A precast pavement slab with prestressing characteristics for compensating slab end stress

Abstract

The present invention discloses a precast pavement slab with end-stress compensation properties. The precast pavement slab comprises a slab body, a self-stress compensation device, and a concrete isolation device. The slab body is constructed of ordinary concrete and multiple steel strands. The self-stress compensation device comprises expansive concrete, self-stressing steel bars, and a self-stressing plate. The ends of the steel strands are cast in the expansive concrete, and a self-stressing plate is installed in the expansive concrete at the end of each steel strand. The self-stressing steel bars are positioned around the strands, with their outer ends fixed to the inner wall of the self-stressing plate. The length of the self-stressing steel bars is no less than the stress transfer length of the strands. The precast pavement slab of the present invention achieves a complementary effect, with the steel strands gradually reaching their designed values within the transfer length from zero at the slab ends in the expansive concrete, thereby compensating for the insufficient stress at the slab ends and ensuring the durability of the self-stressing plate.

Description

Technical Field

[0001] The present invention relates to a pavement prefabricated plate, and more particularly to a pavement prefabricated plate with the characteristic of compensating plate end stress. Background Art

[0002] Reinforced concrete road slabs are prone to cracking, which in turn leads to corrosion of the steel bars and poor durability. Post-tensioned precast slabs are subject to significant temperature fluctuations in grouting, are difficult to compact, and offer limited rust protection for the steel strands. Furthermore, the anchor concrete at the slab ends is difficult to support and exhibits poor adhesion to the slab ends. Pre-tensioned precast slabs, after the steel strands are released, have a transfer length at both ends of the prestressed steel strands. The stress gradually increases from zero at the slab ends to the design value within this transfer length. Therefore, stress at the slab ends within this transfer length does not meet the design requirements, necessitating stress compensation. This patent discloses a pavement pre-tensioned precast slab structure that compensates for slab end stress. Expansive concrete is poured within the stress transfer length of the steel strands at both ends of the slab, and self-stressing tendons of a certain length welded to the self-stressing tensioning plate are arranged. The expansion of the concrete causes the tensioning plate to move outward, and the self-stressing tensioning plate drives the self-stressing steel bars to be tensioned. The self-stressing steel bars apply pressure to the slab ends in reverse to generate self-stress. The length of the self-stressing steel bars is set to be greater than the stress transfer length of the steel strands. The self-stress generation range of the self-stressing steel bars is consistent with the stress transfer length of the steel strands, and the self-stress size decreases from large to small from the slab ends, thereby compensating for the insufficient stress at the slab ends of the pre-tensioned precast slabs. Summary of the Invention

[0003] In order to overcome the disadvantages of the above technical problems, the present invention provides a pavement pre-tensioned prefabricated slab with the characteristic of compensating the stress at the slab ends.

[0004] The pavement prestressed slab with the characteristic of compensating slab end stress of the present invention is composed of a slab body, a self-stress compensating device and a concrete isolation device. The slab body is composed of ordinary concrete and a plurality of steel strands uniformly cast in the ordinary concrete, and self-stress compensating devices are provided on both sides of the ordinary concrete; the characteristic is that the self-stress compensating device is composed of expansive concrete, self-stressing steel bars and a self-stressing tensioning plate, the expansive concrete is located on the outside of the ordinary concrete, and the concrete isolation device is located between the ordinary concrete and the expansive concrete; both ends of the steel strand are cast in the expansive concrete, a self-stressing tensioning plate is provided in the expansive concrete at the end of each steel strand, and a steel strand reserved hole for the steel strand to pass through is opened in the center of the self-stressing tensioning plate; the self-stressing steel bars are located on the periphery of the steel strand and their direction is consistent with the direction of the steel strand, the outer end of the self-stressing steel bar is fixed on the inner wall of the self-stressing tensioning plate, and the self-stressing steel bar is cast in the expansive concrete; the length of the self-stressing steel bar is not less than the stress transfer length of the steel strand.

[0005] The pavement prestressed slab with the characteristic of compensating for plate end stress of the present invention has four self-stressed steel bars around the outer end of each steel strand, and the four self-stressed steel bars are distributed on the vertices of a square centered on the steel strand. The diameters and models of the four self-stressed steel bars are the same, and the resultant force of the four self-stressed steel bars on the self-stressed tensioning plate coincides with the steel strand; the four self-stressed steel bars are tied with stirrups at equal intervals along their length.

