U.S. patent application number 12/089558 was filed with the patent office on 2009-09-03 for modular composite floor units.
Invention is credited to John Window.
Application Number | 20090217612 12/089558 |
Document ID | / |
Family ID | 35430032 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090217612 |
Kind Code |
A1 |
Window; John |
September 3, 2009 |
Modular Composite Floor Units
Abstract
The invention provides a modular composite floor unit and a
method for its manufacture. The floor unit is factory-made. An edge
frame (10) is provided from cold-rolled sheet metal members (24 and
32) welded or brazed together to create edge shuttering. A cast
concrete ceiling slab (12) is cast within the edge frame (10) over
a smooth casting surface. The cast ceiling slab (12) encases a
first inturned lip of the edge frame (10), a first lattice (26) of
reinforcing rods or wires anchored at their ends to opposite sides
and ends of the edge frame (10), and the bottom edges, or hangers
(70) suspended below the bottom edges, of an array of mutually
parallel spaced metal joists (18) which are welded or brazed to the
edge frame (10) at their opposite ends. An infill layer is then
created from blocks (16) or particulate material filling most of
the height of the exposed portions of the array of mutually
parallel spaced joists (18). A concrete floor slab (14) is cast
within the edge frame (10) over the top of the infill layer,
encasing an upper inturned lip of the edge frame (10), a second
lattice (28) of reinforcing rods or wires anchored at their ends to
opposite sides and ends of the edge frame (10), and the top edges,
or anchorage members (60) secured to the top edges, of the mutually
parallel spaced joists (18). The top surface of the cast floor slab
(14) is float-finished to create a final floor unit that requires
no screeding. The bottom surface of the cast ceiling slab (12) has
a finish defined by the surface on which it was cast, and is
visible without further treatment as the ceiling of the room below
the floor unit when the unit is used in the construction of a
multi-storey building.
Inventors: |
Window; John; (Douglas,
GB) |
Correspondence
Address: |
PIETRAGALLO GORDON ALFANO BOSICK & RASPANTI LLP
ONE OXFORD CENTRE, 38TH FLOOR, 301 GRANT STREET
PITTSBURGH
PA
15219-6404
US
|
Family ID: |
35430032 |
Appl. No.: |
12/089558 |
Filed: |
September 20, 2006 |
PCT Filed: |
September 20, 2006 |
PCT NO: |
PCT/GB2006/003474 |
371 Date: |
December 8, 2008 |
Current U.S.
Class: |
52/414 ;
52/745.05 |
Current CPC
Class: |
E04C 2/384 20130101;
E04B 5/04 20130101 |
Class at
Publication: |
52/414 ;
52/745.05 |
International
Class: |
E04B 5/40 20060101
E04B005/40 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2005 |
GB |
0520482.1 |
Claims
1. A modular composite floor unit for an above-ground-level floor
of a building, comprising: an edge frame made from cold-rolled
sheet metal edge members welded or brazed together to form an
accurately sized and proportioned edge shuttering for the floor
unit: a cast cement-based or gypsum-based ceiling slab cast within
the edge frame and encasing a first lattice of reinforcing rods or
wires; and a cast cement-based flooring slab spaced from the
ceiling slab and cast within the edge frame, encasing a second
lattice of reinforcing rods or wires which are welded or brazed at
their ends to opposite edge members of the edge frame; each of the
ceiling and flooring slabs being supported across its width by an
array of mutually parallel spaced metal joists which extend across
the floor unit between the cast slabs and are welded or brazed at
their opposite ends to opposite edge members of the edge frame; and
the space between the ceiling and flooring slabs containing a sound
insulating material of lower density than that of the cast ceiling
and floor slabs.
2. A floor unit according to claim 1, wherein the sound insulating
material completely or substantially completely fills the
inter-joist space between the cast ceiling and floor slabs.
3. A floor unit according to claim 2, wherein the sound insulating
material comprises an array of blocks of lower density than that of
the material of the cast ceiling and floor slabs.
4. A floor unit according to claim 3, wherein the blocks are blocks
of a cinder-based or porous aggregate-based cement walling block
material, expanded polystyrene, rockwool, compressed straw or balsa
wood; or are plastic or cardboard boxes filled with loose
particulate material such as rockwool, shredded newspaper, paper
mache, chopped straw, glass fibre matting or reclaimed particulate
rubber.
5. A floor unit according to claim 3, wherein the cast floor slab
has been cast directly over the tops of the array of blocks and has
been allowed to flow around and between the blocks of the
array.
6. A floor unit according to claim 2, wherein the sound-insulating
material comprises a layer of a lightweight sound absorbing
material laid over the top of the cast ceiling slab and between the
joists, and a solid board or an array of solid boards placed over
the sound absorbing material, the board or boards being supported
by the sound absorbing material or by the joists.
7. A floor unit according to claim 6, wherein the cast floor slab
has been cast over the top of the solid board or boards.
8. A floor unit according to claim 1, wherein the sound insulating
material only partially fills the space between the cast ceiling
and floor slabs.
9. A floor unit according to claim 8, wherein the sound insulating
material comprises a layer of lightweight sound absorbing material
laid over the top of the cast ceiling slab and between the joists,
and a solid board or an array of solid boards supported by the
joists at a level spaced from the top of the layer of
sound-absorbing material.
10. A floor unit according to claim 9, wherein the cast floor slab
has been cast over the top of the solid board or boards.
11. A floor unit according to claim 1, wherein each joist has one
longitudinal edge embedded in the material of the cast ceiling slab
and an opposite longitudinal edge embedded in the material of the
cast floor slab.
12. A floor unit according to claim 11, wherein the joists are made
from cold-rolled C-section steel.
13. A floor unit according to claim 1, wherein each joist has one
longitudinal edge embedded in the material of one of the cast slabs
and an opposite longitudinal edge in the space between the cast
slabs, in an alternating sequence of joists or pairs of joists
across the floor unit.
14. A floor unit according to claim 13, wherein the joists are made
from cold-rolled J-section steel, the inturned longitudinal edge of
each section being that which is located in the space between the
cast slabs.
15. A floor unit according to claim 13, wherein the joists having a
longitudinal edge embedded in the material of the cast ceiling slab
are offset laterally from those having a longitudinal edge embedded
in the material of the cast floor slab, the wall portions of the
respective joists extending more than half way across the space
between the cast ceiling and floor slabs.
16. A floor unit according to claim 15, wherein pairs of adjacent
joists, one having an edge embedded in the material of the cast
ceiling slab and the other having an edge embedded in the material
of the cast floor slab, are closely adjacent one another and
separated by a greater distance from adjacent similar pairs of
joists.
17. A floor unit according to claim 16, wherein free edges of
adjacent joists having edges embedded in the material of the same
cast slab, those free edges being the edges located in the space
between the slabs, are joined together at intervals along the
length of the joists by straps which transfer buckling loads
between the joists.
18. A floor unit according to claim 10, wherein the joists are
hollow box section joists or hot rolled parallel flanged channel
joists.
19. A floor unit according to claim 18, wherein the cast ceiling
slab is supported by the joists across its width by hangers
suspended from the joists or from some of the joists and supporting
the first lattice of reinforcing rods or wires across the width of
the cast ceiling slab.
20. A floor unit according to claim 19, wherein the hangers are
wire hangers.
