Method for replacing a tie rod of a tied arch bridge

Abstract

The application discloses a method for replacing a tie rod of a tied arch bridge and belongs to the technical field of tie rod replacement, and aims at solving the technical problem of stable conversion of force systems among temporary tie rod force, old tie rod force and new tie rod force, and the method comprises a temporary tie rod loading, old tie rod unloading force system conversion stage and a new tie rod loading, temporary tie rod unloading force system conversion stage, in the temporary tie rod loading, old tie rod unloading force system conversion stage, the temporary tie rod is loaded so that the temporary tie rod force plus all the old tie rod force is always greater than all the old tie rod force before replacement, and the arch foot is pre-displaced inward to reach the allowable control value; the single steel strand of the old tie rod to be replaced is heated in turn through a local heating mode, so that the steel strand to be heated is yielded and fractured until all the steel strands of the old tie rod to be replaced are fractured, and the old tie rod to be replaced is unloaded. In the force system conversion process, the closed-loop control is performed on the arch foot horizontal pre-displacement, and the quick and refined construction of the tie rod replacement is realized.

Description

Technical Field

[0001] This invention relates to the field of tie rod replacement technology, and more specifically, to a method for replacing tie rods in a tie rod arch bridge. Background Technology

[0002] Currently, the tie rods in tied arch bridges are mostly composed of multiple steel strands. When replacing tie rods in tied arch bridges, temporary tie rods are often used as a replacement method. The temporary tie rods achieve two force system conversions with the old tie rods and the new tie rods. The tie rod replacement process involves changes in the internal force redistribution of various components of the bridge structure. In particular, the relationship between the temporary tie rod cable force, the old tie rod cable force, the new tie rod cable force, and the horizontal displacement of the arch foot is quite complex during the force system conversion process. How to achieve a smooth force system conversion between the temporary tie rod cable force and the old tie rod cable force and the new tie rod cable force while minimizing the impact on the redistribution of internal forces in the main structure of the arch bridge is a major challenge in the tie rod replacement process. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the above-mentioned shortcomings of the prior art. The purpose of the present invention is to provide a method for replacing tie rods in a tied arch bridge, which can realize a smooth conversion of the force system between the temporary tie rod cable force, the old tie rod cable force, and the new tie rod cable force.

[0004] The technical solution of this invention is: a method for replacing tie rods in a tied-rod arch bridge, including a temporary tie rod loading and old tie rod unloading force system conversion stage, and a new tie rod loading and temporary tie rod unloading force system conversion stage. During the temporary tie rod loading and old tie rod unloading force system conversion stage...

[0005] First, the temporary tie rod is loaded so that the force of the temporary tie rod plus the force of all the old tie rods is always greater than the force of all the old tie rods before replacement, and the arch foot is pre-displaced inward to the allowable control value.

[0006] Then, the individual steel strands of the old tie rod to be replaced are heated sequentially by local heating, causing the heated steel strands to yield and break until all the steel strands of the old tie rod to be replaced break, thus completing the unloading of the old tie rod to be replaced.

[0007] As a further improvement, the inward pre-displacement change of the arch foot is monitored in real time. When the pre-displacement approaches 0, the temporary tie rod is actively loaded to ensure that the horizontal pre-displacement of the arch foot always moves inward until the last steel strand of the old tie rod to be replaced breaks, and the horizontal pre-displacement of the arch foot approaches 0.

[0008] Furthermore, the local heating method includes any one of induction coil local heating, flame local heating, laser local heating, plasma local heating, and heating tube local heating.

[0009] Furthermore, the induction coil is an elongated "Y"-shaped induction coil.

[0010] Furthermore, anti-side-breakage mechanisms are provided on both sides of the old tie rod to be replaced at the position to be cut.

[0011] Furthermore, the anti-side collapse mechanism includes a first cable clamp and a second cable clamp located on the outer walls of both sides of the old tie rod to be replaced. The first cable clamp and the second cable clamp together wrap around the outer wall of the old tie rod to be replaced, and the first cable clamp and the second cable clamp are locked by a locking member.

[0012] Furthermore, anti-slip pads are provided between the first cable clamp and the old tie rod to be replaced, and between the second cable clamp and the old tie rod to be replaced.

