U.S. patent number 3,903,667 [Application Number 05/487,981] was granted by the patent office on 1975-09-09 for structural floor system accomodating multi-directional ducts.
This patent grant is currently assigned to Lev Zetlin Associates, Inc.. Invention is credited to Lev Zetlin.
United States Patent |
3,903,667 |
Zetlin |
September 9, 1975 |
Structural floor system accomodating multi-directional ducts
Abstract
A structural floor system of precast, prestressed, reinforced
concrete beams arranged longitudinally and transversely in a
square-grid pattern. Yoke members separate the ends of adjacent
beams and longitudinal and transverse tension rods extend through
the respective beams and through each of the yoke members for
integrally tying the structure together. Each beam comprises a pair
of spaced stems defining an axial channel. The yoke member adjacent
the end of the beam spans the distance between the stems but leaves
uncovered a sufficiently large portion of the open end of the
channel to accommodate a duct extending through said open end.
Thus, ducts may change direction and/or branch off at any of the
yoke locations throughout the structure while remaining within the
dimensional height confines of the floor beams.
Inventors: |
Zetlin; Lev (Roslyn, NY) |
Assignee: |
Lev Zetlin Associates, Inc.
(New York, NY)
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Family
ID: |
27005218 |
Appl.
No.: |
05/487,981 |
Filed: |
July 12, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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371050 |
Jun 18, 1973 |
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Current U.S.
Class: |
52/223.7; 52/252;
52/283; 52/263; 52/602; 52/220.3 |
Current CPC
Class: |
E04B
5/43 (20130101); E04B 5/48 (20130101) |
Current International
Class: |
E04B
5/48 (20060101); E04B 5/43 (20060101); E04C
003/10 (); E04C 003/22 () |
Field of
Search: |
;52/220,227,228,231,236,252,606,583,221,283,602,301,563,562,503,341,340,294,258 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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58,106 |
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Sep 1953 |
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FR |
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626,097 |
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Jul 1949 |
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GB |
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55,042 |
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Aug 1912 |
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OE |
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60,490 |
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Jan 1948 |
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NL |
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Primary Examiner: Purser; Ernest R.
Assistant Examiner: Braun; Leslie A.
Attorney, Agent or Firm: Sternberg, Esq.; Henry
Parent Case Text
This is a continuation of application Ser. No. 371,050, filed June
18, 1973, now abandoned.
Claims
What is claimed as new and desired to be protected by Letters
Patent is:
1. In a floor structure, in combination:
a pair of longitudinal and a pair of transverse reinforced concrete
beams, each having a horizontal flange portion and a pair of spaced
parallel stem portions depending from said flange portion and
defining between themselves an axial channel open at opposite
ends;
a horizontally disposed rectangular yoke means having a first pairr
of spaced parallel longitudinal side portions and a second pair of
spaced parallel transverse side portions defining between
themselves an opening;
each of said beams having a first end portion adjacent said yoke
means and a second end portion spaced from said yoke means, said
stem portions of said longitudinal beams being in substantial
alignment with the respective ones of said longitudinal side
portions of said yoke means, and said stem portions of said
transverse beams being in substantial alignment with the respective
ones of said transverse side portions of said yoke means;
a first pair of tension means extending in lengthwise direction
through said respective stem portions of said longitudinal beams
and said longitudinal side portions of said yoke means for
integrally connecting together said pair of longitudinal beams with
said yoke means and a second pair of tension means extending in
lengthwise direction through said respective stem portions of said
transverse beams and said aligned transverse side portions of said
yoke means for integrally connecting together said pair of
transverse beams with said yoke means whereby the entire structure
is integrally connected together;
said yoke means spanning the distance between the stem portions of
each of said beams and having a depth sufficiently smaller than the
depth of the channels in said beams so as to leave uncovered a
substantial portion of the open ends of said channels whereby said
open ends are adapted to accommodate a duct extending
therethrough.
2. The floor structure according to claim 1 wherein said yoke means
is square and is comprised of reinforced concrete.
3. The floor structure according to claim 2 wherein said yoke means
has a pair of sleeves extending lengthwise through the longitudinal
side portions thereof and a second pair of sleeves extending
lengthwise through the transverse side portions thereof, said
sleeves being adapted to loosely receive the respective tension
means extending therethrough.
