC matrix strength, fiber bridging effect, interface slip development process, and the staged collaborative stress mechanism of the composite connectors on the load-bearing performance. Furthermore, under multi-nail, multi-hole arrangements, stress redistribution and mutual interference exist among the connectors, making it impossible to simply linearly superimpose the ultimate bearing capacity of the composite connectors based on the bearing capacity of individual connectors.

[0004] Therefore, the existing methods for determining the shear capacity of composite shear connectors in steel-lightweight ultra-high performance concrete composite beams cannot comprehensively consider the material properties of lightweight ultra-high performance concrete, the multiple bearing mechanisms of composite connectors, and the quantitative effect of multiple nails and holes, resulting in insufficient accuracy in predicting shear capacity. There is an urgent need to propose a method that can accurately determine the shear capacity of composite shear connectors. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method for determining the shear bearing capacity of composite connectors, thereby solving the technical problem of insufficient accuracy in predicting the shear bearing capacity of composite connectors in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: This invention provides a method for determining the shear bearing capacity of a composite connector, comprising: obtaining the structural parameters of the composite connector, which includes shear studs, a perforated steel plate, and through reinforcing bars; the perforated steel plate being disposed between a steel beam and a lightweight ultra-high performance concrete slab; and the through reinforcing bars being inserted into the holes of the perforated steel plate to form concrete tenons within the holes; and, based on the stress characteristics of the composite connector, dividing its shear bearing capacity into end-bearing capacity, concrete tenon capacity, through reinforcing bar capacity, and shear stud capacity, and... The shear capacity of the composite connector is determined based on the bearing capacity of each component. Based on the load-slip curves obtained from the push-out test, calculation parameters for the end bearing capacity, concrete tenon bearing capacity, through-bar bearing capacity, and shear stud bearing capacity are determined respectively. The equivalent number of connections is determined based on the number and arrangement of the connection units in the composite connector, and a quantity effect reduction factor is determined based on the equivalent number of connections. Based on the bearing capacity of each component and the quantity effect reduction factor, the shear capacity of the composite connector for the steel-lightweight ultra-high performance concrete composite beam is determined.

[0007] In some embodiments, the shear bearing capacity of the composite connector satisfies: , To enhance the shear bearing capacity of composite connectors; The bearing capacity provided for end bearing; The load-bearing capacity provided by the concrete tenon; The load-bearing capacity provided for the through-bar reinforcement; The load-bearing capacity provided by shear studs.

[0008] In some embodiments, the end-bearing capacity satisfies: , This represents the cross-sectional area of ​​a single perforated steel plate. This represents the compressive strength of a concrete cube.

[0009] In some embodiments, the bearing capacity of the through-bar reinforcement satisfies:

[0010] This represents the fiber volume fraction. Fiber length; Fiber diameter; This refers to the number of concrete tenons; The cross-sectional area of ​​a single concrete tenon.

[0011] In some embodiments, the bearing capacity of the through-bar reinforcement satisfies: , The number of through-bars, This refers to the cross-sectional area of ​​a single through-bar rebar. This represents the yield strength of the through-steel reinforcement.

[0012] In some embodiments, the bearing capacity of the shear studs satisfies: , For the number of shear studs, The cross-sectional area of ​​a single shear stud This represents the tensile strength of the shear stud.

[0013] In some embodiments, when the composite connector adopts a multi-nail, multi-hole arrangement, the equivalent number of connections is determined based on the number of shear nails and the number of concrete tenons, satisfying the following:

[0014] For the equivalent number of connections, This refers to the number of shear studs. This refers to the number of concrete tenons.

[0015] In some embodiments, the quantity effect reduction factor is determined based on the equivalent number of connections, satisfying: , This is the quantity effect reduction factor.

[0016] In some embodiments, the bearing capacity of concrete tenons, through-bar reinforcement, and shear studs is corrected using a quantity effect reduction factor to satisfy the following relationship: .

