Note: Descriptions are shown in the official language in which they were submitted.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
1
PRECAST CONCRETE FORMWORK, FLOOR SYSTEM AND A METHOD OF
CONSTRUCTION
TECHNICAL FIELD
The present invention relates to the field of construction and more
specifically relates
to a floor system and an associated method of forming a floor system.
BACKGROUND
Any references to methods, apparatus or documents of the prior art are not to
be
taken as constituting any evidence or admission that they formed, or form part
of the
common general knowledge.
Suspended flooring systems with pre-cast components are gaining popularity for
both
residential and commercial construction projects. Formwork is a structural
component
that is temporarily used during construction phase and plays a significant
role in the
concrete building industry. Improper design of the formwork may cause partial
or full
collapse of a building during construction and/or excessive cracking and
deformation
at the operational stage. Furthermore, inappropriate stiffness of the formwork
affects
the surface finishes of the concrete structure. Therefore, a stiff formwork
results in a
flatter and smoother finish.
The shape of the formwork is also affected by the shape of the final
structural
elements. Hence, preparation and assembling of formworks can be time consuming
and a costly process. Eliminating the step of preparation and assembling of
formwork
is also highly desirable because minimizing the use of formwork may enhance
safety
for construction personnel and increase the speed of construction whilst also
decrease the cost associated with it.
Depending on the slab type, steel or timber formworks have been previously
used. In
some instances, where propping of the formworks is not possible precast
concrete
slabs have been used.
One of the commonly used floor systems with precast concrete slabs comprises
joists and blocks. The joists are mostly placed with gaps ranging between 400
to 600
mm. The gap between the joists is filled with concrete or other types of
masonry
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
2
blocks and the joists and blocks are subsequently covered by a fresh concrete
overlay of 60 to 120 mm thick concrete layer. The system acts as a one-way
ribbed
slab. Such a floor system uses a simple construction method but can be time
consuming and is not suitable for use in long spans and normally results in a
thick
floor system.
Another commonly used floor system is known as the composite floor system.
Composite floors are mostly used with steel structures. The distance between
beams
used in these systems varies from 900 mm to 3000 mm with economical distance
of
about 1200 mm to 2400 mm. Steel beams used in these system must be fire rated
to
meet relevant building code requirements which makes these floor systems
expensive. Further, shear studs must be installed at the top flange of the
beam to
shape proper connections between the concrete slab and the supporting steel
beam.
The process of installing such composite floor systems can be time consuming
and
demands onsite welding and the integrity of the system depends on the strength
of
shear studs and their connections to the steel beam.
Yet another floor system is known as the waffle slab system. The waffle slab
system
comprises a two-way slab that is made of GRP (fibreglass) moulds. The system
contains integrated joists that extend in both directions. The distance
between joists
varies between 600 mm to 1200mm. Even though, the waffle slab system is
suitable
for covering long spans, this system is not economical for use in large scale
construction. Construction of the waffle type slab system can also be time
consuming.
There is a need for providing an improved floor system that overcomes the
deficiencies of the prior art floor systems.
SUMMARY OF THE INVENTION
In a first aspect, the invention provides formwork for constructing a floor
system in a
building, the formwork comprising:
a plurality of pre-cast concrete joists positioned in a generally parallel
arrangement, wherein one or more of the joists comprises: a horizontal base
portion;
and an upwardly directed portion extending substantially along the length of
the joist,
the upwardly directed portion having spaced apart surfaces extending upwardly
from
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
3
the base wherein respective shelf portions of the base are located adjacent
said
upwardly directed portion;
a plurality of pre-cast concrete members for extending along a length of the
joists for receiving wet concrete; and
a supporting arrangement to support opposite ends each of the pre-cast
concrete members upon oppositely arranged shelf portions of two adjacent
joists.
In one embodiment, one or more of the pre-cast concrete members comprises a
shell
for receiving wet concrete, the shell being adapted to be coupled with
respective
downwardly directed supporting portions for supporting the shell on the
oppositely
arranged shelf portions of two adjacent joists.
In an embodiment, the supporting portions are integrally formed with the pre-
cast
members.
In an alternative embodiment, each of the pre-cast supporting portions
comprises an
in-use lower portion for being positioned on the respective shelf portions and
an in-
use upper portion for being coupled with lateral ends of the pre-cast members.
