Pre-cast concrete wall panel and joist assembly and method of construction

A pre-cast concrete panel and joist assembly and a method for forming and constructing this pre-cast concrete panel and joist assembly used as a wall member, comprising the steps of creating a mold to receive wet concrete, positioning reinforcing members, joist attachment plates and weld plates within the mold, pouring wet concrete into the mold, embedding anchor members in the concrete, attaching joists to the concrete panel, and attaching bridging members between the joists and the concrete panel. The joists may be constructed with or without an exterior chord.

BACKGROUND OF THE INVENTION 
The invention relates to the field of constructing pre-cast concrete panel 
and joist assemblies used in the construction industry, and more 
particularly to the field of forming such assemblies off-site and 
subsequently transporting the completed assemblies to the construction 
site for use as exterior wall members. Specifically, the invention relates 
to the field of pre-cast wall panels with lateral bridging members to 
counter the effects of wind load and suction, and the method of 
constructing such assemblies. 
In traditional construction practice, walls in buildings are constructed 
from masonry blocks or are poured directly into forms set on the floor 
slab and then tilted into place after hardening. Both these methods are 
time consuming and the latter method greatly interferes with other 
construction operations because the floor space is occupied during the 
forming phase. Furthermore, the walls must be made relatively thick to 
withstand the effects of wind load and suction. 
To provide a better system, a method has been developed for pre-fabricating 
concrete slab and joist assemblies to be used as walls. A number of 
pre-cast concrete panel and joist assemblies can be made and transported 
to the construction site, ready for installation at the first opportunity. 
Since the assemblies are pre-cast, construction is not delayed to wait for 
the setting of the poured concrete. The assemblies are modular in the 
sense that a number of assemblies are placed in position by crane and then 
joined together to form a continuous wall assembly. Because the assemblies 
are combined concrete slabs and joists, the slab itself can be thinner 
than a standard slab, saving expense and weight without sacrificing 
strength. A standard wall slab made in the traditional manner without 
joists is much thicker and too massive to transport easily. As with all 
construction, it is desirable to reduce the number of steps required, use 
less materials and simplify the operations. The concrete panel and joist 
assemblies are easily transportable and can be erected on site using 
light-weight equipment. 
While it is well known to form pre-cast concrete panel and joist assemblies 
for use as floors or other load bearing members, this type of construction 
has not been applied to walls. Pre-cast wall panels must take into 
consideration and account for wind effects not encountered in floor 
situations. With floor panels, load forces in the downward or weight 
bearing direction are the only forces encountered. With wall panels 
however, the effect of wind on the upright exterior walls means that 
either wind load or wind suction may be present. That is, a pre-cast wall 
panel must be able to withstand stresses in both directions--a compressive 
load toward the interior of the building and a tensile load or suction 
toward the exterior of the building. The interior chords of the joists 
will be in tension in the compressive load situation and in compression in 
the suction situation. The standard methods for forming pre-cast panels do 
not take these factors into consideration, and if panels made from such 
methods are used in exterior walls, can result in a construction not able 
to withstand the stresses caused by wind. 
To overcome the problems outlined above, the method of the invention 
provides for constructing a pre-cast concrete panel and joist assembly 
able to withstand both compressive loads and suction. The method 
incorporates the step of adding bridging members to interconnect the 
joists and concrete panel, the bridging providing the necessary lateral 
stability to overcome the problems of the wind effects. The specific 
structure and design of the bridging members and joist enable quick, 
efficient construction, and the resulting concrete panel and joist 
assembly is distinct from previously known assemblies. 
It is an object of this invention to provide a pre-cast concrete panel and 
joist assembly able to be used as a wall member, and to provide a method 
of pre-casting and constructing such assembly. 
It is an object of the invention to provide a method of pre-casting and 
constructing concrete slab and joist assemblies with lateral bridging 
members which is simple in operation. 
It is a further object of this invention to provide such a method where 
pre-constructed joists are attached to a pre-cast, hardened concrete panel 
and lateral bridging members are easily interlocked with the joists. 
It is a further object of the invention to provide a pre-cast panel and 
joist assembly having interlocking lateral bridging members. 
