STRUCTURAL ELEMENT AND METHODS OF USE THEREOF
A pre-formed structural concrete element for use in the formation of a composite concrete floor of a building or the like, the element comprising: a generally planar base portion having opposing faces; a series of generally parallel spaced apart formations extending from one said faces of the base portion each defining along with an adjacent formation a void space therebetween and wherein the formations terminate in a plateau and have at least a narrow portion and a wide portion between the plateau and the one said faces of the base portion.
The present invention relates to structural engineering and more specifically to a structural member capable of use in the construction of structures such as concrete slabs and elements. The invention further relates to methods of use of the structural member including its application in preparatory formwork and as an element in a composite structure including in layered concrete. The invention also relates to structures which employ the structural member. The invention further relates to lightweight structural members used in a variety of concrete structures.
PRIOR ARTSlab beam concrete constructions is widely used in civil and structural engineering. The typical structure will comprise columns of a size dictated by applied such as dead loads and self weight and live loads and of a spacing dictated by loadings and slab spans. Reinforced and pre stressed concrete floors for buildings are generally made in one of two methods. The floors are either cast in situ using supporting temporary formwork, or are formed from pre-cast concrete planks supported on beams or walls which are then typically covered in a relatively thin in situ layer of concrete. Most major construction work of concrete buildings typically relies on the first cast in situ method in which formwork is constructed as a temporary support for structural reinforcing steel over which is poured structural concrete. Cast in situ reinforced concrete floors, require extensive formwork, are relatively time consuming and labour intensive particularly with respect to the assembly and dismantling of formwork and the time required for the in situ concrete to achieve the required strength. Existing construction systems using pre-cast elements have significant cost and other disadvantages including poor underside surface finish, ribbed profiles on the underside necessitating separate ceilings in many applications, difficulty of running services through and lack of flexibility of the type of structures which can be built. These disadvantages render in situ casting construction the preferred method of slab and floor construction.
There are currently three different types of pre-cast floor systems which are in common use in the building industry.
The first system often known as “Hollow Core” relies on the use of extruded, pre-tensioned, concrete generally rectangular planks which include a series of cylindrical holes or voids extending longitudinally along the plank. The planks are laid on the top of beams or walls and concrete is laid in situ over the top of the planks. This construction system can span relatively long distances, but has the disadvantage that it typically has a very poor surface finish on the underside necessitating in many applications a false ceiling or cladding over the concrete finish. The structural planks are typically produced in quite narrow strips requiring many joints and it is difficult to put services through the floor, as it is very difficult to access the voids. Also the planks are relatively thick and the services typically have to be either hung on the underside, also necessitating false ceilings in some applications or the services may be hidden in thick topping concrete.
A second type of system commonly known as “Ultrafloor employs pre-cast ribs in the shape of an inverted T and which are supported on walls or beams, and these ribs support a thin fibre cement panel such as a “Hardie panel” or the like extending between the ribs. A reinforced concrete floor is then laid over the ribs and panel. This floor system produces a ribbed soffit which necessitates the provision of a cover ceiling in most applications, but it does have the advantage that it is relatively easy to run services through, prior to casting the in situ layer. A further disadvantage of Ultrafloor is that it has a limited span both during concrete pouring and as a finished floor. Ultrafloor is limited in the types of floor structure which can be made from the basic panel and from the panel used in conjunction with the shell beam.
Another prior art system of floor construction is known as “Transfloor” in which a relatively thin 50 mm thick plank of concrete includes longitudinally extending steel reinforcing bars in triangular arrangements of groups of three, with one bar forming an ‘apex’ of the triangle spaced above the upper surface of the concrete plank and joined to the other two bars with steel rods. The planks are placed on top of walls or beams and void/void formers are placed on the concrete plank between the reinforcing and a concrete layer floor laid in situ on top of the plank. In the structural engineering industry the term void typically means an absence of concrete rather than an absence of material.
