FR2795438A1 - STRUCTURE OF A CONCRETE-STEEL MIXED BRIDGE OR GATEWAY, PARTICULARLY A MIXED TWO-GATE APRON BRIDGE - Google Patents

Abstract

The structure consists of at least one hollow steel support (2) for a concrete cover slab (1), the support being totally closed, apart from its ends, and having its inner cavity filled with a hydraulic binding agent (11) such as high performance concrete. The supports can be two in number, located beneath the roadway (5) or to the sides of the bridge above the roadway. Each support can be made, for example, from two I-section beams welded together to form parallel sole plates (12), with the beam webs forming the side walls (13). The material used for the supports can be general structural steel, steel with a high elastic limit, or structural steel with a high resistance to atmospheric corrosion.

Description

The invention relates to the technical field of bridges or walkways to

metal frame.

  The main advantages of the metal frame are: - the excellent weight / performance ratio of the steel material;

- the speed of execution.

  Already known in the prior art, different designs of such bridges or walkways.

  Reference may be made, for example, to the following documents: EP-A-501 730, FR-

  A-2 622 907, FR-A-2 693 491, FR-A-2 616 166, FR-A-2 698 1 1 1.

  The metal bridges most generally comprise a cover, a framework and a support system, the cover being the part of the bridge which directly receives the operating charges and transmits them to the support system, via possibly the metal framework conventionally formed by a network.

  longitudinal (beams) and transverse (bridge parts) beams.

  The bearing system is frequently formed by two main beams connected

  by spacers and provided with stiffeners.

  Recent roofs are generally formed by orthotropic slabs or mixed slabs or reinforced concrete slabs sometimes provided with a

transverse prestress.

  Orthotropic slabs are generally formed from a continuous sheet called decking sheet or rolling sheet more than ten millimeters thick stiffened in two perpendicular directions, by transverse bridge parts and

  by equidistant longitudinal stiffeners called ribs.

  Orthotropic tiles have certain disadvantages.

  In particular, the variation in transverse bending stresses when passing heavy vehicles can lead to the appearance of fatigue cracks

in the decking sheets.

  This risk of fatigue is increased by the presence of numerous welds

in the frame.

  Furthermore, the quantity of steel used is high and the adjustment and

  machining are tricky, so the cover is expensive.

  The mixed slabs comprise a continuous sheet connected to a concrete slab, this sheet forming the lower reinforcement of the slab. The connectors used are most often vertical studs welded to the gun connected at the head by

shooting steels.

  Mixed tiles have drawbacks.

  In particular, they are only suitable for reduced spans, for

  reasons of shape stability during the pouring of concrete.

  Reinforced concrete slabs, sometimes with transverse prestressing, are associated with steel by different connectors, so as to ensure transmission

  efforts of the framework and a certain transverse rigidity.

  The most common connectors are angles or vertical studs.

  Bridges whose supporting system consists of metal beams and whose

  the cover is a reinforced concrete slab are called composite bridges.

  The invention relates more particularly to such bridges or walkways.

  In such mixed bridges, the slab can sometimes rest directly on the main beams braced by triangulated beams for example,

  spacers can be removed when the span of the bridge is small.

  The slab of mixed bridges can in other cases be in longitudinal support on

  the main beams and in transverse support on the bridge parts.

  The slab of mixed bridges can in other cases be supported on the main beams only, these beams then being braced. The usual range of spans for mixed bridges goes from around 30 to 110Om for continuous spans and from around 25 to 90m for independent spans. The types of designs of these mixed bridges currently most frequently used are: - mixed twin girders which, as their name suggests, comprise two beams most often connected: - by bridge parts for the transverse support of the slab ; - by spacers welded perpendicularly and halfway up the beams, for relatively narrow decks; - mixed box bridges: - with concrete slab resting on the walls of the box and on any transverse elements; - with mixed slab as presented above, with single box or multi-boxes.

  The invention relates more particularly to twin-girder composite bridges.

  For twin-girder composite bridges, the beams are most often with a solid core,

  the core and the soles being assembled by four angle weld beads.