It is a further object of the invention to provide such an assembly where 
the joist does not require an exterior chord, so that the overall depth of 
the assembly is reduced. 
SUMMARY OF THE INVENTION 
The invention is a concrete panel and joist assembly comprising a number of 
joists attached to a pre-cast concrete panel by attachment means and 
anchor members embedded in the concrete slab. Preferably, substantially 
V-shaped bridging members are interfit through apertured plates attached 
to the joists and the ends of said bridging members are attached to said 
concrete panel. 
The method of the invention involves initially setting up a form to receive 
the concrete. The form is created by placing four side members in a 
rectangular shape on a flat, smooth surface capable of supporting the 
weight of the concrete. The surface is coated with a release material to 
prevent adhesion of the poured concrete. Reinforcing members, such as 
rebar or welded wire mesh, are positioned in the central portion of the 
mold. Metal joist attachment plates are positioned at each end so that the 
surface of the plates will be flush with the upper surface of the poured 
concrete. The concrete is poured and joist anchor members for attaching 
the joists are set into the wet concrete. The concrete is allowed to 
completely harden. Joists are then attached to the concrete panel by 
welding or mechanically fastening the exterior chords to the metal joist 
attachment plates and attaching each of the joist anchor members. 
Substantially V-shaped bridging members are slotted through apertures in 
the joists, forming a mechanical interlock, and the ends of the bridging 
members are attached to anchoring members in the concrete panel. The 
assemblies are then removed from the molds by crane, transported to the 
construction site, placed upright and set into place. 
In an alternative embodiment, the concrete panel and joist assembly 
comprises joists having no exterior chords, the webbing of the joist being 
attached directly to the concrete panel. An extended chord can be added to 
the webbing of the joists at the ends to allow closer attachment of the 
assembly to other structural members. In this method, joists having no 
exterior chords are prepared. The form is set up, coated and reinforced as 
described above. Concrete is then poured into the form. Before the 
concrete hardens, webbing attachment means are set into the surface of the 
concrete at locations corresponding to the positions of the exposed joist 
webbing. After the concrete has hardened, the joists are positioned on the 
concrete panel and attached by welding the webbing to the webbing 
attachment means. Interlocking bridging members are then secured to the 
joists and attached to the concrete panel. An extended chord can be added 
to the ends of the joists adjacent the concrete panel by welding angle 
iron to the webbing.

DETAILED DESCRIPTION OF THE INVENTION 
The method of constructing the pre-cast concrete wall panel and joist 
assembly comprises initially setting up a mold in which to cast the panel. 
The assemblies can be cast at a manufacturing site and then shipped to 
various installation sites, or the molds can be built at the installation 
location where it is desirable to preclude transporting the finished 
assemblies, if there is enough room to accommodate them without 
interfering with construction. 
Typically, a smooth, planar concrete slab or steel table 11 is used as the 
backer surface and a four sided form is placed on this surface to form the 
perimeter of the panel, as shown in FIG. 1. The form members 12 can be of 
wood or metal and can be bevelled or angled on the interior side of at 
least two of the form members 12. After the form members 12 are set in 
place, the bottom of the mold is coated with a mold release, such as form 
oil or bond breaker, to insure that the wet concrete will not bond to the 
slab or table surface 11. Additionally, liner panels of rubber, fiberglass 
or wood can be placed on the mold bottom to create patterns or designs in 
the finished panel, if desired. 
Reinforcements, of any type generally known in the art, are then positioned 
within the mold so that the reinforcement members will be contained within 
the concrete panel 10 upon completion. For example, rebar, welded wire 
mesh or pre-stressed tendons may be used to provide additional strength 
within the finished concrete panel 10. Also at this time, steel weld 
plates may be positioned adjacent the side of the forms. The weld plates 
have an anchoring member which extends into the interior of the mold such 
that this anchoring member will be embedded in the interior of the 
finished concrete panel. The exterior surface of these weld plates will be 
flush with the edge of the finished concrete panel 10 and are positioned 
so that the weld plates of adjacent panels will abut each other. The 
adjacent weld plates can then be welded together on site to join separate 
wall panels. 