[0017] Compared with existing technologies, the method for determining the shear capacity of composite connectors provided by this invention analyzes different force transmission paths during the shear process of the composite connector, decomposing the overall shear capacity into the end-bearing capacity, the concrete tenon capacity, the through-reinforcement capacity, and the shear stud capacity. It then combines this with push-out tests to obtain calculation parameters for each component's capacity, establishing a method for determining shear capacity based on the synergistic effect of multiple bearing mechanisms. Furthermore, this application considers the quantity effect between connection units under multi-stud, multi-hole arrangement conditions, introducing an equivalent number of connections and a quantity effect reduction coefficient to correct the bearing capacity, thereby improving the consistency between the calculated shear capacity and the actual stress state, and enhancing the accuracy and reliability of the shear capacity prediction for composite connectors. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating a method for determining the shear bearing capacity of a composite connector according to an embodiment of the present invention. Figure 2 This is a structural schematic diagram of a composite connector provided in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 10. Shear studs; 20. Through-bar reinforcement; 30. Perforated steel plate; 40. H-beams; 50. Concrete slab; 60. Structural reinforcement. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] To address the technical problem of insufficient accuracy in predicting the shear capacity of composite connectors in existing technologies, this invention provides a method for determining the shear capacity of composite connectors, which improves the accuracy of predicting the shear capacity of composite connectors in steel-lightweight ultra-high performance concrete composite beams.

[0022] It should be noted that the method for determining the shear bearing capacity of composite connectors described in this invention is applicable to, but not limited to, bridge engineering. For ease of explanation, this invention only uses the application of the method for determining the shear bearing capacity of composite connectors to bridge engineering equipment as an example. The principle of applying the method for determining the shear bearing capacity of composite connectors to other types of equipment is essentially the same as that applied to bridge engineering equipment, and will not be elaborated here.

[0023] To facilitate understanding of the technical solution of this application, the following is combined with... Figure 1 This paper describes a method for determining the shear capacity of a composite connector. This method is applied to steel-lightweight ultra-high performance concrete composite beams. By analyzing the different force transmission paths of the composite connector during shear, the complex stress process is decomposed into multiple bearing mechanisms with clear physical meanings. Furthermore, experimental data is used to quantitatively analyze each bearing mechanism, thereby achieving an accurate determination of the shear capacity of the composite connector.

[0024] like Figure 1 As shown, the method for determining the shear bearing capacity of the composite connector proposed in this embodiment includes steps S110-S150.

[0025] Step S110: Obtain the structural parameters of the composite connector. Before determining the shear capacity, it is necessary to obtain the structural composition parameters and material parameters of the composite connector as the basis for subsequent load-bearing capacity analysis.

[0026] Please refer to the following: Figure 2 , Figure 2This is a schematic diagram of a composite connector provided in an embodiment of the present invention. The composite connector is disposed between a steel beam and a lightweight ultra-high performance concrete slab 50 to realize the transfer of interface shear force between the steel beam and the concrete slab 50. The composite connector includes shear studs 10, perforated steel plates 30, and through reinforcing bars 20. The perforated steel plate 30 is fixedly disposed on the steel beam, and multiple through holes are formed on the perforated steel plate 30. The through reinforcing bars 20 pass through the through holes and together with the lightweight ultra-high performance concrete poured around the perforated steel plate 30, form a concrete tenon structure. The shear studs 10 and the perforated steel plate 30 jointly participate in the load transfer between the steel beam and the concrete slab 50, enabling the composite connector to bear interface shear force through multiple stress modes.

[0027] When obtaining structural parameters, the quantity, size, and arrangement of shear studs 10, the thickness, number, size, and spacing of perforated steel plates 30, and the quantity, diameter, and material properties of through reinforcing bars 20 can be determined based on the actual design scheme. Simultaneously, the material parameters of lightweight ultra-high performance concrete can be obtained. These parameters allow for the establishment of a correspondence between the structural characteristics and stress characteristics of the composite connector, providing a foundation for subsequent analysis of the contribution of different load-bearing mechanisms.

[0028] Step S120: Based on the stress characteristics of the composite connector, the shear capacity is divided into multiple sub-capacities. When the composite connector is subjected to interfacial shear force, the entire load is not borne by a single structural component, but rather by multiple stress-bearing areas working together to transmit the force. Therefore, it is necessary to decompose the overall shear capacity according to different force transmission paths.

[0029] Specifically, the end-bearing effect mainly comes from the local bearing pressure between the perforated steel plate 30 and the lightweight ultra-high performance concrete. Under the action of external shear load, contact pressure is formed between the perforated steel plate 30 and the concrete, and part of the shear force is borne through local bearing pressure.

[0030] The concrete tenon's function primarily stems from the concrete tenon structure formed within the perforated steel plate 30. When relative slippage occurs between the steel beam and the concrete slab 50, the concrete tenon within the perforated plate is subjected to shear forces and resists interface slippage through its own shear resistance.