21. A floor unit according to claim 19, wherein the hangers are
metal straps which pass over the joists from which they are
suspended and hang down on opposite sides of those joists, having
transverse slots in lower ends of the hangers which hook around and
support the reinforcing rods or wires of the first lattice.
22. A floor unit according to claim 18, wherein the cast floor slab
is supported by the joists across its width by being cast on a
solid board resting directly on the top of those joists.
23. A floor unit according to claim 22, wherein the cast floor slab
is anchored to the joists which support it across its width by an
array of anchorage members which are connected to the second
lattice of supporting rods or wires and are screwed to the joists
which support the cast floor slab through the solid board.
24. A floor unit according to claim 23, wherein each of the box
section joists supports both the cast ceiling and floor slabs.
25. A floor unit according to claim 23, wherein alternate ones of
the box section joists across the width of the floor unit support
the cast ceiling slab and intermediate ones of the box section
joists support the cast floor slab.
26. A floor unit according to claim 18, wherein the box section
joists contain a sound-absorbing material.
27. A floor unit according to claim 10, wherein embedded in the
cast ceiling slab and/or the cast floor slab are reinforcing
diagonal cross-struts welded at their ends to the edge frame.
28. A floor unit according to claim 27, wherein the reinforcing
diagonal cross-struts are made from ribbons of sheet metal that
have been unrolled from a roll and prevented from curling by
imparting a longitudinal crease thereto.
29. A floor unit according to claim 10, wherein each of the cast
ceiling and floor slabs has a thickness of from 50 to 100 mm, and
the space between the cast ceiling and floor slabs is from 150 to
300 mm.
30. A floor unit according to claim 29, wherein each of the cast
ceiling and floor slabs has a thickness of about 65 mm.
31. A floor unit according to claim 29, wherein the space between
the cast ceiling and floor slabs is about 225 mm.
32. A floor unit according to claim 10, wherein the surface finish
of the underside of the cast ceiling slab is a paper or fabric
material that has been laid over the casting surface on which the
ceiling slab has been cast.
33. A floor unit according to claim 10, wherein the surface finish
of the underside of the cast ceiling slab is the surface finish of
a board or plate that has been covered with a mould release agent
before casting the ceiling slab.
34. A floor unit according to claim 10, wherein the surface finish
of the top surface of the cast ceiling slab is a power float
finish.
35. A method for the manufacture of a floor unit, which comprises:
forming an edge frame by welding or brazing together cold-rolled
sheet metal edge members; welding or brazing to the edge frame an
array of mutually parallel spaced metal joists; welding or brazing
to the edge frame the ends of the reinforcing rods or wires of the
first lattice; casting the ceiling slab by pouring wet concrete or
gypsum-based plaster into the shuttering created by the edge frame,
to a depth sufficient to encase a first inturned lip of the edge
frame, to encase the first lattice of reinforcing rods or wires,
and to embed lower longitudinal edges of some or all of the
parallel spaced joists of cold-rolled sheet metal or of hangers
suspended from those joists; placing between the parallel spaced
joists of cold-rolled sheet metal the sound insulating material of
lower density than the concrete of the cast slabs and optionally
the array of solid boards to form a base for the cast ceiling slab;
welding or brazing to the edge frame the ends of the reinforcing
rods or wires of the second lattice; pouring wet concrete over the
top layer of sound insulating material or over the tops of the
solid boards to a depth sufficient to encase a second inturned lip
of the edge frame, to encase the second lattice of reinforcing rods
or wires and optionally to embed upper longitudinal edges of some
or all of the parallel spaced joists of cold-rolled sheet metal;
and providing a smooth surface finish to the top of the cast floor
slab using a power float.
Description
FIELD OF THE INVENTION
[0001] The invention relates to modular composite floor units,
being components of modular building systems or of steel frame
building systems for the rapid construction of buildings for use
either as industrial or commercial premises or as dwellings. The
invention also relates to a method for the manufacture of such
modular composite floor units.
BACKGROUND ART
[0002] Modular buildings can be constructed from prefabricated wall
panels which are bolted or welded together on site to create the
framework of the building. The prefabricated wall panels can
include pre-installed window frames, door frames, electrical
connections and/or plumbing connections to reduce the building and
finishing time on-site, and in a typical modular construction
process are assembled on-site by being moved into position by a
crane or other lifting equipment before being connected together to
create a rigid structure. If the building is a steel-framed
building then similarly the girders are lifted into position
on-site and connected together to create the rigid framework of the
building onto and into which are secured the desired external and
internal wall panels.
[0003] The floors of such buildings can be hollow or solid. By
"hollow" floors there is conventionally meant floors created from
planks or panels, generally of timber or timber-based composite
materials such as plywood, chipboard and oriented particle board,
laid over a supporting structure such as timber joists or metal
beams. By "solid floors" there is conventionally meant concrete
floors.
[0004] Solid floors are often preferred for their better sound
insulation properties, and are often specified for multi-occupancy
buildings such as apartments, hotels and student accommodation and
for industrial and commercial premises. Generally solid floors are
made principally from concrete or reinforced concrete, which may be
poured on-site. The edges of the solid floor created by pouring wet
concrete are defined by the brick work or block work defining the
periphery of the building or the room within the building into
which the floor is being laid, or by edge shuttering positioned
on-site. That edge shuttering may then be removed once the concrete
has set, or may remain in position.
[0005] Solid floors may alternatively be created by laying pre-cast
concrete flooring panels. Those panels are pre-cast off-site in
open moulds and generally incorporate metal reinforcement bars.
They are often cast with longitudinal holes or channels to reduce
the overall weight, and also are often cast with a slight convex
shape which assists stress distribution in the final building.
Ultimately however each array of pre-cast solid flooring panels is
covered with a cement screed to smooth out the surface
imperfections and irregularities. The screeded area must be kept
clear of construction personnel while the cement screed dries and
sets, and this of necessity slows down the construction process
requiring work on-site to be stopped or diverted to other areas
until the screed is sufficiently hard and durable to accept foot
traffic without damage.
[0006] EP-A-881067 discloses a modular composite wall or floor;
unit and a method for its manufacture. In fact the strength
requirements and in particular the fire resistance performance
specifications for wall and floor units are vastly different, so
the teaching of EP-A-881067 should not be misunderstood as being
that a single product can be laid vertically as a wall or
horizontally as a floor. The wall and floor units are substantially
different products but according to EP-A-881067 can share common
design concepts. The following summary of the relevant teachings of
EP-A-881067 is therefore restricted to its teachings of floor units
only.
[0007] The floor unit of EP-A-881067 is a modular floor unit in the
sense that t is cast off-site and then transported to the site of
the building under construction. It is a composite floor unit in
the sense that it is not a single cast slab of concrete that would
typify a solid floor unit. It is cast as two concrete slabs
separated by an air space or by a layer of insulation (thermal
and/or acoustic insulation). The two concrete slabs are cast one at
a time in a metal form which has a base and sides. The base gives a
smooth finish to the underside of the first slab to be cast, while
the sides of the form create the side shuttering for the wet
concrete of that first slab. A corrugated plate or array of metal
l-beams is placed over the top of the first slab to be cast, and
creates a support surface for the base of the second slab to be
cast. The sides of the second cast slab are defined by the same
shuttering as that used to define the sides of the first cast slab,
namely the sides of the metal form. If desired, an edge detail such
as a peripheral recess can be added to the second cast slab by
positioning a form liner around the periphery of the form before
casting the second concrete slab. After casting, and after the
concrete has set, the cast composite floor unit is lifted out of
the form and any form liner removed, to obtain the final composite
floor unit in which the valleys of the corrugated sheet or the
bottom flanges of the I-beam are partially immersed in the set
concrete of the first (bottom) cast slab and the peaks of the
corrugated sheet or the top flanges of the I-beams are partially
immersed in the set concrete of the underside of the second (top)
cast slab. The composite structure includes a void between the two
cast slabs, although that void may if desired be filled with a
thermal or acoustic insulation such as a foamed resin
composition.