In an embodiment, the supporting portions are adapted to extend along a length
of
the joist.
In an embodiment, an outer surface of the pre-cast concrete members in
combination
with the surface of the upwardly directed portion of the supporting joists
positioned at
opposite ends defines an in-use receiving portion for receiving wet concrete.
In an embodiment, the pre-cast concrete members comprises edge portions
extending along a length of the pre-cast concrete members wherein preferably
at
least a first edge portion extends along a first lateral side of the pre-cast
concrete
member and at least a second edge portion extends a second lateral side of the
pre-
cast concrete member.
In an embodiment, one or more of the pre-cast concrete members comprises:
a pan for receiving the wet concrete; and
shoulder portions located at opposite ends of the pan, said shoulder
portions being adapted to be supported on the oppositely arranged shelf
portions of
two adjacent joists.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
4
In an embodiment, the pan in combination with the surface of the upwardly
directed
portion of the supporting joists positioned at opposite ends defines an in-use
receiving portion for receiving wet concrete.
In an embodiment, the pre-cast concrete joists are supported by a plurality of
beams
extending generally in a perpendicular direction relative to the general
direction of the
said pre-cast concrete joists.
In an embodiment, the beam comprises a beam portion with a substantially flat
profile
with two spaced apart formations extending upwardly from the beam portion, the
said
formations extending along a length of the beam and joist receiving portions
extending outwardly from the said formations for supporting an end portion of
a
plurality of joists.
In an embodiment, an outwardly projecting end portion of the plurality of
joists is
supported upon a joist receiving portion of the beam portion, the joist
receiving
portion of the beam preferably extending in a perpendicular direction relative
to the
said projecting end portions of the joist.
In an embodiment, an underside bottom surface of the beam substantially lies
in the
same plane as a bottom surface of the joist.
In an embodiment, the formwork further comprises:
a first connecting mechanism for connecting a first joist positioned on a
first lateral
side of the beam with a second joist positioned on a second lateral side of
the beam,
said connecting mechanism being further adapted for preferably applying a
negative
bending force to the first and second joists during use; and
a second connecting mechanism for connecting two adjacently located beams
supported simultaneously on a column, the connector being provided for
applying
negative bending to said adjacently located beams.
In an embodiment, the formwork further comprises column formwork members for
forming columns to support said beams wherein each of the column formwork
members can be inter-connected to define a hollow portion for receiving wet
concrete.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
In an embodiment, end portions of each of the column formwork members
comprises
connecting portions for inter-connecting the column formwork members such that
imaginary plane of a first column formwork member is transversely arranged
relative
to an imaginary plane of second column formwork member inter-connected with
the
5 first column formwork member.
In an embodiment, said locking portions extend along a longitudinal edge of
the
column formwork member such that in an inter-connected configuration the
locking
member is adapted to be received in a recess of another of said column
formwork,
said recess extending along a longitudinal edge of said another column
formwork.
In an embodiment, the formwork further comprises one or more permanent
formwork
members for being positioned in between two spaced joists and wherein
preferably
the permanent formwork members comprise a substantially L-shaped or U-shaped
cross section.
In an embodiment, the joists of the formwork further comprise one or more
apertures
for receiving reinforcing bars, the reinforcing bars extending in a transverse
direction
relative to the general direction of the joists, the reinforcing bars being
adapted for
being tensioned (by way of post-tensioning) after pouring concrete into the
pre-cast
concrete receiving members.
In another aspect, the invention provides a pre-cast concrete joist
comprising: a
horizontal base portion; and an upwardly directed portion extending
substantially
along the length of the joist, the upwardly directed portion having spaced
apart
surfaces extending upwardly from the base wherein shelf portions of the base
are
located adjacent said upwardly directed portion, each of the shelf portions
defining a
seat for receiving a connecting portion of a pre-cast concrete pan member or a
pre-
cast concrete shell member wherein height of the upwardly directed portion is
equal
to or greater than vertical height of the said shelf portions.