[0013] Furthermore, the locking element is a bolt.

[0014] Furthermore, the first cable clamp and the second cable clamp are two-part steel components.

[0015] Furthermore, during the transition phase of the new tie rod loading and the temporary tie rod unloading force system,

[0016] First, load the new tie rod so that the force of the new tie rod plus the remaining force of the old tie rod and the temporary tie rod is always greater than the force of all the old tie rods before replacement, and the arch foot pre-displaces inward to the allowable control value.

[0017] Then, the temporary tie rod is unloaded, and the inward pre-displacement of the arch foot is monitored in real time. When the pre-displacement approaches 0, a new tie rod is actively loaded to keep the horizontal pre-displacement of the arch foot always inward until the force of the temporary tie rod is unloaded to 0 and the horizontal pre-displacement of the arch foot approaches 0.

[0018] Beneficial effects

[0019] Compared with the prior art, the advantages of this invention are as follows:

[0020] 1. The present invention mainly uses the horizontal pre-displacement of the arch foot and the closed-loop control of cable force verification in the two-stage force system conversion process, which can meet the needs of rapid and precise construction for tie rod replacement.

[0021] 2. This invention employs an extended "Y"-shaped non-contact induction heating device. By locally heating the section of a single steel strand to be cut to a controlled temperature, it achieves a stress-release ductile process at the section of the single steel strand to be cut, involving extension, yielding, necking, and fracture. Simultaneously, anti-side-breakage clamps are installed on each side of the tie rod to be replaced and bolted connections are made. Under the buffer protection of the pre-tightening force of the anti-side-breakage clamps, the fractured steel strand is prevented from lateral breakage, achieving a smooth transfer of the old tie rod force system while ensuring the safety of operators. In addition, the induction heating device is compact in size, has controllable heating temperature, and can flexibly adapt to operating spaces with small tie rod spacing. Attached Figure Description

[0022] Figure 1Force diagram of the initial state of the tie-arch bridge before replacement;

[0023] Figure 2 Force diagram for the initial loading of the temporary tie rod;

[0024] Figure 3 A schematic diagram of the force system transformation when the old tie rod to be replaced is unloaded to 0 and a temporary tie rod is loaded;

[0025] Figure 4 Force diagram for when the new tie rod begins to be loaded;

[0026] Figure 5 A schematic diagram of the force system transformation when the temporary tie rod is unloaded to 0 and the new tie rod is loaded;

[0027] Figure 6 This is a schematic diagram of unloading the first steel strand for induction heating.

[0028] Figure 7 This is a schematic diagram of unloading the second steel strand for induction heating.

[0029] Figure 8 This is a schematic diagram of unloading the third steel strand for induction heating.

[0030] Figure 9 This is a schematic diagram of unloading the fourth steel strand for induction heating.

[0031] Figure 10 A schematic diagram of a mechanism to prevent side collapse.

[0032] Among them: 1-Old tie rod to be replaced, 2-Steel strand, 3-Extended "Y"-shaped induction coil, 4-Position to be cut, 5-Anti-side collapse mechanism, 6-First cable clamp, 7-Locking part, 8-Handle, 9-Wire, 10-Electromagnetic induction power supply, 11-Arch foot. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments shown in the accompanying drawings.

[0034] The main span of a certain arch bridge is a 168m span, under-deck steel-concrete tied arch. Each arch has two main arch ribs, with a transverse center distance of 19m between them. The rib rise is 32m, resulting in a rise-to-span ratio of 1 / 5. The rib cross-section is dumbbell-shaped, with upper and lower steel pipes of 1.5m diameter connected by a web. The total height is 3.75m, and No. 50 concrete is injected into the steel pipes and web. At the arch foot of each rib, eight high-strength, low-relaxation prestressed steel strand tie cables are installed. Each tie cable consists of 37 strands of 7×φ5mm steel strands, with a standard strength Ryb = 1860MPa. The tie cables are positioned between the crash barriers under the two arch ribs and anchored to the back wall at the arch foot. The anchorages are type 15-37 anchorages with limit plates, and the tie cables are protected by a high-density polyethylene sheath. High-strength concrete was poured into the pre-embedded pipes in the anchorage zone and at the anchor sealing ends of the tie rods. All tie rods on the bridge were replaced.