Pairs of joist attachment means 16 are set into the mold at interior 
positions on opposites sides of the form members 12 where the ends of the 
joists 20 are to be eventually attached to the panel 10. These joist 
attachment means 16 are steel plates to which the exterior chord 21 of the 
joist 20 is welded. The joist attachment plate 16 consists of a steel 
plate positioned to be flush with the surface of the concrete poured into 
the mold, with anchoring mean extending into the interior of the mold to 
be embedded in the interior of the concrete panel 10. The joist attachment 
means 16 can be constructed from short segments of angle iron. For a three 
inch thick panel 10, the joist attachment plate 16 will be positioned so 
that its upper surface is three inches above the mold bottom. 
Wet concrete is now added to fill the mold to the desired level, typically 
three to six inches in depth. The wet concrete surrounds the reinforcement 
members and the anchoring means of the joist attachment plates 16. The 
outer surface of the concrete is flush with the outer surfaces of the 
joist attachment plates 16 and weld plates, if present. 
Before the concrete sets, joist anchor members 22 are inserted into the 
concrete at intervals on lines running between opposite joist attachment 
plates 16. These joist anchor members 22 are used to attach the exterior 
chord 21 of the joist member 20 to the finished concrete panel 10. Joist 
anchor members 22 may be anchor bolts or vertically extending weld plates 
partially embedded in the concrete panel 10. Another alternative for 
attaching the joist members 20 is to allow the panel 10 to harden and then 
drill holes for insertion of wedge or sleeve anchor members. Also at this 
time, bridging anchor members 33 may be inserted into the wet concrete at 
the required locations along both sides of the joist line for attachment 
of the legs of the bridging members 30 during later assembly. 
After the concrete panel 10 has hardened, usually a period of roughly 24 
hours, the joists 20 are attached to the panel 10. The joists 20, as shown 
in FIG. 2, are of the standard construction, having a continuous exterior 
chord 21 and a continuous interior chord 23 made of angle iron connected 
by webbing material 24 alternating between the two chords. 
The joists 20 are attached by inverting them such that the exterior chord 
21 rests on the surface of the hardened concrete panel 10 and extends from 
one joist attachment plate 16 to its opposing joist attachment plate 16, 
following the line of the embedded joist anchor members 22. The exterior 
chord 21 is permanently joined to the concrete panel 10 by attaching the 
joist anchor members 22 to the chord 21, and also welding or mechanically 
fastening the exterior chord 21 to the joist attachment plates 16. 
Because the concrete panel and joist assembly is to be used as a wall, 
consideration must be given to the effects of wind on the panel 10. A wall 
will be exposed to both wind load and to wind suction, wind load being a 
force against the exterior of the panel 10 causing the interior chord 23 
to be in tension and wind suction being a force in the opposite direction 
causing the interior 23 chord to be in compression. Since the interior 
chord 23 is designed to be in tension, wind suction is the main problem to 
be compensated for. 
This is done by adding bridging members to further stabilize the joists. 
Preferably, lateral bridging members 30, as shown in FIG. 3, are attached 
at intervals along the joist 20 which stay the joist 20 laterally and 
provide sufficient additional strength to compensate for the effects of 
wind suction on the panel 10. Apertured plates 19 for receiving the 
bridging members 30 are attached at positions along the joist 20. The 
apertured plates 19 are planar with an elongated aperture or slot, the 
major axis of the slot paralleling the major chord direction. The 
apertured plates 19 are attached by welding the plates 19 to portions of 
the interior webbing 24 near or adjacent the interior chord 23. The 
bridging members 30 are short, substantially V-shaped sections of weldable 
material such as rod steel stock. The bridging members 30 are constructed 
so as to have a vertical slot 32 located at the interior of the V-angle. 
The slot 32 is formed by attaching short flanges or segments 34 of rod 
steel stock on both legs adjacent the V-angle of the bridging member 30, 
separated by a distance equal to the thickness of the apertured plate 19. 
As seen in FIG. 4, the bridging members 30 are inserted through the 
apertures and rotated 90 degrees so that the ends rest on the concrete 
panel 10 on either side of the joist 20. The slot 32 of the bridging 
member 30 interfits tightly with the apertured plate 19 so that no 
additional fastening or welding is required to provide a fixed connection. 
