A prestressed tendon lever-type in-situ tensioning device and a method of using the same

Abstract

The application provides a prestressed tendon lever type in-situ tensioning device and a use method thereof, and belongs to the technical field of bridge construction equipment. One end of a fixed vertical rod of the tensioning device is used for fixing an in-situ prestressed tendon, and the other end of the fixed vertical rod is fixed with one end of a fixed cross beam. One end of a rotating vertical rod is used for fixing the in-situ prestressed tendon, and the other end of the rotating vertical rod is hinged with a hinged end of the fixed cross beam. A piston end of a jack is connected with the rotating vertical rod. A rod body of the rotating vertical rod is provided with an opening in a relative position of the check rod, the opening is used for installing a check bolt, and the check bolt is used for locking the in-situ prestressed tendon after tensioning. The prestressed tendon can be supplemented in-situ, so that the stress of the prestressed tendon is ensured not to be lost when the bridge is repaired.

Description

Technical Field

[0001] This invention provides a lever-type in-situ tensioning device for prestressed tendons and its usage method, belonging to the technical field of bridge construction equipment. Background Technology

[0002] Prestressed concrete hollow slab bridges using the prestressed concrete method are a commonly used structural form for small and medium-span bridges. Due to their lightweight, cost-effectiveness, and ease of construction, prestressed concrete hollow slabs are widely used in both highway and urban bridges. However, prestressed concrete hollow slabs also have their drawbacks. Insufficient compaction of the concrete under the hollow slab often leads to cracking in that area, as well as corrosion of the prestressing tendons and reinforcing bars, thus affecting the bridge's load-bearing capacity and normal use. This is especially true for prestressed hollow slab beams using the foam core molding process, where abnormal bottom slab thickness is common, and exposed or corroded steel strands are frequently observed. Currently, common reinforcement and repair methods for addressing the aforementioned problems include external prestressing, bonding steel plates or fiber composite materials, and increasing the cross-section. The disadvantages of external prestressing include the need to address the localized stress generated in the external prestressing anchorage zone, the need to drill holes in the slab to install prestressing steel reinforcement bundles which can damage the original hollow slab, and the high cost of corrosion protection for the external prestressing tendons. While bonding steel plates or fiber composite materials to reinforce bridges carries the risk of delamination from the hollow slab under long-term repeated vehicle loads, and the need to drill holes in the surface of the hollow slab to install anchor bolts to strengthen the connection can also damage the prestressed concrete hollow slab, affecting its durability. Increasing the cross-section alters the beam height after reinforcement, making this method unsuitable, especially when bridge clearance is limited. Summary of the Invention

[0003] The purpose of this invention is to provide a lever-type in-situ tensioning device for prestressed tendons in pre-tensioned hollow slab beams and its usage method, in order to solve the technical problem that often occurs at the bottom of pre-tensioned hollow slab beams, where the concrete under the cavity is not densely poured, or especially after adopting the new process of in-cavity foam core mold, resulting in insufficient thickness of the bottom slab of the hollow slab beam, and the steel strands cannot be effectively anchored under long-term loads, thus affecting the load-bearing capacity and normal use of the bridge.

[0004] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0005] The present invention discloses a lever-type in-situ tensioning device for prestressed tendons, which acts on the in-situ prestressed tendons of hollow slab beams. It includes a jack, a check rod, a rotating vertical rod, a fixed vertical rod, and a fixed horizontal beam. One end of the fixed vertical rod is used to fix the in-situ prestressed tendon, and the other end of the fixed vertical rod is fixed to one end of the fixed horizontal beam. The other end of the fixed horizontal beam is a hinged end. One end of the rotating vertical rod is used to fix the in-situ prestressed tendon, and the other end of the rotating vertical rod is hinged to the hinged end of the fixed horizontal beam.

[0006] A check rod is provided on the body of the fixed vertical rod, and a jack is arranged on the check rod. The piston end of the jack is connected to the rotating vertical rod. An opening is provided on the body of the rotating vertical rod relative to the check rod. The opening is used to install a check bolt, which is used to lock the stress of the in-situ prestressed tendon after tensioning.

[0007] The lever-type in-situ tensioning device for prestressed tendons described in this invention further includes a V-shaped anchor and a V-anchor bolt; the V-shaped anchor is locked onto the in-situ prestressed tendon by the V-anchor bolt.

[0008] The fixed vertical rod and the fixed end of the in-situ prestressing tendon are provided with a first U-shaped groove, and are fixed to the in-situ prestressing tendon by a first fixing bolt;

[0009] The rotating vertical rod and the fixed end of the in-situ prestressing tendon are provided with a second U-shaped groove, which is fixed to the in-situ prestressing tendon by a second fixing bolt; the V-shaped anchor is arranged on the other side of the rotating vertical rod relative to the fixed vertical rod.

