A device for preventing oblique cracks in the web of a prestressed small box girder at the end anchorage area

Abstract

The present invention discloses a device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder, comprising a plurality of semi-annular sleeves arranged in parallel in sequence, a flat arch plate arranged between two adjacent semi-annular sleeves, the arc openings of the flat arch plate and the semi-annular sleeves are opposite, a transverse support plate is fixed on the arch surface of the plurality of flat arch plates, transverse connecting rods are fixedly connected at both ends of the transverse support plates, the other ends of the two transverse connecting rods are respectively fixed on the first and last semi-annular sleeves, and each flat arch plate is provided with a circular channel corresponding to the stirrups. The device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder of the present invention can effectively prevent cracks in the web of the anchorage area at the end of a prefabricated prestressed small box girder.

Description

Technical Field

[0001] The invention belongs to the technical field of crack control devices for the end anchorage zone of a prefabricated prestressed small box girder, and relates to a device for preventing oblique cracks in the web of the end anchorage zone of a prestressed small box girder. Background Art

[0002] Prestressed prefabricated small box girder, its structure includes top plate, bottom plate and web plate, among which the main function of web plate is to bear shear stress and main tensile stress. In addition to longitudinal prestressed steel bars, this type of main beam is also equipped with stirrups, frame steel bars, longitudinal horizontal distribution steel bars and other structural steel bars. Among them, the main function of stirrups is to improve the shear resistance of the main beam, the main function of frame steel bars is to fix stirrups and other steel bars to form a steel skeleton, and the main function of longitudinal horizontal distribution steel bars arranged outside stirrups is to prevent cracks caused by temperature, concrete shrinkage and other reasons.

[0003] Prestressed concrete small box girders are widely used in highway bridge construction because of their advantages such as high torsional rigidity, uniform force, good integrity, convenient construction and low cost. However, during the prestressing and anchoring process of prefabricated prestressed small box girders, cracking of the web in the anchoring area at the end of the beam is a problem that is difficult to control.

[0004] For prefabricated prestressed small box girders, due to the relatively small cross-sectional size of the web and the large tension force applied, oblique cracks along the direction of the prestress are often generated in the end anchoring area during the prestressing and anchoring stage. These oblique cracks have an adverse effect on the durability and bearing capacity of the beam. Studies have shown that under the anchor plate and at a distance of 0.15 to 1.2 times the height of the beam from the anchoring surface, a large uneven transverse tensile stress perpendicular to the direction of the anchoring force will be generated. The resultant force of the tensile stress at this local position is the splitting force. Due to the lack of sufficient attention to the splitting force in the structural analysis and design of the end anchoring area, when the tensile stress at this local position reaches the ultimate tensile strength of the concrete, the web of the beam will crack.

[0005] At present, in order to better solve the problem of web cracking in the anchorage area at the end of the box girder, the following methods are mainly used: (1) improve the concrete construction process and strengthen the vibration and maintenance of concrete. (2) configure a certain number of indirect steel bars such as spiral steel bars and steel mesh. (3) appropriately increase the cross-sectional size of the web. However, due to the complex stress state in the anchorage area at the end of the box girder, cracking in this area often occurs even if the above measures are taken. Summary of the invention

[0006] The purpose of the present invention is to provide a device for preventing the occurrence of oblique cracks in the web of the end anchorage zone of a prefabricated prestressed small box girder, which can effectively prevent the occurrence of cracks in the web of the end anchorage zone of the prestressed small box girder.

[0007] The technical solution adopted by the present invention is a device for preventing oblique cracks from occurring in the web of the anchorage area at the end of a prefabricated prestressed small box girder, comprising a plurality of semi-annular sleeves arranged in parallel in sequence, a flat arch plate being arranged between two adjacent semi-annular sleeves, the arc-shaped openings of the flat arch plate and the semi-annular sleeves being opposite, a transverse support plate being commonly fixed on the arch surfaces of the plurality of flat arch plates, transverse connecting rods being fixedly connected at both ends of the transverse support plates, the other ends of the two transverse connecting rods being respectively fixed on the first and last semi-annular sleeves, and a circular hole corresponding to the longitudinal horizontally distributed steel bars being arranged on each flat arch plate.

