Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF THE INVENTION
This invention relates to building structures
and in particular to a multistory structure which is
suitable for mass production.
BACKGROUND TO THE INVENTION
Multistory buildings are generally built using
floor and ceiling slabs which are poured in place or
prefabricated and are fixed to vertical columns or wall,
which are also poured in place or prefabricated. The
walls could be one story high modules, an example of
which may be found in Canadian Patent 1,188,125 issued
June 4, 1985 and invented by William Teron.
Such structures are unsuitable for the
production of plural identical or nearly identical
multistory buildings such as schools that require large
expanse of uninterrupted interior space, due to
relatively high cost and excessively heavy construction.
Part of the high cost is due to the requirement for
substantial prestressing of the cast elements to provide
the column free space. The high cost is also due to the
requirement for heavy temporary formwork to support the
poured in place concrete, and skilled labor needed on
site to build the forms, pour the concrete and remove
the forms. The construction process is also slow.
SUMMARY OF THE INVENTION
The present invention is a building structure
that is inexpensive, can be produced in large volumes
using standard precast elements, and which requires
prestressing in only supporting parts of a slab and
which forms both a floor and a ceiling to the stories of
the building.
The building structure of the present invention
utilizes a prefabricated slab that has a large central
region and peripheral legs forming a rim. Cantilevered
arms extend outwardly from a pair of the legs on
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opposide sides of the slab, offset downwardly from the
central region. The arms can be used as exterior
walkways, window overhangs, etc.
Vertical preferably precast modular slab-
supporting structures containing windows, doors, etc.interface with the junctions of the legs and the
cantilevered overhangs. Due to the offset between the
arms and the legs, a natural rain sill is created
against the intrusion of rain. The offset provides a
location which is evident to relatively unskilled
persons where to place the slab-supporting structures
during construction.
Since the slab-supporting structures bear
against each other to footings through the part of the
cantilevered arms immediately next to the legs, they
cause no bending stress on the slabs, and the legs are
the only parts of the slab structures that require major
reinforcing or prestressing to support floor loads.
In accordance with an embodiment of the
invention, a building structure is comprised of a
plurality of precast slabs, each slab having a
prestressed downwardly extending rim at its perimeter,
and a pair of arms extending outwardly adjacent the
bottoms of the rims at a pair of opposite sides of the
slabs so as to form steps between upper surfaces of the
arms and the upper surface of the slab, and a wall unit
extending from an upper surface of each arm of a lower
- slab adjacent the outside of the rim to a corresponding
lower surface of a corresponding arm of an upper slab,
so as to support the upper slab.
BRIEF INTRODUCTION TO THE DRAWINGS
A better understanding of the invention will be
obtained by reading the description of the invention
below, with reference to the following drawings, in
which:
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Figure 1 is a crossection of a building in
accordance with an embodiment of the invention,
Figure 2 is an enlarged isometric view of a
part of the building shown in Figure 1,
5Figure 3 is an isometric view of the building
of Figure 1 at various stages of construction,
Figure 4 is a crossection of a a pair of
adjacent legs of a precast element, and
Figure 5 is a cross-section of a pair of
adjacent wall modules.
DETAILED DESCRIPTION OF THE INVENTION
With reference to Figures 1, 2 and 3, a
multistory building is constructed of a precast
floor/ceiling element 1. The precast element 1 is
formed of a slab portion 3 cast with and having legs 5A
running along each of its sides, forming a rim.
Cantilevered arms 7A and 7B extend outwardly from a pair
of opposite legs 5 along preferably short sides of the
precast element 1, but are downwardly offset from the
upper surface of the slab portion 3.
Precast wall modules 9 are vertically supported
outside the legs 5 along the corner formed by the legs 5
and the arms 7A and 7B, and thus the planes of the wall
modules 9 are aligned. Below the building poured
footings 11 or other foundation systems support the
bottom of the lowermost wall modules.
As a result of the described structure, the
weight of the wall modules are all transmitted through
each other and through aligned portions of each of the
cantilevered arms 7A or 7B to the footings. There is no
bending stress on the cantilevered arms caused by the
wall modules 9. Indeed, the weight of the wall modules
9 helps to relieve bending stress on the legs 5 that
would otherwise be caused by the structure and load of
the cantilevered arms.
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The weight of the slab 3 and eventual floor
loads will cause some bending stress on legs 5, but
other than for that reason, there is no substantial need
for other prestressing elements to be cast in the slab.