[0008] Both the thermal and the acoustic performance of the
composite floor unit of EP-A-881067 leaves much to be desired.
Acoustically, the I-beams or spans of the corrugated metal sheet
connecting the top and bottom cast slabs provide a direct sound
path from one cast slab to the other, so the filling of the void
with an acoustic insulating material does very little to prevent
the transmission of sound from the floor defined by the top face or
the top slab to the ceiling defined by the bottom face of the
bottom slab. Fire resistance is also very poor. In a first test,
the bottom slab would rapidly detach from the corrugated metal
sheet or I-beams, and the structural integrity of the composite
floor unit would soon be lost. The composite floor unit of
EP-A-881067 would therefore fall very far short of compliance with
British Standard 476, Part 21: 1987, clause 7. That fire resistance
standard requires that the structural integrity of the floor unit
should be maintained within specified limits even after exposure of
one face of the floor unit to a furnace temperature rising to over
1150.degree. C. over a period of 4 hours, and that the mean
temperature rise of the face remote from the furnace should be no
more than 140.degree. C., with a peak temperature rise of no more
than 180.degree. C. Test results are normally reported in terms of
the time duration that elapses before one of the monitored
parameters indicates failure of the test specimen, either by some
loss of structural integrity or by an unacceptable temperature rise
at the face remote from the furnace.
[0009] It is an object of the invention to create a modular
composite floor unit which exhibits both good thermal and good
acoustic insulation and is capable of markedly better performance
characteristics than that of EP-A-881067.
[0010] It is desirable that both the upper and lower surfaces of
the composite floor unit are smooth. Therefore without on-site
screeding the floor unit will present an acceptably smooth finish
suitable for tiling or carpeting; whereas the underside is
preferably smooth enough or has a sufficiently accurate surface
finish to be visible as a decorative smooth or patterned ceiling
finish to the room below.
[0011] Most importantly, however, it is a further object of the
invention to create a modular composite floor unit which can meet
the fire resistance performance demands of British Standard 476,
Part 21: 1987, clause 7.
THE INVENTION
[0012] The invention provides a modular composite floor unit as
defined in claim 1. The invention also provides a method for the
manufacture of such a floor unit, as defined in claim 26.
[0013] One feature of the floor unit of the invention that is not
found in the floor unit described in EP-A-881067 is that according
to the invention the edge frame forms a permanent part of the floor
unit, whereas according to EP-A-881067 it is a temporary form from
which the floor unit is removed prior to use. The edge frame of the
floor unit of the invention is welded or brazed to the ends of the
lattice of reinforcing rods which ultimately will reinforce the
material of the ceiling slab. Also the spaced metal joists which
take the weight of the two cast slabs are, according to the
invention, welded or brazed at their ends to the metal of the edge
frame. The result is a composite floor unit which considerably
outperforms that of EP-A-881067 in fire resistance tests, and which
can survive the test of BS 476, Part 21: 1987, clause 7 for the
full 4 hours of the test duration without failure. At first it
appeared desirable to weld or braze to the edge frame the lattice
of reinforcing rods which ultimately will reinforce the material of
the flooring slab. Surprisingly however it has been found that the
above excellent fire resistance is obtained when only the
reinforcing rods of the cast ceiling slab are welded or brazed to
the edge frame, and the reinforcing rods of the cast flooring slab
are free from the edge frame. Freeing the ends of the reinforcing
rods of the flooring slab in this way makes it possible for the
flooring slab to be constructed as a floating floor, which gives
the composite floor unit of the invention really outstanding
acoustic insulation properties. Although fire resistance could in
theory be improved further by connecting the ends of the flooring
slab reinforcing rods to the edge frame, this would be at the
expense of increased sound transmission through the composite floor
unit, and it has been established that the preferred composite
floor unit according to the invention is one with only the
reinforcing mesh of the ceiling slab welded or brazed to the edge
frame.
[0014] The supporting joists fulfill two different functions.
Support for the second (top) slab must be to building regulation
standards for the strength and fire resistance of a load-bearing
floor. That may be provided by having the top slab simply rest on
the joists, but preferably the top slab is physically anchored to
the joists by having the longitudinal top edges of the supporting
joists embedded in the material of the top slab or by having
anchorage members secured to the longitudinal top edges of the
supporting joists and embedded in the material of the top slab.
Support for the first (bottom) slab may be to the lower building
regulation standard for the strength and fire resistance of a
suspended ceiling, although according to the invention it is
possible to surpass that standard by a very considerable margin.
The required support may be provided by having the longitudinal
bottom edges of the supporting joists embedded in the material of
the bottom slab or by having suspension members supported by the
relevant supporting joists and embedded in the material of the
bottom slab.
[0015] The sound insulating material may wholly or partially fill
the space between the two cast slabs, which may be of the same or
different materials, and the same thickness as each other or of
different thicknesses. The top slab must be of a cement based
material, such as concrete. The bottom slab may be of a cement
based material such as concrete or a gypsum based material. Typical
dimensions are that the individual slabs may be from 50 to 100 mm
thick with a separation of from 150 to 300 mm. Preferably each slab
has a thickness of about 65 mm and preferably the separation is
about 225 mm. Other preferred or optional features of the invention
will be apparent from the following description of the
drawings.
DRAWINGS
[0016] FIG. 1 is a perspective view of a modular composite floor
unit according to the invention, with a generally rectangular
periphery;
[0017] FIG. 2 is a section taken along the line A-A of FIG. 1;
[0018] FIG. 2A is an enlarged section of the right hand end portion
only of FIG. 2;
[0019] FIG. 2B is a section through the cold-rolled sheet metal
edge member of FIG. 2A illustrating its method of construction;
[0020] FIG. 2C is a section through one of the joists of
cold-rolled sheet metal visible in FIG. 2A, illustrating its method
of construction;
[0021] FIG. 3 is a section similar to that of FIG. 2A, but taken
along the line B-B of FIG. 1 through another of the cold-rolled
sheet metal edge members;
[0022] FIG. 3A is a section through the cold-rolled sheet metal
edge member of FIG. 3, showing its method of construction;
[0023] FIG. 4 is a perspective view similar that of FIG. 1, but
through the modular composite floor unit before the top layer of
concrete is poured;
[0024] FIG. 4A is a section, greatly enlarged, through one of the
reinforcing cross-straps visible in FIG. 4;
[0025] FIGS. 5 to 12 are enlarged sections, similar to that of FIG.