[0010] The lever-type in-situ tensioning device for prestressed tendons of the present invention has a first hemispherical hinge at the piston end of the jack; and a second hemispherical hinge is provided between the V-shaped anchor and the second U-shaped groove.

[0011] The lever-type in-situ tensioning device for prestressed tendons of the present invention has a U-shaped anchor plate on one side of the first U-shaped groove.

[0012] The fixed vertical rod has a first rectangular hole and a second rectangular hole at its lower part; the rotating vertical rod has a third rectangular hole and a fourth rectangular hole at its lower part.

[0013] The tensioning method of the prestressed tendon lever-type in-situ tensioning device of the present invention comprises the following steps:

[0014] Step 1: Determine the effective length and failure length of the in-situ prestressed tendons of the pre-tensioned hollow slab beam to be repaired;

[0015] Step 2: Open a hole at the bottom of the prestressed concrete hollow slab beam near the end of the hollow slab where the in-situ prestressed tendons fail, so that the steel bars and in-situ prestressed tendons inside the prestressed concrete hollow slab are completely exposed.

[0016] Step 3: After checking that the in-situ prestressing tendons are intact, install the tensioning device;

[0017] Step 4: Use the jacks in the tensioning device to tension the prestressed tendons in batches until the tension force of the in-situ prestressed tendons reaches the design requirement, then stop applying pressure.

[0018] Step 5: Align the hemispherical groove on one side of the check rod and tighten the check bolt;

[0019] Step 6: Perform rust and corrosion prevention treatment on the in-situ prestressing tendons and steel bars, and re-pour concrete. After the concrete, in-situ prestressing tendons and steel bars are repaired, loosen the check bolts so that the prestress of the in-situ prestressing tendons in the failed section gradually decreases until it is zero. Remove the tensioning device and seal the opening excavated in Step 2.

[0020] The tensioning method of the prestressed tendon lever-type in-situ tensioning device of the present invention, wherein the step of installing the tensioning device in step 3 is as follows:

[0021] (1) Embed the in-situ prestressed tendons into the first U-shaped groove and the second U-shaped groove of the rotating vertical rod and the fixed vertical rod, and tighten the first U-shaped groove and the second U-shaped groove with the first fixing bolt and the second fixing bolt to keep the first U-shaped groove and the second U-shaped groove in close contact with the in-situ prestressed tendons;

[0022] (2) V-shaped anchors are arranged on the in-situ prestressing tendons at the outer end of the rotating vertical bar. The V-shaped anchors are installed on the in-situ prestressing tendons using wedges and V-anchor bolts.

[0023] (3) Place the jack horizontally on the check rod, ensuring that the piston rod of the jack is in close contact with the rotating vertical rod. Installation is now complete.

[0024] In step 4 of the tensioning method of the prestressed tendon lever-type in-situ tensioning device described in this invention...

[0025] Let the final tension of the prestressing tendon be F1, the external force provided by the jack be F2, and the self-locking internal force of the check bolt be F3; let L be the distance from the center of the prestressing tendon to the center of the pin, L2 be the distance from the center of the jack piston rod to the center of the pin, and L3 be the distance from the center of the check bolt to the center of the pin; the final tension of the prestressing tendon is:

[0026] F1 = (L2 / L1)F2

[0027] Based on the oil pressure gauge reading, when the reading starts to decrease, continue to tighten the check bolt until the internal force of the check bolt reaches F3=(L2 / L3)F2. At this time, the oil pressure gauge reading is zero, the check bolt is finally tightened, and the jack is removed.

[0028] Beneficial effects

[0029] The present invention provides a lever-type in-situ tensioning device for prestressed tendons and its method of use, which has the following advantages: the present invention can perform supplementary tensioning of prestressed tendons in situ, so that the stress of the prestressed tendons is not lost during bridge repair.

