EP3336255B1 - Fire protection device of a structural cable - Google Patents

Description

The present invention relates to the fire protection of cables having a structural role in construction works, especially structures having guyed portions, suspended or stiffened by cables.

BACKGROUND

One of the major risks for a cable structure in the operating phase is fire, in particular of a vehicle, particularly near a rope anchoring zone, for example on a bridge road.

A structural cable of such a structure comprises tensile metal reinforcements for transmitting the required forces between its ends. The reinforcements are, for example, metal strands possibly contained in individual plastic sheaths. The bundle of metal reinforcements is often surrounded by a collective plastic sheath which gives the cable aerodynamic properties, an aesthetic appearance and / or an anti-vandalism function.

WO 2007/093703 A2 describes a fire protection system comprising a mattress made of a flexible insulating material which directly surrounds the bundle of reinforcements of the cable and which is contained in the collective sheath.

This system has the limitation of not allowing to effectively protect the cable at certain singular points where it is interacting with other organs of the structure. For example, if a deflector or damper is applied against the cable, the presence of the flexible material of the mattress prevents good communication of efforts and a good functioning of this body.

Singular points of this type are often present near cable anchors. This is the case, for example, for installing stay dampers. Examples are described in EP 0 343 054 A1 and WO 2015/059413 A1 .

These singular points are weak points of fire protection.

In the event of a fire, the priority is to protect the cable bundle, even if it means replacing peripheral equipment such as a shock absorber or a deflector.

One difficulty is that the fire protection of the singular points where are connected Peripheral equipment must not impair their proper operation during normal operation of the structure. For example, a shock absorber or diverter collar must provide a fairly rigid fulcrum between the cable itself and the damper or deflector device. This constraint can be contradictory with the implementation of good fire-fighting solutions, especially those using a flexible mattress enveloping the cable frames. This mattress passing through a collar would be a flexible interface, decreasing, for example, the performance of a transverse damper anchored on this collar. Typically, the value of the transverse rigidity, in any direction orthogonal to the longitudinal axis of the cable, of the collar is never less than 10 ⁶ N / m (100 kgf / mm) and advantageously greater than 10 ⁸ N / m ( 10 t / mm).

An object of the present invention is to provide another mode of protection capable of overcoming at least in part the above difficulties.

ABSTRACT

• un matelas protecteur enveloppant le câble de structure au moins dans les premier et deuxième tronçons et interrompu dans la zone de connexion ; et
• un anneau thermiquement isolant plus rigide que le matelas protecteur, disposé entre les armatures et le collier dans la zone de connexion et coopérant avec le matelas protecteur pour procurer aux armatures une protection thermique continue le long du premier tronçon, de la zone de connexion et du deuxième tronçon.

It is proposed a fire protection device for a structural cable of a construction structure, the structural cable comprising tensile metal reinforcements and having a first section, a second section and a connection zone of a collar located between the first and second sections. The fire protection device includes:

• a protective mattress wrapping the structural cable at least in the first and second sections and interrupted in the connection area; and
• a thermally insulating ring which is stiffer than the protective mat, arranged between the reinforcements and the collar in the connection zone and cooperating with the protective mattress to provide the reinforcements with continuous thermal protection along the first section, the connection zone and the second section.

The device provides an auxiliary protection to the singularities of the connection areas of collars while protecting the armature bundle by a protective mat on both sides of such connection areas.

The continuity of the protection avoids the thermal bridges that would be likely to transmit to the metal frames the heat generated by a fire near the cable.

Fire protection may be limited to an area adjacent to an anchorage of the cable, or extend over the entire length of the cable, depending on the fire hazard to be considered for the structure.

In one embodiment, the insulating ring comprises a plurality of elements assembled around the reinforcements, in mutual contact with surfaces lined with a fire seal.

A plastic diverter tube can be placed between the insulating ring and the reinforcements in the connection area.

A fiber concrete is used, among other materials, to make the insulating ring. Fiber concrete may include metal fibers and polypropylene fibers

The protective mattress may consist of several segments disposed end-to-end in at least one of the first and second sections of the structural cable, a covering mat being placed around two adjacent segments to ensure the continuity of the thermal protection.

To ensure the continuity of the thermal protection on both sides of the connection zone, the protective mattress may be placed longitudinally in contact with the insulating ring on the side of the first section and on the side of the second section.