[0035] See Figures 1-10 The present invention provides a method for replacing tie rods in a tie rod arch bridge, comprising a temporary tie rod loading and old tie rod unloading force system conversion stage, and a new tie rod loading and temporary tie rod unloading force system conversion stage.

[0036] During the transition from temporary tie rod loading to old tie rod unloading force system:

[0037] 1) First, load the temporary tie rods so that the force of the temporary tie rods plus the force of all the old tie rods is always greater than the force of all the old tie rods before replacement, and the arch foot 11 pre-displaces inward to the allowable control value. For example... Figure 1 , 2 As shown,

[0038] That is, F1+N1>N0, until dL1=dL;

[0039] When dL1 = dL = 10mm (inward),

[0040] F1=3360kN, N1=29368.6KN, N0=31571.8kN.

[0041] In the formula:

[0042] F1 - Initial load force value of the temporary tie rod;

[0043] N1 - The sum of the tension values ​​of all old tie rods, composed of n steel strands with a cross-section of A0;

[0044] N0 - the sum of the tension values ​​of all old tie rods before replacement, composed of n steel strands with a cross-section of A0;

[0045] dL1 - Temporary tie rod initial loading, arch foot horizontal pre-displacement inward;

[0046] dL - Allowable control value for the arch foot's inward horizontal direction.

[0047] Then, the individual steel strands 2 of the old tie rod 1 to be replaced are heated in turn by local heating, so that the heated steel strands 2 yield and break until all the steel strands 2 of the old tie rod 1 to be replaced break, thus completing the unloading of the old tie rod 1 to be replaced.

[0048] 2) During the force unloading and conversion process of heating the steel strands 2 one by one in the old tie rod 1 to be replaced, the arch foot 11 horizontally displaces outward. The inward pre-displacement of the arch foot 11 is monitored in real time. When the pre-displacement approaches 0, i.e., dL1 approaches 0 (if dL1 < 1mm), a temporary tie rod is actively loaded to ensure that the horizontal pre-displacement of the arch foot always moves inward. This forms a closed-loop control system with the horizontal pre-displacement of the arch foot as the main factor and the cable force as the verification factor, until the last steel strand 2 of the old tie rod 1 to be replaced breaks, and the horizontal pre-displacement of the arch foot approaches 0. This meets the requirements for rapid and precise tie rod replacement construction. Figure 3 As shown,

[0049] F2↑+N2↓>N0, the arch foot horizontal pre-displacement dL1↓, until the last strand of the old tie rod to be replaced is unloaded, dL1 decreases to dL2 close to 0.

[0050] When the last strand of the old tie rod to be replaced is unloaded, dL2 approaches 0.

[0051] dL2 = 1 mm (inward), F2 = 4420 kN, N2 = 27192.5 kN, N0 = 31571.8 kN

[0052] In the formula:

[0053] F2 - Temporary tie rod continues to apply cable force;

[0054] N2 - The old tie rod to be replaced is unloaded one by one, and the sum of the cable force values ​​of the remaining old tie rod is composed of nt steel strands with an area of ​​A0.

[0055] During the force conversion process between the temporary tie rod and the old tie rod to be replaced, the arch foot undergoes horizontal pre-displacement inward.

[0056] During the force system transition phase of new tie rod loading and temporary tie rod unloading:

[0057] 1) First, load the new tie rod so that the force of the new tie rod plus the remaining force of the old tie rod and the temporary tie rod force is always greater than the total force of all old tie rods before replacement, and the arch foot pre-displaces inward to the allowable control value. For example... Figure 4 As shown,

[0058] F2+F3+N3>N0, until dL3=dL;

[0059] When dL3 = dL = 10mm (inwards)

[0060] F2=4420kN, F3=3360kN, N1=24948.6KN, N0=31571.8kN

[0061] In the formula:

[0062] F2 - Temporary tie rod loading cable force value;

[0063] F3 - The new tie rod begins to apply cable force;

[0064] N3 - The sum of the remaining old tie rod cable forces, composed of nt cross-sections and A0 area steel strands;

[0065] N0 - the sum of the tension values ​​of all old tie rods before replacement, composed of n steel strands with a cross-section of A0;

[0066] dL3 - The arch foot is pre-displaced horizontally inward during the first loading of the new tie rod to be replaced;

[0067] dL - Allowable horizontal control value for the arch foot towards the inside.