[0030] The prestressed tendon lever-type in-situ tensioning device of the present invention has a simple overall structure, is convenient to use, improves work efficiency, solves construction problems, saves investment costs, has strong practicality, and is worthy of promotion and application. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the lever-type in-situ tensioning device for prestressed tendons according to the present invention;

[0032] Figure 2 This is a structural side view of the fixing frame of the lever-type in-situ tensioning device for prestressed tendons according to the present invention;

[0033] Figure 3 This is another side view of the structure of the fixing frame for the lever-type in-situ tensioning device for prestressed tendons according to the present invention;

[0034] Figure 4 This is a schematic diagram illustrating the application scenario of the lever-type in-situ tensioning device for prestressed tendons according to the present invention;

[0035] Figure 5 This is a schematic diagram of the V-shaped anchor structure of the present invention;

[0036] The markings in the diagram are as follows: 1. Prestressed tendon; 2. V-shaped anchor; 3. Second U-shaped groove; 4. Second fixing bolt; 5. First fixing bolt; 6. First U-shaped groove; 7. U-shaped anchor plate; 8. Jack; 9. Clamping plate; 10. V-anchor bolt; 11. Second hemispherical hinge; 12. Check bolt; 13. Check rod; 14. Hemispherical groove; 15. Rotating vertical rod; 16. Pin; 17. Fixed vertical rod; 18. Fixed crossbeam; 19. Second rectangular hole; 20. First rectangular hole; 21. Third rectangular hole; 22. Fourth rectangular hole; 23. First hemispherical hinge. Detailed Implementation

[0037] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 , Figure 2 , Figure 3The diagram shows a structural schematic of a lever-type in-situ tensioning device for prestressed tendons according to the present invention, including a fixed vertical rod 17, a fixed horizontal beam 18, a rotating vertical rod 15, a check rod 13, and a check bolt 12.

[0039] The lower end of the fixed vertical rod 17 is rigidly connected to the left end of the fixed horizontal beam 18 by welding; the lower end of the rotating vertical rod 15 is hinged to the right end of the fixed horizontal beam 18 by a pin 16, and the rotating vertical rod 15 rotates around the pin 16.

[0040] The upper end of the fixed vertical rod 17 is provided with a first U-shaped groove 6, and the upper end of the rotating vertical rod 15 is provided with a second U-shaped groove 3; the first U-shaped groove 6 and the second U-shaped groove 3 are used to place the in-situ prestressing tendon 1, the first U-shaped groove 6 and the first fixing bolt 5 are used to fix one end of the in-situ prestressing tendon 1, and the second U-shaped groove 3 and the second fixing bolt 4 are used to fix the other end of the in-situ prestressing tendon 1.

[0041] A check rod 13 is installed slightly above the left fixed vertical rod 17 and is rigidly connected to the left fixed vertical rod 17. A hemispherical groove 14 is provided at the right end of the check rod 13 for anchoring the check bolt 12. The jack 8 rests on the check rod 13.

[0042] The piston end of the jack 8 is placed on one side of the rotating vertical rod 15, and the rotating vertical rod 15 is provided with a first hemispherical hinge 23 at the position corresponding to the piston of the jack 8.

[0043] like Figure 5 The diagram shows a schematic of the V-shaped anchor 2. A V-shaped anchor 2 and a V-anchor bolt 10 are located on the right side of the second U-shaped groove 3. A second hemispherical hinge 11 is positioned between the V-shaped anchor 2 and the second U-shaped groove 3 to ensure that the prestressing tendon is under axial stress during tensioning. A clamping piece 9 is installed at the corresponding position of the in-situ prestressing tendon 1 on the V-shaped anchor 2. A hole is drilled on the rotating vertical rod 15 at the position corresponding to the check rod 13, and a check bolt 12 is installed thereon. The check bolt 12 is used to lock the stress of the in-situ prestressing tendon 1 after tensioning.

[0044] The left side of the first U-shaped groove 6 is provided with a U-shaped anchor plate 7, which is in contact with the concrete.

[0045] The lower part of the fixed vertical rod 17 is provided with a first rectangular hole 20 and a second rectangular hole 19. The lower part of the rotating vertical rod 15 is provided with a third rectangular hole 21 and a fourth rectangular hole 22 to reduce the weight of the tensioning device.

[0046] like Figure 4 The following steps are shown in the diagram: The method of using a lever-type in-situ tensioning device for prestressed tendons.

[0047] Step 1: Determine the effective length and failure length of the in-situ prestressed tendon 1 in the prestressed concrete hollow slab to be repaired.

[0048] Step 2: Make a hole in the bottom of the prestressed concrete hollow slab. The hole is located at the end of the in-situ prestressing tendon 1 failure section near the hollow slab. The planar dimensions of the hole are sufficient to install the tensioning device, and the depth is the thickness of the concrete slab below the cavity of the prestressed concrete hollow slab.