2A, through eight different embodiments of the invention, the
sequence of Figures being chosen to illustrate sound proofing
considerations and the techniques that can be used according to the
invention to decrease the sound transmission in various wavebands
through a series of modular composite floor units according to the
invention;
[0026] FIG. 13 is a perspective view of a connector cradle for
connecting the hollow beams of FIG. 12 to the top lattice of
reinforcing rods or wires;
[0027] FIG. 13a is a plan view of a sheet metal blank which can be
folded to form an alternative connector cradle;
[0028] FIG. 13b is a perspective view of the alternative connector
cradle created by folding the blank of FIG. 13a;
[0029] FIG. 14 is an enlarged section, similar to that of FIG. 2A,
through a ninth embodiments of the invention to illustrate another
sound proofing technique that can be used according to the
invention to decrease the sound transmission in various wavebands
through a modular composite floor unit according to the
invention;
[0030] FIG. 15 is a perspective view of a connector hanger for
connecting the lower row of hollow beams of FIG. 12 to the bottom
lattice of reinforcing rods or wires;
[0031] FIGS. 16 and 17 are enlarged sections through sheet metal
edge members of an edge frame of a modular composite floor unit
according to the invention, being the edge members of respectively
a side and an end of the edge frame, and showing an alternative
cold-rolled sheet metal profile to those shown in FIGS. 2B and
3A;
[0032] FIG. 18 is a vertical. section though the junction between
two floor units according to the invention as installed in a
building and two wall panels of the building, to illustrate the
support of the floor units by their out-turned flanges;
[0033] FIG. 19 is an enlarged section, similar to that of FIG. 2A,
through a preferred embodiment of the invention;
[0034] FIG. 20 is a perspective view of the linking strut XX as
used in FIG. 19; and
[0035] FIG. 21 is a detail illustrating the construction of the
metal edge member of FIG. 19.
[0036] The modular composite floor unit of FIG. 1 comprises an edge
frame 10 made from cold-rolled sheet metal edge members brazed or
welded together to form an accurately sized and proportioned edge
shuttering for the floor unit. Into that edge frame 10 is built up
a composite floor assembly comprising two, spaced layers of poured
reinforced concrete separated by filler materials, as will be
particularly described below.
[0037] The overall structure of the layered infill for the edge
frame 10 is illustrated in FIG. 2. A bottom layer of poured
concrete 12 and a top layer of poured concrete 14 are separated by
a space containing a layer of significantly less dense material
such as lightweight walling blocks 16. The walling blocks 16 are
supported and separated by an array of mutually parallel spaced
joists 18 of cold-rolled sheet metal, the precise shapes of which
are better illustrated in FIGS. 2A and 2C. The parallel spaced
joists 18 are welded or brazed to the edge frame 10 at their
opposite ends, and L-section pieces of cold-rolled sheet metal 20
and 22 are welded or brazed to the joists 18 and to the respective
edge frame members 24 which make up the edge frame 10, so as to
provide runners for supporting the walling blocks 16.
[0038] The bottom slab of poured concrete 12 is poured around a
reinforcing lattice of rods or wires 26 which are welded or brazed
to the edge frame 10 all around its periphery. A similar lattice of
rods or wires 28 provides reinforcement for the top layer of poured
concrete 14. The fact that the rods or wires 28 are secured at
their ends to the edge frame 10 by welding or brazing has proved to
be of enormous importance in providing the fire resistance of the
composite floor unit according to the invention. The ceiling and
floor slabs with those rods or wires as internal reinforcement are
joined integrally to the edge frame 10 in a row of such welded or
brazed connections which preferably extend completely around the
periphery of the composite floor unit. Furthermore the anchorage of
the cast slabs (ceiling and floor) to the edge frame 10 can be
considerably enhanced by allowing the unset material of the cast
slabs to flow into an around channel ends of C-shaped cold rolled
sections of the edge frame 10, and preferably through apertures
formed in the material of the C-shaped sections. For example the
poured concrete of both the bottom and top concrete slabs extends
through apertures 25, 31 formed in the edge frame members 24 and 30
into the internal cavities of the edge frame members 24 (FIG. 2A)
and 30 (FIG. 3) so that the edge frame becomes an integral part of
the composite floor unit. The mutually parallel spaced joists 18
which support the walling blocks 16 are also embedded at their top
and bottom edges in the concrete of the bottom and top layers 12
and 14, which adds to the reinforcement of those concrete slabs and
to the strength of the finished floor unit.
[0039] The edge frame members 24 and 30 (FIGS. 2A and 3) could
conceivably have the same section as one another, although the
corner joints of the edge frame 10 would then have to be mitered.
An alternative is illustrated in FIG. 3, in which the edge frame
member 30 sits inside the generally C-shaped section of the edge
frame member 24 of FIG. 2A, with an end plate 32 being welded or
brazed to the edge frame member 30 to bring it to the full height
of the edge frame 10.
[0040] The method of construction of the modular composite floor
unit of FIG. 1 will now be described. First of all the edge frame
10 is built up in factory conditions. The edge frame members 24 and
30 can be laser-cut to a very high degree of accuracy. The edge
frame members are then preferably set out on a factory floor or
work bench and held in a jig while they are welded together to the
precise size and proportions of the intended final floor unit. The
joints 18 are welded or brazed to opposite edge frame members 30
while the edge frame 10 is held in the jig, and in this way the
tolerances to which this work can be completed are vastly superior
to those attainable on a building site. The first lattice of rods
or wires 26 is then welded or brazed into position. Each of the
lattices of rods or wires 26 and 28 may be a mesh of reinforcing
rods or wires welded together into a square or rectangular grid of
crossing rods or wires, such as the reinforcing mesh sold under the
Trade Mark WELDMESH. If desired the top lattice 28 may be of
heavier duty than the bottom lattice 26 because the bottom lattice
26 will in the final multi-storey building become a part of the
ceiling of the room below, and will therefore be subject to less
strict building regulations. The securing of the bottom lattice 26
takes place all around the periphery of the edge frame 10, and all
of the assembly up to and including this stage is carried out with
the floor unit under assembly being inverted, so that the lattice
of rods or wires 26 is welded to inturned flange portions 24A and
to what will ultimately become the lower surface 30a of the edge
frame members 24 and 30 respectively. If desired, instead of a
pre-welded mesh of rods or wires the lattice 26 could be of
pre-tensioned wires 26 as described in GB 0515075.0, the individual
wires being drawn through apertures in the outer walls of the edge
frame members 24 and 30, placed under tension, and then welded from
the outside of the edge frame 10. This pre-tensioning of the
reinforcing lattice 26 can be repeated for the reinforcing lattice
28, and is possible because the edge frame 10 is securely held in
the jig on the work floor or work bench. The pre-tensioning of the
lattice is not, however, essential to the method of construction of
the composite floor unit according to the invention, and an
alternative or additional method of using pre-tension to create a
very stable edge frame structure is to incorporate diagonal
cross-braces 32 as illustrated in FIG. 4. Each cross-brace 32 is
formed by unrolling a strip of sheet metal from a roll. If a slight
crease 34 is formed in the strip metal of the cross-brace 32, by
cold-forming the strip into a slight apex along the line 34 as
shown in FIG. 4A along most of its length, then the tendency of the
cross-brace strip to reform into a curl can be largely or
completely eliminated. Each cross-brace 32 is welded or brazed at
its ends to inturned flange portions of the edge frame 10, and
preferably the cross-braces 32 when cold are under a slight tension
to ensure complete stability of the edge frame 10. The cross-braces
32 may extend generally from corner to corner of the edge frame 10,
or may be arranged in any other pattern of triangulation.
