The present invention relates to the field of construction and to composite floor decks. It more specifically relates to a composite floor deck member comprising metal and wood and to the composite floor deck assembly thereof. The present invention also relates to the prefabricated composite floor assembly thereof and to the composite floor deck thereof.

Composite floor decks are well known in the field of construction. They traditionally comprise a corrugated I profiled metallic sheet, a wire mesh and concrete encompassing the wire mesh and fastened to the profiled metallic sheet by chemical bonding and/or mechanical or frictional interlocking. The metallic sheet and concrete work in synergy to provide good resistance capabilities in tension (due to the metallic sheet) and in compression (due to concrete).

It is also known from EP1528175 a composite floor deck member comprising a metallic tray having a horizontal central area and two substantially vertical lateral webs, an insulation material positioned in the metallic tray, a wire mesh extending between the tops of the webs and a layer of concrete covering the insulation material and surrounding the wire mesh. Composite floor deck members can be positioned on site one adjacent to another to form a composite floor deck.

In the construction industry, there is currently a trend for prefabricated elements that, on one hand, can be easily and rapidly installed on site and that, on the other hand, are the source of fewer greenhouse gas emissions.

In addition to these requirements, the prefabricated elements must have a good fire resistance and must reach sufficient spans.

The aim of the present invention is therefore to remedy the drawbacks of the prior art by providing an eco-friendly prefabricated composite floor deck member which can reach sufficient spans while having a good fire resistance.

For this purpose, a first object of the present invention consists of a composite floor deck member extending along a longitudinal axis X and comprising a metallic tray, an insulation material positioned in the metallic tray and a wood slab resting on the metallic tray, wherein the metallic tray comprises:

- A central part substantially lying down in a plane P and comprising a first longitudinal edge, a second longitudinal edge, a first transverse edge and a second transverse edge,

- A first flange extending upwards, from the first longitudinal edge of the central part, substantially perpendicularly to plane P and comprising a first end wing extending parallel to plane P and inwards,

- A second flange extending upwards, from the second longitudinal edge of the central part, substantially perpendicularly to plane P and comprising a second end wing extending parallel to plane P and inwards, the first flange and the second flange having shapes that allow them to be positioned adjacent to one another, wherein the insulation material covers the central part, wherein the wood slab rests on the first end wing and the second end wing and is stitched to them, wherein the wood slab is further stitched to at least a first metallic profile resting against the bottom side of the wood slab between the first end wing and the second end wing of the metallic tray, extending substantially along the longitudinal axis X and having longitudinal extremities anchored to end caps substantially closing the gap between the metallic tray and the wood slab at the first and second transverse edges of the central part of the metallic tray.

The composite floor deck member according to the invention may also have the optional features listed below, considered individually or in combination:

- the wood slab has a first longitudinal edge and a second longitudinal edge and comprises a first edge rabbet along its first longitudinal edge and a second edge rabbet along its second longitudinal edge,

- the first edge rabbet and the second edge rabbet have substantially the same dimensions, - the wood slab is stitched to the first end wing and the second end wing with stitching fasteners spaced less than 500 mm apart from one another,

- the first metallic profile is stitched to the wood slab with profile fasteners spaced less than 500 mm apart from one another,

- the height of the first metallic profile is between 0.5 and 2 times the thickness of the wood slab,

- the lower end of the first metallic profile is above the half height of the metallic tray,

- the composite floor deck member further comprises a second metallic profile resting against the bottom side of the wood slab, extending substantially along the longitudinal axis X and having longitudinal extremities anchored to the end caps,

- the first metallic profile is positioned in the first third of the wood slab width and the second metallic profile is positioned in the last third of the wood slab width,

- the end caps present a recess, on their internal side, substantially at the shape of the cross-section of the first metallic profile,

- the recess in the end caps is a through recess,

- the longitudinal extremities of the first metallic profile are flush with the external sides of the end caps,

- the insulation material fills in the metallic tray at least up to the first metallic profile,

- the insulation material extends higher than the bottom ends of the first metallic profile,

- the insulation material comprises a cutout to accommodate the first metallic profile,

- the wood slab has a first longitudinal edge and a second longitudinal edge and comprises a main part, substantially parallelepiped rectangular, a first longitudinal extension resting against the underside of the main part along the first longitudinal edge of the wood slab and a second longitudinal extension resting against the underside of the main part along the second longitudinal edge of the wood slab. - The wood slab has substantially the size of the central part of the metallic tray,

- The wood slab has substantially the length of the metallic tray,

- the width of the wood slab is substantially a multiple of the width of the central part of the metallic tray.

