A steel-concrete composite connection structure under concrete tension

Abstract

The present invention discloses a steel-concrete composite connection structure under a concrete tension state. By utilizing a bolt shear connector with a self-constrained structure and utilizing its superior and stable force-bearing performance in terms of shear stiffness of the steel-concrete interface, a series of new structural construction methods are proposed. The use of the above-mentioned new structural construction method under the concrete axial tension or bending tension state can effectively reduce the adverse effects of concrete tensile cracking in the steel-concrete composite connection, and can simply and effectively strengthen or enhance the connection strength and connection stiffness of the composite connection under axial tension or bending tension. For example, the new connection construction method is applied to the negative moment zone of the composite beam, which can effectively control and prevent the tensile cracking of the concrete in the negative moment zone of the composite beam, thereby strengthening or enhancing the bending stiffness in the negative moment zone of the composite beam, and solving the engineering problem of low degree of combined application of the steel-concrete composite connection in the negative moment zone due to concrete cracking.

Description

Technical Field

[0001] The invention relates to the technical field of bolt shear connectors, and in particular to a steel-concrete composite connection structure under a concrete tension state. Background Art

[0002] In the negative moment zone, the steel-concrete continuous composite beam will produce the unfavorable situation that the concrete is tensile and the steel beam is compressed, especially the cracking of the concrete slab, which will cause the composite beam stiffness to decrease and the durability to decline. Therefore, taking effective design, construction methods and treatment measures to effectively control and prevent concrete cracking in the negative moment zone has become a key issue in the design of continuous composite beams. Currently, the commonly used treatment methods include: preloading method, support pre-lifting method, prestressing method, reinforcement to limit the width of concrete cracks, post-combination prestressed concrete bridge deck method, steel beam bottom slab pouring concrete method, and strengthening the steel-concrete bonding strength method.

[0003] However, the prior art has the following disadvantages:

[0004] (1) The on-site construction is complex, the workload is large, the construction period is long, and it is difficult to partially renovate the composite beam in the future;

[0005] (2) Some technologies will cause local stress concentration, and necessary structural measures need to be taken to improve the stress concentration problem, which makes the design complicated;

[0006] (3) The cost is high and uneconomical, and the effect is not ideal. It is often necessary to use several methods at the same time to solve the problem of negative bending moment area of ​​composite beams. Summary of the invention

[0007] The purpose of the present invention is to provide a steel-concrete composite connection structure under concrete tension, which increases the bending stiffness of the negative bending moment zone of the composite beam and solves the problem of effectively controlling and preventing concrete cracking in the negative bending moment zone of the composite beam.

[0008] To achieve the above-mentioned purpose, the present invention provides the following solution: The present invention provides a steel-concrete composite connection structure under concrete tension state, including bolts for connecting steel beam flanges and reinforced concrete flange plates, the bolts are fixedly connected to the steel beam flanges by bolting and welding, and the cross-section of the composite beam concrete flange plate is also provided with either or both of oblique tensile short steel bars or tensile steel plates, the oblique tensile short steel bars are arranged at the neutral axis of the cross-section of the composite beam concrete flange plate, and the tensile steel plate is arranged at the place where the tensile stress of the cross-section of the steel beam concrete flange plate is maximum.

[0009] Preferably, a circle of high-strength fine-stone concrete is fixedly formed on the outer edge of the stud, the strength of the high-strength fine-stone concrete is greater than the concrete strength of the cast reinforced concrete flange, and an embracing tension is applied to the high-strength fine-stone concrete and its internal components at its outer edge by embracing the tensile unit of the high-strength fine-stone concrete. At the same time, spiral reinforcement is also provided on the outside of the tensile unit of the high-strength fine-stone concrete, and the spiral reinforcement is concentrically surrounded by the outside of the high-strength fine-stone concrete and formed in the reinforced concrete flange by casting.

[0010] Preferably, the top surface of the steel beam upper flange steel plate and the bottom surface of the additional steel plate are connected to the reinforced concrete flange plate through the studs, and the studs on the top and bottom surfaces are arranged side by side or staggered with each other.

[0011] Preferably, when only oblique short tensile steel bars are provided on the cross section of the steel beam concrete flange plate, the oblique short tensile steel bars can work together with the transverse steel bars in the steel beam concrete flange plate to balance the shear force transmitted by the studs.

[0012] Preferably, when only tensile steel plates are provided on the cross section of the composite beam concrete flange plate, the tensile steel plates provided at the location where the tensile stress of the steel beam concrete flange plate is maximum are directly used to bear the tensile stress at this location.

[0013] Preferably, when oblique tensile short steel bars and tensile steel plates are provided on the cross section of the composite beam concrete flange plate at the same time, the studs arranged in an up-and-down staggered manner in the composite beam concrete flange plate are used together with the oblique tensile short steel bars and tensile steel plates to resist tensile stress.

[0014] Preferably, the connection method of the steel flange plate and the composite beam concrete flange plate can be an assembled connection.