It can also be provided that the protective mat has a portion having a longitudinal overlap with the thermally insulating ring between the reinforcements and the thermally insulating ring.

Another possibility, which may also supplement the previous ones, is to have an intumescent material at the interface between the protective mat and the insulating ring on the side of the first section and the side of the second section.

An embodiment of the fire protection device further comprises, in at least one of the first and second sections, a tube in which are housed the reinforcements of the structural cable, the protective mat being arranged around this tube.

In a typical embodiment, the insulating ring has a rigidity at least 100 times greater than that of the protective mat.

• un matelas protecteur enveloppant le câble de structure au moins dans les premier et deuxième tronçons ; et
• un anneau thermiquement isolant plus rigide que le matelas protecteur, disposé entre les armatures et le collier dans la zone de connexion et coopérant avec le matelas protecteur pour procurer aux armatures une protection thermique continue le long du premier tronçon, de la zone de connexion et du deuxième tronçon.

Another aspect of the invention relates to a construction structure comprising at least one structural cable and a collar connected to the structural cable in a connection area. The structural cable comprises tensile metal reinforcements and has a first section and a second section on either side of the connection zone of the collar. The building structure further comprises a fire protection device including:

• a protective mattress wrapping the structural cable at least in the first and second sections; and
• a thermally insulating ring which is stiffer than the protective mat, arranged between the reinforcements and the collar in the connection zone and cooperating with the protective mattress to provide the reinforcements with continuous thermal protection along the first section, the connection zone and the second section.

According to one embodiment of the structure, the structural cable further comprises an outer sheath surrounding the reinforcements and the protective mat in at least one of the first and second sections.

The collar may have the function of providing a connection of at least one damping element to the structure cable for damping vibrations of the structural cable.

The construction work may consist in particular of a cable-stayed bridge, an extradossed bridge, a suspension bridge or a cable-stayed tower.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue schématique de profil d'un pont à haubans ;
• la figure 2 est une vue en coupe axiale d'un hauban au voisinage d'un collier de connexion d'un dispositif amortisseur ; et
• la figure 3 est une vue en coupe transversale du hauban au niveau du collier.

Other features and advantages of the present invention will appear in the following description of a nonlimiting exemplary embodiment, with reference to the accompanying drawings, in which:

• the figure 1 is a schematic side view of a cable-stayed bridge;
• the figure 2 is an axial sectional view of a stay in the vicinity of a connection collar of a damping device; and
• the figure 3 is a cross-sectional view of the stay at the collar.

DESCRIPTION OF EMBODIMENTS

The invention is described below in its non-limiting application to bridges with wire. It will be understood that it is also applicable advantageously in extradossed bridges, suspension bridges or guyed towers. The structural cables to be protected against fire may still be external prestressing cables of concrete structures.

In the example of the figure 1 the structural cables considered 16 are the stays of a bridge which extend between a pylon 20 of the bridge and its apron 14 for suspending the deck 14.

One or more of the stays 16 are equipped with a damping device 22 comprising an arm extending transversely to the stay 16 between an attachment point P situated near its low anchorage (for example a few% of the length total of the stay) and apron 14.

To connect the arm of a damping device 22 to its stay 16 at point P, a collar 30 such as that shown in FIG. figures 2 and 3 .

A similar collar can be used to connect the structural cable to a fixed deflector (without damper) by which it is supported, for example, on a guyed structure or a guying pylon. Another example of application is for a hanger collar located near the deck of a suspension bridge. When a hanger collar is at a height of less than about 10 m, or even up to 18-20 m, it is likely to be impacted by a vehicle light, so that the measures described below can be advantageously adopted.

The structural cable constituted by the stay 16 comprises a bundle of metal frames 32, which are stretched between two anchoring devices (not shown) arranged at its ends, one on the deck 14 and the other on the pylon 20. The reinforcements 32 are, for example, strands, in particular strands individually sheathed and greased or waxed.

In the common part of the stay 16, the frames 32 are protected against fire by a flexible protective mat 34, which may, for example, be similarly constituted, in particular with the same materials as that described in FIG. WO 2007/093703 A2 . The mattress 34 may extend over the entire length of the stay, or only on a part of it if the fire protection is not required for the entire length.