  These solid core beams have various drawbacks: - their sensitivity to shape instabilities, by unusual deformation compared to those which can be expected by the resistance of conventional materials. In particular, the shocks linked for example to the passage of an oversized convoy lead to plasticity in large deformations, difficult to predict by calculation. Such shocks, if they do not always lead to the ruin of the structure, cause damage that is difficult to repair without major work; - their sensitivity to fatigue, despite the strict standards in force (Eurocodes) cannot be overlooked, especially since, more often than not, crack initiations exist from the construction of the structure, by

  penetration of corner welds for example.

  The invention relates to a twin-girder composite bridge structure, in particular but not exclusively to twin-girder composite bridges with beams under the roadway, not having the drawbacks of bridges of this type known in the prior art. In particular, the invention reveals a simple structure of a twin-girder mixed bridge resistant to lateral impacts by oversized convoys for example, this structure also avoiding the use of gussets and spacers, the construction of said bridge also not requiring stopping traffic on the tracks

crossed by the bridge.

  To this end, the invention relates, according to a first aspect, to a composite concrete-steel bridge or gangway structure, comprising at least one steel support beam of the concrete cover slab, said support beam comprising a

internal cavity filled with a binder.

  In one embodiment, the bridge structure comprises two beams placed under

pavement.

  In another embodiment, the bridge structure comprises two beams placed

  laterally above the roadway.

  Each support beam can be provided with internal reinforcement. Each support beam can be produced by longitudinal welding of at least two

elementary beams.

  In a particular embodiment, each support beam is produced by welding two H-shaped beams so that the support beams have two flanges substantially opposite one another and parallel to each other, connected by two walls d 'soul substantially perpendicular to each other and facing each other. In one embodiment, each support beam is made of steel with high elastic limit and is filled with a hydraulic binder such as concrete, for example concrete

high performance.

  The support beams are assembled to the cover slab by studs placed in reservations of said slab, a support piece being placed in a reservation of the cover slab, between the upper flange of each support beam and said slab, this support piece being provided with a

  projection projecting against said upper sole.

  Other objects and advantages of the invention will become apparent during the course of the

  following description of embodiments, description which will be made

  with reference to the accompanying drawings in which: - Figure 1 is a partial cross-sectional view of a twin-girder composite bridge structure with beams under the road, according to an embodiment of the invention; - Figure 2 is a detail view of an embodiment of the connecting connectors between beam and cover slab; - Figure 3 is a view similar to Figure 2 of another embodiment

of said connectors.

  We first refer to Figure 1.

  A bridge deck, of which only half is shown in cross section in this figure 1 - the other half being symmetrical with the first half shown - comprises a concrete slab 1, covering, resting on two

beams 2.

  In other embodiments, not shown, the second half of the bridge is not symmetrical with the first, and / or the concrete slab 1 rests on

  more than two beams 2, for example three beams 2.

  The section plane of Figure 1 is defined by a first substantially horizontal direction D1 called transverse and a second direction D2

substantially vertical.

  A third direction D3 forms with the other two directions a trihedron,

  this third direction being said to be longitudinal.

  The terms "wide", "width" will be used with reference to the first

direction D1.

  The terms "top", "height", "thickness" will be used with reference to

the second direction D2.

  The terms "longitudinal", "length" will be used with reference to the

third direction D3.

  In the embodiment shown, the deck is supported by two beams

2 placed under the floor.

  In other embodiments, not shown, the deck is only supported by a single longitudinal beam, or on the contrary by more than two longitudinal beams. In still other embodiments, not shown, the two beams

  are placed laterally above the roadway.

  The cover slab 1 is of variable thickness, in the embodiment shown: starting from a longitudinal longitudinal edge of this slab and going towards the center of the latter, the thickness increases, reaching a maximum value below each beam 2 then decreases then remains constant over a certain width of

the slab.

  A central thickness of cover slab of 20cm, for a distance E of beams of 4.5m and lateral cantilevers 3 of approximately 2m can be obtained by an embodiment in accordance with Figure 1. A deck width of 8m

approximately is thus obtained.

  In the rest of the text, the digital indications will refer to the above dimensioning, carried out for a span bridge of the order of fifteen to thirty meters at one two or three spans, commonly implemented by

  example for highway crossings.