[0008] The present invention is also characterized in that

[0009] The flat arch plate and the semi-annular sleeve are connected by welding.

[0010] The transverse support plate is fixed on the arch surfaces of the plurality of flat arch plates by welding and is located at a position in the middle of the height of the flat arch plates.

[0011] Two ends of the transverse connecting rod are respectively welded to the transverse supporting plate and the semi-annular sleeve.

[0012] The flat arch plate is a plate with ribs on the surface. The flat arch plate has a curved longitudinal section along the horizontal direction, and the axis of the flat arch plate is a parabola or a catenary.

[0013] The flat arch plate and the semi-annular sleeve are installed in the web within a certain distance range of the end anchorage area along the long direction of the small box girder. The semi-annular sleeve is nested on the stirrups. The upper ends of the flat arch plate and the semi-annular sleeve extend into the top plate frame steel bars and are connected to them by welding. The lower ends of the flat arch plate and the semi-annular sleeve extend into the bottom plate frame steel bars and are connected to them by welding.

[0014] When using it, please follow the steps below:

[0015] Step 1, connecting the flat arch plate and the semi-annular sleeve by welding;

[0016] Step 2, after the tying of the stirrups, the top plate frame steel bars, and the bottom plate frame steel bars is completed, according to the influence range of the end anchorage area, the flat arch plate and the semi-annular sleeve are installed in the web within a certain distance range of the end anchorage area along the beam length direction, and the semi-annular sleeve is nested on the stirrups, and the upper ends of the flat arch plate and the semi-annular sleeve are extended into the top plate frame steel bars and connected thereto by welding, and the lower ends of the flat arch plate and the semi-annular sleeve are extended into the bottom plate frame steel bars and connected thereto by welding;

[0017] Step 3, after the flat arch plate and the semi-annular sleeve are fixed in place, the longitudinal horizontal distribution steel bars arranged on both sides of the web plate are passed through the circular hole;

[0018] Step 4, connect the transverse support plate to the middle part of the flat arch plate by welding, then weld one end of the transverse connecting rod to the semi-annular sleeve, and weld the other end to the end of the transverse support plate;

[0019] Step 5, during the concrete pouring process, in the web range where a device for preventing oblique cracks from occurring in the web of the end anchorage area of ​​the prefabricated prestressed small box girder is installed, vibrate the concrete to ensure that the concrete is dense.

[0020] The beneficial effects of the present invention are:

[0021] After the flat arch plate and the semi-annular sleeve are installed in the web of the end anchoring area along the length direction of the beam, during the prestressed tensioning and anchoring process, the flat arch plate forms a constraint on the inner core concrete, generating radial pressure, and the ability to resist the splitting force can be enhanced by relying on the radial pressure and the tensile strength of the flat arch plate itself, thereby limiting the generation and development of cracks in the web of the end anchoring area. The present invention has a simple structure, strong practicality, convenient construction, significant economic benefits, and good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a stereoscopic diagram of a device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder according to the present invention;

[0023] Figure 2 It is a plan view of a device for preventing oblique cracks in the web of a prestressed small box girder end anchorage zone according to the present invention;

[0024] Figure 3 yes Figure 2 AA section diagram;

[0025] Figure 4 yes Figure 2 BB section diagram;

[0026] Figure 5 It is a three-dimensional schematic diagram of a prefabricated prestressed small box girder;

[0027] Figure 6 yes Figure 5 CC cross-section diagram;

[0028] Figure 7 yes Figure 5 DD cross-section diagram.