A second object of the invention consists of a composite floor deck comprising a first composite floor deck member and a second composite floor deck member, both according to the invention.

The composite floor deck member according to the invention may also have the following optional feature: the second flange of the first composite floor deck member is adjacent to the first flange of the second composite floor deck member and both members are locked to one another.

A third object of the invention consists of a prefabricated composite floor deck assembly comprising a first composite floor deck member and a second composite floor deck member, both members being according to the invention, wherein the second flange of the first composite floor deck member is adjacent to the first flange of the second composite floor deck member and wherein both members are locked with a metallic plate resting in and attached to both the second edge rabbet of the first composite floor deck member and the first edge rabbet of the second composite floor deck member.

As it is apparent, the invention is based on a wood slab reinforced:

- on one hand, with a metallic tray, the wood slab and the metallic tray having a composite behavior and

- on the other hand, with at least one metallic profile which, in case of a fire, can take over the loads in place of the metallic tray and thus maintain the integrity of the floor deck.

Other characteristics and advantages of the invention will be described in greater detail in the following description. The invention will be better understood by reading the following description, which is provided purely for purposes of explanation and is in no way intended to be restrictive, with reference to:

- Figure 1 , which is a perspective view of a composite floor deck member according to the invention,

- Figure 2, which is a cross-section of the composite floor deck member of Figure 1 ,

- Figure 3, which is a perspective view of a metallic tray of a composite floor deck member according to the invention,

- Figure 4, which is a perspective view of some parts of a composite floor deck member according to the invention,

- Figure 5, which is a cross-section of a variant of the composite floor deck member according to the invention,

- Figure 6, which is a view of another variant of the composite floor deck member according to the invention,

- Figure 7, which is a cross-section of an assembly of two composite floor deck members according to the invention,

- Figure 8, which is a cross-section of another variant of the composite floor deck member according to the invention,

- Figure 9, which is a cross-section of another variant of the composite floor deck member according to the invention,

- Figure 10, which is a cross-section of another variant of the composite floor deck member according to the invention.

It should be noted that spatially relative terms such as “lower”, “inwards”, “outwards”, “upwards”, “top”, “bottom”, “above”... as used in this application refer to the positions and orientations of the different parts of the composite floor deck member when the latter is lying down on the ground or on a building structure.

Throughout the text, a sheet is understood to mean an element that has a flat shape, i.e., its thickness is low compared to its other dimensions. Generally speaking, its thickness is 500 to 4000 times lower than its width. The sheet may be made of a single material or a composite assembly. In the latter case, the sheet is a stack of a plurality of layers of the same material or different materials. The material in question may be, among others, a metallic material or a polymer. Steel, aluminum, copper and zinc may be cited as non-restricting examples of metallic materials. The sheet is preferably a metallic sheet, more preferably a steel sheet. It is preferably made of galvanized and pre-coated steel to protect it against corrosion.

The metallic tray is an example of metallic sheet which has been previously formed with the aid of any known forming method, including, by way of nonrestricting examples, bending, forming, stamping and molding.

This forming leads among other things to the formation of ribs, stiffeners or grooves on the surface of the sheet. Throughout the text, a rib is understood to mean a projection formed on the surface of the sheet. The rib may have a trapezoidal shape or a rectangular, corrugated, sinusoidal or even omega shape, for example. It includes a top central part and two lateral wings. A stiffener is a rib of limited height, generally 10 to 30 times lower than a rib. Throughout the text, a groove is understood to mean a recess formed on the surface of the sheet. The groove can have shapes similar to the ones offered for ribs. Ribs, stiffeners or grooves are generally parallel to the longitudinal edges of the sheet notably to render the sheet more rigid.

With reference to Figure 1 , the composite floor deck member 1 according to the invention extends along a longitudinal axis X and comprises a metallic tray 2, an insulation material 3 positioned in the metallic tray and a wood slab 4 resting on the metallic tray.