4. The floor structure according to claim 3 wherein said tension
means are tension rods.
5. The floor structure according to claim 4 wherein said
longitudinal tension rods extend from one longitudinal end of the
structure to the other and said transverse tension rods extend from
one transverse end of the structure to the other.
6. The floor structure according to claim 1 wherein each of said
stem portions of said beams is provided with a sleeve extending in
lengthwise direction through the respective stem and adapted to
loosely receive the respective tension means extending
therethrough.
7. The floor structure according to claim 6 wherein the sleeves
extending through said longitudinal beams are embedded therein at a
different elevation than the sleeves extending through said
transverse beams.
8. The floor structure according to claim 3 wherein said sleeves in
said longitudinal side portions are at a different elevation than
said sleeves in said transverse side portions.
9. The floor structure according to claim 5 further comprising
anchoring means at the ends of said tension rods for anchoring the
latter to the structure in tensioned condition.
10. The floor structure according to claim 1, further comprising
lower vertical column means supporting said yoke means and the end
portions of said beams adjacent said yoke means.
11. The floor structure according to claim 10 for use in a
multi-story structure, further comprising upper vertical column
means supported on said yoke means, said yoke means and said upper
and lower column means having aligned vertical through-bores and
the structure further comprising vertical tension means extending
through said through-bores and being anchored at the upper and
lower portions of the structure for tying together multiple floors
of the structure.
12. The floor structure according to claim 11 wherein said yoke
means comprises parallel planar top and bottom surfaces and further
comprising metal bearing plate means embedded in said top and
bottom surfaces of said yoke means and cooperating metal bearing
plate means in the respective cooperating top surface of said lower
vertical column means and in the bottom surface of said upper
column means.
13. The floor structure according to claim 1 wherein said yoke
means comprises parallel planar top and bottom surfaces and the
vertical distance between said top and bottom surfaces is less than
half the vertical inside depth of the channel of the adjacent
beams.
14. A multi-story structure comprising:
first and vertically spaced second horizontal floor systems each
including a plurality of transverse and longitudinal beams of
reinforced concrete arranged in a square grid pattern and each of
said beams defining therein an elongated channel open at opposite
ends, a plurality of square frame-shaped yoke means, each
longitudinal beam being separated from the next longitudinal beam
in the same longitudinal row by one of said yoke means and each
transverse beam being separated from the next transverse beam in
the same transverse row by one of said yoke means, said yoke means
spanning the open end of the channel of the adjacent beams and
being dimensioned so as to leave uncovered a portion of each such
channel opening;
vertical column means including first vertical column means
supporting at least one of said yoke means of said lower floor
system, and second vertical column means supporting at least one of
said yoke means of said upper floor system, said first and second
vertical column means being in vertical alignment with each other
and with each said one yoke means, said second vertical column
means being supported on said one yoke means of said lower floor
system and each said column means and said one yoke means including
vertical through-openings in alignment with each other and
communicating with the channels in adjacent ones of said beams;
tension means for tying the structure together including
longitudinal tension means extending lengthwise through each
longitudinal row of beams and yokes in each floor system,
transverse tension means extending lengthwise through each
transverse row of beams and yokes in each floor system, and
vertical tension means extending lengthwise through said upper and
lower column means and through each said one yoke means in
alignment therewith.
15. The structure according to claim 14, further comprising duct
means including longitudinal duct means extending lengthwise
through the channel of at least one of said longitudinal beams in
one of said floor system,
transverse duct means extending lengthwise through the channel of
at least one of said transverse beams in said one floor system and
communicatively connected with said longitudinal duct means in the
region of one of said yoke means and vertical duct means extending
lengthwise through at least one of said column means and at least
one of the yoke means associated therewith and communicatively
connected with at least one of said longitudinal and transverse
duct means.
