Method for demounting a prestressing cable, and device for carrying it out

• US 20020113231A1
• Filed: 12/21/2001
• Published: 08/22/2002
• Est. Priority Date: 12/27/2000
• Status: Active Grant

• Current Assignee: Freyssinet International
• Original Assignee: Freyssinet International
• Inventors: Salmon, Philippe, Stubler, Jerome, Lecinq, Benoit
• Granted Patent: US 6,701,599 B2
• Time in Patent Office: Days
• US Class Current: 254/134.3R
• CPC Class Codes: E01D 2101/28 prestressed
• CPC Class Codes: E01D 22/00 Methods or apparatus for repairing or strengthening existing bridges electrochemical desalination or re-alkalisation C04B41/00; Methods or apparatus for dismantling bridges
• CPC Class Codes: E04C 5/12 Anchoring devices tools or methods for tensioning in situ E04G21/12
• CPC Class Codes: E04G 21/12 Mounting of reinforcing inserts; Prestressing shell tubes for prestressing members E04C5/10; anchoring means E04C5/12; connections of reinforcing elements and spacers E04C5/16
• CPC Class Codes: E04G 23/02 Repairing, e.g. filling cracks; Restoring; Altering; Enlarging compositions of filling material C04B; strengthening, widening, repairing of bridges E01D22/00; drying damp layers by temporary mechanical ventilation E04B1/7092
• CPC Class Codes: Y10T 29/49776 Pressure, force, or weight determining
• CPC Class Codes: Y10T 29/49821 by altering or destroying work part or connector
• CPC Class Codes: Y10T 29/49822 by applying force
• CPC Class Codes: Y10T 29/5383 having fluid operator

Abstract

The invention addresses the problem of demounting a prestressing cable having a sheath, tendon extending in the sheath and tensioned between two anchoring devices, and a hardened material filling the sheath around the tendons. An energy dissipation device is installed between a zone of the structure and an accessible portion of the cable. The energy dissipation device has a first end applied to a bearing zone and a second end. It is suitable for limiting the force to which it is subjected as a function of the speed of relative displacement between its first and second ends. A first member for retaining the cable is arranged adjacent to the aforesaid portion of the cable. This portion is clamped in a second retaining member engaging the sheath and connected to the second end of the energy dissipation device. The cable can then be severed between the first and second retaining members.

Claims

1. A method for demounting a prestressing cable of a structure, the cable comprising a sheath, at least one tendon extending in the sheath and tensioned between two anchoring devices, and a hardened material filling the sheath around said at least one tendon, the method comprising the steps of:

installing at least one energy dissipation device between a zone of the structure and an accessible portion of the cable, the energy dissipation device having a first end applied to a bearing zone and a second end, and being suitable for limiting the force to which it is subjected as a function of the speed of relative displacement between said first and second ends, said portion of the cable being adjacent to a first member for retaining the cable;

clamping said portion of the cable in a second retaining member engaging the sheath and connected to the second end of the energy dissipation device; and

severing the cable between the first and second retaining members.

2. A method according to claim 1, further comprising the step of anchoring the first retaining member to the structure.

3. A method according to either claim 1, further comprising the step of applying the first end of the energy dissipation device to a bearing zone formed by a zone of the structure.

4. A method according to claim 1, further comprising the step of applying the first end of the energy dissipation device to a bearing zone formed by said first retaining member.

5. A method according to claim 1, wherein the energy absorbed by the energy dissipation device when the cable is detensioned responsive to the severing step is used for driving back the second retaining member in the direction of the position which it occupied before the cable was severed.

6. A device for demounting a prestressing cable of a structure, the cable comprising a sheath, at least one tendon extending in the sheath and tensioned between two anchoring devices, and a hardened material filling the sheath around said at least one tendon, the device comprising at least one energy dissipation device having a first end to be applied to a bearing zone and a second end, and being suitable for limiting the force to which it is subjected as a function of the speed of relative displacement between said first and second ends, and a second retaining member connected to the second end of the energy dissipation device, in order to engage the cable sheath in an accessible portion thereof located adjacent to a first member for retaining the cable.

7. A device according to claim 6, wherein the energy dissipation device comprises at least one hydraulic cylinder/piston system extending between the second retaining member and the bearing zone, the demounting device further comprising a circuit for bringing towards an accumulator chamber a hydraulic fluid expelled in response to the relative displacement between the piston and the cylinder, said circuit comprising a flow-limiting member.

8. A device according to claim 7, wherein the accumulator chamber houses a first fluid brought to the accumulator chamber in response to the relative displacement between the piston and the cylinder and a second, gaseous fluid, and comprises a free surface separating said first and second fluids to ensure equilibrium between the pressure of said first and second fluids.

9. A device according to claim 6, wherein the energy dissipation device provides laminating of the hydraulic fluid being transferred between the cylinder and the accumulator chamber.

10. A device according to claim 6, wherein the second retaining member comprises a jaw having a clamping capacity of up to 40 tons.