Void formers are most commonly formed by polystyrene blocks although other non cementitious materials such as pipe clay or the like can be used to form voids in concrete members. This system has the disadvantage that it is limited to relatively short spans of about 7 m or so. Also there is a requirement to support the floor with props and bearers at relatively close spacings of between 2 and 4 m while insitu concrete is being poured and is gaining strength. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
INVENTIONThe present invention seeks to provide an improved plank for use in forming concrete flooring which addresses and at least partially alleviates some of the problems of the prior art assemblies as discussed above.
The present invention provides a structural member capable of use in the construction of structures such as floor assemblies, concrete slabs and structural elements. The invention further provides methods of uses for the structural member including its application in preparatory formwork and as an element in a composite structure including in situ layered concrete. The invention also provides structures which employ lightweight structural concrete members.
In a first aspect of the present invention, there is provided;
a pre-formed structural element for use in forming a concrete floor of a building or the like, the plank comprising: a generally planar base portion; and a series of formations extending from the base portion, defining voids there between and wherein the upper portion of the formation is generally thicker than the lower portion of the formations at the junction with the base.
Preferably the element is manufactured from concrete cast in a mould and the formations are generally parallel spaced apart ribs. The formations have sides which are inclined relative to the planar base.
In its broadest form the present invention comprises:
a generally elongated pre cast structural element for use in the construction of a composite floor and beam slab construction, the structural element comprising;
a base and an upper surface,
at least one formation extending from the upper surface and including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess; the side walls disposed for at least part of their length at an angle other than normal to the to the upper surface.
In another broad form the present invention comprises:
a generally elongated pre cast structural element for use in the construction of a composite floor and beam slab construction, the structural element comprising;
a base and an opposing upper surface,
at least two spaced apart formations extending from the upper surface and including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a tapered recess.
According to a preferred embodiment the tapered recess has a wide portion at the upper surface of the base of the structural element and a narrow portion at or near the plateau of the formations.
Preferably the formations form longitudinal ribs along the length of the element.
Preferably each longitudinal rib is parallel to each other rib with even spacing therebetween. In an alternative embodiment, the element may be tapered along its longitudinal axis such that the ribbed formations converge in the direction of one end and diverge in the direction of an opposite end. This embodiment might be used in a case where the elements are placed in a horizontal curve. Preferably, each rib includes an outward taper such that the plateau of the formation is wider than a junction between the formation and the upper surface of the element. In one embodiment, the taper extends from the plateau of each formation at least part way towards the junction between the formation and the upper surface of the element. In another embodiment, the taper extends the full distance from the plateau to the upper surface of the base of element. In another embodiment the taper is terminated short of the plateau. In a further embodiment there is provided a shoulder associated with the plateau which receives a cover over the recess thereby maintaining a void space in the element.
Preferably each formation has a generally dovetail geometry with a narrow portion at the junction between the upper surface of the element and the formation tapering out to a wide portion at the plateau.
In another broad form the invention comprises: a construction system using a generally elongated pre cast structural element comprising;
a base having a lower underside surface and an opposing upper surface, at least two spaced apart formations extending from the upper surface and including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a tapered recess; wherein the system employs at least one said elements as part of a composite concrete slab, wherein the slab is formed by said at least one element and an overlay layer which abuts said plateau of each said formations.
In another broad form the present invention comprises:
a composite structural floor comprising;
at least one pre cast structural element having
a base having an underside surface and an opposing upper surface,
at least two spaced apart formations extending from the upper surface and each including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess, the side walls disposed at an angle other than normal to the upper surface of the base of the element;
an overlay layer which engages the at least one element via the formations.
In another broad form the present invention comprises:
a composite structural floor comprising;
at least one pre cast structural element having
a base having an underside surface and an opposing upper surface,
at least one spaced apart formation extending from the upper surface and each including a plateau and side walls each defining, a recess, the side walls disposed at an angle other than normal to the upper surface of the base of the element;
an overlay layer which engages the at least one element via the at least one formation.
According to one embodiment when two elements having one formation are abutted the upper surfaces and adjacent walls of each element combine to define a void recess which receives either a void former or overlay concrete.