16. In a floor structure, in combination:
a reinforced concrete beam having a horizontal flange portion and a
pair of parallel horizontally elongated stem portions depending
from said flange portion and defining between themselves an axial
channel open at opposite ends, said stem portions being spaced a
given distance apart;
a horizontally disposed rectangular yoke means comprising a first
pair of parallel leg portions spaced apart a distance substantially
equal to said given distance and a second pair of spaced parallel
leg portions transverse to said first pair of leg portions and
connected thereto;
said beam having a first end portion abutting one of said second
pair of leg portions and a second end portion spaced from said yoke
means, each of said parallel pair of elongated stem portions of
said beam being in substantial alignment in the direction of
elongation thereof with a corresponding one of said first pair of
leg portions of said yoke means;
a pair of tension means each extending in length wise direction
through a respective one of said stem portions and through the leg
portion of said yoke means aligned therewith for integrally
connecting together said beam with said yoke means;
and
said yoke means spanning the distance between said stem portions
and having a depth sufficiently smaller than the depth of the
channel in said beam so as to leave uncovered a substantial portion
of the open end of said channel whereby said open end is adapted to
accommodate a duct extending therethrough.
17. The floor structure according to claim 16, further conprising a
second beam of reinforced concrete having a flange portion and a
pair of spaced parallel stem portions depending from said flange
portion and defining between themselves an axial channel open at
opposite ends, said stem portions of said second beam being aligned
with a corresponding pair of leg portions of said yoke means,
and
a second pair of tension means each extending in lengthwise
direction through a respective one of said stem portions of said
second beam and through the corresponding one of the last mentioned
pair of leg portions of said yoke means aligned therewith, for
integrally connecting together said second beam with said yoke
means whereby the entire structure is integrally connected
together.
18. The floor structure according to claim 17, wherein said stem
portions of said one beam are aligned with said first pair of leg
portions of said yoke means and said stem portions of said other
beam are aligned with said second pair of side portions of said
yoke means.
19. The floor structure according to claim 16, wherein said first
pair of leg portions of said yoke means and said second pair of
side portions of said yoke means define between themselves and
opening extending substantially vertically through said yoke
means.
20. The floor structure according to claim 17 further comprising a
second pair of reinforced concrete beams, each having a horizontal
flange portion and a pair of spaced parallel stem portions
depending from said flange portion and defining between themselves
an axial channel open at opposite ends;
said stem portions of said second pair of beams each being in
alignment with a pair of leg portions of said yoke means.
Description
BACKGROUND OF INVENTION
This invention pertains to structural floor support systems
comprising precast reinforced concrete beams.
More specifically this invention pertains to a structural floor
system of reinforced concrete beams arranged in such a manner that
horizontal ducts for heating, cooling, etc. may, at any floor
level, be positioned entirely within the dimensional confines of
the structural floor beams themselves and yet extend in a multitude
of longitudinal and transverse directions throughout the structure
with numerous changes of direction and branch-offs readily
possible.
It has been known, in the case of structures having a metal frame,
to construct these of tubular metal members which are then bolted
or welded together and to use the interior spaces of such tubular
members as a duct. Examples of the latter are illustrated in U.S.
Pat. Nos. 2,970,676 and 3,415,024. For structures comprised of
parallely arranged beams of reinforced concrete extending from one
side of the structure to the other, however, which are in wide use
today, a simple and economical way had not yet been found to
position ducts entirely within the vertical space required by the
beams themselves, yet permit such ducts to change direction and/or
branch-off at a multitude of locations throughout the structure as
must invariably be the case with such ducts. In order to utilize
the axial channels of the beams for housing the ducts, it has in
the past been attempted to provide apertures in the stems of the
beams for the duct in the channel to branch through such aperture
in a transverse direction. An example of an apertured beam is shown
in U.S. Pat. No. 3,363,375. Unfortunately such apertures in
structural beams are likely to result in a weakened beam or one
which is expensive to manufacture. Another system taught by the
prior art is that illustrated in U.S. Pat. No. 2,477,256 where
spaces between various independent groups of beams are utilized for
duct work. Such a system, however, could not be used in a structure
where all floor beams are to be integrally tied together and
pre-tensioned both longitudinally and transversely.
