Tie anchor and method for manufacturing insulated concrete sandwich panels

A tie anchor for sandwich panels of reinforced concrete is formed as a flat strap. The reinforced concrete sandwich panel is formed by placing a plurality of tie members vertically in the bottom of a horizontal form with reinforcing rods extending through holes in the ends of the ties adjacent to cross-feet. A network or grid of reinforcing steel is supported from a chair provided by the ties and cross-feet and the concrete for the first layer of the panel is poured about the ties, cross-feet and reinforcing steel grid. A layer of rigid insulation material is placed on top of the first layer of wet concrete about the projecting tie members immediately after pouring the first layer of concrete and a second grid of reinforcing steel rods is supported from the holes in the projecting upper ends of the tie members. The second layer of concrete may be immediately poured about the upper end of the tie members and reinforcing steel. The insulation material may occupy the entire area between the two concrete layers of the panel except for an 8-10 inch solid concrete section along the bottom edge of the panel connecting the layers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a tie anchor or link for structurally 
connecting two spaced concrete slabs or layers of a tilt-up wall panel 
which has a layer of rigid insulation sandwiched therebetween. The 
invention further relates to a novel panel structure and the method or 
system for assembling such sandwich panels wherein the tie anchor also 
acts as a support "chair" and spacer for the reinforcing steel grids 
during formation of the concrete slabs. 
2. Description of the Prior Art 
Steel reinforced concrete sandwich panels having an intermediate layer of 
rigid insulation are generally known in the prior art. It is also known in 
the prior art to provide structural tying members of various designs which 
extend through the intermediate insulation layer and are anchored in the 
spaced concrete slabs. Examples of this type of panel construction are 
found in the U.S. Patent to Fricker U.S. Pat. No. 4,283,896 and the two 
U.S. Patents to Haeussler U.S. Pat. Nos. 3,757,482 and 3,996,713. These 
patents also illustrate the common expedient of passing the concrete slab 
reinforcing bars or rods through openings in the tie members to 
structurally connect the spaced concrete slabs. Although not specifically 
disclosed in these three patents, one method used in forming the concrete 
slabs is to pour them in a vertical orientation between vertical mold 
members or forms with the steel reinforcing grid assembly serving to 
support the tie members during formation of the sandwich panel. The two 
Haeussler patents illustrate a tubular tie anchor having extremely rigid 
structural characteristics whereby only one such tie member may usually be 
used for each composite panel or slab. This is discussed in Haeussler U.S. 
Pat. No. 3,996,713, the problem being one of accommodating a limited 
relative mobility of the concrete slabs to accommodate thermal dimensional 
changes and the like. 
The U.S. Patent to Garrett U.S. Pat. No. 4,541,211 illustrates a second 
type of tie anchor for concrete sandwich panels wherein a metal strap 
extends completely through the two concrete slabs and the intermediate 
rigid insulation layer. The Garrett ties additionally connect the vertical 
form panels so as to maintain them at a predetermined distance during the 
pouring operation. The strap ties serve to support the reinforcing rods 
which pass through holes in the body of the ties. 
When it is desired to fabricate sandwich panels utilizing horizontal forms, 
one method has been to support the grids of reinforcing rods for the 
spaced concrete slabs by such means as holes in the forms as illustrated 
by U.S. Pat. No. 4,117,639 to Steenson et al. Another common practice is 
that of initially supporting the reinforcing grid or mesh of metal wires 
or bars on suitable spacer elements placed in the bottom of the form. U.S. 
Pat. No. 4,624,089 to Dunker discloses this method of construction and 
U.S. Pat. No. 3,378,981 to Horne illustrates a typical reinforcing rod 
chair or support for spacing the reinforcing members for horizontal 
pouring. In the Dunker patent, the tie anchors extend through the 
intermediate rigid insulation layer and are embedded in the spaced 
concrete slabs with the anchors being supported by the reinforcing grid 
during the pouring of the slabs. 