[0006] The pavement pre-tensioned precast slab of the present invention has the characteristic of compensating for the stress at the slab ends, and the concrete isolation device is perpendicular to the bottom surface and both end surfaces of the pre-tensioned precast slab. The concrete isolation device is composed of a single-layer fine-mesh steel wire mesh, a plurality of transverse stand steel bars and a plurality of vertical stand steel bars. The fine-mesh steel wire mesh is tied together with the transverse stand steel bars and the vertical stand steel bars by tying steel wires, and a stand steel bar cross base is fixed to the lower end of the vertical stand steel bars.

[0007] The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress of the present invention has a tension of not less than 3 MPa applied to the self-stressed tensioning slab by the self-stressed steel bars after the expansion of the expansive concrete.

[0008] The pavement pre-tensioned precast slab of the present invention has the characteristic of compensating for the stress at the plate ends, wherein the height of the self-stressed tensioned slab is equal to the thickness of the pre-stressed precast slab, and the self-stressed steel bars are vertically welded to the self-stressed tensioned slab via welding points; the self-stressed steel bars are secondary steel bars, and the length of the self-stressed steel bars is not less than 30 times of their diameter.

[0009] The pavement pre-tensioned precast slab of the present invention has the characteristic of compensating the stress at the slab end, wherein the height of the steel strand from the bottom of the pre-tensioned precast slab is equal to half the thickness of the pre-tensioned precast slab, and the steel strand is a high-strength, low-relaxation type steel strand.

[0010] The pavement pre-tensioned prefabricated slab with the characteristic of compensating slab end stress of the present invention has a slab body and a self-stress compensating device both in the shape of a rectangular parallelepiped.

[0011] The pavement pre-tensioned prefabricated slab of the present invention has the characteristic of compensating for slab end stress. The length of the pre-tensioned prefabricated slab is 6.9-9.0 m, the width is 3.5-4.0 m, the thickness is 20-24 cm, and the grade of ordinary concrete is 40-45 MPa; the height of the self-stressed tensioned slab is 20-24 cm, the width is 15-18 cm, and the thickness is 0.4-0.6 cm; the diameter of the self-stressed steel bar is 20-22 mm, and the length of the self-stressed steel bar is 60-70 cm; the diameter of the steel strand is 12.7 mm, and the tensile strength is not less than 1860 MPa.

[0012] The beneficial effects of the present invention are as follows: the pavement pre-tensioned precast slab of the present invention is provided with self-stress compensation devices on both sides of the slab body, the self-stress compensation devices are composed of expansive concrete, self-stressed steel bars cast in the expansive concrete, and self-stressed tensioning plates fixed to the outside of the expansive concrete, and the self-stressed steel bars are fixedly connected to the self-stressed tensioning plates. In this way, the self-stressed steel bars are tensioned during the expansion of the expansive concrete, so that the tension of the self-stressed steel bars acts on the self-stressed tensioning plates, so that the expansive concrete is subjected to a pressure gradually increasing from the outside to the inside. This pressure gradually decreasing from the outside end to the inside realizes the complementarity of the steel strands in the expansive concrete from zero at the slab end to the design value within the transfer length, thereby compensating for the insufficient stress at the slab end of the pre-tensioned slab and ensuring the firmness and durability of the self-stressed tensioning plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a front view of a pavement pre-tensioned prefabricated slab with the characteristic of compensating slab end stress according to the present invention;

[0014] Figure 2 It is a left view of the pavement pre-tensioned prefabricated slab with the characteristic of compensating slab end stress of the present invention;

[0015] Figure 3 A top view of a pavement pre-tensioned prefabricated slab with the characteristic of compensating slab end stress according to the present invention;

[0016] Figure 4 A three-dimensional diagram of the connection between the self-stressed steel bar and the self-stressed tensioning plate in the present invention;

[0017] Figure 5 It is a structural schematic diagram of the concrete isolation device in the present invention.

[0018] In the figure: 1 ordinary concrete, 2 expansive concrete, 3 fine mesh steel wire mesh, 4 steel strand, 5 self-stressed steel bars, 6 self-stressed tensioning plate, 7 cross base for erection steel bars, 8 reserved holes for steel strands, 9 stirrups, 10 pre-tensioned precast slab, 11 welding point, 12 horizontal erection steel bars, 13 vertical erection steel bars, 14 tying wire. Implementation Method

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] During the production process of pre-tensioned precast panels, the tensioning platforms on both sides apply tension to the outer ends of the steel strands 4. After the concrete solidifies (strength reaches a certain requirement), the tensioning platforms release the tension on the steel strands 4 and cut off the steel strands 4 protruding from the sides of the precast panel. In this way, due to the certain slippage of the ends of the steel strands 4, the stress of the precast panel gradually reaches the design value from zero within the transfer length. That is, after the steel strands are released, the stress transfer of the steel strands at the panel ends requires a certain length, such as Figure 1 As shown in the figure, the stress in the precast panel gradually increases from zero from point A to point A'. Similarly, the stress in the precast panel also gradually increases from zero from point B to point B' until it reaches the design value. The distance from point A to point A' is the stress transfer length, L, and the distance from point B to point B' is the stress transfer length, M, where L = M. Therefore, insufficient stress exists within the stress transfer length at the end of the precast panel. The pavement pretensioning precast panel of the present invention, which has the characteristic of compensating for panel end stress, addresses this problem.