As a result, the more common method in use today, of installing
ducts, is to install the latter entirely below the concrete floor
beams. Since all horizontal ducts are, in the latter construction,
located entirely below the beams they can, of course, extend in any
desired direction. The latter arrangement, on the other hand, while
the most common, wastes a substantial amount of head room just for
the duct system. A system which will eliminate this waste of
precious vertical space, particularly in buildings having multiple
stories, has long been sought.
While structural systems comprised of hollow reinforced concrete
beams are per se known (as illustrated in U.S. Pat. No. 3,074,209),
these had never been configurated in such a way as would permit
multi-directional ducts to be housed entirely within the
dimensional height confines of the beams themselves.
SUMMARY OF THE INVENTION
The present invention avoids the foregoing disadvantages by
providing a structural system of reinforced transversely and
longitudinally pretensioned concrete .pi.-shaped beams which are
arranged and joined together in such a manner that not only do they
form a rigid structure but the additional headroom space previously
required for the duct system below beam level can now be used to
better advantage. The arrangement is such that the ducts extend
horizontally at each floor level entirely within the dimensional
confines of the beams themselves. At numerous locations throughout
the structure the ducts may change direction and/or branch off as
desired.
According to the present invention there is provided, between each
pair of aligned beams, a yoke member which cooperates with the
adjacent beams to provide at numerous locations through the
structure facilities for changing direction or branching-off of the
duct. The yokes are preferably of reinforced concrete and each yoke
has the shape of a rectangular frame. The sides of the yoke are
dimensioned such that each spans the distance between the stems of
an adjacent .pi.-shaped beam and the depth of the yoke is such as
to leave uncovered a portion of the open end of the channel of such
beam sufficiently large to accomodate a duct extending there
through and over the yoke which is in position between the beams.
In such position the yoke holds adjacent, aligned, mutually
post-tensioned beams in spaced relation. Thus, while the
longitudinal and transverse beams and the intermediate yoke are
integrally connected to and tensioned against one another there is
nevertheless available an access space for a duct, through the
interior of the yoke member, into the channels of the longitudinal
beams as well as into the channels of the transverse beams at that
location.
In its preferred form, the invention comprises modified .pi.-shaped
reinforced concrete structural beams. These beams have a pair of
depending parallel stems connected by a central horizontal flange
and include triangular flange extensions on opposite sides of the
beam. Each such flange extension is preferably in the shape of a
right triangle so that four such beams placed at right angles to
one another (so as to form the sides of a square) completely cover,
with their inwardly facing triangular flange extensions, the space
therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a portion of a composite structural
floor system according to a preferred embodiment of the present
invention;
FIG. 2 is a diagrammatic bottom view of the floor structure of FIG.
1, showing the duct system;
FIG. 3 is a perspective view of a beam according to the preferred
embodiment;
FIG. 4 is a partially perspective, exploded, view representative of
any of the yoke locations of FIG. 2, enlarged and showing a yoke
member, an associated longitudinal beam and an associated
transverse beam, and showing also the support column means at
representative vertical support location "A" or "G" of FIG. 2;
FIG. 5 is a perspective, partial view representative of any of the
lettered yoke and beam connection locations "A" or "G" of FIG. 2,
enlarged, and showing a vertical duct branching at said location in
longitudinal and transverse directions;
FIG. 6 is a fragmented transverse sectional view in the direction
of arrows 6--6 of the portion of the composite floor structure
shown in FIG.1;
FIG. 7 is a fragmented transverse sectional view taken in the
direction of the arrows 7--7 in FIG. 1
DESCRIPTION OF THE PREFERRED EMBODIMENT
As seen in FIG. 1 a plurality of beams 10a, 10b and yokes 20 are
supported on vertical columns 40 and integrally tied into a
composite floor structure by longitudinally extending and
transversely extending pairs of tension rods 30a and 30b,
respectively.
FIG. 3 shows a typical beam as used in the structural system of the
present invention. The beam 10 (representative of each of the beams
10a and 10b) comprises an integrally cast, reinforced concrete
structure including two parallel spaced, elongated stem portions 11
and a flange 12 comprising a central flange portion 12a connecting
the stem portions 11 and a pair of triangular flange extensions 13.