The figure 2 shows the zone 40 connecting the collar 30, which is located between a first section 41 and a second section 42 of the stay 16. Each section 41, 42 extends from the connection zone 40 to an anchoring of the stay, either to another singular point, or to a point in the running part from which the protective mat is no longer required.

The protective mat 34 envelopes the stay 16 in the first and second sections 41, 42, and it stops in the connection zone 40. Indeed, the flexibility of the mattress 34 is not necessarily suitable for the function of the connected equipment to the stay 16 via the collar 30. A stiffer interaction is typically required at this level.

For this, a ring 36, more rigid than the protective mat 34 (K times stiffer with K ≥ 100 for example, or K ≥ 10,000), is disposed between the plates 32 and the collar 30 in the connection zone 40. The rigidity of the insulating ring 36 may be greater than 10 ⁶ N / m, or even 10 ⁸ N / m.

The ring 36 also serves to avoid the thermal bridges between the metal reinforcements of the stay 16 and the collar 30. It is thermally insulating and cooperates with the protective mat 34 to provide the reinforcements with continuous thermal protection throughout the first section 41, of the connection zone 40 and the second section 42.

The insulating ring 36 may be made of a fiber-reinforced concrete, in particular an ultra-high performance fiber-reinforced concrete (UHPC). The fibers used in the composition of fiber concrete may comprise metal fibers and polypropylene fibers. The metal fibers improve the mechanical strength of the ring 36, while the polypropylene fibers improve its resistance in case of temperature rise, limiting the embrittlement due to wrinkles.

The insulating ring 36 is made of several molded elements 36a, 36b which are then assembled around the bundle of reinforcements 32. In the example shown in FIG. figure 3 , the ring 36 consists of two molded half-shells 36a, 36b assembled around the reinforcements 32. A fire seal 37 is placed on the mutual contact surfaces of the two molded half-shells 36a, 36b.

It is desirable to avoid contact of the concrete on the metal reinforcement 32 of the stay. For this, a deflection tube 38 is inserted between the ring 36 and the bundle The tube 38 is made of plastic, for example a high density polyethylene (HDPE). It has a toric geometry on its internal face to accommodate small deviations undergone by the bundle of reinforcement 32 to the right of the collar 30. If the bundle of reinforcements 32 has a polygonal cross-section (hexagonal in the case of the figure 3 ), the deflector tube 38 can be constituted by arranging several plastic plates against the faces of the bundle before setting up the elements 36a, 36b of the ring 36.

The left part of the figure 2 shows that in option, there can be provided a tube 44 which contains the bundle of reinforcements 32 and which is surrounded by the protective mat 34. This tube 44, for example HDPE, adds a blade of air between the frames 32 and the mattress 34 and, in this way, further increases the thermal protection of the frames in case of fire. Such a tube may be present in one of the sections 41, 42, or in both.

To cover a sufficient length along the stay 16, it will generally be necessary to put end-to-end several segments 34a, 34b of the protective mattress 34 in at least one of the sections 41, 42 ( figure 2 ). To ensure the continuity of the fire protection in the current part of the stay, a cover mat 35 is placed around two adjacent segments 34a, 34b so as to completely cover the joint existing between them.

The mattress 34 is held on the cable 16 with an adhesive or strapping ties, or a combination of these two types of means.

The figure 2 shows again that the protective mat 34 is placed longitudinally in contact with the insulating ring 36 on the side of the first section 41 and the side of the second section 42. Some additional measures can be taken to complete the continuity of the protection between the connection area 40 and one or other of the sections 41, 42.

In particular, it can be provided a longitudinal overlap between the thermally insulating ring 36 and a portion of the protective mattress 34 ( figure 2 ). This overlapping portion 48 of the protective mat 34 is inserted between the plates 32 and the ring 36, in contact with the bundle of frames 32.

When a tube 44 is present between the reinforcements 32 and the protective mattress 34, fireproof mattress thicknesses 45, 46 may be added in the vicinity of the ring 36 to compensate for the thickness of the air gap and the tube 44.

In addition, it will often be necessary to coat an intumescent material at the interface between the protective mat 34 and the insulating ring 36. In the event of excessive heating, this material swells to prevent the conduction of heat towards the frames 32.