The strength of the legs allows the slab 3 to be very
thin.
The structure shown in Figure 1 does not show a
precast element 1 such as is used in higher stories of
the structure, as the lowest floor, which can be cast in
place, but if desired such a precast element can be used
as the lowest floor. Since the precast element 1 is
used both as a floor for the story above and as a
ceiling for the story below, a precast element is used
as a ceiling for the highest story, by which a roof 13
is supported. The roof can be supported from the top
precast element 1 (which in this case has no arms) by
triangular supports 15 as shown, or can be supported by
trusses, or any other suitable structure. A traditional
roof of trusses could also be built above the ceiling
slab.
Each precast element 1 can be e.g. 10 feet wide
by 25 feet long, plural elements being aligned along
their 25 foot edge to form a long plane surface as shown
in Figures 2 and 3. Fences and handrails 17 can be
fixed to the ends of the upper surfaces of cantilevered
arms 7A, whereby these cantilevered arms can be used as
a protected walkway. Sun visors 19 can be hung from the
ends of the bottom surfaces of cantilevered arms 7A and
7B to shield the sun from the windows contained in the
wall modules 9 of the stories below.
The legs (rim) of the precast elements
preferably are about 6 inches thick and 1 foot deep, and
contain metal reinforcing or prestressing bars. The
cantilevered arms 7A and 7B can be several inches thick,
sufficient to support their dead weight and live loads.
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Construction of the building will be understood
with reference to Figure 3, which shows increasing
finish of the building from left to right. Concrete
footings 11 (shown in the form of posts) are poured,
followed by wall module supports 21 over the posts. The
lowest story of wall modules 9 are placed over the wall
module supports 21 and are abutted and fixed to each
other by anchors or the like.
The precast elements 1 are then disposed over
the tops of the wall modules 9, abutting each other over
the length of the building. The tops of the wall
modules 9 should abut the bottoms of the cantilevered
arms just outside the legs 5.
A second story of abutting wall modules 9 is
then stood vertically on the top surface of the
cantilevered arms, just outside and abutting the legs 5,
and in alignment with the wall modules below. Precast
elements 1 are then disposed over the tops of this story
of wall modules 9 in a manner similar to the previous
story of precast elements. This sequence continues for
as high as the design of the building permits.
Roof supporting elements 15 are stood
vertically on the top-most precast elements 1,
supporting roof 13.
Once a floor of precast elements is in place,
workers can affix fences and handrails 17 as well as sun
visors 19 to the outer edges of the cantilevered arms.
It should be noted that due to the presence of
the cantilevered arms on each side of the building,
workers can stand on them during construction, e.g. to
fix windows into window openings of the wall modules,
minimizing the need for scaffolding.
It is preferred that the shape of the legs 5
should be somewhat angled inwardly or the undersides of
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the slabs, in order to give an architectural shape to
the ceiling.
It will be noted that since the legs border the
adjacent edges of the slabs, from underneath each
ceiling of a constructed building will have an
attractive waffled apprearance with a polished smooth
finish from polished formwork. It is preferred that the
legs of adjacent precast elements shown should be
indented slightly inward of the end of the slab, as
shown in Figure 4, in order to create a slight overhang
23. Overhangs 23 of adjacent slabs are placed abutting
each other, thus creating a cavity or pocket 25 running
laterally across the room at the junction of each slab.
Utilities 27 such as light fixtures, wiring,
water pipes, etc. can be contained within the pockets as
required by other aspects of the building design, and
the pockets can be covered to hide the utility
structures as desired.
By providing such spaces for services, a
suspended ceiling does not have to be installed
throughout allowing the smooth waffled concrete to be
the finished ceiling. The result is cost and time
savings. In addition services are not exposed.
With each precast element having a similar
width as each wall module 9, and the junctions of
adjoining wall modules forming a similar cavity aligned
with the cavity at the junctions of the legs of the
slab, the utilities can be run vertically through the
building and laterally across the ceilings within the
cavities as shown in Figure 5.
Due to its modular structure, minimum
prestressed elements, cantilevered arms which form sun
visors, walkways and floors for construction workers,
dropped walkways, and large uninterrupted spaces, the
building has been found to be easily constructed by
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relatively unskilled workers, inexpensive, and suitable
for rainy underdeveloped countries as schools, meeting
halls, etc.
A person understanding this invention may now
conceive of alternative structures and embodiments or
variations of the above. All of those which fall within
the scope of the claims appended hereto are considered
to be part of the present invention.