The central flange portion 12a and the flange extensions 13 are
located in the same, generally horizontal, plane and form a
continuous flat surface at the top of the beam. Each of the flange
extensions 13 is preferably of right-triangular shape with the
hypotenuse of the triangle being adjacent to and parallel with the
corresponding stem 11 of the beam. The shape of the flange
extension 13 is such that when four beams 10 are positioned at
right angles to one another, as seen in FIGS. 1 and 2, the inwardly
facing flange extensions 13 of the beams will cooperate to form a
continuous surface covering the enclosed space. The outwardly
facing flange extensions 13 of each of the beams 10 are meanwhile
in position to cooperate with additional beams for covering
additional spaces. It will be readily understood that half-beams
10a', as shown in FIG. 1, can be positioned around the entire
periphery of the illustrated structure so that the resulting
structure would then be square and have linear longitudinal and
transverse sides. The stems 11 of each beam form between themselves
an axial channel open at both ends and open downwardly in the usual
position of the beam, as shown in FIG. 3.
Each stem 11 is provided in its lower portion with a longitudinal
through-bore 11a, 11b. The bores 11b in the transverse beam 10b
have their axes at a higher elevation (measured from the lower edge
of the stem) than the corresponding bores 11a in the longitudinal
beams 10a. Otherwise, beams 10a and 10b are identical. The
through-bores 11a, 11b preferably have inserted therein sleeves
11a', 11b' suitable for loosely receiving tension rods extending
therethrough, as will be more fully explained below.
Preferably, a yoke member 20 (FIG. 4) is positioned at each corner
of each of the squares forming the grid pattern of the structure.
The longitudinally aligned beams 10a are tied to one another and to
the intermediate yoke members 20 by tension means which are
preferably in the form of longitudinal tension rods 30. Similarly,
the beams 10b in each row of aligned transverse beams are tied to
one another and to the intermediate yoke members 20 by transverse
tension rods 30. Since the same yokes 20 which are tied to the
longitudinal beams are also tied to the transverse beams, by having
both longitudinal and transverse tension rods 30 extending through
each yoke, the entire structure becomes a composite integral
structure.
Yokes 20 preferably consist of reinforced concrete and are
preferably in square-frame shape (FIG. 4). The pair of longitudinal
arms 20a and the pair of transverse arms 20b of each yoke 20 define
therebetween a central opening 20c.
Through each of the longitudinal arms 20a of the yokes 20 there
extends a longitudinal sleeve 21a adapted for alignment with the
sleeves 11a' of an adjacent beam 10a (FIG. 4).
Through each of the transverse arms 20b of the yokes 20 there
extends a transverse sleeve 21b adapted for alignment with the
sleeves 11b' of an adjacent beam 10b. The transverse sleeves 21b
are positioned at a higher elevation in the yoke 20 than the
longitudinal sleeves 21a (or vice versa) so that the longitudinal
and transverse tension rods extending through the yoke will not
interfere with one another. The length of the outer dimension of
each of the arms 20a and 20b of yoke 20 is preferably substantially
equal to the width dimension w.sub.f (FIG. 3) of the stems 11 of a
beam 10. Furthermore, the depth D.sub.y of the yoke member 20 (FIG.
4) is substantially smaller than the depth D.sub.c of the channels
14 (FIG. 3) of the beams 10, so that when a yoke is positioned
adjacent the stems of a beam 10 a substantial portion of the open
end 14' of the channel 14 is left uncovered (FIG. 5). The thickness
T.sub.y of the arms 20a and 20b (FIG. 4) is preferably equal to the
thickness of the corresponding stems 11 of the beam in alignment
therewith.
By way of example, a square yoke 20 may be dimensioned as follows:
each side may have an outer length of 54.0 inches, a depth D.sub.y
of 8.0 inches and a thickness T.sub.y of 8.0 inches. The
corresponding beams 10 (i.e. 10a and 10b) used in conjunction
therewith may be 9.0 feet in length and have channels having a
depth D.sub.c of 24.0 inches and a width of 38.0 inches so as to
have end openings each having an area of 912.0 square inches. Since
the straddling yoke covers approximately 8 inches .times. 38 inches
or 304.0 square inches of the latter area, there will remain
uncovered and suitable for the passage therethrough of a duct a
cross-sectional area equal to approximately 608.0 square
inches.
