Prestressed steel reinforced concrete composite beam

Abstract

This utility model discloses a prestressed steel-concrete composite beam, including steel connectors and a beam body. The steel connectors adopt a two-section design, with each section embedded at a predetermined depth at one end of the beam body. Each section of the steel connector includes a pair of flanges for connecting the upper and lower longitudinal reinforcements of the beam body, with a web connecting the two flanges. The portion of the web embedded at the beam end extends towards the mid-span of the beam, forming an extension section with a gradually decreasing cross-sectional height. This extension section is used to construct a transition zone in the beam body where the bending stiffness changes continuously and smoothly. Prestress is also applied to the concrete in the beam body through pre-tensioned prestressing tendons. This utility model aims to effectively improve the problems existing in SRC beams in terms of stiffness transition, complexity of joint construction, and reliability of connection methods. By adopting a two-section steel connector design, combined with a special variable cross-sectional height design, a smooth transition of beam end stiffness is achieved, avoiding the adverse effects caused by abrupt changes in stiffness.

Description

Technical Field

[0001] This utility model relates to the technical field of building components, and in particular to a prestressed steel-concrete composite beam. Background Technology

[0002] Steel-concrete composite beams (SRC beams) are a type of high-efficiency structural component. By organically combining steel and concrete, they fully leverage the dual advantages of steel beams (high load-bearing capacity and good ductility) and concrete beams (high stiffness, fire resistance, and durability). This composite structure not only significantly improves the load-bearing capacity and stiffness of components but also effectively enhances the seismic performance of the structure. Therefore, it has been widely used in modern high-rise buildings, large-span spatial structures, and important infrastructure projects.

[0003] Traditional SRC beam designs typically employ a construction method where steel sections are arranged along the entire length of the beam within the concrete beam. This design concept is reflected in several patented technologies. For example, the H-shaped steel arrangement scheme disclosed in "A Wave-Shaped Steel-Concrete Composite Beam" (Patent No. ZL201910179952.7) and the T-shaped steel application method demonstrated in "A Prestressed Steel-Seat T-Shaped Steel-Concrete Composite Beam" (Patent No. ZL201310499946.2) are examples of this approach. In these traditional constructions, the connection nodes between the beam ends and columns are critical components of the entire structural system, and their mechanical properties directly determine the seismic safety and reliability of the overall structure.

[0004] However, existing SRC beam technology still faces several technical challenges that urgently need to be addressed in practical engineering applications: Firstly, there are significant defects in the stiffness transition. The traditional design of continuous steel sections abruptly ending at the beam end section height leads to a sharp change in stiffness from the concrete beam section height to the core area of ​​the joint. This abrupt change in stiffness not only causes significant stress concentration in the joint area but also severely affects the ductility and energy dissipation performance of the joint, thereby reducing the overall seismic performance of the structure.

[0005] Secondly, the joint construction is overly complex. In the beam end area, especially the anchorage treatment of longitudinal reinforcement, multiple construction measures are required, including intensive operations such as rebar perforation and bending. These complex construction requirements not only increase the construction difficulty but also easily affect the reliability of the joint due to difficulties in ensuring construction quality.

[0006] Thirdly, the introduction and application of prestressing technology in composite beam structures is also a key technical challenge that needs to be addressed. Summary of the Invention

[0007] To address the aforementioned problems, this invention aims to provide a prestressed steel-concrete composite beam, whose design effectively improves the issues of stiffness transition, complex joint construction, and reliable connection methods in SRC beams. By employing a two-section steel connector design combined with a special variable cross-section height design, this invention achieves a smooth transition of stiffness at the beam ends, avoiding the adverse effects caused by abrupt stiffness changes. Simultaneously, the simplified structural design greatly simplifies the construction requirements of the beam end area, reduces construction difficulty, and improves joint reliability. Furthermore, the application of prestressed tendons to the concrete enhances the overall load-bearing capacity and crack resistance of the beam. This prestressing technology not only further improves the mechanical properties of the composite beam but also creates conditions for its application in a wider range of engineering fields.