[0015] Compared with the prior art, the present invention has achieved the following technical effects:

[0016] The steel-concrete composite connection structure under the tensile state of concrete proposed in the present invention is specifically three embodiments of the negative bending moment zone of the continuous composite beam. In the three embodiments, a stud shear connector with a constraint structure is used. Since the shear connector can effectively constrain the splitting and splitting development of concrete, it has excellent interface shear bearing capacity and strong and stable interface shear stiffness. In particular, large-diameter studs (studs with diameters of 22mm, 25mm and above) can be more reliably applied to the composite beam structure connection. Through the reasonable design of the concrete part and the steel structure part of the composite beam and the shear connector, the shear connector will not be damaged before the concrete or steel beam, which can fully meet the basic force requirements of the composite structure of the strong composite connection, and give full play to the advantages of the respective materials of steel and concrete. The composite connection structure can be widely used in other parts of other steel-concrete composite connections that are jointly tensile.

[0017] Compared with the commonly used treatment methods, it can give full play to the respective advantages of steel and concrete materials, effectively reduce the tensile stress level in the concrete flange plate, improve the effective stiffness of the negative moment zone of the composite beam, and increase the ductility and energy dissipation capacity of the negative moment zone of the composite beam; it is simple to construct and has strong operability. It effectively solves the problem that the cracking load of the steel-concrete continuous composite beam in the negative moment zone is low, and does not relax or reduce the combined effect of the negative moment zone of the continuous composite beam. With the help of this connection structure, the negative moment zone of the continuous composite beam can also give full play to the advantages of the respective materials of steel and concrete, thereby promoting the application of composite components in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 Schematic diagram of the stress characteristics of the composite section in the negative moment zone of a typical traditional continuous composite beam.

[0020] Figure 2 This is a schematic diagram of the force characteristics of the composite section of a typical continuous composite beam in the negative moment zone according to the third embodiment of the present invention.

[0021] Figure 3 The diagram is a distribution diagram of the bending moment in the maximum negative bending moment section and the maximum positive bending moment section of the continuous composite beam in Example 1.

[0022] Figure 4 It is a schematic diagram of the force balance of the steel beam part with studs and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam in Example 1.

[0023] Figure 5 Schematic diagram of the longitudinal arrangement of studs in the negative bending moment section and the maximum positive bending moment section of the continuous composite beam in Example 1.

[0024] Figure 6 Schematic diagram of the planar arrangement of studs in the negative moment section of the continuous composite beam in Example 1.

[0025] Figure 7 For Example 1 Figure 6 The AA section is shown as a schematic diagram of the transverse arrangement of studs.

[0026] Figure 8 For Example 1 Figure 6 The schematic diagram of the longitudinal arrangement of studs in the BB section is shown.

[0027] Fig. 9This is the bending moment distribution diagram of the maximum negative bending moment section and the maximum positive bending moment section of the continuous composite beam in Example 2.

[0028] Fig.10 It is a schematic diagram of the force balance of the steel beam part with studs and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam in Example 2.

[0029] Fig.11 Schematic diagram of the longitudinal arrangement of studs in the negative bending moment section and the maximum positive bending moment section of the continuous composite beam in Example 2.

[0030] Fig.12 Schematic diagram of the planar arrangement of studs in the negative moment section of the continuous composite beam in Example 2.

[0031] Fig.13 For Example 2 Fig.12 Schematic diagram of the transverse arrangement of studs in the AA section in the negative bending moment section is shown.

[0032] Fig.14 For Example 2 Fig.12 Schematic diagram of the transverse arrangement of CC section studs in the negative bending moment section is shown.

[0033] Fig.15 For Example 2 Fig.12 Schematic diagram of the longitudinal arrangement of BB section studs in the negative bending moment section is shown.

[0034] Fig.16 The diagram is a diagram showing the moment distribution of the maximum negative moment section and the maximum positive moment section of the continuous composite beam in Example 3.

[0035] Fig.17 It is a schematic diagram of the force balance of the steel beam part with studs and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam in Example 3.

[0036] Fig.18 Schematic diagram of the longitudinal arrangement of studs in the negative bending moment section and the maximum positive bending moment section of the continuous composite beam in Example 3.

[0037] Fig.19 Schematic diagram of the planar arrangement of studs in the negative moment section of the continuous composite beam in Example 3.

[0038] Fig. 20 For Example 3 Fig.19 Schematic diagram of the transverse arrangement of studs in the AA section in the negative bending moment section is shown.

[0039] Fig.21 For Example 3 Fig.19 Schematic diagram of the transverse arrangement of CC section studs in the negative bending moment section is shown.

[0040] Fig. 22 For Example 3 Fig.19 Schematic diagram of the longitudinal arrangement of BB section studs in the negative bending moment section is shown.

[0041] Fig.23 Schematic diagram of the planar arrangement of studs in the negative moment section of the continuous composite beam in Example 3 (one row of studs is arranged on the steel beam).

[0042] Fig.24 for Fig.23 Schematic diagram of transverse stud arrangement of AA section in the negative bending moment section (one row of studs arranged on the steel beam) is shown.

[0043] Fig.25 Schematic diagram of the planar arrangement of studs in the negative moment section of the continuous composite beam in Example 3 (three rows of studs are arranged on the steel beam).