[0068] 2) Then, the temporary tie rods are tensioned and unloaded using jacks. During the unloading and conversion of the temporary tie rod force system, the horizontal displacement of the arch foot moves outward. The inward pre-displacement of the arch foot is monitored in real time. When the pre-displacement approaches zero, a new tie rod is actively loaded to ensure that the horizontal pre-displacement of the arch foot always moves inward. This forms a closed-loop control system with the horizontal pre-displacement of the arch foot as the main factor and the cable force as the verification factor, until the temporary tie rod force unloading is zero and the horizontal pre-displacement of the arch foot approaches zero. This meets the requirements for rapid and precise tie rod replacement. Figure 5 As shown,

[0069] F3'↑+F2′↓+N4↓>N0, the arch foot is horizontally pre-displaced by dL3↓ until the temporary tie rod force is unloaded to 0, and dL3 decreases to dL4 which is close to 0.

[0070] When the temporary tie rod force is unloaded to 0, dL4 is close to 0.

[0071] dL4 = 0.5 mm (inward), F2′ = 0 kN, F3′ = 4420 kN, F3′ = 27151.8 kN, N0 = 31571.8 kN

[0072] In the formula:

[0073] F2' - Temporary tie rod loading cable force value;

[0074] F3 - Waiting for replacement of the new tie rod; continue applying cable force.

[0075] N4 - The sum of the remaining old tie rod cable forces during the force conversion process of the new tie rod to be replaced and the temporary tie rod, composed of nt cross-section steel strands with an area of ​​A0;

[0076] dL4 - During the force conversion process of the new tie rod and temporary tie rod to be replaced, the arch foot is horizontally pre-displaced inward.

[0077] This process is repeated for each old tie rod: replacing one old tie rod, then applying the temporary tie rod loading and old tie rod unloading force system conversion, and then applying the new tie rod loading and temporary tie rod unloading force system conversion, until all old tie rods are replaced, thus replacing all the tie rods of the entire tie-arch bridge.

[0078] Local heating methods include any one of induction coil local heating, flame local heating, laser local heating, plasma local heating, and heating tube local heating.

[0079] Preferably, the induction coil local heating adopts an extended "Y"-shaped non-contact electromagnetic induction heating device. By locally heating the cut position 4 of the single steel strand of the old tie rod to be replaced, the local part is heated to a controllable temperature. During the heating process, the elastic modulus and yield strength of the local part of the steel strand decrease, realizing the stress release ductility process of local extension-yield-necking-fracture of the single steel strand at the cut position 4.

[0080] like Figures 6-9 As shown, the extended "Y"-shaped non-contact electromagnetic induction heating device consists of an electromagnetic induction power supply 10, wires 9, a handle 8, and an extended "Y"-shaped induction coil 3. An alternating current is passed through the extended "Y"-shaped induction coil 3, generating an alternating magnetic field around it. Under the influence of this alternating magnetic field, a localized portion of the steel strand placed within the "Y"-shaped induction coil 3 generates an electromotive force (EMF). Driven by this EMF, electrons flow in this localized portion of the steel strand 2, forming an eddy current, which flows in the opposite direction to the current in the induction coil. Due to the very small reactance of the metal, the eddy current can reach a very high value, generating a high amount of heat in the localized portion of the steel strand 2, thus heating the localized portion itself. By designing the generated heat parameters, the designed temperature parameters for heating the localized portion can be achieved. The induction heating device is compact in size, has a controllable heating temperature, and can flexibly adapt to operating spaces with small rod spacing.

[0081] like Figure 10 As shown, anti-side-breakage mechanisms 5 are provided on both sides of the old tie rod 1 to be replaced at the cut-off position 4. The anti-side-breakage mechanism 5 includes a first cable clamp 6 and a second cable clamp located on the outer walls of the old tie rod 1 to be replaced on both sides respectively. The first cable clamp 6 and the second cable clamp together wrap around the outer wall of the old tie rod 1 to be replaced, and the first cable clamp 6 and the second cable clamp are locked by locking member 7.