  In other embodiments, not shown, the thickness of the slab is substantially constant over its entire width. The slab can be made of conventional concrete. In one embodiment, the slab is made of high performance concrete, its mechanical strength in compression at 28 days being for example

greater than 80MPa.

  The slab can be prestressed transversely, in particular when the deck is very wide. Mono strands of the order of 150KN of useful tension arranged with a pitch of 30cm can for example be used, the

  active anchors being placed alternately on one side and the other of the slab.

  In the considered embodiment, twelve SEEE 4T15S prestressing cables

are provided in ducts 4.

  In the embodiment shown, the cover slab 1 supports, in addition to the road surface of the roadway 5, longitudinal passages in the edges of cables 6 of different diameters for telephone, electrical and other networks. A border 7 separates the roadway 5 from the sidewalks 8 under which are placed

the cable passages 6.

  In other embodiments, only one sidewalk is provided and / or only one of the two sidewalks is placed above cable passages. A bodyguard 9 is placed at the side edge of the sidewalk (s) 8. A

  facing 10 is secured to the longitudinal side faces of the deck.

  We now describe more specifically the longitudinal beams 2 and their

  fixing on the cover slab 1.

  Each beam 2 is with a core filled with a rigid material based on hydraulic binder 11, called "binder", or any other material having

  mechanical characteristics comparable to those of such a binder 11.

  This binder can be chosen from the group comprising concretes based on Portland cements, blast furnace cements, pozzolanic cements, aluminous cements, high performance concretes, concretes based on

  resin, fiber concretes and their equivalents.

  As will be clear to those skilled in the art, the choice of binder 11 depends inter alia on the dimensions and efforts to be taken into account for the

beams 2.

  In the embodiment under consideration, each beam 2 comprises two substantially facing and horizontal flanges 12, of thickness e12 greater than the width 113 of the two substantially vertical walls 13 and facing these two

soles 12.

  The beams can be formed by the assembly of two H sections, for example HE 800A, welded together by longitudinal weld beads. These weld beads being arranged longitudinally are not

  highly sensitive to fatigue damage phenomena.

  In other embodiments, the beams have polygonal cross sections, in particular hexagonal. In still other embodiments, the two walls of cores 13 are

pleated regularly or not.

  The materials used to make the beams 2 can be chosen from the group comprising general-purpose structural steels (and in particular those mentioned in standard EN-10-025), steels with high elastic limit (and in particular those defined EN-10-113), structural steels with improved resistance to atmospheric corrosion and their

equivalent.

  In one embodiment, the webs of beams and the flanges are formed

by a single steel.

  In other embodiments, the cores are made of a material different from that of the soles (for example, a steel with high elastic limit

  for souls and general purpose structural steel for soles).

  The beams 2 can be provided with an internal reinforcement, the fixing of the stirrups, frames and reinforcement of this reinforcement being able to be at least partly

  internal to beam 2 so as not to affect its visual appearance.

  The workability of the binder used and its flow capacity in a confined medium must be adapted as it appears to those skilled in the art, to ensure the

  desired filling of reinforced beams.

  The filling of these beams can be partial.

  Several concretes, of different types, can be used for this filling, depending for example on the distribution of the forces provided for.

  service along the length of the beams.

  For the dimensions of the deck mentioned above, the width of the flanges 12 was 60 cm, the height of the beams was 79 cm, the beams filled with concrete being formed by assembling two sections of HE 800A type welded.

  We now refer to Figures 2 and 3.

  The beams 2 are in the embodiment shown fixed to the slab of

  cover 1 by studs 14 such as Nelson studs.

  These studs are placed in reservations 15 of the slab 1, plumb with the upper flange of the beams and substantially perpendicular to this flange. These reservations are for example cylindrical and pass through the entire thickness of the slab 1 A support piece forming renformis 16 or equivalent is provided in a reservation located on the underside of the slab 1, in line with the sole

top of each beam 2.

  This support piece has a substantially horizontal lower face 17, with the exception of its central part provided with a projection 18 bearing against

  the upper sole of the beam 2 placed opposite.