The legs of the bridging member 30 are then attached to the concrete panel 
10 by chemical bonding or with expansion bolts drilled into the panel 10, 
or by attaching the legs of the bridging member 30 to previously embedded 
bridging anchor members 33. 
The concrete panel and joist assembly is then lifted by crane from the 
mold, transported to the installation site, stood upright and set into 
place. The assembly comprises a number of joists 20 permanently attached 
to the concrete panel 10, each joist 20 being further attached to said 
concrete panel 10 by a number of V-shaped bridging members 30 extending to 
each side where the ends are attached to the panel 10. The bridging 
members 30 have a slot 32 which interfits with the openings in apertured 
plates 19 attached to the webbing 24 near the interior chord 23, such that 
an firm mechanical attachment is achieved and no further fastening is 
required. The bridging members 30 provide the necessary lateral stability 
to allow the relatively thin concrete panel 10 to be used as an exterior 
wall. 
In an alternative embodiment, the panel and joist assembly is constructed 
using joist members 40 that do not have exterior chords, as shown in FIG. 
5. Each joist 40 consists of an interior chord 41 and webbing 42, where 
the folded ends of the webbing 42 are exposed. By eliminating the exterior 
chord, a significant savings in construction costs can be realized. 
Furthermore, the overall depth of the panel and joist assembly is reduced 
roughly fifteen percent without sacrificing strength. The direct 
attachment of the webbing 42 to the concrete panel 10 in combination with 
the lateral bridging members 30 enables the assembly to withstand both the 
wind load forces and suction. 
The mold is prepared as previously outlined by setting up the forms, 
applying the mold release material and positioning the reinforcing 
members. However, no joist attachment plates are required, so the next 
step is to pour the wet concrete into the mold to the desired level. 
Before the concrete has hardened, webbing attachment means 44, as seen in 
FIG. 6, are inserted into the concrete at intervals along the desired 
joist line at distances matching the distance between the ends of the 
exposed webbing 42. These webbing attachment means 44 are preferably 
constructed from short segments of angle iron. The webbing attachment 
means 44 are set into the concrete such that the angle is contained within 
the interior of the panel 10 to anchor the webbing attachment means 44 
once the concrete has hardened. A planar portion of the angle iron extends 
vertically from the concrete a few inches, each planar portion being 
aligned along the joist position line. After the concrete has hardened, 
joists 40 having only an interior chord 41 and webbing 42, but no exterior 
chord, are positioned on the panel 10 such that the each extended portion 
of the webbing 42 contacts the webbing attachment means 44. The joists 40 
are then permanently attached to the concrete panel 10 by welding the 
webbing 42 to the webbing attachment mean 44. 
As before, bridging members 30 are now attached to the joist 40 at 
intervals by interlocking the bridging member 30 to the bridging 
attachment plates 19 affixed to the webbing 42. The bridging members 30 
are then attached to the concrete by any of the methods outlined above. 
The resulting concrete panel and joist assembly is fully capable of 
withstanding the wind stresses, yet is more compact in depth and lighter 
because of the lack of the exterior chords in the joists. Furthermore, 
such joists are less expensive since less materials are required for their 
construction. 
In a further embodiment of this assembly, a short segment of chord is 
attached to the webbing 42 on one or both ends of the joists 40 so that 
this extended chord 50 is adjacent the concrete panel 10 and extends 
beyond the end of the interior chord 41. This extended chord 50, shown in 
FIG. 5, may be attached to the concrete panel 10 by any suitable method as 
previously described, including the method of embedding joist attachment 
plates 16 in the concrete slab. This extended chord 50, because it extends 
beyond the ends of the interior chord 41, allows the panel and joist 
assembly to be attached to other building components in a more compact 
manner, since the building components will abut the extended chords 50 
rather than being attached to the interior chords 41 of the assembly. 
It will be obvious to those skilled in the art that equivalents and 
substitutions may be made in the above descriptions. The full scope and 
definition of the invention therefore is to be as set forth in the 
following claims.