[0008] To achieve the above objectives, this utility model discloses a prestressed steel-concrete composite beam, comprising steel connectors and a beam body. The key features are: the steel connectors adopt a two-section design, with each section embedded to a predetermined depth at both ends of the beam body; each section of the steel connector includes a pair of flanges for connecting the upper and lower longitudinal reinforcements of the beam body, respectively, with a web connecting them; the portion of the web embedded at the beam end extends towards the mid-span of the beam, forming an extension section with a gradually decreasing cross-sectional height; this extension section is used to construct a transition region in the beam body where the bending stiffness changes continuously and smoothly; and prestress is applied to the concrete in the beam body through pre-tensioned prestressing tendons.

[0009] Furthermore, at least a portion of the cross-sectional height of the extension exhibits a linear or non-linear variation.

[0010] Furthermore, the overall cross-sectional height of the extension section varies linearly, with its upper and lower edges extending obliquely and converging relatively to form a wedge-shaped structure.

[0011] Furthermore, a beam end steel plate is provided between the flange plates. The plate size of the beam end steel plate is adapted to the end face size of the beam body. On the one hand, it serves as the end template for the beam body casting, and on the other hand, it serves as the cut-off plate for the flange plates and the web plate to be embedded.

[0012] Furthermore, the upper longitudinal reinforcement of the beam is welded and fixed to the upper flange plate of the steel connector using an upper steel pad; the lower longitudinal reinforcement of the beam is welded and fixed to the lower flange plate of the steel connector using a lower steel pad; and the web reinforcement of the beam is welded and fixed to the web plate of the steel connector and / or the beam end plate using a web steel pad.

[0013] Furthermore, the upper longitudinal bars, lower longitudinal bars, and web bars of the beam are enclosed by several spaced stirrups to form a steel reinforcement skeleton, and the stirrup spacing in the embedded part of the steel connector is smaller than the stirrup spacing in the non-embedded part of the steel connector.

[0014] Furthermore, a through groove is pre-reserved on a section of the web plate embedded at the beam end, which is used to arrange tie bars through the web reinforcement of the beam.

[0015] Furthermore, a fixing hole is provided on a section of the web that is not embedded in the end of the beam, and the fixing hole is used to install high-strength bolts.

[0016] Compared with the prior art, the significant advantages of this utility model are: (1) The steel connector adopts a two-section design. After each section is embedded into the end of the beam at a predetermined depth, its flange stops penetrating, while the web continues to extend a distance towards the mid-span of the beam. In the extended section, its cross-sectional height gradually decreases in a linear or nonlinear manner, eventually forming a smaller residual cross-sectional height. This design constructs a stiffness buffer / transition zone, the core objective of which is to achieve a continuous and smooth transition of the beam cross-sectional height from the pure concrete region to the region containing the complete steel section, avoiding stress concentration caused by abrupt changes and delaying crack propagation. In this region, concrete cracks appear later and are more dispersed and finer, which helps to maintain the contribution of concrete and makes the overall stiffness degradation more gradual. At the same time, this design can also improve hysteresis performance. The smoother stiffness change and reduced stress concentration help to obtain a fuller hysteresis curve with less pinching effect, which means that the structure has a stronger energy dissipation capacity and a smaller degree of stiffness / strength degradation.

[0017] (2) In terms of structural design, the steel connector adopts a two-section design, which not only simplifies the construction of the composite beam, but also avoids the complexity brought about by the continuous arrangement of steel along the beam in the traditional design. This design not only significantly reduces the amount of steel used and lowers the cost, but also makes the assembly and welding work in the construction process simpler and more efficient. At the same time, due to the simple and clear structure of the steel connector, the error and uncertainty in the construction process are greatly reduced, and the reliability of the node and the safety of the overall structure are improved. On the other hand, this utility model simplifies the detailed design of the beam end area by using the flange plate to bear the load, and reduces the cumbersome construction of dense openings on the steel flange or complex bending of the reinforcing bars. This simple structural design not only reduces the construction difficulty and improves the construction efficiency, but also reduces the potential reliability hazards of the node caused by construction quality problems. In addition, the through groove reserved on the web provides convenience for the through arrangement of tie bars, further enhancing the connection performance of the node.