The flexible anti-fire mattress disposed on either side of the collar 30 and the insulating ring 36 will not generally be exposed directly to the open air. It will be covered by a tubular sheath (not shown) consisting of either a steel tube or a plastic sheath (HDPE). This sheath gives the guy an aerodynamic and aesthetic profile and mechanically protects the mattress.

The embodiments described above are a mere illustration of the present invention. Various modifications can be made without departing from the scope of the invention which emerges from the appended claims.

Claims (15)

1. Fire protection device for a structural cable of a construction work, with the structural cable (16) comprising taught metal reinforcements (32) and having a first stretch (41), a second stretch (42) and a connection zone (40) of a collar (30) located between the first and second stretches, with the dire protection device including:

   a protective mat (34) surrounding the structural cable (16) at least in the first and second stretches (41, 42) and interrupted in the connection zone (40); and

   a thermally insulating ring (36) more rigid than the protective mat (34), arranged between the reinforcements (32) and the collar (30) in the connection zone (40) and cooperating with the protective mat in order to provide the reinforcements with a continuous thermal protection along the first stretch (41), of the connection zone (40) and of the second stretch (42).
2. Fire protection device according to claim 1, wherein the insulating ring (36) comprises several elements (36a, 36b) assembled around reinforcements (32), in mutual contact along surfaces lined with a firebreak seal (37).
3. Fire protection device as claimed in any preceding claim, wherein a deviator tube (38) made of plastic material is placed between, the insulating ring (36) and the reinforcements (32) in the connection zone (40).
4. Fire protection device as claimed in any preceding claim, wherein the insulating ring (36) is made from a fibre-reinforced concrete.
5. Fire protection device according to claim 4, wherein the fibre-reinforced concrete includes metal fibres and polypropylene fibres.
6. Fire protection device as claimed in any preceding claim, wherein the protective mat (34) is comprised of several segments (34a, 34b) arranged end-to-end in at least one of the first and second stretches (41, 42) of the structural cable (16), with an overlay mat (35) being placed around two adjacent segments in order to pride the continuity of the thermal protection.
7. Fire protection device as claimed in any preceding claim, wherein the protective mat (34) is placed longitudinally in contact with the insulating ring (36) on the side of the first stretch (41) and on the side of the second stretch (42).
8. Fire protection device as claimed in any preceding claim, wherein the protective mat (34) has a portion (48) that has a longitudinal overlay with the thermally insulating ring (36), between the reinforcements (32) and the thermally insulating ring.
9. Fire protection device as claimed in any preceding claim, wherein an intumescent material is arranged at the interface between the protective mat (34) and the insulating ring (36) on the side of the first stretch (41) and on the side of the second stretch (42).
10. Fire protection device as claimed in any preceding claim, further comprising, in at least one of the first and second stretches (41, 42), a tube (44) wherein are housed the reinforcements (32) of the structural cable (16), with the protective mat (34) being arranged around said tube (44).
11. Fire protection device as claimed in any preceding claim, wherein the insulating ring (36) has a rigidity at least 100 times greater than that of the protective mat (34).
12. Construction work comprising at least one structural cable (16) and a collar (30) connected to the structural cable in a connection zone (40), the structural cable comprising taught metal reinforcements (32) and having a first stretch (41) and a second stretch (42) on either side of the connection zone of the collar, with the construction work further comprising a fire protection device including:

    a protective mat (34) surrounding the structural cable (16) at least in the first and second stretches (41, 42) and interrupted in the connection zone (40) ; and

    a thermally insulating ring (36) more rigid than the protective mat (34), arranged between the reinforcements (32) and the collar (30) in the connection zone (40) and cooperating with the protective mat in order to provide the reinforcements with a continuous thermal protection along the first stretch (41), from the connection zone (40) and of the second stretch (42).
13. Construction work according to claim 12, wherein the structural cable (16) further comprises an outer sheath surrounding the reinforcements (32) and the protective mat (34) in at least one of the first and second stretches.
14. Construction work according to any of claims 12 and 13, wherein the collar (30) provides a connection of at least one damper element (22) to the structural cable (16) in order to dampen vibrations of the structural cable.
15. Construction work according to any of claims 12 to 14, comprised of a cable-stayed bridge, an extradosed bridge, a suspension bridge or a guyed tower.

Images