[0031] The primary function of the through-bar 20 is derived from the reinforcing steel structure that penetrates the perforated steel plate 30. The through-bar 20 can restrain the concrete tenon, improve the stability of the concrete tenon during shearing, and participate in the transfer of interface loads through its own shear and tensile strength.

[0032] The function of the shear stud 10 mainly comes from the shear stud 10 structure welded to the steel beam. The shear stud 10 forms a mechanical connection with the surrounding lightweight ultra-high performance concrete, and the shear force at the interface is jointly borne by the shear stud 10 itself and the confinement effect of the concrete.

[0033] Based on the different force transmission mechanisms mentioned above, the overall shear capacity of the composite connector is divided into the end bearing capacity, the concrete tenon bearing capacity, the through steel bar 20 bearing capacity, and the shear stud 10 bearing capacity. The overall shear capacity is determined according to the combination relationship between the bearing capacities of each component.

[0034] By using the above processing method, we can avoid the problem that traditional calculation methods, which only consider a single connection form, cannot accurately reflect the actual stress state of composite connectors, and make the calculation model more consistent with the stress characteristics of composite connection structures.

[0035] Step S130: Based on the load-slip curve obtained from the push-out test, determine the calculation parameters corresponding to each component's bearing capacity. To obtain the calculation parameters corresponding to different bearing mechanisms, it is necessary to test the actual stress performance of the composite connector through a push-out test.

[0036] In practice, a push-out specimen comprising a steel beam, a lightweight ultra-high performance concrete slab 50, and composite connectors can be prepared, ensuring that the specimen's structural form matches the actual composite beam connection area. During the experiment, a shear load is applied to the specimen along the interface direction, and the relative slippage between the steel beam and the concrete slab 50 is collected in real time using a displacement measuring device, thereby obtaining the load-slip relationship during the loading process.

[0037] Based on the development process of the load-slip curve, the load-bearing characteristics of the composite connector at different stress stages can be analyzed. For example, in the initial loading stage, the local contact effect between the perforated steel plate 30 and the concrete gradually comes into play; as the load increases, the concrete tenon, the through steel bar 20, and the shear stud 10 gradually participate in the load-bearing and jointly resist the interface slip; after reaching the ultimate state, the contributions of each load-bearing mechanism reach a steady state.

[0038] Furthermore, the influencing factors of each load-bearing mechanism can be analyzed by combining test results between specimens with different structural parameters. For example, by changing the opening size, the parameters of the through-reinforcement 20, the arrangement of the shear studs 10, and the parameters of lightweight ultra-high performance concrete, the influence of different factors on the load-bearing performance can be obtained, and the parameters required in the calculation of each component's load-bearing capacity can be determined accordingly. By obtaining calculation parameters based on derivation tests, the established method for determining shear bearing capacity can be matched with the actual stress process, improving the reliability of the calculation results.

[0039] Step S140: Determine the equivalent number of connections based on the number and arrangement of connection units, and determine the quantity effect reduction factor. In practical engineering applications, composite connectors are usually not existing as single connection units, but are arranged in a combination of multiple nails and holes according to the structural load-bearing requirements. When the number of connection units increases, the connection units will affect each other. On the one hand, stress diffusion and force transmission area overlap may occur between adjacent concrete tenons, causing changes in the local stress state; on the other hand, when multiple shear nails 10 act together, it will cause the interface stress to redistribute, making it impossible for each connection unit to fully exert its independent load-bearing capacity.

[0040] Therefore, when determining the overall shear capacity under conditions of multiple connection units, it is not possible to simply superimpose the bearing capacity and quantity of individual connection units linearly, but rather to consider the quantitative effect between connection units.

[0041] In practical implementation, the equivalent number of connections is determined based on the number of shear studs 10, the number of holes, and the arrangement of connection units in the composite connector. The impact of the combined effect of multiple connection units on the load-bearing efficiency is then analyzed based on the equivalent number of connections, thereby determining the quantity effect reduction coefficient. By introducing the quantity effect reduction coefficient, the load-bearing capacity reduction caused by the mutual influence of connection units under multi-stud, multi-hole arrangement conditions can be corrected.