In yet another aspect, the invention provides a pre-cast concrete member for
being
positioned in between and supported spaced apart joists or beams, the precast
member extending along a length of the joists or beams for receiving wet
concrete,
the precast member comprising a supporting arrangement to support opposite
ends
each of the pre-cast concrete members upon oppositely arranged joists or
beams.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
6
In another aspect, the invention provides a method of constructing a suspended
floor
in a building, the method comprising the steps of:
positioning a plurality of pre-cast concrete joists in a generally parallel
arrangement,
wherein one or more of the joists comprises: a horizontal base portion; and an
upwardly directed portion extending substantially along the length of the
joist, the
upwardly directed portion having spaced apart surfaces extending upwardly from
the
base wherein shelf portions of the base are located adjacent said vertical
portion;
positioning a plurality of pre-cast concrete members in between adjacently
located
joists, said pre-cast concrete members being positioned for extending along a
length
of the joists for receiving poured concrete;
supporting opposite ends of each of the pre-cast concrete members upon
oppositely
arranged shelf portions of two adjacent joists; and
pouring fresh concrete into a receiving portion defined by the pre-cast
concrete
members.
In at least some embodiments, the invention also comprises modular precast
concrete formworks (MPCF) that includes joists, infill thin shells, beams,
columns,
and walls designed to eliminate or minimize the use of formwork and propping
systems in concrete structures. The MPCF has been designed to withstand its
self -
weight together with construction related loads prior to on-site concreting.
After
installation, additional reinforcing bars (if required) are placed over the
MPCF. A
concrete overlay with a nominal thickness of not more than 70 mm is then
placed
over the MPCF to generate the final one-way or two-way flooring system. The
MPCF
looks a permanent formwork that is integrated and will be part of the final
flooring
system to bring the following superior benefits to the construction industry:
= High-Quality Soffit Finishes;
= Less on-site concreting (in this invention 1 m3 covers between 11.5 m2 to
14
m2 of floor area where as in the traditional method it only covers between 3
m2 to 6
m2);
= Less on-site reinforcing (Normally, single reinforcing mesh is enough
even for
long spans);
= No additional formworks;
= Minor propping (single prop at mid span of joists in large span floors or
no
prop for medium to small span floors);
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
7
= Edge beams are equipped with proper connections for installation of
temporary suspended scaffolding platform. Hence, no need for full scaffolding
system;
= The use of this invention offers a better serviceability limits in the
final floor
system;
= The invention deems to satisfy minimum 2 hour fire rating.
= A rapid increase in the construction speed and a reduction in
construction
costs.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred features, embodiments and variations of the invention may be
discerned
from the following Detailed Description which provides sufficient information
for those
skilled in the art to perform the invention. The Detailed Description is not
to be
regarded as limiting the scope of the preceding Summary of the Invention in
any way.
The Detailed Description will make reference to a number of drawings as
follows:
Figure 1 is a perspective view of a one-way floor system 400 and a two-way
floor
system 400' used in a building 1000 in accordance with a first and second
embodiment of the present invention.
Figure 2A is a perspective view of a pre-cast concrete member in the form of a
plank
member 100 in accordance with an embodiment of the present invention.
Figure 2B is a right hand sectional view of the plank member 100.
Figure 2C is a sectional view of a second embodiment of the plank member 100'.
Figure 2D is a sectional view of a third embodiment of the plank member 100".
Figure 2E is a perspective view of a step plank unit 100".
Figure 3 is an in-use sectional view of the plank member 100 having an
indefinite
length.
Figure 4 is a sectional view of plank supporting member 110' in accordance
with an
embodiment of the invention.
Figure 5A is an in-use sectional view of the plank member 100" supported upon
the
supporting member 110'.
Figure 5B is a perspective view of the plank member 100" supported upon the
supporting members 110' located at either lateral end of the plank member
100".
Figure 6A is a perspective view of a pre-cast joist 140 in accordance with an
embodiment of the invention.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
8
Figure 6B is a sectional view of the pre-cast joist 140.
Figure 6C is a sectional view of an alternative embodiment of a pre-cast joist
140'.
Figure 7 is a sectional view of the two-way floor system 400" in accordance
with an
embodiment of the present invention.
Figure 8A is a U-shaped permanent formwork member 120' in accordance with an
embodiment of the present invention.
Figure 8B is a sectional view of the U-shaped permanent formwork member 120'.
Figure 9A is an L-shaped permanent formwork member 120 in accordance with an
embodiment of the present invention.