[0049] Step 3: After drilling, fully expose the reinforcing bars and in-situ prestressing tendons 1 inside the prestressed concrete hollow slab. Remove the corrugated pipe on the surface of the in-situ prestressing tendon 1, check that the in-situ prestressing tendon 1 is intact, and then install the tensioning device. First, place the in-situ prestressing tendon 1 into the first U-shaped groove 6 and the second U-shaped groove 3, and tighten the first fixing bolt 5 and the second fixing bolt 4; install the V-shaped anchor 2, the clamp 9, and the V-anchor bolt 10 on the right end onto the in-situ prestressing tendon 1; place the jack 8 horizontally on the check rod 13, with the bottom of the jack 8 pressed against the fixed vertical rod 17 on the left, and the piston rod of the jack 8 in close contact with the rotating vertical rod 15. Install the oil pipe, pressure gauge, and oil pump.

[0050] Step 4: Calibrate the jack 8 and its supporting equipment. Before tensioning, conduct a comprehensive inspection to ensure that all components are correctly installed. After completion, turn on the oil pump and tension in batches according to the design requirements. Observe the pressure gauge and stop pressurizing after the tension of the in-situ prestressing tendon 1 reaches the design required tension. The final tension of the prestressing tendon 1 is F1, the external force provided by the jack 8 is F2, and the self-locking internal force of the check bolt 12 is F3. The distance from the center of the prestressing tendon 1 to the center of the pin 16 is L, the distance from the center of the piston rod of the jack 8 to the center of the pin 16 is L2, and the distance from the center of the check bolt 12 to the center of the pin 16 is L3. The final tension of the prestressing tendon 1 is F1 = (L2 / L1)F2, that is, the final tension of the prestressing tendon needs to be calculated based on the lever formula and the tension provided by the jack.

[0051] Step 5: After the tensioning device is held in the tensioning position by jack 8, align the hemispherical groove on one side of the check rod 13 and screw the check bolt 12, which is aligned with the check rod 13, into the check rod 13 to lock the check bolt 12 and the check rod 13 together. During this process, gradually tighten the check bolt 12 with a torque wrench. When the internal force of the check bolt 12 reaches a certain value, carefully observe the reading of the oil pressure gauge. When the reading begins to decrease, continue to tighten the check bolt 12 until the internal force of the check bolt 12 reaches F3 = (L2 / L3)F2. At this time, the oil pressure gauge reading is zero, the check bolt 12 is finally tightened, and the jack 8 is removed.

[0052] Step 6: Remove the concrete that needs to be repaired to fully expose the in-situ prestressing tendon 1. Then, perform anti-rust and anti-corrosion treatment on the in-situ prestressing tendon 1 and the reinforcing steel. After the treatment is completed, re-pour the concrete. After the concrete, in-situ prestressing tendon 1 and reinforcing steel are repaired, slowly loosen the check bolt 12 so that the prestress of the in-situ prestressing tendon 1 in the failed section gradually decreases until it is zero. Remove the tensioning device and seal the opening with concrete to restore the prestressed concrete hollow slab to its original state.

[0053] This invention's method of partially replacing concrete effectively solves quality defects such as concrete cracking and prestressing tendon corrosion without altering the bridge's appearance. For bonded prestressing tendons in prestressed concrete hollow slabs, prestress is lost after concrete removal. Therefore, the prestressing tendons in the hollow prestressed concrete slab should be tensioned and anchored in situ before concrete replacement to ensure no loss of internal force after concrete removal. This equipment can perform in-situ tensioning and anchoring of the prestressing tendons, thereby resolving quality defects in the prestressed hollow concrete slab and prestressing tendons.

[0054] This invention has been described through several embodiments. Those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of this invention, modifications can be made to these features and embodiments to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention.

Claims

1. A lever-type in-situ tensioning device for prestressed tendons, acting on in-situ prestressed tendons (1) of hollow slab beams, characterized in that: Includes a jack (8), a check rod (13), a rotating vertical rod (15), a fixed vertical rod (17), and a fixed crossbeam (18). One end of the fixed vertical rod (17) is used to fix the in-situ prestressed tendon (1), and the other end of the fixed vertical rod (17) is fixed to one end of the fixed crossbeam (18); The other end of the fixed crossbeam (18) is a hinged end. One end of the rotating vertical rod (15) is used to fix the in-situ prestressed tendon (1), and the other end of the rotating vertical rod (15) is hinged to the hinge end of the fixed crossbeam (18). A check rod (13) is provided on the rod body located on the fixed vertical rod (17), and a jack (8) is arranged on the check rod (13). The piston end of the jack (8) is connected to the rotating vertical rod (15). The rotating vertical rod (15) has an opening at the position opposite to the check rod (13). The opening is used to install the check bolt (12), and the check bolt (12) is used to lock the in-situ prestressed tendon (1) after tensioning. It also includes a V-shaped anchor (2) and a V-anchor bolt (10); the V-shaped anchor (2) is locked to the in-situ prestressing tendon (1) by the V-anchor bolt (10); The fixed vertical rod (17) and the fixed end of the in-situ prestressing tendon (1) are provided with a first U-shaped groove (6), and are fixed to the in-situ prestressing tendon (1) by the first fixing bolt (5); The rotating vertical rod (15) and the fixed end of the in-situ prestressing tendon (1) are provided with a second U-shaped groove (3), which is fixed to the in-situ prestressing tendon (1) by a second fixing bolt (4); The V-shaped anchor (2) is arranged on the other side of the rotating vertical rod (15) relative to the fixed vertical rod (17).