[0021] like Figure 1 、 Figure 2 and Figure 3 The figure shows the front, left, and top views of a pre-tensioned pavement slab with end-stress compensation properties according to the present invention. The pre-tensioned slab 10 comprises a slab body, a self-stress compensating device, and a concrete isolation device. The slab body is composed of ordinary concrete 1 and multiple steel strands 4 evenly spaced within the ordinary concrete 1. The self-stress compensating device comprises expansive concrete 2, self-stressing tensioning plates 5, and self-stressing steel bars 5. The concrete isolation device separates the ordinary concrete 1 from the expansive concrete 2 to prevent mixing during the pouring process. The self-stress compensating device is installed on both sides of the ordinary concrete 1, and both ends of the steel strands 4 are cast within the expansive concrete 2. The concrete isolation device is perpendicular to the bottom and both end surfaces of the pre-tensioned slab 10. This ensures a vertical interface between the expansive concrete 2 and the ordinary concrete 1. This ensures that the expansive concrete 2 in the compensation device exerts a vertical force on the slab body as it expands outward, resulting in uniform force within the slab body.

[0022] Self-stressing plates 6 are fixed in the expansive concrete 2 at both ends of the steel strands 4. Four self-stressing steel bars 5 are positioned around the periphery of each steel strand 4, oriented in the same direction as the strands 4. The outer ends of the self-stressing steel bars 5 are fixed to the inner wall of the self-stressing plates 6, while the inner ends are free. A steel strand hole 8 is provided in the center of the self-stressing plates 6, through which the steel strands 4 pass. The length of the self-stressing steel bars 5 is no less than the stress-transfer length of the steel strands 4.

[0023] It can be seen that during the pouring of the pre-tensioned precast slab 10, the expansion of the expansive concrete 2 causes the self-stressed tensioning plate 6 to move outward, and the self-stressed tensioning plate 6 drives the self-stressed steel bars 5 to be tensioned. The self-stressed steel bars 5 apply a pressure from large to small from the outer end to the inner end to the self-stressed tensioning plate 6 in reverse, thereby compensating for the lack of stress at the end of the pre-stressed precast slab 10.

[0024] like Figure 4The figure shows a three-dimensional diagram of the connection between the self-stressing steel bars and the self-stressing tensioning plate according to the present invention. Four self-stressing steel bars 5 are shown around the outer ends of each steel strand 4, distributed at the vertices of a square centered on the steel strand 4. Stirrups 9 are evenly spaced along the length of the four self-stressing steel bars 5. Thus, the self-stressing steel bars 5 and stirrups 9, cast in the expansive concrete 2, exert tension on the self-stressing tensioning plate 6. The four self-stressing steel bars 5 are of the same diameter and type, ensuring that the compensating stresses applied by the four self-stressing steel bars 5 are equal in magnitude. This ensures that the combined tensile force exerted by the four self-stressing steel bars 5 on the self-stressing tensioning plate 6 coincides with that of the steel strand 4, preventing uneven stress compensation.

[0025] like Figure 5 As shown, a structural schematic diagram of the concrete isolation device in the present invention is given. The concrete isolation device shown is composed of a single-layer dense steel wire mesh 3, a plurality of transverse frame steel bars 12 and a plurality of vertical frame steel bars 13. The single-layer dense steel wire mesh 3 is tied to the transverse frame steel bars 12 and the vertical frame steel bars 13 through binding wires 14. The lower end of the vertical frame steel bars 13 is fixed with a frame steel bar cross base 7. The frame steel bar cross base 7 plays a fixing and supporting role to ensure the stability of the concrete isolation device during the casting of the precast plate.

[0026] After the expansion of the expansive concrete 2, the tensile force exerted on the self-stressing plate 6 by the self-stressing steel bars 5 is no less than 3 MPa. The height of the self-stressing plate 6 is equal to the thickness of the pre-tensioned precast slab 10. The self-stressing steel bars 5 are welded perpendicularly to the self-stressing plate 6 at welding points 11. The self-stressing steel bars 5 are grade-two steel bars, and their length is no less than 30 times their diameter. The height of the steel strands 4 from the bottom of the pre-tensioned precast slab 10 is equal to half the thickness of the pre-tensioned precast slab 10. The steel strands 4 are high-strength, low-relaxation steel strands.