Figure 9B is a sectional view of the L-shaped permanent formwork member 120.
Figure 10A is a perspective view of a pre-cast band beam 150 in accordance
with an
embodiment of the present invention.
Figure 10B is a sectional view of the pre-cast band beam 150.
Figure 11A is a perspective view of a pre-cast edge beam 160 in accordance
with an
embodiment of the present invention.
Figure 11B is a sectional view of the pre-cast edge beam 160.
Figure 12 is a perspective view of the band beam 150 supported on column units
170.
Figure 13A is a sectional view of a square-shaped column unit 170 in
accordance
with an embodiment comprising column formwork members 300 being inter-
connected to form a hollow portion to receive fresh concrete.
Figure 13B is a sectional view of a rectangular column unit 170'.
Figure 13C is a sectional view of the column formwork member 300.
Figure 14 is a perspective view of the two-way flooring system 400'.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Figure 1 a building structure 1000 comprising a one-way floor
system
400 and a two-way floor system 400' in accordance with a first and second
embodiment of the present invention. It shall be understood by the person
skilled in
the art that it is not necessary to use both flooring systems 400 and 400' in
the same
building structure. By way of example, either a one-way floor system 400 or a
two-
way floor system 400' may be used in an alternative building structure without
departing from the spirit and scope of the invention.
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
9
Referring to Figures 1 and 7, the suspended one-way floor system is built by
using
modular precast concrete formworks. The system may comprise an array of
parallel
pre-cast concrete joists 140 positioned in a generally parallel arrangement.
Each of
the joists 140 spans between supporting elements such as a pair of elongate
band
beams 150. Each of the joists 140 is supported upon two band beams 150
positioned
along either end of the joists 140. The band beams 150 and the joists 140 are
generally arranged in a mutually perpendicular orientation. The band beams 150
are
positioned and supported by upright columns or posts 170.
A plurality of pre-cast concrete members in the form of pan units 110 extend
in
between adjacently located pre-cast joists 140. Referring to Figure 5A and 5B,
it is
clearly illustrated that each pan unit 110 comprises a pre-cast plank 100"
that
extends in between two lateral sides 101A and 101B. At each of the lateral
sides,
supporting structures 110' are provided for supporting the pan unit 110 upon
the two
adjacently located joists 140.
Referring Figures 2A to 2E and Figure 3, each of the plank units 100 or 100'
comprises a horizontal base portion 101. The longitudinal edges of the plank
unit 100
or 100' contain a recess 102 positioned at either lateral ends 101A and 101B
of the
plank units 100 , 100', or 100". The recess 102 allows the plank unit 100,
100', 100"
to be seated upon the supporting structures 110'. The plank units contain a
horizontal
mesh 103 that extend through the length of the plank units. Z shape wire ties
104 is
connected to the main horizontal mesh 103 to enhance the cracking capacity of
the
recess portion of the plank units. Furthermore, mechanical shear connector 105
may
be provided at the top surface of the plank unit to ensure 100% bonding
between the
plank units and the fresh concrete 108 above that. The soffit of the plank
units 100,
100', 100" is equipped with equally spaced cast-in-ferrules 106 to ease
installation of
a ceiling structure109 that supports ceiling plaster boards 109'. Since the
plank unit
100" is used to make the pan unit 110, the top face of the pan unit 110 is
also
equipped with equally spaced cast-in-ferrules 107 for installation of the
negative
bending connectors 145 (refer to Figure 7). The thickness of the plank units
100,
100', and 100" may vary between 50 mm to 80 mm. The thickness of the step
plank
unit 100" depends on the step height and is only used when a step needs to be
generated within the floor system. The step plank unit 100" contains an
upwardly
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
portion 106 that extend along the plank unit. This portion act as an edge
formwork to
keep the wet concrete in the required level.
Alternatively, the installation of the one-way floor system 400 or two-way
floor system
5 400' may involve positioning a plurality of the plank units 100 or the pan
units 110 in
between adjacently located joists 140 or 140'. As Shown in Figures 4 and 5,
the pan
unit 110 comprises of the plank unit 100" and the plank supporting unit 110'.