[0041] When the welding of the edge frame 10, the lattice 26 and
the optional cross-braces 32 is complete, the edge frame 10 is
turned over onto a smooth flat casting surface, ready for the
casting of the bottom layer 12 of poured concrete. The casting
surface (not illustrated in the drawings) may be any smooth flat
surface coated with a concrete mould release agent. It may, for
example, be a flat metal surface such as the smooth flat surface of
a steel plate decking in the factory. Mirror steel may be used to
provide an even smoother cast finish to the concrete that is
poured. Alternatively, the casting surface may be textured, to give
an attractive textured appearance to the underside of the cast
floor unit, which will become the ceiling of the room below in the
finished building. Clearly any texturing must be carefully
regulated so that it does not interfere with the mould release.
[0042] Alternatively, the casting surface may be covered with paper
or fabric that is preferably wetted, for example by spraying, with
a bonding adhesive that causes it to adhere to the concrete that is
poured into the edge frame 10. That provides a paper or textured
fabric finish to the underside of the resulting floor unit, which
provides the best possible paintable surface for ultimate ceiling
decoration.
[0043] The concrete layer 12 may be poured as a single layer of
liquid concrete, or it may be built up in layers. For example a
first layer, about 5 mm deep, of a grano gel coat may be poured
first, followed by 25 mm of C30 grade concrete. Concrete with a
lightweight or porous aggregate is preferred, and the depth of the
concrete is preferably marginally above the level of the runners 20
and 22, as shown by a broken lead line 36 in FIG. 2A and in FIG. 3.
It will be noted that the concrete layer 12 flows through the
apertures 25 into the edge cavities 38 and 40 created by the shape
of the edge frame members 24 and 30 respectively (see FIGS. 2A and
3). Care should be taken to fill those cavities completely for
maximum strength.
[0044] While the poured concrete is still unset, rows of walling
blocks 16 are placed on the runners 20 and 22 and between adjacent
parallel spaced joists 18, completely to fill the floor space as
defined by the edge frame 10. The walling blocks 16 are preferably
wetted before installation using a water-based bonding agent to
ensure good adhesion to the concrete, and are preferably pressed
into the unset concrete until they rest on the runners 20 and 22,
so that the displaced concrete is pushed up between adjacent
walling blocks, to provide better bonding with the walling blocks
16. The top edges of the walling blocks 16 create a generally
planar surface, indicated in FIGS. 2A and 3 by the broken lead line
42, for the pouring of the top layer of concrete 14.
[0045] Before the top layer of concrete 14 is poured, however, the
second lattice 28 of rods or wires is placed over the protruding
tops of the parallel spaced joists 18, and welded to an inturned
flange 44 of the edge frame members 24 and to an inturned flange 46
of the edge frame members 30. Over the top of the lattice 28 there
are then preferably welded diagonal cross-braces 32 as illustrated
in FIGS. 4 and 4A.
[0046] The top layer of poured concrete 14 is then poured over the
tops of the walling blocks 16. The concrete will settle down into
any gaps between the walling blocks, and will flow through
apertures in the edge frame members 24 as indicated by the shaded
portions 48 of the joist members 18 in FIGS. 2A and 2C, further to
enhance the stability and rigidity of the resulting floor unit.
Although the top layer of poured concrete 14 will flow down and
around the individual warning blocks 16, that concrete flow will
not be sufficient to fill every void between the top and bottom
layers of concrete 14 and 12, and simply for ease of
representation, in FIGS. 2A and 3 the seepage of the top layer of
poured concrete 14 down below the level of the tops of the walling
blocks 16 is not shown. The top layer of concrete 14 may be the
same thickness as that of the bottom layer 12, or may be a
different thickness. In FIGS. 2A and 3 the top layer is shown as
being of a lesser thickness. Finally, the top surface of the top
layer of poured concrete 14 is finished with a power float, to
create a final finished floor unit which has a surface finish at
least as smooth as the final screeded finish of conventional
building techniques. That finish is certainly smooth and flat
enough to take carpet, or tiles, or laminate flooring in the final
building, without requiring a final top screed.
[0047] To lift the finished floor unit from the casting surface,
lifting apertures or hooks or other handling formations (not shown)
are formed around the edge frame 10, and the finished floor unit
can be lifted, after the concrete has set, by suitable handling
equipment directly onto a lorry or other transport vehicle, to the
final site of the building under erection. The accuracy of the
dimensions of the floor unit, made under factory conditions, is
such that it can be presented up to pre-established mounting bolts
or spigots on or in the building under construction, with a virtual
guarantee of accurate alignment
[0048] Many modifications are possible to the method of
construction described above. The function of the walling blocks
16, being less dense than concrete, is to reduce the overall weight
of the floor unit. For this reason, the above description refers by
way of example to the use of lightweight walling blocks. Walling
blocks made from a cinder or porous aggregate are highly suitable,
such as those sold under the Trade Mark THERMALITE.TM.. The blocks
16 are provided for their sound insulation properties and to create
additional thickness to the floor unit without adding unduly to the
overall weight, and a number of alternative materials may therefore
be used. For example, in place of walling blocks there may be used
blocks of expanded polystyrene, blocks of balsa wood, sheets of
rockwool, sheets of fibreglass matting, or hollow moulded plastic
boxes. The blocks 16 could even be replaced by hollow boxes made
from waxed cardboard. Plastic or cardboard boxes, when used, are
preferably filled with a sound absorbing material such as rockwool,
fibreglass matting, shredded newspaper, paper mache, compressed
straw, reclaimed particulate rubber or other lightweight products
of the rubbish recycling industry. Alternatively the longitudinal
spaces between the bottom and top layers 12 and 14 of poured
concrete can be filled by a lightweight particulate material such
as chopped straw, pelleted newspaper waste, hollow balls or
polystyrene beads. Boards of wood or of a wood-based product such
as plywood or oriented particle board may then be placed over the
fill material to create the generally planar surface 42 onto which
the top layer of concrete 14 is to be poured, and the remainder of
the method of assembly is exactly as described above. If the loose
or particulate fill material is compressible, or if it does not
completely fill the space separating the two cast concrete slabs 12
and 14 of the finished floor unit, then it will be preferred to
incorporate runners (not illustrated) similar to the runners 20 and
22 of FIG. 2A, to support the boards.
[0049] The complete floor units may be transported quite easily and
safely and with very little added protection required during
transport, because they are protected from accidental edge damage
by the edge frame 10 which becomes an integral part of the
construction.
[0050] It will be seen from FIGS. 1, 3, 3A and 4 that the edge
frame members 30 are formed with out-turned flanges 33 on their end
plates 32. Similar out-turned flanges could if desired be formed on
the edge frame members 24 although they are not illustrated. The
function of the out-turned flanges is to support the floor unit
during transportation and in the final building, where the floor
unit can be laid in position to span an assembly of pre-assembled
wall panels suspended initially by the flanges before being
screwed, bolted, riveted or welded for final securement.