According to one embodiment, the overlay layer spans between the plateaus of each said formations closing said recess thereby forming voids in said slab. The system is preferably used in the construction of a composite suspended beam and floor slab assembly. The voids improve the structural performance of the element both during construction carrying wet concrete and in the permanent composite structure. They also provide through passages for services. Preferably, the structural elements are formed in a mould which includes a steel base which imparts a smooth high quality surface finish to the element soffit. The voids reduce the weight of the element. The structural geometry of the formations allow more efficient use of concrete in that the so formed composite has a large compression flange at the top of the formations imparting to the composite a high strength to weight ratio for a given span. The elements may therefore be much thinner for a given span than a prior art conventional slab. In one embodiment the side walls of the formations are generally planar and are inclined at an angle less than 90 degrees and around 40° to 70° to the upper surface of the element. The structural element has a versatility allowing the voids to be filled with polystyrene, cement or concrete Alternatively the voids may be retained with empty spaces.
The base portion is preferably reinforced with fabric or steel rods and/or reinforcing fibres and may be pre-stressed respectively by pre tensioning or post-tensioning. Alternatively, the element may be non stressed. In one embodiment the top of the formations receive and support a sheet of material. In use, the building slab elements may be supported on walls or transverse beams arranged to define a floor. Gaps between adjacent like elements are sealed with part of a composite layer. The void spaces in each element are sealed and an in situ layer is poured over the plateaus of each formation.
The present invention will now be described according to a preferred but non limiting embodiments and with reference to the accompanying illustrations in which:
Formations 5, 6 and 7 comprise ribs with longitudinal extent and whose width increases as the distance from surface 4 increases so that there is more material at the top of the formations 5, 6 and 7. The embodiment of
Alternatively, element 21 may be extruded through a die using a relatively stiff concrete mix. Extrusion is the preferred method where polystyrene void formers are not used, although either method may be used. In use, with reference to
Because the base 49 of the element 51 is relatively thin, it is possible to place reinforcing 67 inside the voids close to the base 49 of the resultant spine beam (element 51) to resist bending of the beam. It is also possible, to place reinforcement 65 at the top of the beam when concrete overlay layer 66 is poured in situ into the spine beam 51 and over adjacent elements 63 and 64.
In a variant of the element cross-section shown in
It should be noted that Elements 77 and 78 may or may not incorporate void formers. There are two different junctions shown between elements 77 and 78 and the columns 71, 72, 73 and 74. Columns 71 and 72 are either cast with the floor or are precast and are provided with shear keys and the spine beams 77 and 78 abut the columns. In the second form there is a drop panel 79 formed by conventional formwork which connects the spine beams and adjacent slab beams to the column.
The in situ panel 79 produced with conventional formwork may be terminated at the underside plane of the precast panels 77 and 78 or may project below the general floor soffit. Throughout the specification the term soffit will betaken to mean an underside surface of a structural member. Temporary supports 99 may be required as shown to support the whole floor assembly while concrete is being poured and until it acquires sufficient strength.
An advantage of the above elements is that where a floor is required to resist bending in a lateral as well as a longitudinal direction, and/or to locally enhance the elements shear capacity, it is possible to remove portions 143 of fibre reinforced cement formwork where present and simply fill the voids with concrete in those areas where such lateral resistance to bending and/or shear capacity, is required. Similarly it is possible, though not as convenient to remove the void formers of
The versatile use of the structural elements described above provides distinct advantages over existing pre-formed concrete elements. The first advantage is that it is relatively easy to put services through the floor in voids between the formations/ribs of the elements. Secondly, the elements can be formed in a mould having a steel base which allows a high quality finish to the soffit of the element.
Thirdly, the provision of the voids reduces the weight of the element and the shape of the formations/ribs provides more concrete at the upper reaches of the composite thereby providing a large compression flange at the top of the ribs where it is required which allows the elements to be much thinner for a given span.