During
the installation, opposite ends of each of the pre-cast concrete pan unit 110
are
supported upon oppositely arranged shelf portions of two adjacent joists 140
or 140'
10 (as illustrated in Figures 1 and 7).
The pre-cast plank supporting structure 110' is elongate and extends along the
length
of the plank unit 100". An outwardly facing surface of the pan unit 110 and
the
vertical surface of a supporting joist 140 or 140' together define a receiving
portion for
receiving wet concrete during construction (best illustrated in Figure 7).
Referring to
Figure 4, each supporting unit 110' comprises a seat portion 111 at its top
surface to
bond it to the recess 102 of the plank unit 100". Each supporting structure
110'
comprises a bottom reinforcing bar 112 and the top reinforcing bars 113. The
bottom
reinforcing bars are connected to the top reinforcing bars using specific
shear
ligatures 114. The top face of the supporting structure 110' is also equipped
with
equally spaced cast-in-ferrules 115 for installation of the negative bending
connectors 145 (refer to Figure 7). The pan unit 110 can be cast for providing
span
lengths of between 1750mm and 2800mm. The pre-cast concrete plank unit 110 or
110' or 110" are designed to withstand live loads of up to 4 kPa with total
serviceability limit of span/ 250. The deflection under live load maybe kept
under
span / 500.
Figures 6A to 6B illustrate a joist 140 and Figure 7 illustrates an
alternative
embodiment of the joist 140'. Each of these joists (140 or 140' comprises a
horizontal
base portion 141; and a vertically oriented portion 142 extending
substantially along
the length of the joist 140 or 140'. The vertically oriented portion 142
comprises
spaced apart upwardly extending surfaces. The spacing between the vertical
surfaces is denoted by b1. The length of the top surface (b1) is less than the
length
of an in use bottom surface (b) of the base. The length of the top surface
(b1) is in
the range of 150mm to 300mm and length of the bottom surface (b) is in the
range of
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
11
300mm to 500mm. Each of the vertical surfaces includes a chamfered portion
located
in between the shelf portion 141 and the respective almost vertical surfaces.
Shelf portions 141 are located adjacent on lateral sides of the vertically
oriented
portion 142 and each of the shelf portions 141 defines a seat for receiving a
connecting portion of a pre-cast concrete pan unit 110 or plank unit 100'. The
joist
unit also includes the bottom reinforcing bars 143 located in the shelf
portion 141 and
the top reinforcing bars 144 that are partially located in vertically oriented
portion 142.
At least one of the top reinforcing bars, in some embodiments may be located
outside
of the vertically oriented portion 142 to enhance the connectivity between the
joist
and the fresh concrete 108 above that. The joist unit 140 may also be equipped
with
vertical ligature 146 that connect the bottom reinforcing bars 143 to the top
reinforcing bars 144. The top surface of the joist 140 may also be equipped
with
equally spaced cast-in-ferrules 147 that are used to assemble the negative
bending
connectors 145 (refer to Figure 7). To use the Joist 140 in the two-way action
flooring
system 400', equally spaced voids 148 passing across the vertically oriented
portions
142 to enhance the connectivity between joists 140 and the fresh concrete 108
and
to assist with placing reinforcing bars or post-tensioning tendons/ducts for
two-way
floor system where the applied loads are transferred in direction of the joist
140 as
well as in direction perpendicular to that.
The joists 140 or 140' may be designed for covering spans of up to 12m and the
distance between adjacently located joists 140 and 140' may vary between
1750mm
to 3300mm. The joist unit 140' (shown in Figure 6C) is particularly useful
when a step
down in the floor system needs to be generated. The joist may be prestressed
to
shape downward curvature for covering longer spans or when high magnitude of
construction loads are applied. The height of the vertically oriented portion
may vary
between 50mm to 400mm and the thickness of the base portion may vary between
50mm and 120mm.
In the presently described embodiment, the joist 140 has been designed to
carry up
to 6kPa live load which is much higher than the required levels for both
residential
(less than 2 kPa) and commercial (mostly 3 kPa and in some location 4 kPa)
buildings with a total deflection of less than span to 250 and deflection
under live load
of less than span to 500. Higher serviceability requirements can also be
achieved by
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
12
decreasing the clear distance between joists 140 when required. In the case
when
higher shear capacity is required, the web (142) of joists 140 and 140' may be
thickened at the support areas where the joist 140 or 140' resting on the
supporting
elements (such as a band beam150, edge beam 160, or a wall system 190-shown in
Figure 14).