[0018] (3) Regarding the connection method, this utility model further optimizes the connection design to ensure the reliability and efficiency of the connection method. The connection between the steel connector and the beam adopts a strategy combining multiple fixing methods. On the one hand, the flange plate of the steel connector is welded and fixed to the longitudinal reinforcement of the beam with the help of steel pads. This rigid connection method can provide a stable force transmission path and ensure the integrity and coordination of the structure under stress. On the other hand, fixing holes are opened in the part of the web that is not embedded in the beam end for installing high-strength bolts. This bolt connection method is not only convenient for construction and installation, but also has the ability to slip and deform, which can dissipate some seismic energy and meet the seismic performance requirements.

[0019] (4) Regarding the introduction of prestress, this utility model applies prestress to the concrete by means of pre-tensioned prestressing tendons, which effectively enhances the load-bearing capacity and crack resistance of the entire beam. The prestressing tendons ensure that the concrete beam is subjected to uniform stress after the application of prestress, thereby improving the overall stability and durability of the structure. In addition, the application of prestressing technology further optimizes the mechanical properties of the composite beam, enabling it to better adapt to various complex working conditions and extreme load conditions. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the prestressed steel-concrete composite beam in Example 1; Figure 2 This is a schematic diagram of the steel reinforcement skeleton structure of the prestressed steel-concrete composite beam in Example 2; Figure 3 This is a schematic diagram of the end structure of the prestressed steel-concrete composite beam in Example 1 (I). Figure 4 This is a schematic diagram of the end structure of the prestressed steel-concrete composite beam in Example 1 (II). Figure 5 This is a schematic diagram of the end structure of the prestressed steel-concrete composite beam in Example 1 (III); The following labels are used in the drawing: 1-steel connector, 2-beam body, 101-flange plate, 102-web plate, 103-extension section, 104-beam end steel plate, 105-upper steel pad, 106-lower steel pad, 107-waist steel pad, 108-through groove, 109-fixing hole, 201-upper longitudinal reinforcement, 202-lower longitudinal reinforcement, 203-prestressed tendon, 204-waist reinforcement, 205-stirrup, 206-tie bar. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0023] In the description of this utility model, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, in the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] Figures 1 to 3 The first embodiment of this utility model is shown: a prestressed steel-concrete composite beam, including a steel connector 1 and a beam body 2. The steel connector 1 adopts a two-section design, with the two sections embedded at predetermined depths at both ends of the beam body 2. Each section of the steel connector 1 includes a pair of flanges 101 for connecting the upper longitudinal reinforcement 201 and the lower longitudinal reinforcement 202 of the beam body 2, respectively, with a web 102 connecting the two. The portion of the web 102 embedded at the beam end extends towards the mid-span of the beam, forming an extension section 103 with a gradually decreasing cross-sectional height. This extension section 103 is used to construct a transition region in the beam body 2 with a continuously and smoothly changing bending stiffness. Prestress is also applied to the concrete in the beam body 2 by pre-tensioned prestressing tendons 203. The prestressing tendons 203 are tensioned using a pre-tensioning method to ensure uniform distribution of prestress and effectively improve the prestress level of the concrete. During the pouring of beam 2, the prestressing tendons 203 are firmly fixed in the preset position. After the concrete reaches the design strength, the prestressing tendons 203 are released so that the concrete can obtain the expected prestressing effect.