With reference to Figures 2 and 3, the metallic tray 2 first comprises a central part 5 substantially lying down in a plane P and comprising a first longitudinal edge 6, a second longitudinal edge 7, a first transverse edge 8 and a second transverse edge 9. For the sake of clarity, longitudinal edges are parallel to the longitudinal axis X and transverse edges are perpendicular to the longitudinal axis X. The central part is substantially flat. It can be stiffened with stiffeners 10 as defined above, i.e. ribs of limited height, extending parallel to the longitudinal edges of the central part. The number and positions of the stiffeners is not limited.

The metallic tray 2 further comprises a first flange 11 extending upwards, from the first longitudinal edge 6 of the central part, substantially perpendicularly to plane P. Its upper end is in the form of a first end wing 12 extending parallel to plane P and inwards. The end wing increases the rigidity of the composite floor deck member.

The metallic tray 2 further comprises a second flange 13 extending upwards, from the second longitudinal edge 7 of the central part, substantially perpendicularly to plane P. Its upper end is in the form of a second end wing 14 extending parallel to plane P and inwards.

The first flange 11 and the second flange 13 have shapes that allow them to be positioned adjacent to one another. According to one variant, they both are flat from the longitudinal edge of the central part to the end wing. According to a preferred variant, one flange has a male shape, the other a female shape and both shapes can be interlocked. In particular, the first flange comprises a rib 15 as defined above, i.e. a protrusion formed on the surface of the flange, and the second flange comprises a groove 16 as defined above, i.e. a recess formed on the surface of the flange. The dimensions and positions of the rib and the groove are such that they can interlock. Preferably, they have a trapezoidal shape. Preferably they are positioned substantially at half-height of the flange. Alternatively, the first flange comprises a groove 16 and the second flange comprises a rib 15. The rib and the groove increase the rigidity of the composite floor deck member and the rigidity of an assembly of composite floor deck members.

With reference to Figures 1 and 2, the composite floor deck member 1 further comprises a wood slab 4 resting on the metallic tray 2. This slab can be made of any variety of wood or any kind of wood composite. The wood slab is preferably made of Cross-Laminated Timber (CLT). CLT is an engineered wood product consisting of layers of kiln-dried dimension lumber (usually three, five, seven or nine) oriented at right angles to one another and then glued to form structural panels. By gluing layers of wood at right angles, the panel delivers excellent structural rigidity in both directions.

The length and width of the wood slab are adapted so that two wood slabs are substantially contiguous when two composite floor deck members are positioned adjacent to one another. In particular, the wood slab has substantially the length of the metallic tray. Its thickness depends on the desired mechanical performances of the composite floor deck member.

According to the variant illustrated on Figures 1-3, the first longitudinal edge 17, the second longitudinal edge 18, the first transverse edge 19 and second transverse edge 20 of the wood slab are straight. It makes the installation of the composite floor deck members easy. Preferably, the first longitudinal edge 17 of the wood slab is substantially plumb with the first longitudinal edge 6 of the central part of the metallic tray and the second longitudinal edge 18 of the wood slab is substantially plumb with the second longitudinal edge 7 of the central part of the metallic tray. More preferably the first transverse edge 19 of the wood slab is substantially plumb with the first transverse edge 8 of the central part of the metallic tray and the second transverse edge 20 of the wood slab is substantially plumb with the second transverse edge 9 of the central part of the metallic tray. It makes the installation of the composite floor deck members easy.

According to another variant illustrated on Figure 6, the first longitudinal edge 17 and the second longitudinal edge 18 are crenellated. In particular, they are crenellated so that the crenels of the first longitudinal edge can interlock with the crenels of the second longitudinal edge. More particularly, the crenels of the first longitudinal edge and the second longitudinal edge have the same shape and the crenels of the second longitudinal edge are shifted by half a crenel in the longitudinal direction compared to the crenels of the first longitudinal edge. Preferably, the base of the crenel is recessed from the longitudinal edge 6 or 7 of the central part of the metallic tray. Thanks to this configuration, when two composite floor deck members are positioned adjacent to one another, the second longitudinal edge 18 of the wood slab 4 of the first member is partially lying on the first end wing 12 of the metallic tray 2 of the second member and the first longitudinal edge 17 of the wood slab 4 of the second member is partially lying on the second end wing 14 of the first member. Crenels can have, for example, a rectangular shape, a trapezoidal shape (as visible on Figure 6), an omega shape.