[0051] The top surface of the floor unit is as flat and smooth as
the power float operator can produce, which is a smoothness equal
to that of conventional floors screeded on-site. The under-surface
is as smooth as the casting surface on which the floor unit is made
which, being in factory conditions, is a very high standard of
smoothness. Alternatively it may be paper-covered by casing onto
paper as described above. Alternatively it may be textured, by
casting onto a textured fabric which adheres to the underside of
the floor unit after casting and which thus establishes the texture
of the resulting visible ceiling; or by casting onto a textured
casting surface.
[0052] The embodiment of FIGS. 1 to 4 utilises a sound insulating
material shown in FIGS. 2, 2A and 3 as walling blocks, which fill
the full height of the space between the bottom and top cast
concrete slabs 12 and 14. That creates a floor unit which provides
good acoustic insulation over a range of wavelengths, but for
better sound insulation and also, incidentally, for better thermal
insulation the sound insulating material should occupy less than
the total space between the first and second concrete slabs. FIGS.
5 to 11 show seven alternative embodiments of modular composite
floor units according to the invention in which the sound
insulation material is provided in a layer confined to the bottom
portion of the space between the first and second concrete slabs,
with an air gap above that insulation. In FIGS. 5 to 11 the same
reference numerals have been used wherever possible to those used
in FIGS. 1 to 4, and the following description is limited to the
differences between the different embodiments.
[0053] The sound insulating material illustrated in FIGS. 5 to 11
is represented as a series of mats 50 of a sound insulating
material such as rockwool. It will be understood that any
alternative particular sound insulating material could be used, or
any of the other materials discussed earlier in this specification.
In the embodiment of FIGS. 1 to 4 the joists 18 have a J
configuration as shown in FIG. 2C, the upturned flange at the
bottom of the J being used as a ledge on which to locate the
walling blocks 16. A simpler shape of joist 18A is shown in FIG. 5,
being of C section. Advantageously the level to which the bottom
layer of concrete 12 is to be poured may be marked on the joists
18A by means of a scribe mark (not shown) or an aperture (not
shown) punched through the vertical wall of the joists 18A before
assembly, so that the bottom layer of concrete 12 can be poured
until it reaches the scribe marks or the tops or bottoms of the
punched apertures. As with the previous embodiment, the first and
second lattices of reinforcing rods or wires 26 and 28 are welded
to the edge frame, as are the ends of the joists 18A.
[0054] After the bottom concrete slab has been cast to the required
depth, the insulation mats 50 are laid between the joists, and
boards 52 are placed on longitudinal supporting runners 54 which
have been welded or brazed to the supporting joists. A similar
runner 56 is spot welded or brazed to the inside of the edge frame
member 24. The boards 52 provide a base for the pouring of the
second concrete slab 14 which is poured and float-finished as
described earlier.
[0055] The air gap above the mats 50 in FIG. 5 reduces some of the
sound transmission between the top and bottom concrete slabs 14 and
12, and of course enhances the thermal insulation of the composite
floor unit of FIG. 5. The longitudinal division of that air gap
into relatively narrow horizontal channels, by virtue of the joists
18A does act to reduce the sound transmission laterally along the
floor unit, but the joists 18A themselves provide a direct linkage
and sound transmission path from one floor slab to the other, and
therefore provide a path for the transmission of sound of certain
frequencies. That sound transmission path can be broken by ensuring
that the joists are divided into two. sub-groups of joists, namely
joists 18B anchored at their ends in the top concrete slab 14 as
shown in FIG. 6, and joists 18C anchored at their lower ends in the
bottom concrete slab 12. In FIG. 6 those joists 18B and 18C are
shown as having a J section, the additional inturned flange portion
of the J section as opposed to the simple C section of FIG. 5
providing the joists with increased stability and strength against
buckling along their unsupported edges. Nevertheless the joists 18B
and 18C of FIG. 6, which are shown arranged directly aligned one
above the other, necessarily have a wall portion depending from the
top slab of concrete 14 or a wall portion upstanding from the
bottom concrete slab 12 spanning less than half of the base between
the two concrete slabs. The reinforcing effect of the joists 18B
and 18C can be enhanced significantly by using wider joists as
shown in FIG. 7, and staggering them so that the joists 18B are
offset on one side of the joists 18C. By having a relatively small
spacing between pairs of adjacent joists as shown in FIG. 7, the
turning moment transmitted from one joist to the other at the
outside edge of the edge frame is maximised, for maximum strength.
The number of joists 18B and 18C used, and their mutual spacing, is
dependent on the width of the floor unit and the length which each
joist has to span.
[0056] FIG. 8 shows an alternative arrangement of joists, with a
pair of joists 18C bedded in the bottom concrete slab 12
alternating with a pair of joists 18B embedded in the top concrete
slab 14 across the width of the floor unit. The advantage of this
arrangement is that if desired reinforcing straps 80, one only of
which is shown in FIG. 8, can be welded or brazed between the free
edges of the pairs of adjacent joists, to strengthen the joist
assembly and resist buckling.
[0057] It will be seen in each of FIGS. 6 to 8 that the runners 54
supporting the boards 52 are welded or brazed to the joists 18B
which are ultimately to be embedded in the concrete of the top slab
14. One alternative method of supporting the boards 52 is shown in
FIG. 9. Blocks of expanded polystyrene 90 are placed on the top
edges of the joists 18C, and taller blocks of expanded polystyrene
92 are placed on the inturned and upturned bottom edges of the
joists 18B. The boards 52 are simply balanced between adjacent
pairs of blocks 90 or 92 prior to pouring the concrete of the top
layer 14. Expanded polystyrene is a very poor conductor of sound,
so that there is very little sound transmission from the top
concrete slab 14 to the bottom concrete slab 12 through the blocks
90 and 92, which do not play any structural role in the final floor
unit once the concrete layer 14 has set. It will be understood of
course that a combination of polystyrene blocks and runners could
be used. For example FIG. 10 shows a combination of the polystyrene
blocks 90 placed on the tops of the joists 18C, and runners 54
welded to the joists 18B. FIG. 10 also illustrates how service
ducts can be incorporated into the floor units of the invention.
FIG. 10 illustrates a service duct 100, which may be for example a
plastic conduit, extending laterally of the joist 18B and 18C. The
duct 100 is suitable for carrying electrical wiring either
completely across the floor unit or from an outside edge to a mid
position where it could be taken down through the ceiling, up
through the floor, or simply turned at 90.degree. to run parallel
with the joists. The conduit 100 passes through holes punched in
the joists 18B and 18C, but those holes are of different sizes so
that the conduit contacts and is supported by the joists 18B as
illustrated in FIG. 10, whereas it makes no contact at all with the
joists 18C. Equally, the relative sizes of the holes punched in the
joists could be reversed so that the conduit is supported by the
joists 18C and makes no contact with the joists 18B. By avoiding
contact with the joists of one set, it can be ensured that sound
transmission through the floor unit does not travel through the
conduit 100.
[0058] FIG. 11 shows an alternative location for the service
conduit 100, beneath the joists 18B and supported by holes punched
in the joists 18C. The acoustic insulation mats 50 in FIG. 11 are
shown as thicker than those in FIGS. 5 to 10, but that is
principally because in this embodiment the mats have to be wrapped
up and over the conduit 100, giving them increased height along the
section line of FIG. 11. Of course, the acoustic insulation mats 50
of FIGS. 5 to 11 can be of any thickness, even occupying the full
height between the bottom concrete slab 12 and the boards 52 on
which the top concrete slab 14 is laid.
