Transverse prestress structure of midspan bottom plate of variable cross-section box girder

Abstract

The utility model provides a cross-section-variable box girder midspan bottom plate transverse prestress structure, and belongs to the technical field of box girder construction. Comprising a top plate, flange plates are arranged on the two sides of the top plate, top plate transverse prestressed steel beams are arranged below the top plate, vertical prestressed tendons and webs are arranged between the top plate and the flange plates, and bottom plates are connected to the lower portions of the vertical prestressed tendons and the webs and provided with bottom plate transverse prestressed steel beams and bottom plate longitudinal prestressed steel beams. And the bottom plate transverse prestressed steel beams and the bottom plate longitudinal prestressed steel beams are tensioned. By applying transverse prestress to the midspan bottom plate of the variable cross-section box girder, splitting force and other transverse force generated by longitudinal prestress of the bottom plate are eliminated, the bottom plate is prevented from generating longitudinal cracks, and it is guaranteed that the structure is safe and durable; diseases such as cracking and overlarge downwarping of the variable cross-section box girder can be greatly avoided, and the service life of the structure is prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of box girder construction, and particularly relates to a transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder. Background Technique

[0002] The box girder is a common structural form in the field of bridge engineering, and has a series of advantages such as good overall performance, high stiffness, convenient construction and maintenance, etc., and is widely used in various forms of bridges such as continuous girder bridges or continuous rigid frame bridges. For medium and large-span girder bridges, in order to reduce the self-weight of the structure and improve the bearing capacity, the upper main girder generally adopts a variable cross-section box girder structure, and the beam height gradually decreases from the pier top to the mid-span in the form of a circular curve or a parabola, and three-way prestress is tensioned to avoid cracking of the box girder.

[0003] In order to resist the positive moment generated at the mid-span under the action of dead load and live load, longitudinal prestressed steel bundles are often arranged at the mid-span bottom slab to avoid diseases such as cracking and excessive deflection of the bottom slab. Since the bottom slab is curved, a downward radial force will be generated under the action of the longitudinal prestress of the bottom slab, resulting in splitting cracks along the longitudinal prestress near the mid-span bottom slab, which greatly endangers the safety of the bridge.

[0004] Therefore, the technical personnel in this field are committed to developing a transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder, which can provide transverse prestress for the mid-span bottom slab of the variable cross-section box girder, prevent longitudinal cracking of the box girder bottom slab, and is convenient for construction. Content of the Utility Model

[0005] The purpose of the utility model is to overcome the above deficiencies and provide a transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder.

[0006] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0007] A transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder, including a bottom slab, and a transverse prestressed steel bundle of the bottom slab is arranged on the bottom slab and tensioned.

[0008] The transverse prestressed steel bundle of the bottom slab adopts high-strength low-relaxation steel strands.

[0009] The longitudinal line at the center position of the bottom slab is the mid-span closure section center line, and the transverse prestressed steel bundle of the bottom slab is densely arranged at the mid-span closure section center line.

[0010] The transverse prestressed steel bundle of the bottom slab is tensioned in a single-end staggered manner, and the tension control stress is 0.75 .

[0011] It includes a top plate, with flange plates arranged on both sides of the top plate. There are transverse prestressed steel tendons of the top plate below the top plate. Vertical prestressed tendons and webs are arranged between the top plate and the flange plates, and the vertical prestressed tendons and the webs are connected to the bottom plate below.

[0012] Longitudinal prestressed steel tendons of the bottom plate are arranged on the bottom plate, and transverse prestressed steel tendons of the bottom plate are arranged below the longitudinal prestressed steel tendons of the bottom plate.

[0013] The prestressed steel tendons are sheathed with corrugated pipes.

[0014] The transverse prestressed steel tendons of the bottom plate and the longitudinal prestressed steel tendons of the bottom plate maintain a spacing of 5 cm.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] The utility model provides a transverse prestressed structure for the mid-span bottom plate of a variable cross-section box girder, which includes a top plate, with flange plates arranged on both sides of the top plate. There are transverse prestressed steel tendons of the top plate below the top plate. Vertical prestressed tendons and webs are arranged between the top plate and the flange plates, and the vertical prestressed tendons and the webs are connected to the bottom plate below. Transverse prestressed steel tendons of the bottom plate and longitudinal prestressed steel tendons of the bottom plate are arranged on the bottom plate, and the transverse prestressed steel tendons of the bottom plate and the longitudinal prestressed steel tendons of the bottom plate are tensioned. By applying transverse prestress to the mid-span bottom plate of the variable cross-section box girder, the splitting force and other transverse forces generated by the longitudinal prestress of the bottom plate are eliminated, the longitudinal cracks on the bottom plate are prevented, and the structural safety and durability are ensured.