The wood slab can optionally comprise a first edge rabbet 21 along its first longitudinal edge and a second edge rabbet 22 along its second longitudinal edge. For the sake of clarity, the edge rabbets are into the top side of the wood slab. The first edge rabbet and second edge rabbet preferably have substantially the same dimensions. They are preferably continuous. They preferably extend along the full length of the longitudinal edges of the wood slab. Alternatively, notably in the case of the variant illustrated on Figure 6, the edge rabbet is discontinuous and present on the portions of longitudinal edge between the crenels.

Thanks to the edge rabbets 21 , 22, two adjacent composite floor deck members can be locked together. It provides the corresponding composite floor deck with a diaphragm action. Consequently, the lateral loads (mainly wind and earthquake actions), both traction and compression, and in both horizontal directions, are transmitted to the vertical resisting elements of a structure (such as shear walls or frames).

As illustrated on Figure 7, two adjacent members are preferably locked with a metallic plate 25. More preferably, the metallic plate rests in, and is attached to, both the second edge rabbet 22 of the first composite floor deck member and the first edge rabbet 21 of the second composite floor deck member. The metallic plate is preferably attached to the edge rabbets with rabbet fasteners 26, such as screws. The locking of the two adjacent members can be done with one single metallic plate or with a plurality of metallic plates along the length of the longitudinal edges of the wood slab. More preferably, the thicknesses of both the edge rabbets and the metallic plate are adjusted so that the heads of the rabbet fasteners are flush with the top side 23 of the wood slab. More preferably, the metallic plate has chamfered holes for the rabbet fasteners so that the metallic plate can also be flushed with the top side 23.

Two adjacent members can be locked together differently. For example, according to the variant of the composite floor deck member with crenellated longitudinal edges, the two adjacent members can be locked by fastening parts of the second longitudinal edge of the first member lying on the first end wing of the second member to that first end wing and by fastening parts of the first longitudinal edge of the second member lying on the second end wing of the first member to that second end wing.

According to one variant illustrated on Figures 1 and 2, the bottom side 24 of the wood slab 4 is substantially flat, more preferably flat. According to another variant illustrated on Figure 5, the bottom side 24 of the wood slab 4 is shaped. In particular, the cross-section of the wood slab is substantially an inverted II with a main part 27, substantially parallelepiped rectangular, and a first longitudinal extension 28 resting against the underside of the main part along the first longitudinal edge 17 and a second longitudinal extension 29 resting against the underside of the main part along the second longitudinal edge 18. The main part and the first and second longitudinal extensions can be part on a single piece shaped accordingly. Alternatively, the main part and the first and second longitudinal extensions can be different pieces assembled together to form the wood slab. Thanks to the inverted U-shape, the inertia of the composite floor deck member can be increased, possibly without increasing the weight of the wood slab. An increased inertia allows longer spans.

The wood slab 4 rests on the first end wing 12 and the second end wing 14. It further stabilizes the composite floor deck member. It also facilitates the fixing of the wood slab on the metallic tray. Moreover, the surfaces of the first end wing and second end wing help the stitching fasteners to resist the shear forces when the floor is loaded.

The wood slab 4 is stitched to the metallic tray, in particular to the first end wing 12 and the second end wing 14 of the flanges 11 , 13. Stitching is fastening at regular intervals. Stitching the wood slab and the metallic tray make them behave as a single piece (also referred to as composite behavior). It ensures the transmission of the compression forces of the wood slab to the tensile forces taken up by the metallic tray. Stitching is done with stitching fasteners 30, such as screws, rivets or nails. Preferably stitching fasteners are spaced less than 500 mm apart from one another. The fastener spacing is more preferably between 100 and 400 mm, even more preferably between 200 and 300 mm.

The wood slab 4 is further stitched to at least a first metallic profile 31 resting against the bottom side 24 of the wood slab between the first end wing and the second end wing of the metallic tray and extending substantially parallel to the longitudinal axis X. In other words, the metallic tray faces a first metallic profile resting against the bottom side 24 of the wood slab between the first end wing and the second end wing of the metallic tray and extending substantially along the longitudinal axis X.