Tie anchors have also been devised in the prior art for mechanically 
connecting double-wall masonry panels wherein one or both of the panels of 
the slab comprises bricks or masonry blocks. Examples of this type of 
construction are found in the Atecheson U.S. Pat. No. 2,261,510 and the 
Narr U.S. Pat. No. 3,217,457. In these instances, the tie strap must be 
imbedded in the mortar as the blocks or bricks are laid up in a 
conventional manner. In the Narr patent, the tie straps are supported by 
the spaced bricks until the mortar is set about the end of the strap and 
the concrete slab is cast in a form around the upper ends of the tie 
straps through which reinforcing rods have been placed. The form for the 
concrete slab must then be removed before the panel is erected. As may be 
appreciated this method of constructing brick or block double-wall 
structures is limited to relatively small size panels. 
The construction of relatively large structures such as warehouses, cold 
storage structures and the like has become extremely competitive with 
reinforced concrete insulated sandwich walls being one of the common 
methods of building the structures. These sandwich walls are commonly 
fabricated in horizontal forms on the ground, either at the building site 
or at a fabricating yard. The assembled panels are then moved into place 
and erected at the final building wall position. The problems associated 
with formation of sandwich panel walls involve not only the positioning of 
tie anchors with sufficient tensile strength to support the spaced 
concrete slabs during moving and raising but also considerations of heat 
transfer from one concrete slab to the other by the tie anchors 
themselves. This latter consideration becomes of primary importance in the 
construction of cold storage facilities for instance. Another problem is 
in devising a method for placing the reinforcing steel grid accurately in 
the body of the concrete slabs in the successive formation of the two 
slabs separated by the rigid insulation. In larger building walls which 
may be as much as 60 feet in height the rebar or reinforcing steel grid 
for both concrete layers must be tied and held in place in a horizontal 
plane at the proper distance from the bottom of the form. The grids may 
weigh several tons depending on the size of the wall being formed. In 
addition, it is necessary to vibrate the wet concrete during or after 
pouring for proper settling. This is true of both concrete layers, of 
course, and having to pick up a collapsed reinforcing grid which has lost 
its support during the pour or vibrating operation is extremely costly in 
terms of the amount of time and labor it takes to relocate the grid. 
Because of the competition in forming the insulated panel walls, time and 
labor saving have become of paramount concern. 
SUMMARY OF THE INVENTION 
The tie anchor of the present invention is especially constructed to 
facilitate the horizontal pouring of the successive concrete layers with a 
layer of rigid insulation therebetween. A plurality of tie anchors are 
placed upright in the bottom of a form and act as "chairs" or supports and 
spacers for a grid of reinforcing steel rods in preparation for the 
horizontal pouring of each of the successive concrete layers. According to 
the present method and system for assembling the sandwich panel, a first 
horizontal reinforced concrete layer, an intermediate layer of rigid 
insulation material and a second reinforced concrete layer may be 
successively laid down in a horizontal form with no time loss between the 
formation of the successive layers of the sandwich panel. 
The tie anchor extends through the intermediate layer of rigid insulation, 
is connected to the reinforcing steel of both slabs and imbedded in the 
concrete of both slabs of the panel. The tie anchor may be made from any 
material which has sufficient tensile strength to tie the concrete slabs 
together during the maximum stress condition incurred during the raising 
of the finished panel from the horizontal position to the vertical. The 
maximum stress is actually experienced between 0 and approximately 50 
degrees of angle. After casting, the walls are normally raised by means of 
a crane with lifting and brace inserts being cast into the body of the 
slabs in a conventional manner during the pour. A typical wall panel will 
be in rectangular form measuring about 20 feet by 24 feet and utilizing 
approximately 25 tie anchors spaced strategically over the panel 
dimensions. A 91/4 inch thick panel suitable for such structures as cold 
storage buildings for instance will utilize a 4 inch concrete inside slab, 
2 inches of rigid insulation board such as styrofoam or any other suitable 
commercially available insulating board and a 31/4 inch outside concrete 
slab. 