FIG. 5 shows a yoke 20 in position adjacent longitudinal and
transverse beams 10a and 10b, respectively, each of which is in
contact with a respective side surface of the yoke member and each
of which has its bores 11a, 11b in alignment with the corresponding
sleeves 21a and 21b in the yoke, so that a pair of tension rods 30
may respectively pass, without interference, through the yoke and
each said beam aligned therewith.
The bores 11a and 11b are located near the lower edges of the
respective stems 11 so that the bottom surface of the yoke member
20 will be located in substantially the same, preferably
horizontal, plane as the bottom surfaces of the stems 11.
The column support arrangement is such that the entire floor
structure according to the present invention is supported by
vertical columns 40 at spaced locations as shown in FIG. 1.
Relatively widely spaced columns 40 may thus support this structure
which is comprised of a relatively large number of longitudinal and
transverse rows of aligned beams 10a and 10b, respectively. For
example, the portion of the structure illustrated in FIG. 1 is
supported by four vertical columns 40. Each of the columns 40, in
turn, may consist of four separate columns 41 each having an
L-shaped cross-section over the major portion of its length, and
each preferably having a pair of projections 42 adjacent their
uppermost portions, so as to provide the column at its top with an
X-shaped cross-section. Each column 41 is vertically aligned with a
respective one of the four corners of the yoke member supported
thereon. The X-shaped cross-sectioned top permits these columns to
support not only the yoke but also the ends of the corresponding
stems of the adjacent beams.
As seen in FIG. 6 the individual tension rods 30 extend from one
end of the structure to the other and may be pre-tensioned during
construction. They are anchored at their ends with conventional end
anchorage means 30' for prestressed rods.
According to the present invention, therefore, the main
reinforcement means, namely the tension rods 30, span
longitudinally and transversely, respectively, across the full
width of the building. The spaces above the yoke member 20 may be
covered with rectangular slabs 16, supported on shoulders 15, for
forming, together with the flanges 12, a continuous floor surface
(FIG. 1). The slabs 16 may be precast or poured in place, as
desired.
The space 25 formed between the top surface of a yoke 20 and the
bottom surface of the corresponding slab 16 communicates, as may be
seen in FIGS. 5 and 6, with the central opening 20c in the yoke
and, through the uncovered openings 14', with the interior of the
longitudinal channels 14 in each of the beams 10a and 10b adjacent
such yoke.
In modern buildings with large areas of floor space it is desirable
to run under-floor ducts in longitudinal as well as in transverse
directions and, in order to provide the greatest flexibility, it is
desirable that the ducts change direction and/or branch off in
various directions at numerous locations throughout the
structure.
By arranging the floor beams as described herein and by providing
the described cooperation between the beams and the yokes, there
results a network of passages extending throughout the entire
structure, as for example illustrated in FIG. 2, which represents a
view of the bottom of a floor structure according to the
invention.
The network of passageways formed in accordance with the present
invention may be used for ducts of all types including all
necessary electrical conduits, air ducts for heating, ventilating
and cooling purposes, plumbing and other services required in the
building.
In FIG. 2 the ducts 60 are seen to extend in a multitude of
directions throughout the structure. It will be understood that the
duct can extend through any of the longitudinal or transverse beams
in the respective channels thereof, can continue in its
longitudinal or transverse direction, as the case may be, through
any of the spaces 25 left uncovered by the yoke members 20, or may
at any of the yoke locations change direction or, as seen in FIG.
5, branch off into other directions, e.g., transverse and
longitudinal, and/or continue in the vertical direction to the next
higher or lower floor. Thus, at any of the yoke locations the duct
may either change directions from the longitudinal to the
transverse or from either the longitudinal or transverse to the
vertical, up or down, or may branch off into any desired number of
branches at such location.
In FIG. 2 a vertical duct 60.sub.v at location "A" extends
vertically through the yoke 20 at that location and branches off
transversely as duct 60b.Duct 60b extends horizontally over and
past the yoke 20 at location "B" to location "C". There the duct
changes horizontal direction and becomes a longitudinal duct 60a
which continues to locatin "D" where it changes direction once more
to become a transverse duct 60b'. Then, at location "E" another
change of direction to become longitudinal duct 60a' which then
extends past location "F" to location "G" where the duct merges
with another vertical duct 60v' which extends upwardly to the next
higher floor level.