[0029] In the figure, 1. flat arch plate, 2. semi-annular casing, 3. circular channel, 4. transverse support plate, 5. transverse connecting rod, 6. web plate, 7. stirrups, 8. longitudinal horizontal distribution steel bars, 9. top plate frame steel bars, 10. bottom plate frame steel bars. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The present invention discloses a device for preventing oblique cracks in the web of a prestressed small box beam at the end anchorage area. The structure of the device is as follows: Figure 1-4 As shown, it includes a plurality of semi-annular sleeves 2 arranged in parallel in sequence, a flat arch plate 1 is arranged between two adjacent semi-annular sleeves 2, the arc openings of the flat arch plate 1 and the semi-annular sleeve 2 are opposite, a transverse support plate 4 is commonly fixed on the arch surface of the plurality of flat arch plates 1, and transverse connecting rods 5 are fixedly connected at both ends of the transverse support plate 4, and the other ends of the two transverse connecting rods 5 are respectively fixed on the first and last semi-annular sleeves 2, and each flat arch plate 1 is provided with a circular channel 3 corresponding to the longitudinal horizontal distribution steel bar 8.

[0032] The flat arch plate 1 and the semi-annular sleeve 2 are connected by welding.

[0033] The transverse support plate 4 is fixed on the arch surfaces of the plurality of flat arch plates 1 by welding and is located at a position in the middle of the height of the flat arch plates 1 .

[0034] Two ends of the transverse connecting rod 5 are welded to the transverse supporting plate 4 and the semi-annular sleeve 2 respectively.

[0035] The flat arch plate 1 is a plate with ribs on the surface. The flat arch plate 1 has a curved longitudinal section along the horizontal direction, and the axis of the flat arch plate 1 is a parabola or a catenary.

[0036] like Figure 5-7 As shown, the flat arch plate 1 and the semi-annular sleeve 2 are installed in the web 6 within a certain distance from the end anchorage area along the long direction of the small box girder, the semi-annular sleeve 2 is nested on the stirrup 7, the upper ends of the flat arch plate 1 and the semi-annular sleeve 2 extend into the top plate frame steel bars 9 and are connected thereto by welding, and the lower ends of the flat arch plate 1 and the semi-annular sleeve 2 extend into the bottom plate frame steel bars 10 and are connected thereto by welding.

[0037] When using it, please follow the steps below:

[0038] Step 1, connecting the flat arch plate 1 and the semi-annular sleeve 2 by welding;

[0039] Step 2, after the binding of the stirrups 7, the top plate frame steel bars 9, and the bottom plate frame steel bars 10 is completed, according to the influence range of the beam end anchorage area, the flat arch plate 1 and the semi-annular sleeve 2 are installed in the web 6 within a certain distance range from the end anchorage area along the beam length direction, and the semi-annular sleeve 2 is nested on the stirrups 7, the upper ends of the flat arch plate 1 and the semi-annular sleeve 2 extend into the top plate frame steel bars 9 and are connected thereto by welding, and the lower ends of the flat arch plate 1 and the semi-annular sleeve 2 extend into the bottom plate frame steel bars 10 and are connected thereto by welding;

[0040] Step 3, after the flat arch plate 1 and the semi-annular sleeve 2 are fixed in place, the longitudinal horizontal distribution steel bars 8 arranged on both sides of the stirrups 7 are passed through the circular channel 3;

[0041] Step 4, connecting the transverse support plate 4 to the middle part of the flat arch plate 1 by welding, and then welding one end of the transverse connecting rod 5 to the semi-annular sleeve 2, and welding the other end to the end of the transverse support plate 4;

[0042] Step 5, during the pouring of concrete, in the range of the web 6 where a device for preventing oblique cracks in the web of the anchorage area at the end of the prestressed small box girder is installed, steel bars or other methods are used to vibrate the concrete to ensure that the concrete is dense.

[0043] The curvature radius of the parabola or catenary of the flat arch plate 1 of the present invention is determined by comprehensively considering its stress state and the thickness of the concrete protective layer. The material of the flat arch plate 1 should have the characteristics of high rigidity and strong corrosion resistance. The flat arch plate 1 is placed in the web 6 within a certain distance range of the end anchoring area along the length direction of the beam. Its function is to generate radial pressure on the inner core concrete, thereby reducing the tensile stress of the concrete. A single flat arch plate and the core concrete can be regarded as a small arch structure. The second function is to rely on its own strength to bear a certain tensile stress, thereby limiting the generation and development of cracks.