[0042] Step S150: Determine the shear bearing capacity based on the bearing capacity of each component and the quantity effect reduction factor. After determining the calculation parameters of each component bearing capacity and performing the quantity effect analysis, the bearing capacities corresponding to each bearing mechanism are combined, and the bearing capacity under the multi-connection unit condition is corrected according to the quantity effect reduction factor, thereby obtaining the shear bearing capacity of the composite connector.

[0043] Specifically, for a single connection unit, the shear bearing capacity of the foundation is determined by the end bearing action, the concrete tenon action, the through reinforcement 20 action, and the shear stud 10 action. For composite connectors with a multi-stud and multi-hole arrangement, the quantity effect reduction coefficient is further combined to correct the bearing contribution of the connection units that are greatly affected by each other, so as to obtain an overall shear bearing capacity that is more in line with the actual stress state.

[0044] Through the above steps, this implementation plan can comprehensively consider the characteristics of lightweight ultra-high performance concrete materials, the multiple force transmission mechanisms of composite connectors, and the quantitative effect generated by the arrangement of multiple connection units, so as to accurately determine the shear bearing capacity of composite connectors in steel-lightweight ultra-high performance concrete composite beams.

[0045] In one embodiment, the shear bearing capacity of the composite connector is determined based on the bearing contribution corresponding to different stress mechanisms, specifically satisfying the following: ,in, To enhance the shear bearing capacity of composite connectors; The bearing capacity provided for end bearing; The load-bearing capacity provided by the concrete tenon; The bearing capacity provided for the through-bar 20; The load-bearing capacity provided for the shear stud 10.

[0046] Based on the actual stress state of the composite connector, the interfacial shear force transmitted between the steel beam and the lightweight ultra-high performance concrete slab 50 is decomposed according to different force transmission paths. Among them, the end bearing capacity is mainly used to characterize the local bearing pressure generated between the perforated steel plate 30 and the lightweight ultra-high performance concrete; the concrete tenon capacity is mainly used to characterize the shear resistance generated by the concrete tenon formed in the hole of the perforated steel plate 30 during the interface slippage process; the through reinforcement 20 capacity is mainly used to characterize the constraint effect of the through reinforcement 20 on the concrete tenon and its own shear resistance; and the shear stud 10 capacity is mainly used to characterize the mechanical connection formed between the shear stud 10 and the surrounding lightweight ultra-high performance concrete.

[0047] When calculating the shear capacity of the composite connector, the bearing capacity contribution corresponding to each of the above-mentioned load-bearing actions is first determined, and then combined according to the synergistic force relationship between the various load-bearing mechanisms to obtain the overall shear capacity of the composite connector. By calculating the load-bearing contributions corresponding to different force transmission mechanisms separately, the combined effect among the perforated steel plate 30, the through steel bar 20, the shear stud 10, and the lightweight ultra-high performance concrete in the composite connector can be more accurately reflected.

[0048] Furthermore, in one specific embodiment, to verify the effectiveness of the above-mentioned method for determining the shear bearing capacity of composite connectors, multiple push-out specimens with different structural forms were prepared for shear performance tests, and the influence of different bearing mechanisms on the shear performance of composite connectors was analyzed based on the test results.

[0049] In this embodiment, the lightweight ultra-high performance concrete is prepared using PO52.5 cement, fly ash, silica fume, ceramsite sand, water-reducing agent, and steel fiber. The fly ash content is 18%, the silica fume content is 16%, the water-cement ratio is 0.17, the binder-mortar ratio is 1.8, and the steel fiber volume fraction is 2%. Material performance testing shows that the lightweight ultra-high performance concrete has a cubic compressive strength of 152 MPa, an axial compressive strength of 130.1 MPa, and an elastic modulus of 42.2 GPa.

[0050] The steel beams are made of Q355B steel with a yield strength of 360 MPa and a tensile strength of 500 MPa. The through-bar reinforcement 20 and structural reinforcement 60 are made of HRB400 steel with a yield strength of 400 MPa and a tensile strength of 570 MPa. The shear stud 10 is made of ML15AL material with a yield strength of 340 MPa and a tensile strength of 460 MPa. These material parameters allow us to obtain the stress performance of the composite connector under different material compositions, providing a basis for determining the parameters of the subsequent load-bearing capacity model.