In case of a fire below the composite floor deck member impairing the mechanical properties of the metallic tray 2, the first metallic profile, less affected by the fire, takes over the metallic tray and behaves with the wood slab as a single piece. In other words, the first metallic profile works in traction while the wood slab work in compression. Consequently, additional fire protections, such as dropped ceiling or fire-resistant flocking can be avoided, which increases the construction speed.

For the sake of clarity, a metallic profile, also known as metallic section, is a metallic piece whose thickness and width are significantly low compared to its length and which has been previously extruded or formed, with the aid of any known method, to obtain, in cross-sections, portions extending in different directions. It can be a metallic sheet which has been bent longitudinally, like a metal angle or a metal channel. It can also be a metal tube. It can also be an I- beam or H-beam formed, for example, by hot-rolling, cold-rolling, extrusion or welding. The metallic profile is preferably made of steel.

In one variant illustrated on Figures 1 and 2, the wood slab 4 is stitched to a first metallic profile 31 and a second metallic profile 32. In another variant illustrated on Figure 8, the wood slab is stitched to one single metallic profile 31 . Variants with different numbers of metallic profiles are of course possible.

The stitching of the metallic profile(s) on the wood slab, similarly to the stitching of the metallic tray on the wood slab, ensures the transmission of the compression forces of the wood slab to the tensile forces taken up by the metallic profile(s). Stitching is done with profile fasteners 33, such as screws, rivets or nails. Preferably profile fasteners are spaced less than 500 mm apart from one another. The fastener spacing is more preferably between 100 and 400 mm, even more preferably between 200 and 300 mm.

The shape of the metallic profile(s) is not particularly limited. It can have, for example, in cross-section, a L shape, a Z shape, a T shape, a H shape, an omega shape. The height of the metallic profile(s) is preferably comprised between 0.5 and 2 times the thickness of the wood slab. It further increases the mechanical properties of the composite floor deck member during a fire. The lower end of the metallic profile(s) is preferably at least 30mm away from the central part of the metallic tray, more preferably above the half height of the metallic tray. It further prevents the metallic profile(s) from heating up too quickly in case of a fire heating up the metallic tray. For the sake of clarity, the height of the metallic tray is the distance, along the vertical axis, from the longitudinal edge 6 or 7 of the central part to the end wing 12 or 14. Also, for the sake of clarity, no part of the metallic profile(s) is in contact with the metallic tray.

In the variant with one single metallic profile, it is preferably centered in the width of the metallic tray. In the variant with two metallic profiles, the first metallic profile is preferably positioned in the first third of the wood slab width and the second metallic profile is preferably positioned in the last third of the wood slab width. More preferably, the first metallic profile is preferably positioned in the first quarter of the wood slab width and the second metallic profile is preferably positioned in the last quarter of the wood slab width. It further improves the mechanical behavior of the composite floor deck member during fire.

As illustrated on Figure 4 (where the wood slab 4 has been removed for the purpose of illustration), the composite floor deck member further comprises end caps 34, 35 substantially closing the gap between the metallic tray 2 and the wood slab 4 at the first and second transverse edges 8, 9 of the central part 5 of the metallic tray. The first end cap 34 is positioned transversally along the first transverse edge 8 of the central part, and preferably also along the first transverse edge 19 of the wood slab. The second end cap 35 is positioned transversally along the second transverse edge 9 of the central part, and preferably also along the second transverse edge 20 of the wood slab. The shape of the end caps is not particularly limited. They can be pieces, blocks or panels cut substantially at the shape of the cross-section of the cavity delimited by the metallic tray and the wood slab.

The end caps 34, 35 are fastened to the metallic tray 2 and/or to the wood slab 4. This fastening gives stiffness at the support point, where shear forces are more important. It helps to maintain the geometry of the floor deck member.

The end caps 34, 35 are used to anchor the longitudinal extremities of the metallic profile(s) 31 , 32. With this anchoring, in case of fire, the loads taken over by the metallic profile(s) in place of the metallic tray can be transmitted to the building structure through the end caps.