Fourthly, the void formers may be removed to allow overlay concrete to flow around (undercast) the dovetailed formations and engage them for shear connection. This allows these units to be readily joined to adjacent structural elements with in situ concrete producing both neat appearance and a joint which is readily fire rated as opposed to the external steel connections often employed which need to be separately fire protected.
The structural elements which form the composite floor slab have the capacity for long span without intermediate support both during construction when supporting wet concrete and when integral with the completed composite structure. Element dimensions including depth, rib shape, rib spacing, panel width, and the plan shape of the panel may be varied according to design requirements. For instance, wide panels are not restricted by fixed extrusion equipment allowing quick erection of floors with fewer joints.
The elements may be tapered relative to their longitudinal axis, for instance in a case where the elements form a horizontal radiused corner. Reinforcement in both the tensile and compression regions may be varied according to design requirements. No extrusion tools are needed to fabricate panels and the formation/ rib shape and height is largely determined by the void former shape and size which may be readily changed. The elements may be fabricated as plain reinforced, pre tensioned reinforced or post tensioned reinforced members allowing for flexibility of manufacture dictated by design requirements. Since the elements are lightweight pre cast elements, this allows economic transport and efficient lift by crane.
The use of lightweight elements allows for more lightly loaded columns and consequently smaller footings. Shallow structural depth allows more efficient buildings saving on the lengths of services, facades, and allows for more usable building space in areas where there is a height restriction.
Each element has a smooth flat soffit over whole panel width which can be treated as a final finish with no mandatory need for separate suspended ceilings are claddings. The flat soffit combined with shallow structural depth and lack of ceiling space realizes economic operation of air conditioning with no wasted “dead air” between ribs or in ceiling spaces. A further advantage of the element is the access to voids during construction allowing the installation of services in the void areas and through the relatively thin base slab of the composite. The dovetail formations with void blockouts removed provide shear connections to adjacent elements which are both neat, easily made and fire resistant as opposed to the conventional methods of other pre cast systems which either require bulky expensive and unsightly corbels or exposed steelwork which requires fire protection. Very little tooling required for the manufacture of the elements which means a low cost set up, manufacture. Also mobile manufacturing plants are economically feasible. The elements may also be manufactured on the construction site. Finally, irrespective of whether the elements are manufactured with air voids or voids filled with an insulating polystyrene, a floor is created which has optimal sound, heat and fire separation properties.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Claims
1-51. (canceled)
52. A pre cast structural element for use in the construction of a composite floor and beam slab construction, the structural element comprising:
- a base having an underside surface and an upper surface,
- at least two spaced apart formations extending from the upper surface at a web junction and each including a plateau and a wall defining, in conjunction with an opposing wall of an adjacent formation, a recess, the walls disposed at an angle other than normal to the upper surface of the base of the structural element;
- wherein the plateau width dimension of each said formations as viewed in cross section is greater than a width dimension of a corresponding web junction of each said formations.
53. A structural floor system comprising a composite slab supported by a plurality of support columns; the composite slab comprising;
- at least one generally elongated pre cast structural element comprising;
- a base and an upper surface, at least two spaced apart formations extending from the upper surface at a web junction and including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess; wherein the plateau width dimension of each said formations as viewed in cross section is at least seventy percent greater than a width dimension of a corresponding web junction of each said formations; and wherein the composite concrete slab, also comprises an overlay layer which abuts said plateau of each said formations, the composite supported directly or indirectly by said columns.
54. A suspended composite floor assembly including an array of pre cast structural elements disposed in a first orientation and an array of pre cast structural elements disposed in a second orientation; each structural element comprising:
- a base having an underside surface and an upper surface,
- at least two spaced apart formations extending from the upper surface and each including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess, wherein the plateau width dimension as viewed in cross section of each said formations is at least seventy percent greater than a width dimension of a corresponding web junction of each said formations;
- the side walls disposed at an angle to the opposing upper surface of the base of the element’ the floor assembly further comprising an overlay layer engaging the plateau of the formations.