[0017] Furthermore, the anchoring points are arranged inside the bottom plate, and the overall appearance is not affected after sealing the anchors.

[0018] Furthermore, under the combined action of the transverse prestress and the longitudinal prestress of the bottom plate, the cracking and excessive deflection of the variable cross-section box girder can be greatly avoided, and the service life of the structure can be prolonged. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the utility model, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic diagram of the basic structure of a variable cross-section box girder;

[0021] Figure 2 It is a schematic diagram of the action of the radial force generated by the longitudinal prestress of the bottom plate of a variable cross-section box girder;

[0022] Figure 3 It is a schematic diagram of the longitudinal splitting of the bottom plate caused by the longitudinal prestress of the bottom plate of a variable cross-section box girder;

[0023] Figure 4 It is a plan view of the prestress layout of the mid-span bottom slab of a variable cross-section box girder;

[0024] Figure 5 It is a top view of the prestress layout of the mid-span bottom slab of a variable cross-section box girder.

[0025] Explanation of the reference numerals in the figure: 1. Flange plate; 2. Top slab; 3. Transverse prestressed steel tendons of the top slab; 4. Vertical prestressed tendons; 5. Web; 6. Transverse prestressed steel tendons of the bottom slab; 7. Longitudinal prestressed steel tendons of the bottom slab; 8. Bottom slab; 9. Center line of the mid-span closure segment; 10. Radial force; 11. Tensile force. Detailed implementation manners

[0026] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0028] In the present invention, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present utility model, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, the meaning of "a plurality of" is two or more, unless otherwise clearly and specifically defined.

[0031] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0032] It should also be understood that the terms used in the specification of the present utility model are merely for the purpose of describing specific embodiments and are not intended to limit the present utility model. As used in the specification of the present utility model and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0033] It should be further understood that the term " / and" used in the specification of the present utility model and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0034] Structural schematic diagrams according to the disclosed embodiments of the present utility model are shown in the drawings. These drawings are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the drawings and their relative sizes and positional relationships are merely exemplary, and may actually deviate due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0035] The embodiments of the present utility model will be described in detail below with reference to the accompanying drawings.

[0036] A transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder has the following structure:

[0037] As Figure 1 shown, a transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder includes a top slab 2, flange plates 1 are arranged on both sides of the top slab 2, a transverse prestressed steel tendon 3 of the top slab is arranged below the top slab 2, vertical prestressed tendons 4 and webs 5 are arranged between the top slab 2 and the flange plates 1, the vertical prestressed tendons 4 and the webs 5 are connected to a bottom slab 8 below, and a transverse prestressed steel tendon 6 and a longitudinal prestressed steel tendon 7 of the bottom slab are arranged on the bottom slab 8.

[0038] Preferably, the transverse prestressed steel tendon 6 of the bottom slab and the longitudinal prestressed steel tendon 7 of the bottom slab are sheathed with corrugated pipes.

[0039] Preferably, the transverse prestressed steel tendon 6 of the bottom slab is made of high-strength low-relaxation steel strands, and its tensile strength is 50% - 80% higher than that of ordinary steel strands. This enables it to require a smaller cross-sectional area of materials and a lighter weight when bearing the same load, thus saving materials and costs.

[0040] Preferably, the longitudinal line at the center position of the bottom slab 8 is the mid-span closure segment center line 9, and the transverse prestressed steel tendon 6 of the bottom slab is densely arranged along the mid-span closure segment center line 9. The densely arranged prestressed steel tendons can significantly improve the bearing capacity of the mid-span closure segment, making the structure more stable and reliable when bearing external loads. The dense arrangement of the prestressed steel tendons helps to reduce the deformation of the structure during long-term use and maintain the geometric shape and dimensional stability of the structure.

[0041] A method for using a transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder is as follows:

[0042] As Figures 2 - 5 shown, in this embodiment, taking the center of the bottom slab 8 as the origin, the longitudinal direction as the x-axis, and the transverse direction as the y-axis, the transverse prestressed steel tendon 6 of the mid-span bottom slab of the variable cross-section box girder is arranged along the x-axis within a certain range. The arrangement range is determined according to the bridge span, generally being 4 - 6 times the mid-span beam height H (or 2 - 3 beam segments on both sides of the mid-span closure segment center line 9). The distance between adjacent transverse prestressed steel tendons 6 of the bottom slab can be kept the same as that of the transverse prestressed steel tendon 3 of the top slab, generally being 0.5 m. For areas with large transverse forces at the mid-span closure segment and other parts of the bottom slab, dense arrangement can be carried out.