The installation of the one-way floor system 400 may involve positioning a
plurality of
the pan units 110 or the plank unit 100' or 100" in between adjacently located
joists
140 and 140'. Each of the pre-cast pan 110 or pre-cast plank unit 100' and
100" are
adapted for receiving wet concrete, during construction, once these members
(110,
100', or 100") are positioned in between the respective joists 140 or 140'.
Referring to Figures 8 and 9, permanent formwork flooring end plate units 120
and
120' may also positioned, before pouring the wet concrete, at each of the
respective
edge portions of the pre-cast pan unit 110 or the plank units 100, 100', and
100". The
flooring end plate units 120 or 120' may be provided in the form of L-shaped
120
members (Figure 9) or U-shaped 120' members (Figure 8).
The L-shaped end plate members 120 (depicted in Figure 9) are used at the
connecting location between each of the joists 140 and the joist supporting
members
(band beam unit 150 or edge beam unit 160, or wall unit 190). This arrangement
has
been more clearly illustrated in Figure 14. The U-shaped end plate members
120'
(depicted in Figure 8) are used in the second embodiment of the invention
(400', refer
Figure 15) when a two-way floor system is provided. The U-shaped flooring end
plate
120' can be positioned between the pre-cast pan units 110 and in line with
rectangular or circular penetrations 148 in the j0i5t140 to allow two-way
actions, one
in direction of joist 140 and the other one in transverse direction relative
to the joists
140. The flooring end plates 120 and 120' comprise a reinforcing mesh 121 that
is
bent to conform to the shape of the flooring end plates, i.e. U Shape or L
Shape. To
enhance the connectivity of the flooring end plates to the fresh concrete,
these
permanent formwork members have been equipped with mechanical shear
connectors 122.
Referring to Figures 10 to 12 illustrates the sectional and perspective views
of the
band beam unit 150 and edge beam unit 160. As discussed in the previous
sections,
the plurality of the pre-cast concrete joists 140 and 140' are supported by a
plurality
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
13
of band beams 150 and or edge beams 160 that extends generally in a
perpendicular
direction relative to the general direction of the said pre-cast concrete
joists 140 and
140'. When dealing with a low magnitude of the applied loads or dealing with
short
spans, the beam 150 may have a shape similar to the joist 140 but may be
larger in
size. Otherwise, the beam 150 comprises of two spaced apart formations 150A
and
150B extending upwardly from the beam 150. The edge beam 160, contains one
formation of 160A extending upwardly from the beam 160. The formations 150A
and
150B extend along a length of the beam 150. Similarly, formation 160A also
extends
along a length of the edge beam. Joist receiving portions for the band beam
150
extend outwardly from the said formations 150A and 150B for supporting an end
portion of a plurality of joists 140. Similarly, joist receiving portions for
the edge beam
160 extend outwardly from the formation 160A. The breadth for each of the
formations (B) may vary between 100 to 300 mm depending on span of the band
beam and magnitude of the applied loads. Thicker values may be used at the
support
areas of the beam to assist with transferring shear forces to the column 170.
The
height of the formations (H) may vary between 200 mm to 600 mm depending on
span of the band beam and magnitude of the applied load. The thickness of the
beam (T) may vary between 80 mm to 150.
Referring to Figures 10B and 11B, each of the band beams 150 further comprises
top
reinforcing bars 151 extending through an upper portion of the formation along
a
longitudinal direction of the band beam 150 and or the edge beam 160. Positive
reinforcing bars also 155 extend along the beam 150 and 160. The beams 150 and
160 also comprise torsional and shear ligature bars 152 and 153 for providing
additional shear strength characteristics to the beams 150 and 160. The shear
ligature bars also assist with transferring shear forces acting at the
interface of the
beam 150 or the edge beam 160 and the overlay concrete poured on site.