An important feature of the tie anchor of the present invention is the 
utilization of a cross-foot rigidly connected to one end of one side edge 
of the tie anchor strap extending at right angles to the flat faces of the 
strap. The system for rapidly, efficiently and therefore economically 
assembling the sandwich panel utilizes the multiple tie anchors as 
"support chairs", first for the reinforcing steel of the bottom concrete 
slab and then for the reinforcing steel grid of the second horizontal 
concrete slab. The construction of a panel is begun by assembling a 
horizontal form of suitable dimensions for the finished panel and placing 
reinforcing steel on the bottom of the form. The links are then located on 
the reinforcing rods intended to be the vertical steel with the rods being 
passed through holes or apertures in the ends of the anchors adjacent the 
rigid cross-feet. With the links in the upright or vertical position and 
the reinforcing steel properly tied, the links perform the function of 
supporting the entire lower grid of steel in the proper position for 
reception of the concrete. At this point the lifting and brace inserts may 
be properly located in a well known manner followed by pouring of the 
concrete for the bottom slab. The slab is then vibrated and floated in a 
conventional manner. This of course requires workmen to move about and on 
the reinforcing steel. Just as soon as the first slab is properly prepared 
and with the concrete still wet, a layer of rigid polystyrene insulation 
material is placed directly on the new concrete with the upper ends of the 
links or tie anchors extending upwardly through the layer of insulation. A 
second grid of reinforcing steel is installed, again utilizing the holes 
or apertures in the opposite ends of the tie anchors to support the grid. 
The next layer of concrete is immediately poured directly on the rigid 
insulation about the steel grid and the upper ends of the anchors and 
vibrated. The desired surface treatment such as a broom or a trowel finish 
may then be accomplished. As soon as the concrete has reached the desired 
strength the panels may be raised to a vertical position with a crane and 
secured in place. 
The utilization of the cross-foot on the tie anchor and utilizing the tie 
anchor as the support "chair" for the reinforcing steel ensures the rapid, 
accurate and stable placing of the steel grids in a manner far superior to 
any system known to the prior art. The end of the strap which rests on the 
bottom of the form may be cut away in order to minimize the exposed area 
which appears in the outer face of the bottom slab. The cross-bar or foot 
may be made of cylindrical stock to further minimize the surface exposure. 
The tie anchors may be constructed from strap iron of sufficient 
cross-section and tensile strength or may be made from high tensile 
strength plastics presently available, depending on the dimension of the 
panel. Metal tie anchors may also be dipped or coated with a non metallic 
plastic substance in order to minimize heat transfer from one panel slab 
to the other.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1-3, the tie anchor 1 includes a flat strap body having 
the two wide side faces 2 and 3, the longitudinal narrow side edges 4 and 
5, the top end edge 6 and the bottom end edge 7. In practice, the tie 
anchor has been fabricated from strap steel typically of 3/16th inch 
stock, having a width of 11/2 inches and a total length of 103/4 inches. 
It will be appreciated, however, that these dimensions may vary depending 
upon the size and weight of the particular wall being fabricated. 
Alternatively, the tie anchor may be made from a high tensile strength 
plastic with the appropriate strength characteristics for the wall design 
and accordingly dimensioned. A 5/8ths inch hole 8 is located adjacent the 
upper end edge 6 and a similar 5/8ths inch hole 9 is located adjacent the 
bottom end edge 7 of the strap. The sizing of the holes 8 and 9 will, of 
course, be determined by the diameter of the particular rebar steel being 
utilized. The 5/8ths inch hole is described as being one of the more 
common rebar sizing. A cross-bar or foot 11 is welded to the longitudinal 
edge surface 5 at the bottom end of the anchor. The length of the 
cross-foot may be varied, of course, but should be in the neighborhood of 
several inches in length. In the case of an iron or steel strap member, 
the cross bar 11 may be welded to the body of the strap as illustrated. 