55. A generally elongated pre cast structural element for use in the construction of a composite floor and beam slab construction, the structural element comprising;
- a base and an upper surface,
- at least one formation extending from the upper surface and including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess; the side walls disposed for at least part of their length at an angle other than normal to the to the upper surface wherein a plateau width dimension as viewed in cross section of each said formations is at least twenty percent greater than a width dimension of a corresponding web junction of each said formations.
56. A structural element according to claim 52 wherein each recess is defined by a base and walls.
57. A structural element according to claim 56 wherein each formation is spaced apart from an adjacent formation.
58. A structural element according to claim 57 wherein the formations form longitudinal ribs along the length of the element.
59. A structural element according to claim 58 wherein each recess has a wide portion at the upper surface of the base and a narrow portion adjacent the plateau of the formations.
60. A structural element according to claim 59 wherein each formation has a narrow portion near the upper surface of the base and a wide portion adjacent the plateau of the formation.
61. A structural element according to claim 60 wherein each formation includes a portion between the plateau and the upper surface of the base having a gradual increase in width as the formation extends away from the base.
62. A structural element according to claim 61 wherein a tapered region extends at least part way from the plateau of each formation towards the junction between the formation and the upper surface of the base.
63. A structural element according to claim 62 wherein, the taper extends the full distance from the plateau to the upper surface of the element.
64. A structural element according to claim 62 wherein the taper is terminated short of the plateau.
65. A structural element according to claim 62 wherein the formations include a shoulder adjacent the plateau which receives a cover over the recess thereby maintaining a void space in the element between adjacent formations.
66. A structural element according to claim 63 wherein each formation has a generally dovetail geometry with a narrow portion at the web junction between the upper surface of the element and the formation tapering out to a wide portion at the plateau.
67. A structural element according to claim 66 wherein walls of the formations are planar but inclined at an angle other than 90 degrees to the upper surface of the element.
68. A structural element according to claim 67 wherein, the voids are be filled with material selected from polystyrene, cement or concrete.
69. A structural element according to claim 67 wherein the voids are left empty.
70. A pre-formed structural concrete element for use in the formation of a composite concrete floor of a building or the like, the element comprising:
- a generally planar base portion having an upper face and an underside face;
- a series of generally parallel spaced apart formations extending from the upper face of the base each defining along with an adjacent formation a void space therebetween and wherein the formations terminate in a plateau and have at least a narrow portion and a wide portion between the plateau and the one said faces of the base portion; and wherein the plateau width dimension as viewed in cross section of each said formations is at least twenty percent greater than a width dimension of a corresponding web junction of each said formations.
71. A pre-formed element according to claim 70 wherein the formations are longitudinal spaced apart ribs extending the length of the element.
72. A pre-formed element according to claim 71 wherein the ribs include an outward taper from an upper face of the base portion to the plateau
73. A pre-formed element according to claim 72 wherein the upper portion of the ribs is generally thicker than the lower portion of the ribs.
74. A pre-formed structural element according to claim 73 wherein longitudinal formations at edges of the element are asymmetrical
75. A pre-formed structural element according to claim 74 wherein the formations intermediate the edge formations are symmetrical
76. A pre-formed structural element according to claim 75 wherein an outer edge face of longitudinal formations have a shoulder whose geometry transmits shear forces between abutting elements
77. A pre-formed structural element according to claim 76 wherein the element is tapered towards one end and relative to a longitudinal axis of the element.
78. A composite structural floor comprising;
- at least one pre cast structural element having
- a base having an underside surface and an opposing upper surface,
- at least two spaced apart formations extending from the upper surface and each including a plateau and side walls each defining, with an opposing side wall of an adjacent formation, a recess, the side walls disposed at an angle other than normal to the upper surface of the base of the element; wherein the plateau width dimension as viewed in cross section of each said formations is at least twenty percent greater than a width dimension of a corresponding web junction of each said formations; and wherein an overlay layer which engages the at least one element via the formations.
Type: Application
Filed: May 16, 2007
Publication Date: Feb 4, 2010
Inventor: Trevor Valaire (Balmain)
Application Number: 12/301,002
International Classification: E04B 5/04 (20060101); E04B 1/16 (20060101);