Abstract:
Light weight structural wall panels are made of two layers of load bearing skins, separated by a light-weight concrete, using expanded materials such as Perlite, Pulverized Fuel Ash, Styrene or foam cement to form a sandwiched construction for structural strength. The load-bearing skins, which are sprayed into a mold, are made of glass fiber, sand and cement matrix in different thickness and mix ratios. All edges of the encapsulated panels are made of the same GFRC matrix. The distance between GFRC inner &amp; outer layers dictates the required structural strength of overall finished panel to resist wind &amp; earthquake loadings. The sprayed layers and the core are made/cast while the concrete is green, before its initial setting-time to ensure structural integrity of components after curing.

Description:
[0001]     This application claims priority from provisional application Ser. No. 60/701,993, filed Jul. 25, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to building panels. More particularly, the invention relates to panels having a stressed skin sandwich construction.  
         [0004]     2. Discussion of the Background  
         [0005]     Numerous types of building panels have been heretofore proposed, each offering particular advantages and disadvantages. It is highly desirable to improve insulation and strength properties of such panels, whilst at the same time reducing their weight. In addition, there is a long-felt need for building panels that are resistant to earthquakes, as well as resistant to high winds such as occur in hurricanes and the like.  
         [0006]     These and other problems are overcome by the present invention, as will be further described with reference to the several views, in which like numerals represent like elements.  
       SUMMARY  
       [0007]     Light weight structural wall panels are made of two-layers of load bearing skins, separated by a light-weight concrete, using expanded materials—such as Perlite, Pulverized Fuel Ash, Styrene or foam cement—to form a sandwiched construction for structural strength. The load-bearing skins, which are sprayed into a mold, are made of glass fiber, sand and cement matrix in different thickness and mix ratios. All edges of the encapsulated panels are made of the same—GFRC matrix. The distance between GFRC layers—inner &amp; outer layers—dictate the required structural strength of overall finished panel to resist wind &amp; earthquake loadings. The sprayed layers and the core are made/cast while the concrete is green, before its initial setting-time to ensure structural integrity of components after curing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  shows the detailed construction of a typical panel according to a preferred embodiment of the invention.  
         [0009]      FIG. 2  is a light partition slab for interior use as a partition.  
         [0010]      FIG. 3A  is an exploded view showing a floor slab provided with an adjustable hold-down device during construction to receive a loading arm of a panel holder.  
         [0011]      FIG. 3B  is a detailed view of part of  FIG. 3A .  
         [0012]      FIG. 3C  is a side view of the Beta Link holding end.  
         [0013]      FIG. 3D  shows a typical vertical joint between two adjoining panels filled up by cement grout and a reinforcing bar.  
         [0014]      FIG. 3E  is a plan view of the Beta Link holding end.  
         [0015]      FIG. 4  is a view of a mold with an inset view showing the relation of a GFRC skin to the core material and the mold.  
         [0016]      FIG. 5  illustrates a production line.  
         [0017]      FIG. 6 . is a view of a ceiling panel according to an embodiment of the invention.  
         [0018]      FIG. 7 . is a cross-sectional view along the line VII-VII of  FIG. 6 .  
     
    
     DETAILED DESCRIPTION  
       [0019]     Buildings can use Energy Saving Structural Panels according to a preferred embodiment of the invention to form the desired enclosures. The proposed panels, varying in size and thickness, are made of composite materials in the form of a sandwich construction. The panels can be modular and have a standard size, typically 4′×10′×8″-6″.  FIG. 1  shows the detail construction of a typical panel  100 , consisting of two outer layer stress skins  110  made of sprayed up glass fiber reinforced concrete (GFRC) and a light, insulating yet structural, core  120 .  
         [0020]     The skins  110  can be made of: 
        Cement;     Silicate sand;     Alkali resistant fiber glass;     Water; and     Additives to increase workability        
 
         [0026]     The core  120  can be made of: 
        Cement;     Expanded Perlite stone or any other expanded mineral material to yield strength at low weight;     Sand; and     Water        
 