[0051] Regarding the specimen construction, the specimens include a lightweight ultra-high performance concrete slab 50, an H-beam 40, and a composite connector located at the connection area between the two. The concrete slab 50 measures 600mm × 600mm × 150mm and contains 8mm diameter HRB400 structural steel bars 60. The H-beam 40 is 600mm long with a cross-sectional dimension of 300mm × 300mm × 15mm × 20mm and is made of Q355B steel. The shear stud 10 has a diameter of 16mm and a height of 80mm. The perforated steel plate 30 measures 400mm × 100mm × 16mm with a perforation diameter of 50mm. The through-bar 20 uses 16mm diameter HRB400 steel bars and is 450mm long.

[0052] To analyze the influence of different load-bearing mechanisms on the shear resistance of composite connectors, this embodiment sets up multiple sets of ejection specimens with different structural forms. Specimen numbers are in the form sbdr, where s represents the number of shear studs (10), b represents end bearing, d represents the number of concrete tenons, and r represents the number of through-bar reinforcement (20). The numbers following the letters indicate the number or row of the corresponding structure on one side. For example, s2b1d1r1 indicates that the specimen has two shear studs (10) on one side, providing end bearing, one concrete tenon, and one through-bar reinforcement (20). By changing the number and combination of different load-bearing units, test data under different combined stress mechanisms can be obtained.

[0053] During the loading test, a 1000t servo pressure testing machine was used to apply shear loads to the ejected specimen. Before the formal loading, the specimen underwent three-stage preloading to eliminate initial internal gaps and ensure loading stability. During the formal loading stage, a force-displacement combined control method was used with a loading rate of 0.3 kN / s. When the load reached 90% of the ultimate bearing capacity, the method was switched to displacement control, and the loading rate was adjusted to 0.02 mm / s. Loading was stopped when the specimen slippage reached 40 mm, or when the load dropped below 40% of the ultimate bearing capacity.

[0054] During the experiment, real-time recordings were made of load changes, the relative slip between the H-beam 40 and the concrete slab 50, the strain changes of the shear studs 10 and the through reinforcement 20, and crack development to obtain the load-slip response relationship of the composite connector during its complete stress process. By analyzing the ultimate bearing capacity, peak slip, ductility coefficient, and shear stiffness of different specimens, the bearing contribution corresponding to different bearing mechanisms can be determined, providing experimental basis for determining the parameters in the shear bearing capacity calculation model.

[0055] Based on the above experimental data, the shear performance results of composite connectors with different structural forms can be obtained. For example, the ultimate bearing capacity of specimens with only end bearing, specimens with only concrete tenon, specimens with shear stud 10 acting in conjunction with end bearing, specimens with shear stud 10 acting in conjunction with through reinforcement 20, and specimens of complete composite connectors vary with the combination of bearing units. By comparing the experimental results of different specimens, the contributions of end bearing, concrete tenon, through reinforcement 20, and shear stud 10 to the overall shear bearing capacity can be analyzed.

[0056] The specific experimental results are shown in the table below.

[0057]

[0058] Furthermore, in some embodiments, the end-bearing capacity is used to characterize the local compressive force transmission capacity between the perforated steel plate 30 and the lightweight ultra-high performance concrete, and its calculation relationship satisfies: ,in, For end bearing capacity; The cross-sectional area of ​​a single perforated steel plate of size 30; This represents the compressive strength of a concrete cube.

[0059] During the shearing process of the composite connector, relative slippage occurs between the steel beam and the lightweight ultra-high performance concrete slab 50, causing local compression between the perforated steel plate 30 and the surrounding concrete. Due to the certain thickness and bearing area of ​​the perforated steel plate 30, it can transfer part of the interface shear force to the lightweight ultra-high performance concrete slab 50 through the bearing pressure between the end of the steel plate and the concrete, thereby forming end-bearing capacity.

[0060] When determining the end-bearing capacity, the cross-sectional area of ​​the perforated steel plate 30 is used to characterize the effective compression zone between the perforated steel plate 30 and the concrete, and the compressive strength of the lightweight ultra-high performance concrete is combined to reflect the compressive capacity of the concrete material itself. Specifically, the larger the cross-sectional area of ​​the perforated steel plate 30, the more sufficient the contact compression zone between it and the lightweight ultra-high performance concrete, and the higher the corresponding end-bearing capacity; the higher the compressive strength of the lightweight ultra-high performance concrete, the stronger its resistance to local crushing and deformation.

[0061] In this embodiment, the end-bearing capacity determined by the above method can characterize the local bearing pressure contribution between the perforated steel plate 30 and the lightweight ultra-high performance concrete, and as an important component of the overall shear bearing capacity of the composite connector, it shares the interface shear force with the concrete tenon action, the through steel bar 20 action, and the shear nail 10 action.