[0044] Fig.26 for Fig.25 Schematic diagram of transverse stud arrangement of AA section in the negative bending moment section (3 rows of studs are arranged on the steel beam) is shown.

[0045] Fig. 27 for Fig.25 Schematic diagram of transverse stud arrangement of CC section in the negative bending moment section (3 rows of studs arranged on the steel beam) is shown.

[0046] Fig.28 for Fig.25 Schematic diagram of the arrangement of longitudinal studs in the BB section in the negative bending moment section (three rows of studs are arranged on the steel beam) is shown.

[0047] Fig.29 for Fig.23 Schematic diagram of longitudinal stud arrangement of DD section in the negative bending moment section (3 rows of studs arranged on the steel beam) is shown.

[0048] Fig.30 The stress distribution diagram of the steel beam and the additional steel plate corresponding to the concentrated load of 300kN in the mid-span of the continuous composite beam with 2 spans and a span of 4m in Example 3 is shown in the numerical simulation.

[0049] Fig.31 This is the nominal stress distribution diagram of concrete corresponding to the concentrated load of 300kN in the mid-span of the continuous composite beam with two spans and a span of 4m in Example 3, which is simulated by numerical calculation.

[0050] Fig.32 This is the shear force distribution diagram of the composite beam studs corresponding to the concentrated load of 300kN in the mid-span of the continuous composite beam with 2 spans and a span of 4m in Example 3, which is simulated by numerical calculation.

[0051] Fig.33This is the deflection distribution diagram of the composite beam corresponding to the concentrated load of 300kN in the mid-span, which is a numerical simulation of the continuous composite beam with 2 spans and a span of 4m in Example 3.

[0052] Among them, 1 steel beam flange plate; 2 steel beam concrete flange plate; 3 studs; 4 stud enlarged head; 5 high-strength fine stone concrete; 6 high-strength tension unit; 7 spiral reinforcement; 8 stud welding arc starting point; 9 high-strength fine stone concrete mold; 10 welding auxiliary ring; 11 annular inner tire membrane; 12 transverse reinforcement at the top of concrete flange plate; 13 transverse reinforcement at the bottom of concrete flange plate; 14 longitudinal reinforcement at the top of concrete flange plate; 15 longitudinal reinforcement at the bottom of concrete flange plate; 16 tension steel plate; 17 oblique reinforcement; 18 transverse reinforcement; 19 high-strength bolts. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The purpose of the present invention is to provide a steel-concrete composite connection structure under concrete tension state. The structural connection method increases the bending stiffness of the negative bending moment zone of the composite beam and solves the problem of effectively controlling and preventing concrete cracking in the negative bending moment zone of the composite beam.

[0055] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] The schematic diagram of the force characteristics of the composite section in the negative moment zone of a typical traditional continuous composite beam is shown in Figure 1As shown. It is mainly reflected in that the concrete flange plate in the negative moment zone of the traditional composite beam is in an axial tension or bending tension state as a whole. Microscopically speaking, the steel bar in the concrete flange plate transmits the tensile force by relying on the traditional anchoring and bonding force transmission mechanism between the steel bar and the concrete. The general measures adopted in current engineering research and practice are: sufficient tensile steel bars are arranged in the flange plate to control the crack width of the concrete plate within the allowable value. Usually, when the crack width of the concrete is limited to within 0.2mm, the durability requirements of the structure can be met. Usually, when the reinforcement ratio is above 1% and the stress of the tensile steel bar is below 100MPa, the crack width of the concrete can be basically limited to below 0.2mm. If the stress strength of the tensile steel bar is to be fully utilized at 180-200MPa, engineering research and practice have proved that the circumference rate of the tensile steel bar in the concrete flange plate needs to be controlled to be above 0.04mm / mm2. The above research conclusions show that the use of tensile steel bars in the concrete flange plate of the negative moment zone of the composite beam has low material utilization efficiency. In addition, the existing specifications only consider the stiffness of the tensile reinforcement within the range of the support Le (Le-equivalent span, the effective width be of the concrete wing plate at the support is approximately 58% to 67% of the positive moment zone) in the continuous composite beam, resulting in the continuous composite beam being a variable-section beam, which brings great inconvenience to the calculation analysis and engineering design application of the continuous composite beam.

[0057] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following takes the steel-concrete continuous composite beam in the negative moment zone (the concrete flange plate is in a typical axial tension or bending tension state) as an example, combined with specific diagrams, to further explain the present invention: a series of simple and effective new structural construction connection methods for improving the composite connection stiffness when the concrete plate is in an axial tension or bending tension state.

[0058] The technical problem solved by the connection method adopted by the present invention is achieved by adopting the following specific implementation methods and technical solutions.