The end edge 7 is also cut away as at 12 in any concave configuration so 
as to minimize the end edge surface of the strap which will be exposed in 
the finished concrete panel. The initial position of the tie anchor is 
that shown in FIGS. 1-3 and 5 with the bottom edge surface 7 resting on 
the bottom of the panel form and the bottom longitudinal peripheral edge 
of the cross-bar 11 also seated on the form bottom. In this position the 
anchor is quite stable and, when a plurality of such anchors are placed as 
spaced intervals on the vertical steel of the grid for the bottom slab, 
the entire grid is stabilized. The suspended grid is capable of 
withstanding mechanical impact experienced either by workmen moving about 
the grid or the vibrating action once the concrete is poured. This grid 
with the vertical links and cross-feet becomes a self-supported network in 
the bottom of the form accurately located the proper distance from the 
intended outside slab face. 
FIGS. 4 and 5 illustrate the composition of the sandwich panel in its 
finished form. The vertical steel reinforcing rods 13 of both concrete 
layers extend through the opposite ends of the link 1 by means of the 
holes 8 and 9 with the horizontal steel rods 14 running at right angles 
thereto and also embedded in the concrete layers 15 and 16. The 
intermediate layer of rigid insulation 17 surrounds the links and fills 
the space between the two concrete layers except for the concrete 
connecting portion 20 located at the bottom edge of the panel as indicated 
in FIG. 4. The two concrete layers illustrated in the present embodiment 
are thus connected at their bottom ends along their entire length by a 
solid concrete portion. The connecting links or anchors 1 provide the 
remaining structural tie between the upright concrete layers in their 
upright position. 
FIGS. 6-9 illustrate the various steps involved in the fabrication of a 
typical sandwich panel utilizing the tie anchor and cross-foot method of 
assembling the panel. As illustrated in FIG. 6, the vertical panel form 
walls 18 and 19 are placed in a horizontal plane and will be suitably 
mounted on a form bottom 21 of conventional design. The horizontal and 
vertical steel rods 13 and 14 are initially laid in the bottom of the form 
and tie anchor and cross-foot members 1 are then located on the vertical 
steel rods 13 which serves to support the grid of reinforcing rods a 
proper distance from the bottom wall of the form. As indicated in FIG. 6, 
the rods 13 and 14 may be tied as at 22 in a conventional manner to aid in 
rigidifying the grid prior to pouring. Once the reinforcing rods and tie 
anchors are in place, the first layer of concrete may be poured and 
vibrated ready for the application of the layer of rigid insulation. 
FIG. 7 illustrates the placement of the rigid insulation layer 17, usually 
in the form slabs or blocks of insulation board 23, which is laid down 
immediately on the wet concrete of the bottom slab 15. The rigid 
insulation may be punched or perforated for the purpose of passing over 
the ends of the tie anchors 1. The rigid insulation boards 23 are capable 
of supporting the weight of the workmen during the placement of the 
reinforcing grid for the second concrete slab. As seen clearly in FIG. 7, 
the bottom edge portion of the slab 15 is left exposed or uncovered by the 
layer of insulation blocks 23. The uncovered portion 20 of the slab will 
normally be 8-10 inches wide in a conventional 20.times.25 foot panel such 
that the upper and lower concrete slabs are thus connected along the 
bottom edge of the panel. The layer of rigid insulation is otherwise 
exposed on the remaining three sides of the rectangular panel. 
Once the layer of rigid insulation 23 is in place, the steel grid for the 
top slab 16 may be installed by passing the vertical steel 13 through the 
holes in the upper ends of the anchors and tying the horizontal rods 14 in 
a conventional manner as shown FIG. 8. As previously mentioned, workmen 
may walk directly on the rigid insulation layer 17 for placing the grid. 
Just as soon as the upper grid of reinforcing rods is in place, the top 
slab 16 may be poured on top of the rigid insulation about the upper grid. 
The monolithic connection 20 along the bottom edge of the panel will be 
formed with the wet slab 15 as illustrated in FIG. 9. The panel is 
completed by again vibrating and either troweling, brooming or providing 
any type of aesthetic surface desired to the outside face of the slab 16. 
Once the concrete has hardened to the desired strength, the panel may be 
raised by crane and located in place to form the building wall. 
While the present invention has been described with relation to a single 
embodiment of the tie anchor and the assembly method of one embodiment of 
the sandwich wall, it will be understood that modifications may be made to 
the invention without departing from the spirit and scope of the invention 
defined in the following claims.