[0062] Furthermore, in some embodiments, the bearing capacity of the concrete tenon is used to characterize the shear contribution provided by the concrete tenon formed within the 30 holes of the perforated steel plate under interfacial shear action, and its calculation relationship satisfies:

[0063] in, The bearing capacity of the concrete tenon; This represents the volume fraction of steel fibers. The length of the steel fiber; The diameter of the steel fiber; This refers to the number of concrete tenons; The cross-sectional area of ​​a single concrete tenon; It represents the compressive strength of lightweight ultra-high performance concrete.

[0064] During shear stress in the composite connector, the lightweight ultra-high performance concrete filling the holes in the perforated steel plate 30 forms a concrete tenon structure that interlocks with the perforated steel plate 30. When relative slippage occurs between the steel beam and the lightweight ultra-high performance concrete slab 50, the concrete tenon is subjected to shear stress and resists interface slippage through its own shear resistance, thus providing the main shear load-bearing capacity for the composite connector.

[0065] Compared to ordinary concrete, lightweight ultra-high performance concrete, with the incorporation of steel fibers, can bridge cracks during their propagation, improving the crack resistance and shear stability of the concrete tenon. Therefore, when determining the load-bearing capacity of the concrete tenon, not only the inherent strength of the lightweight ultra-high performance concrete is considered, but also the volume fraction and aspect ratio of the steel fibers are introduced to reflect the influence of steel fiber reinforcement on the load-bearing capacity of the concrete tenon.

[0066] Among them, the number of concrete tenons The cross-sectional area of ​​a single concrete tenon is used to characterize the number of load-bearing units formed at multiple opening locations. This is used to characterize the effective area of ​​a single concrete tenon participating in shear forces. When the number of openings increases or the effective shear area of ​​the concrete tenon increases, the area that can participate in the transfer of interfacial shear forces increases, thereby improving the load-bearing capacity of the concrete tenon. When the compressive strength, steel fiber volume fraction, and steel fiber aspect ratio of lightweight ultra-high performance concrete increase, the concrete tenon's ability to resist shear failure and crack propagation is enhanced.

[0067] In this embodiment, determining the bearing capacity of the concrete tenon in the above manner can fully reflect the influence of the characteristics of lightweight ultra-high performance concrete on the shear resistance of the composite connector, enabling the calculation model to more accurately reflect the actual stress state of the concrete tenon in the composite connector.

[0068] Furthermore, in some embodiments, the bearing capacity of the through-reinforcement bar 20 is used to characterize the bearing contribution provided by the reinforcing steel structure penetrating the hole in the perforated steel plate 30 during shear stress, and its calculation relationship satisfies: ,in, This is to determine the load-bearing capacity of the 20mm through-reinforcement bar; The quantity of 20 through-bar reinforcement; The cross-sectional area of ​​a single through-bar reinforcement bar is 20 mm. The yield strength of the through-steel bar is 20.

[0069] During shear stress in the composite connector, the through-bar 20 passes through the hole in the perforated steel plate 30 and works together with the concrete tenon formed within the hole. When relative slippage occurs between the steel beam and the lightweight ultra-high performance concrete slab 50, the through-bar 20 is subjected to shear stress and simultaneously constrains the surrounding concrete tenon, limiting the failure development of the concrete tenon during shear stress, thereby improving the stability and overall shear resistance of the concrete tenon structure.

[0070] Number of through-bars 20 Used to characterize the number of reinforcing bars involved in bearing the load, with a single through-bar having a cross-sectional area of ​​20. Used to characterize the effective stress-bearing area of ​​a single reinforcing bar, and the yield strength of a through-bar 20mm. This is used to characterize the material properties of reinforcing bars in resisting shear deformation. As the number of through reinforcing bars 20 increases, the cross-sectional area increases, or the material strength increases, the shear load that the through reinforcing bars 20 can bear increases, while the restraining effect on the concrete tenon is enhanced, thus improving the overall shear bearing capacity of the composite connector.

[0071] Furthermore, in some embodiments, the bearing capacity of the shear stud 10 is used to characterize the mechanical connection formed between the shear stud 10 and the lightweight ultra-high performance concrete, and its calculation relationship satisfies: ,in, This is the load-bearing capacity of the shear stud 10. The quantity is 10 shear studs; The cross-sectional area of ​​a single shear stud is 10. The tensile strength of the shear stud is 10.