[0059] Embodiment 1:

[0060] When the upper flange of the steel beam in the negative bending moment zone adopts a stud shear connector with a constraint structure, when the concrete flange plate in the composite section is basically in axial tension or tension-bending combined tension state, the concrete is always in full-section tension state. According to the single stud 3 shear triangular truss balance unit, it can be known that when the concrete is in tension as a whole, it is impossible to rely on it to form an oblique concrete compression rod in the concrete flange plate like the concrete in the compression zone. The stud 3 shear requires the oblique component of the longitudinal and transverse steel bars at the top and bottom of the flange plate to provide the oblique bar tension in the stud 3 shear triangular truss balance unit to balance the longitudinal shear force of the stud 3. Therefore, in order to balance the longitudinal shear force of the stud 3 shear connector with a constraint structure, an oblique tension bar can be added in the flange plate near the spiral reinforcement 6d of the stud 3 with a constraint structure to form a balanced tension rod unit of the single stud 3 shear triangular truss balance unit when the concrete is in tension as a whole (such as Figure 6 Obviously, the cross-sectional elastic shear bearing capacity and shear stiffness of the composite section concrete flange plate and the steel beam flange plate 1 in the negative bending moment zone can be significantly improved, which is conducive to the full utilization of the longitudinal steel bars 14 at the top of the concrete flange plate and the longitudinal steel bars 15 at the bottom of the concrete flange plate in the negative bending moment zone.

[0061] Additional oblique reinforcement 17 and additional transverse reinforcement 18 are added at the neutral axis section of the concrete flange slab section to resist the shear force of the stud 3, and together with the reinforcement at the top and bottom of the concrete flange slab, the shear force transmitted by the stud 3 is balanced. From the shear force transmission mechanism of the stud 3 in the concrete slab, it can be known from the triangular truss balance unit that even if the concrete slab is in axial tension or bending tension, the newly added oblique tension short reinforcement can form a tension rod to effectively meet the force requirement of the reinforced concrete as a whole in tension without a concrete oblique compression rod to balance the shear force of the stud 3.

[0062] Embodiment 1 can be widely used in steel-concrete continuous composite secondary beam supports, or composite beams with small span height (recommended: L0 / h≤15), where it is inconvenient or unnecessary to add additional steel plates to the continuous composite beam supports. Its main force demand characteristics are: relying on the top longitudinal steel bars 14 of the concrete flange plate at the steel-concrete continuous composite beam support, the bottom longitudinal steel bars 15 of the steel beam concrete flange plate, and the additional oblique steel bars 17 added at the neutral axis section to resist the shear force of the studs 3 to bear the tensile force demand of the support section.

[0063] Embodiment 2:

[0064] Directly add steel plates for compensating strength and stiffness and resisting tensile stress at the location where the tensile stress of the concrete flange plate section is the largest, that is, add tensile steel plates 16 on the top of the concrete flange plate 2 of the steel beam. The tensile steel plates added at this position directly bear the tensile stress of the cross section borne by the concrete flange plate at this part. In the negative moment area of the continuous composite beam, stud shear connectors 3 with a constrained structure are used to form a steel-concrete composite slab with the additional steel plates on the top of the concrete flange plate 2 of the steel beam. The transfer of tensile force by the additional steel plates is mainly achieved by the shear force transfer capacity of the stud shear connectors 3 with a constrained structure on the additional steel plates. Due to the use of stud shear connectors 3 with a constrained structure, this shear connector effectively avoids local compression splitting failure, has strong and tough shear stiffness, and still has good internal force redistribution performance when the shear force exceeds the elastic limit state. (For safety reasons, the friction at the interface is not considered. The maximum tensile force that the additional steel plates can transfer can be taken as the sum of the design shear bearing capacities of the stud shear connectors 3 arranged within 0.15Le, that is, Fta = nNv); due to the superior interface shear bearing capacity and strong and tough and stable interface shear stiffness of the stud shear connectors 3 with a concrete constrained structure (see: Master's thesis of Chen Pan from Hunan University of Science and Technology, "Research on the Mechanical Properties of Stud Shear Connectors with Concrete Constrained Structure"), obviously, the additional steel plates have large tensile stiffness and can bear most of the tensile force at the upper part of the composite section in the negative moment area. In this way, most of the tensile force at the tensile edge of the composite section in the negative moment area is borne by the steel plates, and the composite section in the negative moment area can also make full use of the mechanical properties of both steel and concrete materials.

[0065] Embodiment 2 can be widely applied to the supports of steel-concrete continuous composite main and secondary beams, or composite beams with a relatively large span-depth ratio of the composite beam (recommended: 15 < L0 / h ≤ 18), where additional steel plates can be added at the supports of the continuous composite beam. Its main mechanical requirements characteristics are: rely on the longitudinal reinforcement 14 at the top of the concrete flange plate, the longitudinal reinforcement 15 at the bottom of the concrete flange plate, and the additional tensile steel plates 16 on the top of the concrete flange plate 2 of the steel beam at the support of the steel-concrete continuous composite beam to bear the tensile force requirements of the support section.

[0066] Embodiment 3:

[0067] Both of the above connection methods in Embodiment 1 and Embodiment 2 are adopted simultaneously, that is: add additional inclined reinforcement 17 and additional transverse reinforcement 18 for resisting the shear force of the studs 3 at the neutral axis section of the concrete flange plate section, and at the balance tension rod unit of the shear triangle truss equilibrium unit of a single stud 3 when the concrete is in an overall tensile state (as shown in Fig.19 ), and directly add additional tensile steel plates 16 on the top of the composite beam concrete flange plate 2 for compensating the strength and stiffness of the composite beam and resisting tensile stress at the location where the tensile stress of the concrete flange plate section is the largest. The schematic diagram of the mechanical characteristics of the composite section in the typical negative moment area of the continuous composite beam proposed by the present invention is as shown in Figure 2 shown.