2. The lever-type in-situ tensioning device for prestressed tendons according to claim 1, characterized in that, The piston end of the jack (8) is provided with a first hemispherical hinge (23); the V-shaped anchor (2) and the second U-shaped groove (3) are provided with a second hemispherical hinge (11).

3. The lever-type in-situ tensioning device for prestressed tendons according to claim 1, characterized in that, A U-shaped anchor plate (7) is provided on one side of the first U-shaped groove (6); The fixed vertical rod (17) has a first rectangular hole (20) and a second rectangular hole (19) at its lower part; the rotating vertical rod (15) has a third rectangular hole (21) and a fourth rectangular hole (22) at its lower part.

4. A tensioning method using the prestressed tendon lever-type in-situ tensioning device according to any one of claims 1 to 3, characterized in that: The steps are as follows: Step 1: Determine the effective length and failure length of the in-situ prestressed tendons (1) of the pre-tensioned hollow slab beam to be repaired; Step 2: Open a hole at the bottom of the prestressed concrete hollow slab near the end of the hollow slab in the section where the in-situ prestressed tendon (1) fails, so that the steel bars and in-situ prestressed tendons (1) in the prestressed concrete hollow slab are completely exposed. Step 3: After checking that the in-situ prestressed tendons (1) are intact, install the tensioning device; Step 4: Use the jacks (8) in the tensioning device to tension in batches until the tension force of the in-situ prestressed tendons (1) reaches the design tension force and then stop pressurizing; Step 5: After the jack (8) holds the tensioning device in the tensioning position, screw the check bolt (12) aligned with the check rod (13) toward the check rod (13) to lock the check bolt (12) and the check rod (13) together. Step 6: Perform anti-rust and anti-corrosion treatment on the in-situ prestressing tendons (1) and reinforcing bars and re-pour concrete. After the concrete, in-situ prestressing tendons (1) and reinforcing bars are repaired, loosen the check bolts (12) so that the prestress of the in-situ prestressing tendons (1) in the failed section gradually decreases until it is zero. Remove the tensioning device to seal the opening excavated in step 2.

5. The tensioning method of the prestressed tendon lever-type in-situ tensioning device according to claim 4, characterized in that, The steps for installing the tensioning device in step 3 are as follows: (1) Embed the in-situ prestressed tendon (1) into the first U-shaped groove (6) and the second U-shaped groove (3) of the rotating vertical rod (15) and the fixed vertical rod (17), and tighten the first U-shaped groove (6) and the second U-shaped groove (3) with the first fixing bolt (5) and the second fixing bolt (4) to keep the first U-shaped groove (6) and the second U-shaped groove (3) in close contact with the in-situ prestressed tendon (1); (2) V-shaped anchors (2) are arranged on the in-situ prestressing tendons (1) at the outer end of the rotating vertical rod (15). The V-shaped anchors (2) are installed on the in-situ prestressing tendons (1) using clamps (9) and V-anchor bolts (10). (3) Place the jack (8) horizontally on the check rod (13) to ensure that the piston rod of the jack (8) is in close contact with the rotating vertical rod (15). The installation is complete.

6. The tensioning method of the prestressed tendon lever-type in-situ tensioning device according to claim 4, characterized in that, In step 4 The final tension of the prestressing tendon (1) is set to F1, the external force provided by the jack (8) is F2, and the self-locking internal force of the check bolt (12) is F3; the distance from the center of the prestressing tendon (1) to the center of the pin (16) is L1, the distance from the center of the piston rod of the jack (8) to the center of the pin (16) is L2, and the distance from the center of the check bolt (12) to the center of the pin (16) is L3; the final tension of the prestressing tendon (1) is: F1 = (L2 / L1)F2 Based on the oil pressure gauge reading, when the reading starts to decrease, continue to tighten the check bolt (12) until the internal force of the check bolt (12) reaches F3=(L2 / L3)F2. At this time, the oil pressure gauge reading is zero, the check bolt (12) is finally tightened, and the jack (8) is removed.

Images