[0072] During the shearing process of the composite connector, the shear stud 10 is fixedly set on the surface of the steel beam and extends into the interior of the lightweight ultra-high performance concrete slab 50. When relative slippage occurs between the steel beam and the concrete slab 50, the shear stud 10 is subjected to lateral shearing action and transmits the interfacial shear force through its own shear resistance and the anchoring effect formed with the surrounding concrete.

[0073] 10 shear studs The number of shear studs 10 used to characterize the force transmission at the interface, and the cross-sectional area of ​​a single shear stud 10. Used to characterize the effective stress-bearing section of shear stud 10, and the tensile strength of shear stud 10. This is used to characterize the material strength properties of shear stud 10. By comprehensively considering the above parameters, the influence of the size, quantity, and material properties of shear stud 10 on its shear resistance capacity can be reflected.

[0074] By determining the bearing capacity of the through-bar 20 and the shear stud 10 respectively, and combining the bearing capacity of the end bearing and the bearing capacity of the concrete tenon for comprehensive analysis, the synergistic force relationship between steel components, reinforcing steel components and lightweight ultra-high performance concrete in composite connectors can be more comprehensively characterized, thereby improving the accuracy of shear capacity calculation results.

[0075] Furthermore, in some embodiments, when the composite connector adopts a multi-nail, multi-hole arrangement, a quantity effect correction method is introduced to consider the weakening effect of the mutual influence between multiple connection units on the overall load-bearing capacity.

[0076] Specifically, when multiple shear studs 10 and multiple concrete tenons participate in the load-bearing process, the connection units are not completely independent of each other. As the number of connection units increases, the stress transfer areas between adjacent connection units gradually overlap, and the load distribution in the interface area changes, reducing the load-bearing efficiency of a single connection unit. Therefore, the overall shear bearing capacity of the composite connector cannot be simply calculated as a linear sum of the bearing capacity of a single connection unit and the number of connections; the impact of increasing the number of connections needs to be corrected.

[0077] When determining the quantity effect, the equivalent number of connections is determined based on the number of shear studs (10) and concrete tenons, satisfying the following:

[0078] Where N is the equivalent number of connections; The quantity is 10 shear studs; The number of concrete tenons is used. In this embodiment, the quantity effect reduction model is applicable to composite connector arrangements with an equivalent connection number N of 3 to 5. The equivalent connection number within this range characterizes the quantity effect generated by the combined action of multiple connection units.

[0079] By introducing an equivalent number of connections, the multiple connection units contained in composite connectors under different arrangements can be uniformly characterized, reflecting the equivalent contribution of different connection forms in the overall stress process. Furthermore, when the equivalent number of connections N is in the range of 3 to 5, a quantity effect reduction coefficient is determined based on the equivalent number of connections, satisfying: ,in, This is the quantity effect reduction factor.

[0080] The quantity effect reduction factor is used to characterize the degree of reduction in load-bearing efficiency caused by the mutual influence between connecting units under a multi-nail, multi-hole arrangement. As the number of equivalent connections increases, the mutual interference between connecting units intensifies, and the corresponding quantity effect reduction factor changes accordingly, thus reflecting the difference between the stress state of multiple connecting units sharing the same load and the stress state of a single connecting unit operating independently.

[0081] Furthermore, the bearing capacity under the action of concrete tenons, the bearing capacity under the action of 20 through steel bars, and the bearing capacity under the action of 10 shear nails are modified using the quantity effect reduction factor to satisfy: ,in, To enhance the shear bearing capacity of composite connectors; The bearing capacity provided for end bearing; The load-bearing capacity provided by the concrete tenon; The bearing capacity provided for the through-bar 20; The load-bearing capacity provided for the shear stud 10.

[0082] Since the end-bearing capacity is mainly provided by the local bearing pressure between the perforated steel plate 30 and the lightweight ultra-high performance concrete, its stress area is relatively independent and not affected by the synergistic effect of the increased number of connection units. Therefore, the reduction in quantity effect mainly applies to the bearing contribution corresponding to the concrete tenon action, the through reinforcement 20 action, and the shear stud 10 action. Through the above correction method, the actual stress state of the composite connector under the condition of multiple studs and holes can be more accurately reflected, and the reliability of the shear bearing capacity determination result can be improved.