[0082] Anti-slip pads are provided between the first cable clamp 6 and the old tie rod 1 to be replaced, and between the second cable clamp and the old tie rod 1 to be replaced, to increase friction. Preferably, the anti-slip pads are made of rubber material, the locking element 7 is a bolt, and the first cable clamp 6 and the second cable clamp are two-part steel components. After the first cable clamp 6 and the second cable clamp are put together to wrap the old tie rod 1 to be replaced, they are then locked with bolts.

[0083] The anti-side collapse mechanism 5 can prevent the broken steel strand from collapsing (the steel strand bounces outward), and achieve a smooth transfer of the force system of each steel strand of the old tie rod while ensuring the safety of the operators.

[0084] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for replacing tie rods in a tied-rod arch bridge, comprising a temporary tie rod loading and old tie rod unloading force system conversion stage, and a new tie rod loading and temporary tie rod unloading force system conversion stage, characterized in that, During the transition from temporary tie rod loading to old tie rod unloading force system conversion phase First, the temporary tie rod is loaded so that the force of the temporary tie rod plus the force of all the old tie rods is always greater than the force of all the old tie rods before replacement, and the arch foot is pre-displaced inward to the allowable control value. Then, the individual steel strands (2) of the old tie rod (1) to be replaced are heated in turn by local heating, so that the heated steel strands (2) yield and break until all the steel strands (2) of the old tie rod (1) to be replaced break, thus completing the unloading of the old tie rod (1). Real-time monitoring of the inward pre-displacement change of the arch foot. When the pre-displacement approaches 0, actively control the loading of the temporary tie rod so that the horizontal pre-displacement of the arch foot always moves inward until the last steel strand (2) of the old tie rod (1) to be replaced breaks and the horizontal pre-displacement of the arch foot approaches 0. During the force conversion phase of new tie rod loading and temporary tie rod unloading... First, load the new tie rod so that the force of the new tie rod plus the remaining force of the old tie rod and the temporary tie rod is always greater than the force of all the old tie rods before replacement, and the arch foot pre-displaces inward to the allowable control value. Then, the temporary tie rod is unloaded, and the inward pre-displacement of the arch foot is monitored in real time. When the pre-displacement approaches 0, a new tie rod is actively loaded to keep the horizontal pre-displacement of the arch foot always inward until the force of the temporary tie rod is unloaded to 0 and the horizontal pre-displacement of the arch foot approaches 0.

2. The method for replacing tie rods in a tied-arch bridge according to claim 1, characterized in that, The local heating method includes any one of induction coil local heating, flame local heating, laser local heating, plasma local heating, and heating tube local heating.

3. The method for replacing tie rods in a tied-rod arch bridge according to claim 2, characterized in that, The induction coil is an elongated "Y"-shaped induction coil (3).

4. The method for replacing tie rods in a tied-arch bridge according to claim 1, characterized in that, Anti-side collapse mechanism (5) is provided on both sides of the old tie rod (1) to be replaced at the position to be cut (4).

5. The method for replacing tie rods in a tied-arch bridge according to claim 4, characterized in that, The anti-side collapse mechanism (5) includes a first cable clamp (6) and a second cable clamp located on the outer walls of the old tie rod (1) to be replaced, respectively. The first cable clamp (6) and the second cable clamp together wrap the outer wall of the old tie rod (1) to be replaced, and the first cable clamp (6) and the second cable clamp are locked by a locking member (7).

6. The method for replacing tie rods in a tied-arch bridge according to claim 5, characterized in that, Anti-slip pads are provided between the first cable clamp (6) and the old tie rod (1) to be replaced, and between the second cable clamp and the old tie rod (1) to be replaced.

7. The method for replacing tie rods in a tied-arch bridge according to claim 5, characterized in that, The locking element (7) is a bolt.

8. The method for replacing tie rods in a tied-arch bridge according to claim 5, characterized in that, The first cable clamp (6) and the second cable clamp are two-part steel components.

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