[0068] The stud shear connector composite slab with a restraint structure utilizes the tension of the steel plate on the upper surface of the concrete slab to effectively reduce the tensile stress of the concrete slab. Through the staggered engagement effect of the upper and lower rows of shear connectors in the concrete slab, in the embodiment, a tensile steel plate 16 with additional tensile stress is adopted. With the strong shear resistance performance of the stud shear connector with a restraint structure, the tensile steel plate 16 bears most of the tensile stress, thus transforming the original reinforced concrete flange slab 2 from an unfavorable state of repeated tensile cracking into a relatively favorable state of repeated compression and shear of the reinforced concrete slab, achieving the purpose of controlling and reducing the cracking of the concrete slab, and greatly improving the tensile bearing capacity and stiffness of the concrete under repeated tensile states. It is used to meet the needs of maintaining good and stable load-bearing capacity and high composite connection stiffness under high tensile stress of the concrete slab.

[0069] Embodiment 3 can be widely applied to the supports of steel-concrete continuous composite main and secondary beams, or composite beams with a large span-depth ratio of the composite beam (recommended: 18 < L0 / h ≤ 25), such as: the supports of continuous beams in important composite frames. In the requirements of continuous composite beam supports, the mid-span negative moment area needs to have a large ultimate bearing capacity, and at the same time, the mid-span negative moment area needs to have a strong plastic rotation ability with toughness or even be designed as a part with reciprocating hysteretic energy dissipation ability. Its main force requirement characteristics are: relying on the longitudinal reinforcement 14 at the top of the reinforced concrete flange slab, the longitudinal reinforcement 15 at the bottom of the reinforced concrete flange slab, the additional inclined reinforcement 17 that resists the shear force of the stud 3 at the neutral axis section, and the additional tensile steel plate 16 at the top of the steel beam concrete flange slab 2 to bear the tensile force requirements of the support section. In this Embodiment 3, the stud shear connectors between the mid-span support of the continuous composite beam and the inflection point of the composite beam should correspondingly have a higher design value of shear bearing capacity and a stronger shear stiffness of the stud 3 with toughness to ensure the co-force of the shear connectors in the whole process of connecting steel and concrete. A part with strong plastic rotation ability with toughness or even reciprocating hysteretic energy dissipation ability.

[0070] In Embodiments 1, 2, and 3, the connection of the concrete flange slab in the negative moment area of the continuous composite beam to the upper flange of the steel beam (illustrated with an "I-shaped" steel beam as an example, obviously applicable to other forms of steel beams) by studs 3 is taken as an example of arranging two rows of studs 3 to illustrate the specific characteristics in the above embodiments.

[0071] Obviously, when arranging 1 row of studs 3 for the connection between the concrete flange slab in the negative moment area of the continuous composite beam and the upper flange of the steel beam, the 2 rows of studs 3 on the additional tensile steel plate 16 at the top of the steel beam concrete flange slab 2 and the studs 3 on the upper flange of the steel beam (illustrated with an "I-shaped" steel beam as an example) can be arranged in a staggered manner and interlocked with each other to enhance the composite action between the additional steel plate and the upper flange steel plate of the steel beam. Such as Fig.23 、 24As shown in the figure; when multiple rows of studs 3 are arranged between the concrete flange plate in the negative bending moment zone of the continuous composite beam and the upper flange of the steel beam, the studs 3 on the additional tensile steel plate 16 on the top of the concrete flange plate 2 of the steel beam and the studs 3 on the upper flange of the steel beam (the "I-shaped" steel beam is used as an example in the illustration) can be arranged in staggered rows and interlock with each other to enhance the combined effect of the additional steel plate and the upper flange steel plate of the steel beam. Fig.25 , 26 , 27, 28, and 29. The specific features of the staggered arrangement in the above embodiments are explained by taking the third embodiment as an example.

[0072] The connection structure of the present invention has the following characteristics:

[0073] (1) For the first time, a structural measure is proposed to add short oblique tensile steel bars at the neutral axis of the concrete flange section to resist the shear force of the stud 3, and to balance the shear force transmitted by the stud 3 together with the transverse steel bars in the concrete flange.

[0074] (2) For the first time, it is proposed to directly increase the compensatory strength and stiffness of the tensile steel plate to resist the tensile stress at the maximum tensile stress point of the concrete flange plate section. By welding the bolt 3 shear connector with concrete constraint structure on the additional steel plate and the bolt 3 shear connector with concrete constraint structure on the flange plate of the steel beam, the concrete plate can resist the tensile force in the form of a composite plate when it is under the unfavorable stress state of axial tension or bending tension, which greatly improves the tensile bearing capacity and tensile stiffness.