The anchoring is not limited as long as the loads can be transferred. According to one variant of the anchoring, the end cap presents for each metallic profile, a recess 37 on which a longitudinal extremity of the metallic profile can rest. Preferably the recess is substantially at the shape of the cross-section of the metallic profile(s). In that case, the longitudinal extremities of the metallic profile(s) are simply nested in the recesses of the first and second end caps. More preferably, the end cap presents for each metallic profile, a through recess. By “through recess”, it is meant a recess 37 opened on both the internal side of the end cap and the external side of the end cap. In that case (illustrated on Figure 4), the longitudinal extremities of the metallic profile(s) are nested in the through recesses 37 of the first and second end caps. More preferably, the longitudinal extremities of the metallic profile(s) are flush with the external side of the end cap. It further improves the transfer of loads to the building structure. Alternatively, the longitudinal extremities of the metallic profile(s) can be bolted to the end caps or can rest on a bracket fastened to the internal side of the end cap. In this latter case, the longitudinal extremities of the metallic profile(s) are indeed anchored to the end caps even if the anchoring is indirect.

The end caps can be made of various material among which wood and steel. Wood is preferred to limit thermal bridges. As wood has a low thermal conductivity, in case of a fire heating up the metallic tray, the longitudinal extremities of the metallic profile(s) are less affected by the fire than the metallic tray. The metallic profile(s) can further take over the metallic tray and behave with the wood slab as a single piece.

The composite floor deck member further comprises an insulation material 3 covering the central part 5 of metallic tray. It is meant here that substantially no part of the central part is uncovered with insulation material. It provides thermal insulation, and possibly acoustic insulation. The nature of the insulation material is not limited. It can be for example mineral wool, glass wool, glass foam, cellulose. In particular, during a fire heating up the metallic tray, the insulation material slows down the heating up of the wood slab 4 and of the metallic profile(s) 31 , 32. Consequently, there is preferably as much insulation material as possible in the metallic tray or within the cavity formed by the metallic tray and the wood slab. Preferably, the insulation material preferably fills in the metallic tray at least up to the metallic profile, preferably at least up to the bottom end of the metallic profile. More preferably, the insulation material preferably extends up to the half height of the metallic tray. More preferably, the insulation material extends higher than the bottom end of the metallic profile. Even more preferably the insulation material extends substantially up to the bottom side 24 of the wood slab, and the insulation material comprises cutout(s) 36 to accommodate the metallic profile(s). Alternatively, the insulation material can be in pulverulent form so that the insulation material blown in the metallic tray does not block the metallic profile(s) when the wood slab is stitched to the metallic tray.

In the first variant illustrated on Figures 1 and 2, the composite floor deck member comprises one single metallic tray, on which the wood slab is stitched. In that variant, the wood slab has preferably substantially the size of the central part of the metallic tray.

In a second variant illustrated on Figures 9 and 10, the composite floor deck member differs from the first variant in that it comprises a plurality of metallic trays, on which the wood slab is stitched. All details provided above with regard to the metallic tray apply to the metallic trays of this variant.

As the width of the metallic trays is limited by the capacities of the steelmaking industry, and is typically of the order of one meter, manufacturing a composite floor deck member with a large wood slab stitched to a plurality of metallic trays makes the transportation more efficient and the installation at the construction site more efficient and faster.

In that variant, the metallic trays are positioned adjacent to one another along the transverse axis Y. In other words, the second longitudinal edge of the central part of the first metallic tray is adjacent to, preferably in contact with, the first longitudinal edge of the central part of the second metallic tray, and so on, if applicable. More preferably, the second flange of the first metallic tray is adjacent or interlocked with the first flange of the second metallic tray, and so on, if applicable. The metallic trays have preferably the same shape and geometry to ease their positioning.

In that variant, the width of the wood slab is preferably substantially a multiple of the width of the central part of the metallic tray. Preferably, the first longitudinal edge 17 of the wood slab is substantially plumb with the first longitudinal edge 6 of the central part of the first metallic tray and the second longitudinal edge 18 of the wood slab is substantially plumb with the second longitudinal edge 7 of the central part of the last metallic tray of the plurality of metallic trays. More preferably the first transverse edge 19 of the wood slab is substantially plumb with the first transverse edges 8 of the central parts of the metallic trays and the second transverse edge 20 of the wood slab is substantially plumb with the second transverse edges 9 of the central parts of the metallic trays.