[0083] Furthermore, the shear capacity of each specimen was calculated according to the above method for determining shear capacity, and the calculation results were compared with the ultimate bearing capacity obtained from the push-out test. The results are shown in the table below.

[0084]

[0085] As shown in the table above, except for a few specimens with a single concrete tenon action, the calculation results of the other specimens with different structural forms are highly consistent with the test results, and the calculation error is controlled within 8%. This indicates that the shear bearing capacity determination method established in this application can well reflect the synergistic force relationship between end bearing action, concrete tenon action, through reinforcement 20 action and shear nail 10 action, and can effectively consider the quantitative effect under the condition of multiple nails and multiple holes. It has high calculation accuracy and engineering applicability.

[0086] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for determining the shear bearing capacity of a composite connector, applicable to steel-lightweight ultra-high performance concrete composite beams, characterized in that, Includes the following steps: Obtain the structural parameters of the composite connector, which includes shear studs, perforated steel plates, and through reinforcing bars. The perforated steel plates are disposed between the steel beam and the lightweight ultra-high performance concrete slab, and the through reinforcing bars are inserted into the holes of the perforated steel plates to form concrete tenons within the holes. Based on the stress characteristics of the composite connector, the shear bearing capacity of the composite connector is divided into end bearing capacity, concrete tenon bearing capacity, through steel bar bearing capacity, and shear stud bearing capacity, and the shear bearing capacity of the composite connector is determined according to each sub-item bearing capacity. Based on the load-slip curves obtained from the push-out test, the calculation parameters for the bearing capacity of the end bearing, the bearing capacity of the concrete tenon, the bearing capacity of the through steel reinforcement, and the bearing capacity of the shear stud are determined respectively. The equivalent number of connections is determined based on the number and arrangement of the connection units of the composite connector, and the quantity effect reduction factor is determined based on the equivalent number of connections. Based on the bearing capacity of each component and the reduction coefficient of the quantity effect, the shear bearing capacity of the composite connector of the steel-lightweight ultra-high performance concrete composite beam is determined.

2. The method for determining the shear bearing capacity of the composite connector according to claim 1, characterized in that, The shear bearing capacity of the composite connector satisfies: , To enhance the shear bearing capacity of composite connectors; The bearing capacity provided for end bearing function; The load-bearing capacity provided by the concrete tenon; The load-bearing capacity provided for the through-bar reinforcement; The load-bearing capacity provided by shear studs.

3. The method for determining the shear bearing capacity of the composite connector according to claim 2, characterized in that, The bearing capacity of the end bearing meets the following requirements: , This represents the cross-sectional area of ​​a single perforated steel plate. This represents the compressive strength of a concrete cube.

4. The method for determining the shear bearing capacity of the composite connector according to claim 2, characterized in that, The bearing capacity of the through-bar reinforcement satisfies: This represents the fiber volume fraction. Fiber length; Fiber diameter; This refers to the number of concrete tenons; The cross-sectional area of ​​a single concrete tenon.

5. The method for determining the shear bearing capacity of the composite connector according to claim 2, characterized in that, The bearing capacity of the through-bar reinforcement satisfies: , The number of through-bars, This refers to the cross-sectional area of ​​a single through-bar rebar. This represents the yield strength of the through-steel reinforcement.

6. The method for determining the shear bearing capacity of the composite connector according to claim 2, characterized in that, The shear stud's load-bearing capacity satisfies: , For the number of shear studs, The cross-sectional area of ​​a single shear stud This represents the tensile strength of the shear stud.

7. The method for determining the shear bearing capacity of the composite connector according to claim 1, characterized in that, When the composite connector adopts a multi-nail, multi-hole arrangement, the equivalent number of connections is determined based on the number of shear nails and the number of concrete tenons, satisfying the following: For the equivalent number of connections, For the number of shear studs, This refers to the number of concrete tenons.

8. The method for determining the shear bearing capacity of the composite connector according to claim 7, characterized in that, The quantity effect reduction factor is determined based on the equivalent number of connections, satisfying the following: , This is the quantity effect reduction factor.

9. The method for determining the shear bearing capacity of the composite connector according to claim 8, characterized in that, The bearing capacity of the concrete tenon, the bearing capacity of the through steel reinforcement, and the bearing capacity of the shear stud are corrected using the quantity effect reduction coefficient to satisfy the following relationship: .

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