[0027] As a specific size, the length of the prestressed precast panel 10 shown is 6.9~9.0m, the width is 3.5~4.0m, and the thickness is 20~24cm. The grade of ordinary concrete 1 is 40~45MPa; the height of the self-stressed tensioning plate is 20~24cm, the width is 15~18cm, and the thickness is 0.4~0.6cm; the diameter of the self-stressed steel bar 5 is 20~22mm, and the length of the self-stressed steel bar is 60~70cm; the diameter of the steel strand 4 is 12.7mm, and the tensile strength is not less than 1860MPa.

Claims

1. A pre-tensioned pavement slab with a characteristic of compensating slab end stress, the pre-tensioned slab (10) consisting of a slab body, a self-stress compensating device, and a concrete isolation device, the slab body consisting of ordinary concrete (1) and a plurality of steel strands (4) uniformly cast in the ordinary concrete, the self-stress compensating device being provided on both sides of the ordinary concrete; characterized in that: The self-stress compensation device is composed of expansive concrete (2), self-stressed steel bars (5) and self-stressed tensioning plates (6), wherein the expansive concrete is located outside the ordinary concrete, and the concrete isolation device is located between the ordinary concrete and the expansive concrete; both ends of the steel strand are cast in the expansive concrete, a self-stressed tensioning plate is provided in the expansive concrete at the end of each steel strand, and a steel strand reserved hole for the steel strand to pass through is provided in the center of the self-stressed tensioning plate; the self-stressed steel bars are located outside the steel strand and their direction is consistent with the direction of the steel strand, the outer ends of the self-stressed steel bars are fixed on the inner wall of the self-stressed tensioning plate, and the self-stressed steel bars are cast in the expansive concrete; the length of the self-stressed steel bars is not less than the stress transfer length of the steel strand.

2. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1, characterized in that: The number of self-stressed steel bars (5) outside the outer end of each steel strand (4) is 4, and the 4 self-stressed steel bars are distributed at the vertices of a square centered on the steel strand. The diameters and types of the 4 self-stressed steel bars are the same, and the resultant force of the 4 self-stressed steel bars on the self-stressed tensioning plate (6) coincides with the steel strand; stirrups (9) are tied to the 4 self-stressed steel bars (5) at equal intervals along their length direction.

3. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: The concrete isolation device is perpendicular to the bottom surface and both end surfaces of the prestressed precast slab (10), and is composed of a single-layer fine-mesh steel wire mesh (3), a plurality of transverse frame steel bars (12), and a plurality of vertical frame steel bars (13). The fine-mesh steel wire mesh is tied together with the transverse frame steel bars and the vertical frame steel bars via tying wires (14), and a frame steel bar cross base (7) is fixed to the lower end of the vertical frame steel bars.

4. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: After the expansion of the expansive concrete (2), the tension applied to the self-stressed tensioning plate (6) by the self-stressed steel bars (5) is between 3 and 5 MPa.

5. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: The height of the self-stressed tensioning plate (6) is equal to the thickness of the pre-tensioned prefabricated plate (10), and the self-stressed steel bars (5) are vertically welded to the self-stressed tensioning plate via welding points (11); the self-stressed steel bars are secondary steel bars, and the length of the self-stressed steel bars is not less than 30 times their diameter.

6. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: The height of the steel strand (4) from the bottom of the pre-tensioned prefabricated plate (10) is equal to half the thickness of the pre-tensioned prefabricated plate, and the steel strand is a high-strength, low-relaxation type steel strand.

7. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: The plate body and the self-stress compensation device are both in the shape of a cuboid.

8. The pavement pre-tensioned precast slab with the characteristic of compensating slab end stress according to claim 1 or 2, characterized in that: The length of the prestressed prefabricated plate (10) is 6.9-9.0 m, the width is 3.5-4.0 m, and the thickness is 20-24 cm. The grade of the ordinary concrete (1) is 40-45 MPa. The height of the self-stressed tensioning plate is 20-24 cm, the width is 15-18 cm, and the thickness is 0.4-0.6 cm. The diameter of the self-stressed steel bar (5) is 20-22 mm, and the length of the self-stressed steel bar is 60-70 cm. The diameter of the steel strand (4) is 12.7 mm, and the tensile strength is not less than 1860 MPa.

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