[0043] When arranging the transverse prestressed steel tendons 6 and longitudinal prestressed steel tendons 7 of the bottom slab, the construction quality should be controlled. The longitudinal prestressed steel tendons 7 of the bottom slab should be above the transverse prestressed steel tendons 6 of the bottom slab, and there should be at least a 5 cm distance between their edges to ensure that the concrete pouring can be more dense. The transverse prestressed steel tendons 6 of the bottom slab should have a protective layer thickness of at least 3 cm from the lower edge of the bottom slab 8 to avoid excessive local stress in the concrete during tensioning and causing it to fall off.

[0044] After the formwork of the newly constructed beam segment is removed and the concrete strength reaches the strength for prestress tensioning, the transverse prestressed steel tendons 6 of the bottom slab are preferentially tensioned to generate a tensile force 11, making the transverse direction of the bottom slab 8 in a compressive state. Then, the longitudinal prestressed steel tendons 7 of the bottom slab are tensioned to offset the radial force 10 generated by the tensioning of the longitudinal prestressed steel tendons 7 of the bottom slab.

[0045] The transverse prestressed steel tendons 6 of the bottom slab are placed inside the corrugated pipe and tensioned in a single-end staggered manner. The anchorage section of the transverse prestressed steel tendons 6 of the bottom slab should be within 5 cm of the edge of the web 5. The tensioning end is set within 5 cm of the outer edge of the bottom slab 8. After tensioning, the excess steel strands are cut off, and cement slurry with the same concrete grade as the box girder is used for sealing the anchor to ensure that the sealed anchor is smooth and has no color difference from the surrounding concrete, without affecting the overall appearance.

[0046] In this embodiment, the prestressed steel tendons 6 of the bottom slab adopt 3-Φ s 15.2 high-strength low-relaxation steel strands, and are tensioned in a single-end staggered manner. The tension control stress is 0.75 The transverse prestressed steel tendons 6 of the mid-span bottom slab are arranged below the longitudinal prestressed steel tendons 7 of the bottom slab, and there should be a spacing of about 5 cm between their edges to prevent excessive stress on the bottom slab concrete.

[0047] Finally, it should be noted that: The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0048] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A transverse prestressed structure for the mid-span bottom slab of a variable cross-section box girder, characterized in that It includes a top plate (2), with flange plates (1) arranged on both sides of the top plate (2), a transverse prestressed steel tendon (3) of the top plate arranged below the top plate (2), vertical prestressed tendons (4) and a web (5) arranged between the top plate (2) and the flange plates (1), the vertical prestressed tendons (4) and the web (5) are connected to a bottom plate (8) below, and a transverse prestressed steel tendon (6) and a longitudinal prestressed steel tendon (7) of the bottom plate are arranged on the bottom plate (8), and the transverse prestressed steel tendon (6) and the longitudinal prestressed steel tendon (7) of the bottom plate are tensioned.

2. The cross - section variable box - girder mid - span bottom - plate transverse prestressed structure according to claim 1, wherein, The transverse prestressed steel tendon (6) of the bottom plate adopts high-strength low-relaxation steel strands.

3. A variable cross-section box girder transverse prestressed structure at the mid-span bottom plate according to claim 1, characterized in that, The longitudinal line at the center position of the bottom plate (8) is the mid-span closure segment center line (9), and the transverse prestressed steel tendon (6) of the bottom plate is densely arranged on the mid-span closure segment center line (9).

4. A variable cross-section box girder transverse prestressed structure at the mid-span bottom plate according to claim 1, characterized in that, The transverse prestressed steel tendons (6) of the bottom slab are tensioned in a single-end staggered manner, and the tensile control stress is 0.75 .

5. A variable cross-section box girder transverse prestressed structure at the mid-span bottom plate according to claim 1, characterized in that, The transverse prestressed steel tendon (6) of the bottom plate is arranged below the longitudinal prestressed steel tendon (7) of the bottom plate.

6. A variable cross-section box girder transverse prestressed structure at the mid-span bottom plate according to claim 5, characterized in that, The prestressed steel tendon is sleeved with a corrugated pipe.

7. A variable cross-section box girder transverse prestressed structure at the mid-span bottom plate according to claim 6, characterized in that The transverse prestressed steel tendon (6) of the bottom plate and the longitudinal prestressed steel tendon (7) of the bottom plate maintain a spacing of 5 cm.

Images