         [0031]     In a preferred embodiment of the invention, as shown in  FIG. 4 , the core mix is poured into the mold  430  onto the sprayed GFRC  110  while both mixes are green to ensure proper adhesion between the layers and homogeneous bond across the product for cement matrix. The outer layer is sprayed onto the core material  120  to form a stress skin sandwich construction. The panel will be exposed to elevated curing temperatures (up to 130° F.) to have the concrete panels cured in 8 hours, building enough strength for handling and erection. The overall thickness of such panels will preferably be 4″-8″ or even 10″. The thickness of sprayed up GFRC layers will preferably be ⅛″-½″, depending on the structural integrity required. Combining fiberglass and cement matrix layers, once cured and separated by a set distance, will create a rigid concrete panel with adequate strength to withstand the typical design loads for wind, live loading and structural weights. Using expanded Perlite (or mineral material) in the concrete matrix will generate light weight, insulating, concrete, with an R value of 2/in (U=0.06 BTU/° F./hr/ft).  
         [0032]     The insulating value of finished products can vary depending on the percentage use of Perlite and the thickness desired. The weight of such a product would be 8-12 lbs/ft 2  depending on the type of insulation required. Considering the fact that normal concrete panels weigh about 70-100 lbs/ft 2 , the proposed panels will produce lighter structures which require smaller columns and foundations, resulting in lower costs. The above described panels, using cement as the bonding matrix can be used as external panels to withstand weathering. For interior use as partitions, a combinations of plaster and perlite  220  can be used to produce a light partition slab  200  ( FIG. 2 ). The weight of each element is preferably 22-25 lbs. for a typical 18″×24″×4″ block.  
         [0033]     The proposed structural panels are built on the basis of “bone-structure” theory,je: having strong stress skins made of fiberglass and cement matrix, encapsulating an energy efficient insulating light concrete core made of light aggregate (ie: perlite, styrene beads or any other light insulating material) and cement matrix. All these are cast together without using any other bonding agent other than the cement.  
         [0034]     To make the panels according to a preferred embodiment of the invention, stress skins are sprayed into premade molds  430  (see  FIG. 4 ) of various sizes and shapes depending on the requirement of the design engineers. The thickness of the skins  110  may vary from ⅛″ to ½″, depending on the size and loading application of the panels. The sides and bottom of the molds are sprayed at one stage and immediately filled up by light and insulating core concrete  120  varying in density from, e.g. 25 lbs to 120 lbs per cubic foot, depending on the insulation level required. The second stage (core placement) is followed by a third stage which deposits another layer of sprayed up GFRC  110  while the cement matrix  120  from all three stages is still fresh and at its initial stage of setting.  
         [0035]     This ensures homogeneous cement bonding from the outer to inner layers  110  and through the core  120 . The fiberglass cement matrix  120 , which is pre-mixed, is pumped and sprayed through a special gun  510  (shown in  FIG. 5 ) onto the required surfaces. The core material  120  is also pre-mixed in a different mixer using light coarse and fine aggregates and cement and poured on to the freshly sprayed surface by standard pumping and vibrating methods that are well known in the art. The distance between the outer and inner layer stress skins  110  is governed by the load bearing requirement of design, which in a non-limiting example varies between 4″ to 10″.  FIG. 5  illustrates a production line, where gun  510  fills one of a plurality of molds  430 .  
         [0036]     Different textured materials can be used at the bottom of the molds  430  to produce textured surface finishes for the exterior side of panels. The stress skins  110  are preferably reinforced with chopped Alkali-Resistant fiberglass strands, increasing the tensile property of the finished product to about 1000-1400 psi. Therefore, panels produced in this manner do not require any steel reinforcing. Curing of these concrete panels is performed under elevated temperature environments to yield 60% of its strength within 10 hours of casting.  
         [0037]     A unique joinery system can be employed according to a preferred embodiment of the invention to resist earthquake loads: In this system an external panel  300  is attached to the main structure by a special shock absorbing device, called “Beta Link”  310 . The floor slabs  320  (concrete or steel deck) are provided with an adjusting hold-down device ( FIG. 3A ) during the construction to receive the loading arm of panel holders (Beta Link).  FIG. 3C  and  FIG. 3E  show the holding end of the Beta Link  310 , which is provided with a bolt  305  and an adjusting pulley  315 .  
         [0038]      FIG. 3B  details the cross section of Beta Link(TM) which is comprised of an extending load bearing arm, a V shaped shoe  360  welded to the end of the arm, and a special bolt  330  with an adjustable sleeve. The V shaped shoe  360  fits into the upper groove  390  of the panel edge and the special hold down bolt  330 , through the flexible rubber pad  350 , will connect the “Beta Link”  310  to the panel  300 . The extended arm of “Beta Link”  310  is connected to the floor system by means of an adjustable sleeve ( FIG. 3A ). The upper part of special hold down bolt  330  used to connect Beta Link  310  to the panel  300  will receive an adjustable sleeve with a  1 / 4 ″ flexible rubber washer  340 . This mechanism allows for X, Y, &amp; Z directional adjustments &amp; leveling of the panels. Once the levels are adjusted, the next height panel will be lowered into place ( FIG. 3B ) and set freely on the adjustable sleeve dowel pins  370 .  
         [0039]     During the earthquake moments, the panels can act as shear walls with  2  loading points through Beta Link rubber cushions—top and bottom. The rubber padding &amp; washers will absorb the shear loads &amp; dissipate the resonance loads of earthquake, allowing enough flexibility &amp; elasticity of joints without causing damage to the panels or structure. The reduced weight of panels combined with the elasticity of joints will yield an “earthquake resistant” panelling system for different structures.  
         [0040]     All four sides of panels  300  are provided with grooves  390  to create a locking mechanism. A horizontal section through the panels ( FIG. 3D ) shows a typical vertical joint between two adjoining panels  300  which can be filled up by cement grout  380  and a reinforcing bar  390 .  
         [0041]     Ceiling panels  600  (see  FIG. 6 ) according to a preferred embodiment of the invention can be constructed as 4′×8′ modules and are made of a single layer  110  of GFRC, ¼″-½″ thick, which is sprayed into a mold  430 , preferably backed with a special perlite and styrene bead mix, while the concrete  120  is green. The Panel modules are supported using standard steel I beams  650 , spanned between the two structural beams  680 , and topped with normal or light weight concrete to form a completed section of floor for the next level above.  
         [0042]     The light structural concrete panels according to the preferred embodiment of the invention, manufactured in standard and specific sizes, can be used to provide cladding in high-rise buildings, commercial structures, multi-level buildings and single family houses. They provide insulation, as well as structural integrity without the use of steel or wood. For multi level structures, These panels need to be used in conjunction with a structural framing. The panels according to the invention are and energy saving product, lighter than normal concrete, yet durable and strong to withstand hurricanes and earthquake loads. The above products can also yield at least 2 hrs. of fire rating, using non combustible and inflammable gravels for core materials.  
         [0043]     As will readily be appreciated by those skilled in the art, numerous modifications and variations of the above embodiments of the present invention are possible without departing from the scope of the invention.