[0075] (3) For the first time, a targeted system solution for the negative moment zone of continuous composite beams is proposed. Different treatment methods should be adopted for the negative moment zone of continuous composite beams according to their force requirements. For example, the negative moment zone of the continuous composite secondary beam has low requirements for subsequent bearing capacity and stiffness, and simple structural calculations and construction measures that can meet the normal limit state can meet the requirements; while the negative moment zone of the frame beam has high requirements for subsequent bearing capacity and stiffness, so structural calculations and construction measures should be adopted, and it is necessary to give full play to the steel-concrete continuous composite beam in the negative moment zone. The steel is tensile and the concrete is compressed, so as to fully utilize the advantages of the respective force properties of the materials.

[0076] (4) For the first time, it is proposed to design the composite member as a structural member with strong composite connection by utilizing the superior interface shear bearing capacity and strong and stable interface shear stiffness of large-diameter studs 3 (studs 3 with diameters of 22 mm, 25 mm and above). The basic design principles and requirements of strong connection nodes (shear connectors with constraint structures) and weak components (steel structure parts, concrete parts) in composite structure connection design can be met through the reasonable design of the concrete part and steel structure part of the composite beam and the shear connector. The advantages of steel and concrete materials can be fully utilized.

[0077] (5) The series of simple and effective new structural connection methods proposed by the present invention for improving the composite connection stiffness when the concrete slab is under axial tension or bending tension can be used not only to solve the problem of negative bending moment of continuous composite beams, but also to solve the problem of joint tension of other steel-concrete composite structures. For example, the problem of joint tension of the outer concrete of the outer column foot and the steel column foot, the problem of joint tension of the steel plate shear wall under small eccentric tension, etc.

[0078] (6) The present invention proposes a series of simple and effective new structural connection methods for improving the combined connection stiffness when the concrete slab is under axial tension or bending tension. The methods are not limited to the above-mentioned embodiments. The basic principles, main features and advantages of the present invention can also be widely used in steel-concrete prefabricated structures, and can well meet the requirements of building industrialization.

[0079] The steel-concrete composite connection structure under concrete tension in the present invention is based on the invention patent with the authorized patent number ZL201610604260.9 and the invention name "Bolt 3 shear connector capable of restraining concrete splitting and splitting development", and the bolt 3 shear connector with concrete constraint structure has superior interface shear bearing capacity and strong and stable interface shear stiffness. Based on the above research results, it is further proposed: a series of simple and effective new structural connection methods for improving the stiffness of the composite connection when the concrete slab is in axial tension or bending tension. This connection method can effectively solve the technical problem of premature cracking in the negative moment zone of the continuous composite beam. A series of simple and effective new structural connection methods for improving the stiffness of the composite connection when the concrete slab is in axial tension or bending tension. The composite beam is designed as a continuous composite beam component with strong composite connection by using the superior interface shear bearing capacity and strong and stable interface shear stiffness of large-diameter bolts 3 (bolts 3 with diameters of 22mm, 25mm and above). The basic design principles and requirements of strong connection nodes (shear connectors with constraint structures) and weak components (steel structure parts and concrete parts) in composite structure connection design can be met through reasonable design of the concrete part and steel structure part and shear connectors of the composite beam. In this way, in the normal use stage, the slip between the steel and concrete of the composite beam is small, and its force is closer to the plane section assumption. Only when the load is large enough to cause a sufficiently large interface slip between the steel and concrete, the composite beam enters the obvious interface slip stage, and the interface slip calculation theory of the composite structure can be used for research. The composite beams studied in this invention are all composite beams that use shear connectors with bolts 3 with concrete constraint structures and are fully shear connected or enhanced shear connected. From the normal use stage, the slip value between the steel and concrete of the composite beam is less than the elastic limit of the connector, and the cross-section force is basically close to the plane section stress assumption. The basic mechanical principle of the force balance of the steel beam part with bolts 3 and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam is used to illustrate the efficiency and scientificity of the construction measures proposed in this article.

[0080] The existing specifications stipulate that for continuous composite beams, the influence of concrete in the tension zone on stiffness should not be taken into account within the range of 0.15l (l is the span of the beam) on both sides of the intermediate support, but the effect of the longitudinal reinforcement within the effective width be of the wing plate should be taken into account (Le - equivalent span, the effective width be of the concrete wing plate at the support of the composite section is approximately 58% to 67% of the positive bending moment zone). Figure 1 This is a schematic diagram of the force characteristics of the composite section in the negative moment zone of a typical traditional continuous composite beam. Figure 1 The concrete wing plate top reinforcement within the effective width be of the wing plate at the middle support is 14, and the concrete wing plate bottom reinforcement is 15. Figure 1 It can be seen (the contribution of the web is not considered in the schematic diagram) that the typical section equilibrium condition at the support of the continuous composite beam is:

[0081] σb*Ab=σt*At+σsb*Asb+σst*Ast (Formula 1)

[0082] In formula 1: σb is the compressive stress of the steel beam, Ab is the compressive flange area of ​​the steel beam, σt is the tensile stress of the steel beam, At is the tensile flange area of ​​the steel beam, σsb is the tensile stress of the concrete flange bottom steel bar 15; Asb is the cross-sectional area of ​​the concrete flange bottom steel bar 15, σst is the tensile stress Ast of the concrete flange top steel bar 14; Ast is the cross-sectional area of ​​the concrete flange bottom steel bar 14;