In that variant, the wood slab 4 rests on the first end wing 12 and the second end wing 14 of each metallic tray. In the case where the bottom side 24 of the wood slab 4 is shaped, the wood slab preferably comprises a main part 27, substantially parallelepiped rectangular, a first longitudinal extension 28 resting against the underside of the main part along the first longitudinal edge 17, a second longitudinal extension 29 resting against the underside of the main part along the second longitudinal edge 18 and intermediate longitudinal extensions positioned between the first and the second longitudinal extensions so that the wood slab can rest on the first end wings 12 and second end wings 14 positioned between the first end wing of the first metallic tray and the second end wing of the last metallic tray of the plurality of metallic trays.

In that variant, the wood slab 4 is stitched to each metallic tray of the plurality, in particular to each first end wing 12 and each second end wing 14 of the metallic trays.

In that variant, the wood slab 4 is further stitched to at least as many first metallic profiles 31 as there are metallic trays. Each metallic tray faces a first metallic profile resting against the bottom side 24 of the wood slab between the first end wing and the second end wing of the metallic tray and extending substantially parallel to the longitudinal axis X. All details provided above with regard to the metallic profiles of the first variant apply to the metallic profiles of this variant. Variants with a plurality of metallic profiles between the first end wing and the second end wing of a given metallic tray are of course possible.

In that variant, the composite floor deck member further comprises end caps 34, 35 for each metallic tray. All details provided above with regard to the end caps of the first variant apply to the end caps of this variant.

In that variant, the composite floor deck member further comprises an insulation material 3 covering the central part 5 of each metallic tray. All details provided above with regard to the insulation material of the first variant apply to the insulation material of this variant. From a process perspective, the composite floor deck member can be assembled as follows. In a first step, the metallic tray 2, the insulation material 3, the wood slab 4, the first metallic profile 31 and the first and second end caps 34, 35 are provided. In a second step, the insulation material is inserted in the metallic tray. In a third step, done concomitantly with the second step or before or after the second step, the metallic profiles are stitched to the bottom side of the wood slab. For convenience, the wood slab can be turned over. In a fourth step, the wood slab is stitched to the metallic tray. In a fifth step, the end caps are fastened to the metallic tray and/or to the wood slab. The process is similar in the case of a composite floor deck member comprising a plurality of metallic trays, with the exception that the metallic trays are preferably positioned adjacent to one another before the wood slab is stitched to the metallic trays.

From an installation perspective, the composite floor deck members can be shipped to the construction site and lifted to their position on the building structure. Once a second composite floor deck member is in its use position adjacent to a first composite floor deck member, and if applicable, the two adjacent members are locked. According to the variant of the composite floor deck member comprising edge rabbets, the two adjacent members can be locked with a metallic plate 25. More preferably, the metallic plate is inserted in, and is attached to, both the second edge rabbet 22 of the first composite floor deck member and the first edge rabbet 21 of the second composite floor deck member. According to the variant of the composite floor deck member with crenellated longitudinal edges, the two adjacent members can be locked by fastening parts of the second longitudinal edge of the first member lying on the first end wing of the second member to that first end wing and by fastening parts of the first longitudinal edge of the second member lying on the second end wing of the first member to that second end wing.

Alternatively, two composite floor deck members can be locked at the manufacturing site before transportation to the construction site to form a prefabricated composite floor deck assembly. As the width of the metallic trays is limited by the capacities of the steelmaking industry, and is typically of the order of one meter, assembling two composite floor deck members at the manufacturing site make the transportation more efficient and the installation at the construction site more efficient and faster.

The composite floor deck member according to the invention was tested in its variant according to Figures 1 and 2. The member had a width of 600mm. Its height was either of 200 mm (with a wood slab 60mm thick) or 260mm (with a wood slab 120mm thick). Its length was varied between 4m and 6m.

The composite floor deck member was also tested in its variant according to Figure 5. The member had a width of 600mm and a height of 320 mm (with a wood slab 120mm thick and longitudinal extensions 60mm thick). Its length was varied between 4m and 6m.

The floor load capacities were determined by loading the composite floor deck members until the deflection reaches L/350 with L the length of the composite floor deck member in mm.

The following load capacities were obtained:

- 380 daN/m ² at 4m and 184 daN/m ² at 5m for the 200mm thick member,

- 630 daN/m ² at 4m, 426 daN/m ² at 5m and 210 daN/m ² at 6m for the 260mm thick member,

- 7000 daN/m ² at 4m, 492 daN/m ² at 5m and 278 daN/m ² at 6m for the 3200mm thick member.