  Two seals 19 are placed laterally between the underside 17 of the part

  support 16 and the upper flange of each beam 2.

  A binder, not shown, poured into the reservations 15 of the slab allows

  assembling the beams 2 to this cover slab 1.

  It Two studs or four studs can be provided depending on the loads of

scheduled service.

  The bridge structure obtained does not require any reinforcement struts connecting the support beams below and at a distance from the cover slab nor therefore ipso facto no reinforcement gusset between the strut and support beams, unlike the twin-girder composite bridge structures known in the art. prior art. Although the widths of the decks achievable according to the bridge structure described above are quite large, it is no more necessary to provide bridge parts connecting the support beams below the cover slab

  on which the roofing slab rests longitudinally.

  These bridge parts and spacers generate significant assembly costs, must be designed for a given center distance between support beam and their assembly by welding is the cause of damage by fatigue, in

  double girder composite bridges known from the prior art.

  O20 The filling of steel beams with a binder greatly improves the stability of these beams in large deformations, in particular during impacts by

oversized convoys.

  It also ensures the stability of the webs 13 against the risks of spillage or buckling in the area of the zones where are applied to the system carrying concentrated loads, such as for example in the area of the supports on which

the mixed bridge rests.

  The prefabrication of the support beams and the reduction of assembly operations on site makes it possible not to interrupt or modify the traffic on the tracks crossed by the bridge or the gangway, which is an important advantage in the case of crossing large tracks. traffic such as

highways.

Claims (15)

  1. Mixed concrete-steel bridge or walkway structure, comprising at least one steel support beam (2) of the concrete cover slab (1), characterized in that said support beam (2) comprises an internal cavity filled with a binder (11).   2. Bridge structure according to claim 1, characterized in that it   comprises two beams (2) placed under the roadway (5).   3. Bridge structure according to claim 1, characterized in that it   comprises two beams (2) placed laterally above the road.   4. Bridge structure according to any one of claims 1 to 3,   characterized in that each support beam is provided with internal reinforcement.   5. Bridge structure according to any one of claims 1 to 4,   characterized in that each support beam is produced by welding   longitudinal of at least two elementary beams.   6. Bridge structure according to claim 5, characterized in that each support beam (2) is produced by welding two H-shaped beams so that the support beams have two flanges (12) substantially facing the one of the other and parallel to each other, connected by two core walls   (13) substantially perpendicular to each other and facing each other.   7. Bridge structure according to any one of claims 1 to 6   characterized in that the filling binder for the support beams (2) is chosen from the group comprising concretes based on Portland cements, blast furnace cements, pozzolanic cements, aluminous cements, high performance concretes, concretes based on resin, fiber concretes.   8. Bridge structure according to any one of claims 1 to 7,   characterized in that each support beam is made of a material chosen from the group comprising general-purpose structural steels, steels with high elastic limit, structural steels with improved resistance to atmospheric corrosion.   9. Bridge structure according to any one of claims 1 to 8,   characterized in that the support beams (2) are assembled to the cover slab (1) by studs (14) placed in reservations (15) of said o0 slab (1).   10. Bridge structure according to any one of claims 1 to 9,   characterized in that a support piece (16) is placed in a reservation of the cover slab (1) and is placed between the upper flange (12) of each support beam (2) and said slab (1), this support piece (16) being   provided with a projection (18) bearing against said upper sole (12).   11. Bridge structure according to any one of claims 1 to 10,   characterized in that the cover slab (1) is prestressed transversely.   12. Bridge structure according to any one of claims 6 to 11,   characterized in that at least one of the core walls of the support beams (2)   is made of a material different from that of the flanges (12) of these beams.   13. Bridge structure according to any one of claims 1 to 12,   characterized in that it does not have a spacer connecting the support beams   below and away from the cover slab.   14. Bridge structure according to any one of claims 1 to 13,   characterized in that it is devoid of bridge parts connecting the beams   support below the cover slab. 14 '2795438   15. Bridge structure according to claim 13 or 14, characterized in that a transverse dimension or width of the bridge deck is of the order of eight meters, the distance between support beams being four meters fifty and the cantilevers of about two meters, the cover slab resting on the support beams.