[0025] like Figure 2As shown, in specific implementations, at least a portion of the cross-sectional height of the extension segment 103 exhibits linear or nonlinear variations. In this embodiment, preferably, the overall cross-sectional height of the extension segment 103 varies linearly, with its upper and lower edges extending obliquely and converging to form a wedge-shaped structure. This wedge-shaped structure design further enhances the smoothness of the transition region, making the change in bending stiffness more uniform, thereby further optimizing the seismic performance of the structure. In other embodiments, the overall cross-sectional height of the transition segment may also vary nonlinearly, or a combination of linear and nonlinear variations may be used to meet specific engineering requirements or optimize structural performance. Furthermore, using nonlinear variations, or a combination of nonlinear and linear variations in cross-sectional height design, may involve more complex geometries and manufacturing processes. However, in some cases, this design can provide superior performance compared to linear variations. For example, under certain specific dynamic response or load conditions, it can more effectively disperse stress and energy.

[0026] Specifically, the embedment depth of the steel connectors, the stopping position of the flange plate 101, the length of the web plate 102 and the extension section 103, and the gradient slope of the extension section 103 are determined according to construction requirements. In actual engineering, these parameters can be precisely determined based on construction experience and factors such as the span of beam 2 and the magnitude of the load. For beam 2 with a larger span and heavier load, the length of the extension section 103 can be appropriately increased, and the gradient slope can be correspondingly reduced to ensure a smoother transition of bending stiffness. When determining the embedment depth, the stress conditions at the beam ends must be fully considered to ensure that the flange plate 101 and the web plate 102 can effectively transfer the load to the beam.

[0027] In one embodiment, the flange plate 101 of the steel connector is located at a distance of 2 from the end face of the beam. The embedding stops at the point; the web 102 continues to extend its length. The extension segment 103 forms a gradient slope at both the upper and lower edges. The transition region, whose geometric parameters satisfy the relation （Ⅰ） : ...............（Ⅰ） In the formula: : Clear span of the beam; The distance between the end of the flange plate 101 and the end of the beam; : Length of extension segment 103; The total length from the end of the beam to the end of extension 103; : Starting height of extension section 103; Total height of the beam section; Distance from the wing edge stopping position Web height at the location; : Remaining cross-sectional height at the end of extension 103; : Web extension coordinates, with the positive direction pointing towards the mid-span of the beam, and the origin located at the position where flange plate 101 stops embedding; : Gradual slope of extension segment 103; The ratio of the extension length of extension segment 103 to the first flange insertion stop position; The ratio of the minimum embedment depth to the span of the flange 101; The ratio of the residual height of extension segment 103 to the initial height of the web; The ratio of the remaining height of extension section 103 to the height of the beam; : Span utilization rate coefficient ; : Gradual slope adjustment factor for load response; Regarding uniformly distributed loads A monotonically increasing function; : Design value of maximum bending moment at mid-span of the beam; : Yield strength of steel; Design value of uniformly distributed load on beam.

[0028] The application of the aforementioned geometric parameter relationships is of great significance in practical engineering. When determining these parameters, factors such as the beam's clear span and the design value of the uniformly distributed load must be comprehensively considered. By calculating and applying these relationships, reasonable geometric parameters can be accurately determined for steel connectors, thereby ensuring their optimal mechanical performance within the beam.

[0029] For example, when the beam has a large clear span or a high design value for the uniformly distributed load, it is necessary to appropriately increase the embedment depth of the flange plate 101 and the length of the extension section 103 according to the relationship to ensure that the beam has sufficient bending resistance and stability. At the same time, the adjustment of the gradual slope also needs to be accurately calculated according to the actual situation to ensure that the change in bending stiffness in the transition area meets the design requirements.

[0030] Taking the standard floor frame beam of a high-rise office building as an example, the relationship is... （Ⅰ） Verification required: 1. Design input parameters: beam clear span (Structural axis spacing minus support width); Beam section height (Dimensions indicated on the structural construction drawings); Uniformly distributed load design value (Including the combined values ​​of dead load and live load); Maximum bending moment at mid-span (Calculation results from structural analysis software); steel yield strength (Measured values ​​using Q390 grade steel); Extension 103 starting height (Specifications of HN550×200 steel section).