[0044] The function of the semi-annular sleeve 2 of the present invention is to fix the flat arch plate 1 and prevent the flat arch plate 1 from lateral and longitudinal displacement. The function of the lateral support plate 4 and the lateral connecting rod 5 of the present invention is mainly to increase the lateral connection of the flat arch plate 1 and to support the flat arch plate 1 during construction.

Claims

1. A device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder, characterized in that: It comprises a plurality of semi-annular sleeves (2) arranged in parallel in sequence, a flat arch plate (1) being arranged between two adjacent semi-annular sleeves (2), the arc-shaped openings of the flat arch plate (1) and the semi-annular sleeves (2) being opposite, a transverse support plate (4) being fixed on the arch surface of the plurality of flat arch plates (1), both ends of the transverse support plate (4) being fixedly connected with transverse connecting rods (5), the other ends of the two transverse connecting rods (5) being respectively fixed on the first and last semi-annular sleeves (2), and each of the flat arch plates (1) being provided with a circular hole (3) corresponding to the longitudinal horizontal distribution steel bar (8); The flat arch plate (1) is a plate with ribs on the surface, the flat arch plate (1) has a curved longitudinal section along the horizontal direction, and the axis of the flat arch plate (1) is a parabola or a catenary; The flat arch plate (1) and the semi-annular sleeve (2) are installed in the web plate (6) within a certain distance range of the end anchorage area along the length direction of the small box girder, the semi-annular sleeve (2) is nested on the stirrup (7), the upper ends of the flat arch plate (1) and the semi-annular sleeve (2) extend into the top plate frame steel bars (9) and are connected thereto by welding, and the lower ends of the flat arch plate (1) and the semi-annular sleeve (2) extend into the bottom plate frame steel bars (10) and are connected thereto by welding.

2. A device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder according to claim 1, characterized in that: The flat arch plate (1) and the semi-annular sleeve (2) are connected by welding.

3. A device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder according to claim 1, characterized in that: The transverse support plate (4) is fixed on the arch surfaces of the plurality of flat arch plates (1) by welding and is located at a position in the middle of the height of the flat arch plates (1).

4. A device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder according to claim 3, characterized in that: The two ends of the transverse connecting rod (5) are respectively welded to the transverse supporting plate (4) and the semi-annular sleeve (2).

5. The device for preventing oblique cracks in the web of the anchorage area at the end of a prestressed small box girder according to claim 1 is characterized in that: When using it, please follow the steps below: Step 1, connecting the flat arch plate (1) and the semi-annular sleeve (2) by welding; Step 2, after the binding of the stirrups (7), the top plate frame steel bars (9), and the bottom plate frame steel bars (10) is completed, according to the influence range of the beam end anchorage area, the flat arch plate (1) and the semi-annular sleeve (2) are installed in the web plate (6) within a certain distance range of the end anchorage area along the beam length direction, and the semi-annular sleeve (2) is nested on the stirrups (7), the upper ends of the flat arch plate (1) and the semi-annular sleeve (2) extend into the top plate frame steel bars (9) and are connected thereto by welding, and the lower ends of the flat arch plate (1) and the semi-annular sleeve (2) extend into the bottom plate frame steel bars (10) and are connected thereto by welding; Step 3, after the flat arch plate (1) and the semi-annular sleeve (2) are fixed in place, the longitudinal horizontal distribution steel bars (8) arranged on both sides of the stirrups (7) are passed through the circular hole (3); Step 4, connecting the transverse support plate (4) to the middle part of the flat arch plate (1) by welding, and then welding one end of the transverse connecting rod (5) to the semi-annular sleeve (2), and welding the other end to the end of the transverse support plate (4); Step 5, during the concrete pouring process, in the range of the web (6) where a device for preventing oblique cracks in the web of the anchorage area at the end of the prestressed small box girder is installed, vibrating the concrete to ensure that the concrete is dense.

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