[0059] In FIGS. 5 to 8 the top slab 14 is cast over an array of
discrete boards 52. These boards 52 are supported on runners 54
secured to the joists 18A or 18b which support the top slab across
its width. Use of separate boards 52, one between each pair of
adjacent supporting joists 18A or 18B, requires an additional step
of cutting the individual boards 52 to size and assembling them one
by one between the joists and supported on the runners 54. A
preferred construction is to use a single board 52A as shown in
FIG. 12. That board 52A is placed directly over the top of joists
18D which support the top slab 14 across its width. Those joists
18D are shown in FIG. 12 as being hollow box section joists,
although they are made from cold-rolled sheet metal, as are the
joists 18 of FIG. 2C and the joists 18A of FIGS. 5 to 8. The very
fact that the rigid board 52A rests on the hollow section joists
18D means that the joists 18D support the top slab 14 across its
width, but that support is advantageously considerably enhanced by
a series of anchorage members 60 which are screwed to the hollow
joists 18D by means of self-tapping screws 62 which pass through
the solid board 52A. The anchorage members 60 are cradle-shaped as
shown in FIG. 13, each comprising a pair of upright sides 64
upstanding from a flat base 66. Slots 68 are cut in the top
portions of the upright sides 64 to straddle the rods or wires of
the enforcing lattice 28. When the anchorage member 60 is screwed
to the hollow beams 18D through the rigid board 52A, this provides
the total support for the reinforcing lattice 28 both in the upward
direction and the lateral directions, as well as the main load
bearing downward direction.
[0060] Each cradle 60 of FIG. 13 supports the reinforcing rods or
wires of the lattice 28 running in one direction only, but
different cradles 60 can be oriented in mutually perpendicular
directions so that together they support both the longitudinal and
the lateral reinforcing rods or wires of the lattice 28.
Alternatively cradles 60a as illustrated in FIGS. 13a and 13b can
be used. FIG. 13a illustrates a sheet metal blank 60b from which
the cradle 60a of FIG. 13b can be formed by bending. Rows of oval
cut-outs in the blank 60b are separated by relatively narrow metal
webs 63 so as to define fold lines enabling the sheet metal blank
of FIG. 13a to be easily bent by hand to the shape of FIG. 13b. A
pre-formed hole 65 is provided in the flange which becomes the base
of the final cradle 60a to receive the screw 62 of FIG. 12, and
slots 68a and 68b receive the longitudinal and lateral reinforcing
rods respectively of the reinforcing lattice 28. The slots 68a and
68b may be at the same distance from the base as shown in FIG. 13b,
in which case the cradle 60a is easily twisted along one of the
fold lines in use to bring the slots to the mutually different
levels of the longitudinal and lateral reinforcing rods; or the
slots 68a and 68b may be at mutually different heights to reflect
the different levels of the longitudinal and lateral reinforcing
rods.
[0061] FIG. 12 shows that the joists 18C supporting the bottom slab
12 are constructed in the same way as those of FIG. 8, and
connected together at intervals by lateral straps 80. The box
section joists 18D are considerably stronger than the separate
J-section joists 18C even when those joists 18C are joined together
by straps 80, and an even stronger construction is therefore that
shown in FIG. 14 in which the joists supporting the bottom slap 12
are hollow box section joists 18E, similar to the hollow joists 18D
supporting the top slab. The support between the hollow joists 18E
and the bottom slab 12 is provided by a series of hangers 70 which
are as shown in FIG. 15. Each hanger is a metal strap which passes
over the joist from which it is suspended, and hangs down on
opposite sides of that joist. Transverse slots in the lower ends of
the hangers hook around and support the reinforcing rods or wires
of the first lattice 26 to provide the necessary support across the
width of the bottom slab 12.
[0062] It will be understood that instead of the metal of the strap
hangers 70 as shown in FIG. 15, the reinforcing lattice 26 for the
bottom slab could be supported from the hollow joists 18E by wires.
Depending on the length and diameter of the supporting wires, this
will provide very limited sound transmission between the hollow
beams 18E and the lower slab 12, which gives the possibility of a
further embodiment (not illustrated) in which each transverse joist
18 can be formed as a hollow box section joist that both supports
the top slab as shown in FIG. 12 and supports the bottom slab by
means of connecting wires.
[0063] Although not illustrated, the hollow box section joists 18D
and 18E of FIGS. 12 and 14 can be wholly or partially filled by a
sound-absorbing material. Instead of the joists 18 of FIG. 12 and
the joists 18D and 18E of FIG. 14 being formed as hollow box
sections as illustrated, an improvement in strength, as compared
with the simple J-section joists 18B and 18C of FIGS. 6 to 11, can
be obtained by forming each joist of FIG. 12 or 14 from two
identical J-section joists placed back-to-back and secured together
by spot-welding.
[0064] Another modification (not illustrated) is to place a layer
of acoustic rubber over the tops of the box sections 18D or the
single or back-to-back J-sections, together possibly with an edge
trim of acoustic rubber between the cast concrete of the top slab
14 and the edge frame 10. This gives a floating floor without
detracting from the excellent rigidity and acoustic superiority of
the modular floor units as described and illustrated.
[0065] FIGS. 16 and 17 show an alternative section for the edge
frame members 24 and 30 of the edge frame 10. FIG. 16 shows that
the out-turned flange 148 at the top of the edge frame member 30 is
slightly lower than the top level of the concrete slab 14. As with
FIG. 3A the edge frame member 30 is made in two pieces, 30a and
30b, with an outer side plate 30A forming that out-turned flange
148. FIG. 17 shows the out-turned flanges being level with the top
of the top slab 14 of concrete. The way in which the lowered flange
148 of FIG. 16 is useful in the actual construction of buildings
using floor units according to the invention is illustrated in FIG.
18. 140 shows the top of a wall of the building, on which two floor
units according to the invention are supported. FIG. 18 shows one
floor unit 142 to the right of the wall top 140, and one floor unit
144 to the left. A rubber sheet 146 is placed over the top cap of
the wall top 140 to reduce sound transmission through the final
building, before the top floor units are placed in position,
suspended on their out-turned flanges 148. Self tapping screws or
anchorage bolts 150 are passed through downwardly extending
anchorage plates 152 that are welded or brazed to the side plates
32 of FIG. 16 to render the assembly rigid. The building is then
ready to be increased in height by one further storey. If the
flanges were not recessed below the top of the top floor slabs,
there would be no positive line along which to locate the next
higher wall panel 154. By virtue of the recessed nature of the
flanges 148, the next wall panel 154 can be positively located in
the shallow slot formed between adjacent floor units 142 and 144,
and is preferably protected from direct metal to metal contact with
the flanges 148 by another strip of rubber 156. If desired, filler
pieces of rubber, plastic or metal can be placed between the top
edges of the adjacent floor units 142 and 144 and the wall. panel
154 being assembled into position, to shim the wall panel 154 into
totally accurate alignment.
[0066] FIG. 18 also shows a pair of flexible hangers 158 of the
wall panel 154, to which plasterboard panels 160 are attached in
conventional manner. An intumescent strip 162 is placed along the
bottom of each set of plasterboard panels 160, to fill the gap
between the plasterboard and. the floor of the building being
constructed.
[0067] It will be appreciated that the construction detail shown in
FIG. 18 reduces the amount of sound transmission vertically through
the building, so that the sound insulation properties of the floor
units of the invention are put to very good effect.