[0031] 2. Explanation of coefficient values:

[0032] 3. Parameter calculation process: (1) Determine the stop embedding position of the flange 101 : ; Values: ; Note: Meets seismic anchorage requirements ( ); satisfying moment transfer ( ).

[0033] (2) Determine the web extension length : ; Note: Coefficient Achieve efficient transition of short extension segment 103.

[0034] (3) Determine the total length from the end of the beam to the end of the extension 103. : ; Validation constraints: .

[0035] (4) Determine the stiffness adjustment coefficient : ; Note: Logarithmic function response to load intensity, Corresponds to a moderately gradual slope.

[0036] (5) Determine the unilateral cutting slope : ; Note: The slope is positively correlated with the load. It is inversely correlated with span.

[0037] (6) Determine the web height function : ; Key points: ; .

[0038] (7) Determine the height of the residual section : ; Validation constraints: ; (8) Total length of H-beam : ; The beam end extends 200mm outward for column node 4 connection: .

[0039] 4. Cutting rules for extension segment 103: Cutting line on the top edge of the plate: ; Cutting line on the bottom edge: .

[0040] 5. Beam Structure Implementation and Zoning: |← Left section steel-covered area→|← Middle concrete area→|← Right section steel-covered area→| 0 ───────── 3055mm ────────── 4945mm ────────── 8000mm; The complete area of ​​the flange plate 101 and web plate 102 inside the beam: 0 ~ 2350mm (flange + web); Gradient zone of extension section 103: 2350 ~ 3055 mm (section height of extension section 103 550 → 469 mm); Central concrete zone: 3055~4945 mm (pure concrete section); Symmetry: The two covered areas are of equal length (3055 mm each) and their midpoints are aligned.

[0041] 6. Implementation Results: (1) The stress concentration factor was reduced from 2.8 in the traditional design to 1.5; (2) Steel usage is reduced by 28% (compared to continuous arrangement); (3) Construction time for key nodes is reduced by 35%; (4) The rotational capacity of the plastic hinge is increased to 0.032 rad (meeting the seismic requirements of high intensity areas).

[0042] Please see Figure 3 In this embodiment, a beam end steel plate is also provided between the flange plates 101. The plate size of the beam end steel plate is adapted to the end face size of the beam body 2. It serves as an end template for the casting of the beam body 2 and as a stop plate for the embedding of the flange plates 101 and the web plates 102. The beam end steel plate is integrally formed with the flange plates 101 and the web plates 102 or is connected and fixed by welding to ensure the stability and integrity of the connector. During the casting of the beam body 2, the beam end steel plate, as an end template, can effectively prevent concrete leakage and ensure the casting quality. At the same time, as a stop plate, the beam end steel plate can limit the embedding depth of the flange plates 101 and the web plates 102 in the beam body 2, ensuring that the connector functions as designed.

[0043] from Figure 4 and Figure 5 As can be seen, in specific application scenarios, the upper longitudinal reinforcement 201 of the beam 2 is welded and fixed to the upper flange plate 101 of the steel connector 1 using an upper steel pad 105; the lower longitudinal reinforcement 202 of the beam 2 is welded and fixed to the lower flange plate 101 of the steel connector 1 using a lower steel pad 106; and the web reinforcement 204 of the beam 2 is welded and fixed to the web plate 102 of the steel connector 1 and / or the beam end steel plate using a web steel pad 107. This method of welding and fixing the reinforcement to the steel connector 1 using steel pads not only simplifies the beam end structure and connection method but also ensures a firm connection, guaranteeing the stability of the structure under stress. The use of steel pads also provides an additional support surface, which helps to disperse stress and prevent damage caused by excessive local stress. In addition, welding, as a rigid connection method, can provide a reliable force transmission path, enhancing the overall integrity and collaborative working ability of the structure.