It will be seen in FIGS. 2 and 5 that the horizontal ducts are all
positioned entirely within the spaces 14, 14' and 25, i.e., within
the vertical dimensional confines of the beams 10a and 10b. Thus,
the clear head room from the underside of the ducts will
approximate the clear heights from the underside of the beams to
the floor below.
In both the longitudinal and transverse directions, of course, the
channels formed within the beams themselves provide the passageways
for the ducts.
As for the vertical ducts 60v and 60v', these are preferably
arranged within the confines of the columns 40, i.e., in the
vertical passage formed between the four spaced apart vertical
sub-columns 41 of which each column 40 is comprised.
These vertical passages communicate with the spaces 25 above each
yoke member 20 through the opening 20c in such yoke member.
FIG. 5 shows a vertical duct 60v coming from a lower floor level
and branching off, above the yoke 20, into a transverse duct 60b
and a longitudinal duct 60a, while itself continuing on to the next
higher floor level.
It will be seen (FIG. 2) that the ducts may be left exposed at the
underside of the floor structure. They are therefore readily
accessible from below, for easy maintenance.
For constructing a multi-story structure in accordance with the
present invention, additional vertical support columns 40' are
positioned over the floor structure shown in FIG. 1, in alignment
with the lower columns 40. Each of these upper columns 40' is
composed of a group of four upper columns 41', each of which is in
registry with a corresponding lower column 41. The arrangement is
such that the upper columns 41' extend into the space formed
between the end portions 46 of the beams which surround yoke 20 and
bear with their own end portions directly on the upper surface of
the yoke 20. In this manner the entire load of the upper columns
41' is transmitted directly into the intermediate yoke 20 and via
the latter directly to the lower columns 41.
Preferably the stems 11 of the beams 10a, 10b are provided, at
their horizontal end portions 46, with recesses 44 which together
with the top surface of the associated lower column 41 form a
cavity framing the intermediate yoke means 20.
Similarly, the upper columns 41' are formed at their lower ends
with recesses 45 which, together with the top surface of the
associated yoke 20, form a cavity into which the unrecessed
portions of the end portions 46 of the beams 10 extend. Sufficient
vertical clearance is provided in each case by the respective
recesses so that no load is transmitted from the upper columns 41'
to the beams 10a or 10b.
In order to facilitate the transmission of load from the upper
columns directly to the lower columns, through the intermediate
yokes, there are preferably provided flat, L-shaped steel bearing
plates 43, preferably positioned over and embedded in each corner
of the upper and lower surfaces of the yokes 20.
Corresponding L-shaped steel bearing plates 43' are embedded in the
top surface of the lower columns 41 and in the bottom surface of
the upper columns 41', in registry with one another and with the
adjacent plates 43 in the top and bottom surfaces of the yoke, for
providing suitable load bearing surfaces between the yoke 20 and
the upper and lower columns.
Vertical tension rods 31 extend loosely from the upper to the lower
portion of the structure through columns 41 and 41', through
suitably aligned vertical sleeves in the yokes 20, and through
suitably aligned holes in the plates 43 and 43'. The vertical
tension rods are anchored with conventional anchoring means for
tension rods, in both the upper and lower portions of the
structure.
Thus, the structure according to the preferred embodiment of the
present invention is post-tensioned not only in the transverse and
the longitudinal directions but also in the vertical direction
through the use of the yokes 20. Each yoke 20 not only provides a
link between the longitudinal, transverse and vertical tensioning
means, but further provides a communication between transverse,
longitudinal and vertical passageways in the structure so as to
accommodate a system of ducts extending in multiple directions
throughout the structure, all within the dimensional confines of
the structural elements themselves, i.e., without reducing the
clear height from the underside of the structural floor beams to
the floor below.
Whereas certain preferred embodiments have been shown and
described, various other modifications will be apparent to those
skilled in the art, in the light of this disclosure, and the
invention should not, therefore, be deemed as limited, except
insofar as shall appear from the spirit and scope of the appended
claims.
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