[0083] The present invention takes the force characteristic diagram of the combined section in the negative moment zone of the proposed embodiment 3 as an example to illustrate the force superiority of the present invention. The force characteristic diagram of the combined section in the negative moment zone of the typical continuous composite beam is as follows: Figure 2 As shown. Figure 2 It can be seen (the contribution of the web is not considered in the schematic diagram) that the typical section equilibrium condition at the support of the continuous composite beam is:

[0084] σb*Ab=σt*At+σsb*Asb+σst*Ast+σsc*Asc+f*Aa (Formula 2)

[0085] In formula 2: σb is the compressive stress of the steel beam, Ab is the compressive flange area of ​​the steel beam, σt is the tensile stress of the steel beam, At is the tensile flange area of ​​the steel beam, σsb is the tensile stress of the concrete flange bottom steel bar 15; Asb is the cross-sectional area of ​​the concrete flange bottom steel bar 15, σst is the tensile stress Ast of the concrete flange top steel bar 14; Ast is the cross-sectional area of ​​the concrete flange bottom steel bar 14; σsc is the tensile stress Ast of the steel bar 17 at the neutral axis section of the concrete flange; Asc is the cross-sectional area of ​​the steel bar 17 at the neutral axis section of the concrete flange; f is the tensile stress of the additional steel plate at the top of the steel beam concrete flange plate 2, and Aa is the additional steel plate area at the top of the steel beam concrete flange plate 2.

[0086] Depend on Figure 2 And formula 2 and Figure 1 By comparing with formula 1, it can be seen that: no matter in the normal use limit stage or in the elastoplastic bearing capacity limit state, the steel bar 17 at the neutral axis section of the concrete wing plate and the additional tensile steel plate 16 on the top of the steel beam concrete flange plate 2 can significantly increase the tensile bearing capacity and tensile stiffness at the middle support of the continuous composite beam.

[0087] Next, it is necessary to explain how the additional tension steel plate 16 on the top of the steel beam concrete flange plate 2 effectively bears the tension and bears the tension limit that should be borne by the concrete section. Fig.17 This is a schematic diagram of the force balance of the steel beam part with studs 3 and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam. Fig.17 It can be seen that: since the additional steel plate on the top of the steel beam concrete flange plate 2 adopts the bolt 3 shear connector with concrete constraint structure, the bolt 3 shear connector with concrete constraint structure has superior interface shear bearing capacity and strong and stable interface shear stiffness, the connection structure can constrain the concrete splitting and splitting development throughout the whole process, and it firmly combines the additional tension steel plate 16 with the steel beam concrete flange plate 2. From the mechanical equilibrium conditions of the additional steel plate and the steel beam concrete flange plate 2, it can be known that the tension that the additional tension steel plate 16 can transmit should be the sum of the design values ​​of the shear bearing capacity of the bolt 3 shear connector with concrete constraint structure connected to the additional tension steel plate 16, that is, naNv*. In this way, the additional tension steel plate 16 is mainly used to withstand the maximum tension demand generated by the bending of the combined section on the tensile side of the section. Since the neutral axis of the concrete in the negative bending moment zone is in a tensile state as a whole, a steel bar 17 matching the tensile state of the neutral axis is set at the neutral axis section of the concrete wing plate, which is mainly used to withstand the tensile stress of the section at the neutral axis.

[0088] Force characteristics of the middle support section of the continuous composite beam Fig.17 It can be seen that the additional tensile steel plate 16, the steel beam concrete flange plate 22 and the steel beam earth flange plate still have a tendency of tensile dislocation in section, but the steel beam earth flange plate here has a tendency of compression on the interface in the direction of vertical tension. Obviously, the additional tensile steel plate 16 with the concrete constraint structure of the bolt 3 shear connector can be engaged with the concrete constraint structure of the bolt 3 arranged on the upper flange of the steel beam. The tensile force originally transmitted by the steel bars in the concrete slab at the middle support section of the continuous composite beam is converted into the tensile force borne by the additional steel plate, and the reinforced concrete slab provides the shear force na* to balance the tensile force fAa borne by the additional tensile steel plate 16. The force at this location is closer to the force performance of the steel-concrete composite slab, which greatly improves the bearing capacity and stiffness of the composite section. Regardless of the normal use stage, the composite section basically presents a flat section assumption, and the component presents linear elastic characteristics. When the material enters the elastic-plastic state, according to the existing continuous composite beam calculation theory and experimental research results, the stud 3 shear connector is an obvious flexible shear connector. Fig.17 As can be seen from the force balance diagram of the steel beam part with studs 3 and the concrete part in the negative moment section and the maximum positive moment section of the continuous composite beam, the composite beam has excellent internal force redistribution ability. In this way, whether in the normal use limit stage or in the elastic-plastic bearing capacity limit state, a reasonable design can give full play to the respective advantages of steel and concrete materials to cause the predetermined material failure form in the component cross section, which can significantly increase the tensile bearing capacity and tensile stiffness at the intermediate support of the continuous composite beam.