[0044] like Figure 2 As shown, specifically, the upper longitudinal reinforcement 201, lower longitudinal reinforcement 202, and web reinforcement 204 of the beam 2 are enclosed by several spaced stirrups 205 to form a steel reinforcement skeleton, and the spacing of the stirrups 205 in the embedded part of the steel connector 1 is smaller than the spacing of the stirrups 205 in the non-embedded part of the steel connector 1. This stirrup 205 densification design aims to enhance the concrete confinement effect in the embedded area of ​​the steel connector 1, and improve the shear bearing capacity and ductility of this area. By reducing the stirrup 205 spacing, the lateral deformation of the concrete can be more effectively confined, thereby delaying crack propagation and improving the overall seismic performance of the structure.

[0045] Please see Figure 3 In this embodiment, a through groove 108 is pre-reserved on a section of the web 102 embedded at the beam end. This through groove 108 is used to arrange tie bars 206 through the web reinforcement 204 of the beam 2. This design not only simplifies the arrangement of the tie bars 206, but also enhances the connection strength between the web 102 and the concrete beam, further improving the overall performance. In addition, the through groove 108 facilitates concrete pouring, helping to ensure dense filling of concrete around the web 102, thereby enhancing the integrity and durability of the structure. In specific implementations, the shape, size, and position of the through groove 108 can be optimized according to actual engineering needs to achieve the best connection effect and construction convenience. On the other hand, the section of the web 102 with the through groove 108 can also play a role in dispersing stress and energy to a certain extent, further improving seismic performance in conjunction with the variable cross-section design.

[0046] In practical applications, a fixing hole 109 is provided on a section of the web 102 that is not embedded in the end of the beam 2. The fixing hole 109 is used to install high-strength bolts. This high-strength bolt connection method is not only simple and quick to install, but also has high connection stiffness and seismic performance. The high-strength bolts achieve a friction-type connection of the connectors with the help of preload, which facilitates construction positioning and adjustment, and can effectively transfer shear force and bending moment, ensuring the stability of the beam-column connection.

[0047] In summary, in this invention, the steel connector 1 adopts a two-section design. Each section is embedded to a predetermined depth into the end of the beam 2, after which its flange stops penetrating, while the web 102 continues to extend a distance towards the mid-span of the beam. In the extension section 103, its cross-sectional height gradually decreases linearly or non-linearly, ultimately forming a smaller residual cross-sectional height. This design constructs a stiffness buffer / transition zone, the core objective of which is to achieve a continuous and smooth transition of the beam's cross-sectional height from the pure concrete region to the region containing the complete steel section, avoiding stress concentration caused by abrupt changes and delaying crack propagation. In this region, concrete cracks appear later, are more dispersed and finer, which helps maintain the contribution of concrete and makes the overall stiffness degradation more gradual. Simultaneously, this design also improves hysteresis performance. A smoother stiffness change and reduced stress concentration contribute to a fuller hysteresis curve with less pinching effect, meaning the structure has stronger energy dissipation capacity and less stiffness / strength degradation. In terms of structural design, the steel connector 1 adopts a two-section design, which not only simplifies the construction of the composite beam but also avoids the complexity caused by the continuous arrangement of steel along the beam in traditional designs. This design not only significantly reduces the amount of steel used and lowers costs but also makes the assembly and welding work during construction simpler and more efficient. At the same time, due to the simple and clear structure of the steel connector 1, errors and uncertainties during construction are greatly reduced, improving the reliability of the joint and the safety of the overall structure. On the other hand, this utility model simplifies the detailed design of the beam end area by using the flange plate 101 to bear the load, reducing the cumbersome construction of densely opening holes on the steel flange or complex bending of the reinforcing bars. This simple structural design not only reduces the difficulty of construction and improves construction efficiency but also reduces potential reliability hazards of the joint caused by construction quality problems. In addition, the through groove 108 reserved on the web plate 102 provides convenience for the through arrangement of the tie bars 206, further enhancing the connection performance of the joint. In terms of connection method, this utility model further optimizes the connection design to ensure the reliability and efficiency of the connection method. The connection between the steel connector 1 and the beam 2 employs a combination of fixing methods. Firstly, steel plates are used to weld and fix the flange plate 101 of the steel connector 1 to the longitudinal reinforcement of the beam 2. This rigid connection provides a stable force transmission path, ensuring the integrity and synergy of the structure under stress. Secondly, fixing holes 109 are provided in the portion of the web 102 not embedded in the beam end for installing high-strength bolts. This bolted connection not only facilitates construction and installation but also possesses slip deformation capability, dissipating some seismic energy and meeting seismic performance requirements. Regarding prestressing, this invention utilizes pre-tensioned prestressing tendons 203 to apply prestress to the concrete, effectively enhancing the load-bearing capacity and crack resistance of the entire beam 2.The prestressing tendons 203 ensure that the concrete beam 2 is subjected to uniform stress after prestressing is applied, thereby improving the overall stability and durability of the structure. In addition, the application of prestressing technology further optimizes the mechanical properties of the composite beam, enabling it to better adapt to various complex working conditions and extreme load conditions.