Circular or
rectangular penetration openings 156 may also be provided through the 150A and
150B vertical portion of the beam 150. These openings reduce the total weight
of the
beam and generated interlock with the fresh concrete to enhance the composite
actions between them. The beam 150 has also contains another penetration
opening
157 within its horizontal portion along an underside to facilitate connection
of the
band beam 150 onto a supporting column, i.e. column 170. The beam element 150
also contains a recess 158 around the penetration 157. This will restrain the
column
head and transfer loads to the column via bearing at this area. A typical in-
use
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
14
perspective of assembly between column 170 and the band beam 150 has been
shown in Figure 13. Advantageously, each band beam 150 is provided as a single
unit with a width of 800 to 2000 mm and no additional onsite works are
required.
Referring to Figure13, the cross section of column units 170 (square shape)
and 170'
(rectangular shape) that are build using precast column formwork units 300.
The
column formwork units 300 comprises of a horizontal portion with a thickness
of
50mm to 70mm and also contain a recess 301 at one of its edge. A portion of
the
column builder is extend downwardly by about 50 mm (302). The element also
comprises internal reinforcing mesh 303. To enhance the cracking capacity of
the
edge of this unit, both external edges of the column formwork units 300 have
been
reinforced with edge wire ties 304. The column formwork units also contain
connector elements 305 that are located at each end of the unit 300. Different
widths
of the column formwork units 300 can be connected to each other to shape a
square
shape (170) or a rectangular shape (170') columns using structural adhesive.
Mechanical connectors may also be used if required. Additional column cage
containing longitudinal bars 306 and shear ligatures 307 may also be placed
within
the column cavity defined by the column formwork units 300 and secured in
position
using connector 305. A perspective view of column unit 170 have been shown in
Figure 13. The cavity of the column will then be filled with fresh concrete
308 on site.
Referring to Figure 14, using modular precast concrete formwork to build a two-
way
slab system (400') has been illustrated. The beams 150 is installed over the
column
unit 170. The edge beam 160 is spans between wall unit 190 and the beam unit
150.
During the installation, beams 150 are connected to the column 170 using
recess in
the soffit of the beam. The joist units 140 are then placed between the beam
unit 150
and the wall unit 190.
For two-way actions, U shape flooring end plates 120' may be placed in front
of
rectangular or circular penetrations 148 (in Joists 140) and perpendicular to
the Joists
140 to generate a monolithic transverse joist. The pan units 110 are then
positioned
between the joists 140 and the U shape permanent formworks 120'. The positive
reinforcing or post-tensioning tendons/ducts can now be placed inside U shape
flooring end plates and in transverse direction of the Joist 140. These are
passed
through the rectangular or circular penetrations 148 across all joints 140 and
CA 03030304 2018-12-24
WO 2018/018080 PCT/AU2017/050770
continued to the supporting beams 160. The floor system 400' acts as one-way
slab
during construction phase and prior to removing props (that may be placed
temporarily under the joists 140 or beams 150 and 160). After placement and
curing
of the overlay concrete, the final floor system 400' acts as a two-way slab.
5
In at least some embodiments, it is expected that adopting the system 400 or
400' is
likely to provide the following advantages:
= Increase the speed of construction;
= Achieve high-quality surface finishes;
10 = Enhance safety of labours working on a building;
= Decrease construction cost;
= Decrease the volume of the on-site concreting;
= Decrease the amount of reinforcing bars that need to be placed and
arranged
on-site;
15 = Enhance the quality of the concrete structure;
= Reduce the risk on third parties due to construction activities as the
building
will be constructed in a short period of time (compared with the current
construction
time).
In compliance with the statute, the invention has been described in language
more or
less specific to structural or methodical features. The term "comprises" and
its
variations, such as "comprising" and "comprised of" is used throughout in an
inclusive
sense and not to the exclusion of any additional features. It is to be
understood that
the invention is not limited to specific features shown or described since the
means
herein described comprises preferred forms of putting the invention into
effect. The
invention is, therefore, claimed in any of its forms or modifications within
the proper
scope of the appended claims appropriately interpreted by those skilled in the
art.
Throughout the specification and claims (if present), unless the context
requires
otherwise, the term "substantially" or "about" will be understood to not be
limited to
the value for the range qualified by the terms.
Any embodiment of the invention is meant to be illustrative only and is not
meant to
be limiting to the invention. Therefore, it should be appreciated that various
other
changes and modifications can be made to any embodiment described without
departing from the spirit and scope of the invention.