[0068] The most remarkable advantage of all of the embodiments of
composite floor unit according to the invention as illustrated in
FIGS. 1 to 18 is however their fire resistance. There is very
little distortion of the floor units in the event of a fire,
because of the anchorage of the rods or wires of the internal
reinforcement of the two cast slabs to the edge frame by welding or
brazing, and because of the anchorage of the joists 18, 18A, 18B,
18C, 18D and 18E of the various embodiments to the edge frame by
welding or brazing. The joists 18 to 18E of the various illustrated
embodiments described above have been cold-rolled steel profiles. A
further embodiment as illustrated in FIGS. 19 to 21 uses hot-rolled
metal section joists 18F which are of parallel flanged channel
profile. Alternative hot-rolled profiles would be I-beam or
hot-rolled box section. A modular composite floor unit as described
with reference to FIG. 19 was extensively tested in a fire
resistance test and amazingly survived the test for the full 240
minutes of the BS 476 Part 21: 1987, Clause 7 test.
[0069] Referring to FIGS. 19 to 21, the sides of the edge frame 30
are constructed in two pieces as in FIG. 21. The parallel flanged
channel joists 18F are welded or brazed to the edge frame 30 at
their ends. Hangers 70 shaped as in FIG. 16 straddle the joists 18F
and support a welded mesh lattice 26 of reinforcing rods which will
provide the reinforcement for the bottom cast slab 12 (the ceiling
slab). All ends of the welded mesh lattice 26 are welded or brazed
to an upturned and inturned flange portion of the edge frame 30.
The welded mesh reinforcing lattice 26 is therefore supported
across its central portion by the hangers 70 and secured firmly to
the edge frame 80 all around the periphery. At this stage the
ceiling slab 12 is cast, with the cement-based or gypsum-based
casting material flowing into the edge channel of the edge frame 30
all around the periphery of the floor unit and around the
reinforcing lattice 26 across the centre. A bottom portion of each
hanger 70 is encased in the cast slab 12 but the joists 18F are
above the level of the cast slab 12.
[0070] Insulation 50 such as high density rockwool insulation
matting (for example that sold under the Trade Mark BEAMCLAD) is
then packed into the voids above the cast slab and between the
joists 18F, and one or more solid boards 95 placed over the tops of
the joists 18F. A very suitable material for those boards 95 is a
fibre board impregnated with bitumen, as sold under the Trade Mark
BITROC. If desired, additional support for the boards 95 can be
provided by first placing transverse beams 96 between pairs of
adjacent joists 18F at intervals along the length of the joists
18F. Each transverse beam 96, of which one is shown in perspective
view in FIG. 20, comprises a box section support portion for the
solid board 95 and a pair of mounting plates 97, one at each end.
The mounting plates 97 overlie the joists 18F as shown in FIG. 19,
and can if desired be secured in position by self-tapping screws
(not shown) or by spot welds.
[0071] The solid boards 95 provide a base support for the upper
slab of concrete 14 that is to be cast over the top of the
composite floor unit. Before that concrete is poured, however, the
lattice 28 of reinforcing rods is secured in position. Mesh
anchorage members 60 or 60a, as already illustrated in FIG. 13 or
in FIGS. 13a and 13b, are secured at intervals over each joist 18F
and are secured to the joist 18F using self-tapping screws 62 which
pass through the solid board 95 and into the joist. The lattice 28
of welded reinforcing rods is supported by the slots in the
anchorage members 60 or 60a and held spaced above the boards 95
across the width of the composite floor unit. The edge frame 30 is
itself made from two components 30a and 30b welded together as
illustrated in FIG. 21.
[0072] Although not illustrated in FIG. 19, a sheet of polythene is
laid over the boards 95. The edges of the polythene sheet are
trapped in the C-section component 30b of the edge frame 30 by
strips 30c of expanded polystyrene inserted into the C-section
component 30b between its upper and lower flanges. The cast floor
slab 14 is therefore effectively a floating floor, supported across
its width by the parallel flanged channel joists 18F but isolated
from the edge frame 30 by the expanded polystyrene strips 30c. The
improvement in acoustic insulation of the resulting composite floor
unit is remarkable. There is very little sound transmission from
the floor slab 14 to the framework of the building (for example to
the wall top 140 of FIG. 18) because of the provision of the
expanded polystyrene strips 30c and the free floating nature of the
floor slab 14. Fire resistance could of course be improved by
welding or brazing the ends of the reinforcing rods of the lattice
28 of the floor slab 14 to the edge frame 30, just as the ends of
the reinforcing rods of the reinforcing lattice 26 of the ceiling
slab are so welded or brazed. That would however be at the expense
of the sound insulation improvement that is obtained by making the
floor slab free-floating. Surprisingly, it has been found that the
fire resistance is so outstandingly good when only the bottom
reinforcing lattice is welded or brazed to the edge frame 30 that a
similar edge connection of the top reinforcing lattice is
unnecessary.
[0073] The floor unit as illustrated in FIGS. 19 to 21 was tested
for fire resistance in accordance with British Standard 476: Part
21: 1987, clause 7. The unit was tested for its ability to comply
with the performance criteria for load-bearing capacity, structural
integrity and thermal insulation. During the test the specimen
floor unit being tested carried a surface load of 2 KN/m.sup.2
evenly distributed over its top surface. Thermocouples were
positioned over the top surface of the unit being tested, and the
unit was suspended over a furnace which enabled it to be heated
from below. The test was continued for four hours as specified in
BS476, and the specimen survived the full duration of the test.
[0074] Even though the furnace temperature was raised to
1152.degree. C. during the test, the maximum temperature of the top
surface of the floor unit even after 4 hours was only 68.degree.
C., indicating excellent thermal insulation between the top and
bottom slabs of the floor unit. Structural integrity and
load-bearing capability were maintained for the full 4 hours of the
test although there was a slight (but acceptable) bowing or sagging
of a part of the bottom slab towards the end of the test. The
specimen under test still satisfied the test criteria for upper
surface temperature, load-bearing capacity and structural integrity
at the end of the 4-hour test, which represents really astonishing
performance characteristics, way beyond expectations which were for
at most a 90-minute satisfaction of all of the test criteria.
[0075] In addition to the quite unpredictably high fire resistance
of the specimen floor being tested, that same floor unit had
previously been subjected to a test for acoustic insulation. It was
found to be far superior to conventional solid floors and to
conventional hollow floors. The excellent acoustic properties are
thought to be a combination of the dense nature of the top and
bottom slabs, the fact that those slabs are anchored all round
their periphery to the edge frame by virtue of the welded or brazed
connections between the reinforcing lattice of rods or wires and
the edge frame and between the joists and the edge frame, and the
less dense interior of the composite floor unit. The less dense
interior, provided by the rockwool 50 and the air gap over the
rockwool, provides good acoustic insulation. The direct acoustic
paths through the composite floor unit from the top surface to the
bottom surface are largely confined to the self-tapping screws 62
linking the top slab 14 to the joists 18F, and the mesh hangers 70.
By judicious spacing of those hangers 70 the composite floor unit
of the invention achieves, in a total thickness or depth of less
than 300 mm for the floor unit, a level of acoustic insulation that
might be expected of a conventional floor unit at least twice as
thick.
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