[0048] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Those skilled in the art can understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present utility model are still within the scope of the utility model.

Claims

1. A prestressed steel-concrete composite beam, comprising steel connectors and a beam body, characterized in that: The steel connector adopts a two-section design, with the two sections embedded into the two ends of the beam at a predetermined depth. Each section of the steel connector includes a pair of flanges for connecting the upper and lower longitudinal reinforcements of the beam, respectively, with a web connecting them. The portion of the web embedded in the beam end extends towards the mid-span of the beam, forming an extension section with a gradually decreasing cross-sectional height. This extension section is used to construct a transition zone in the beam where the bending stiffness changes continuously and smoothly. Prestress is also applied to the concrete in the beam by pre-tensioned prestressing tendons.

2. The prestressed steel-concrete composite beam according to claim 1, characterized in that: At least a portion of the cross-sectional height of the extension section varies linearly or nonlinearly.

3. The prestressed steel-concrete composite beam according to claim 2, characterized in that: The overall cross-sectional height of the extension section varies linearly, with its upper and lower edges extending obliquely and converging relative to each other to form a wedge-shaped structure.

4. The prestressed steel-concrete composite beam according to any one of claims 1-3, characterized in that: A beam end steel plate is also provided between the flange plates. The plate size of the beam end steel plate is adapted to the end face size of the beam body. On the one hand, it serves as the end template for the beam body casting, and on the other hand, it serves as the cut-off plate for the flange plates and the web plate to be embedded.

5. The prestressed steel-concrete composite beam according to claim 4, characterized in that: The upper longitudinal reinforcement of the beam is welded and fixed to the upper flange plate of the steel connector using an upper steel pad; the lower longitudinal reinforcement of the beam is welded and fixed to the lower flange plate of the steel connector using a lower steel pad; the web reinforcement of the beam is welded and fixed to the web plate of the steel connector and / or the beam end plate using a web steel pad.

6. The prestressed steel-concrete composite beam according to claim 5, characterized in that: The upper longitudinal bars, lower longitudinal bars, and web bars of the beam are enclosed by several spaced stirrups to form a steel reinforcement skeleton, and the stirrup spacing in the embedded part of the steel connector is smaller than the stirrup spacing in the non-embedded part of the steel connector.

7. The prestressed steel-concrete composite beam according to claim 5 or 6, characterized in that: A through groove is pre-reserved on a section of the web plate embedded at the beam end. This through groove is used to arrange tie bars through the web reinforcement of the beam.

8. The prestressed steel-concrete composite beam according to claim 7, characterized in that: A fixing hole is provided on a section of the plate that is not embedded in the end of the beam. The fixing hole is used to install high-strength bolts.

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