[0089] Based on the numerical calculation and analysis method provided by the calculation model analysis method of the steel-concrete composite beam connected by bolt 3 (patent number: 2018103862560.6), a 2-span continuous composite beam with a span of 4m (I-shaped steel beam is 20a, C40 concrete flange is 800mm wide and 120mm thick) is connected by the new structural connection method of embodiment 3 proposed in this paper. The general finite element software midas is used to perform numerical calculation simulation on the 2-span continuous composite beam. The typical calculation results of the numerical calculation simulation of the continuous composite beam are detailed. Fig.30 , 31 , 32, and 33. Using the third embodiment of the present invention, the corresponding load concentration load numerical simulation value (300kN, the calculation simulation results are detailed in Fig.30 ) is about 1.4 to 1.6 times higher than the original experimental research value of 200kN (see Cao Hua. Experimental study and theoretical analysis on seismic performance of steel-concrete continuous composite beams: [Master's thesis]. Changsha: Central South University, 2005).

[0090] Fig.32 For example three: numerical simulation is used to calculate the shear force distribution of the composite beam studs 3 corresponding to the concentrated load of 300kN in the mid-span of the continuous composite beam. It can be seen from the figure that the shear force distribution of the composite beam studs 3 corresponding to the concentrated load of 300kN in the mid-span of the continuous composite beam is not uniform. The shear force of the studs 3 between the support and the inflection point of the composite beam in the continuous composite beam increases significantly compared with the positive moment section, with the maximum value reaching 97kN, while the maximum value in the positive moment section is only 47kN. Obviously, the shear force borne by the studs 3 between the support and the inflection point of the composite beam in the continuous composite beam is the largest, that is, from the support to the most unfavorable inflection point in the continuous composite beam, the stud 3 shear connector should have a higher shear bearing capacity design value and a stronger shear stiffness of the stud 3 to ensure that the shear connector is connected to the steel-concrete joint force throughout the whole process. Based on the basic force mechanism of composite beams and the results of numerical simulation combined with the existing theoretical research mechanism and experimental research results of continuous composite beams (see the book "Steel-Concrete Composite Structure Seismic Resistance and Stability" edited by She Zhiwu and Jiang Lizhong, Science Press, published in June 2015), it can be seen that the new structural connection method proposed in this paper can simply and effectively strengthen or enhance the connection strength and connection stiffness of the composite connection under axial tension or bending tension. Solve the engineering problem of low application degree of steel-concrete composite connection under tension due to concrete opening.

[0091] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A steel-concrete composite connection structure under concrete tension, characterized in that: It includes bolts for connecting steel beam flanges and reinforced concrete flange plates. The bolts are fixedly connected to the steel beam flanges by bolting and welding. The cross section of the reinforced concrete flange plates is also provided with oblique tensile short steel bars. The oblique tensile short steel bars are arranged at the neutral axis of the cross section of the reinforced concrete flange plates. The oblique tensile short steel bars can work together with the transverse steel bars in the reinforced concrete flange plates to balance the shear force transmitted by the bolts.

2. A steel-concrete composite connection structure under concrete tension, characterized in that: It includes bolts for connecting steel beam flanges and reinforced concrete flange plates. The bolts are fixedly connected to the steel beam flanges by bolting and welding. The cross section of the reinforced concrete flange plate is also provided with oblique tensile short steel bars and tensile steel plates. The oblique tensile short steel bars are arranged at the neutral axis of the cross section of the reinforced concrete flange plate, and the tensile steel plates are arranged at the location where the tensile stress of the cross section of the reinforced concrete flange plate is maximum.

3. The steel-concrete composite connection structure under concrete tension according to claim 1 or 2, characterized in that: A circle of high-strength fine-stone concrete is fixedly formed on the outer edge of the stud, and the strength of the high-strength fine-stone concrete is greater than the concrete strength of the cast reinforced concrete flange plate. A hoop tensile force is applied to the high-strength fine-stone concrete and its internal components at its outer edge by embracing the tensile unit of the high-strength fine-stone concrete. At the same time, spiral reinforcement is also arranged on the outside of the tensile unit of the high-strength fine-stone concrete. The spiral reinforcement is concentrically surrounded by the outside of the high-strength fine-stone concrete and is formed in the reinforced concrete flange plate by casting.

4. The steel-concrete composite connection structure under concrete tension according to claim 2, characterized in that: The top surface of the steel beam upper flange steel plate and the bottom surface of the tension steel plate are connected to the reinforced concrete flange plate through the studs, and the studs on the top surface and the bottom surface are arranged side by side or staggered.

5. The steel-concrete composite connection structure under concrete tension state according to claim 4, characterized in that: When oblique short tensile steel bars and tensile steel plates are provided on the cross section of the reinforced concrete flange plate at the same time, the studs arranged in an alternating pattern in the reinforced concrete flange plate and the oblique short tensile steel bars and tensile steel plates are used together to resist tensile stress.

6. The steel-concrete composite connection structure under concrete tension according to claim 1 or 2, characterized in that: The connection method between the steel beam flange and the reinforced concrete flange plate adopts assembled connection.

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