Patent Publication Number: US-2007094968-A1

Title: Lightweight concrete panel and method of building structural members

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      Not Applicable.  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable.  
     BACKGROUND OF THE INVENTION  
      1. Field of the invention  
      This invention relates to concrete structural members and methods of construction using concrete panels for forming structural members.  
      2. Description of the Prior Art  
      There are several types of construction methods using concrete for building structural members: cinderblock type construction; panel construction; and poured cement. Each method has advantages and disadvantages, but no prior construction method combines most of the advantages of each methods. The advantages and disadvantages of these methods will be discussed. The construction of cement structural members using these methods usually requires steel reinforcement which is attached to a foundation.  
      In cinderblock type construction, steel reinforcement attached to the foundation extends only a few feet high at first, and the cinderblocks are lifted over the reinforcement so that the steel reinforcement is in the middle of the cinderblock when it is set down. When a few cinderblocks have been stacked forming the wall, another few feet of steel reinforcement is tied to the steel sticking up out of the cinderblocks. Then more cinderblocks are stacked over the higher steel reinforcement. This process of tying the reinforcement together in sections reduces the strength of the reinforcement compared to a continuous steel rod through the wall. This process is also very labor intensive and requires skilled workers to achieve a quality finished wall.  
      The finished cinderblock wall has the advantage that the wall can be built without the need for equipment such as a crane. The cinderblock wall does not have good insulation characteristics, and is not a good sound barrier. The finished wall, however, does not have the strength of a poured concrete wall. These problems have been addressed with improvements in cinderblock type building such as those shown in U.S. Pat. Nos. 4,905,439; and 5,596,853. These improvements still have the expense of delivering a large amount of material to a construction site, as well as the labor of assembling the block wall.  
      Panel construction is similar to cinderblock construction in that the concrete is poured and cured before setting it in place. The panels are usually reinforced with steel, and then attached to the foundation when set in place. Concrete panel construction can provide a faster method of construction when the structural members are precast, but it does requires heavy equipment to lift the concrete panels into place. The heavy panels must be transported, at substantial cost, to the construction site if cast at a building yard. If the panels are cast at the construction site and then lifted into place, a large area is required to efficiently pour multiple structural members at once. A tilt up concrete panel is described in U.S. Pat. No. 6,658,810. Panels are very heavy, so the weight of panels is addressed in several improvements to panel systems described in U.S. Pat. Nos. 6,230,465; 6,260,329; 6,000,194; 6,898,908; 6,263,638 and U.S. Patent Application 10/970,666. Each of these references requires the use of lifting equipment to move the panel into place.  
      U.S. Pat. No. 6,230,465 discloses a precast concrete panel which is reinforced with steel, and has a rib structure to reduce the weight of the panel. The panel is used as the structural element and has a weight which is much too heavy for manual lifting.  
      Panels, like cinderblock have the disadvantage of heat transfer. Some of the lightweight panels mentioned above address heat transfer characteristics by using a concrete which has insulating characteristics, or adding a foam layer to the structure.  
      Another type of construction method is poured concrete using forms. The forms are used to support the concrete slurry when it is poured and as the concrete cures. The form is then removed and can be reused a limited number of times before it is discarded. The forms must have sufficient strength to prevent bulging or breaking under the pressure of the concrete pour. The forms must be transported from site to site. With a limited number of uses, the forms will be discarded when they can no longer be used, increasing waste and the cost of construction. If utilities are run through the concrete structural members (i.e. electrical, plumbing, cable etc.) then the forms may need to be cut for the outlets, thus increasing waste, or a special form may be used such as the one described in U.S. Pat. No. 4,116,415.  
     BRIEF SUMMARY OF THE INVENTION  
      The invention described and claimed herein comprises a lightweight concrete rib panel, and a method of forming structural members using the panel. The rib panel is made of a lightweight concrete having improved heat transfer properties and has ribs for increased strength. The rib panel is relatively thin and can be handled without the use of lifting equipment.  
      The Method of forming structural members includes erecting a support frame next to a foundation upon which a structural member can be placed; attaching a first set of rib panels to the frame using connectors and spacers, with rib panels stacked on top of each other to the height of a desired structural member; reinforcement and utilities are then placed next to the first set of rib panels; a second set of rib panes are attached to the connectors forming a space where the reinforcement and utilities were placed; finally a concrete slurry is poured into the space formed, to create a complete structural member. The framing is removed and can be reused. The lightweight concrete has improved thermal characteristics and serves as a support structure. The concrete rib panels can be finished on the inside and the outside of the structure without additional layers.  
      Among the objects of the present invention are the following:  
      To provide a Lightweight Rib panel which is light enough to handle without the use of lifting equipment, to reduce the cost of construction.  
      To provide a large Lightweight rib panel with improved characteristics which will be set in place using lifting equipment.  
      To provide a building material with improved thermal characteristics.  
      To provide a building method with improved structural strength.  
      To provide a method of construction where concrete structural members can be poured in one continuous concrete grout at least eight feet high.  
      To provide a method of construction which reduces building time and cost.  
      To provide a method of concrete construction with continuous reinforcement members from the foundation to the roof.  
      To provide a method of construction for structural members with conduits for utilities.  
      To provide a method of concrete construction which reduces the need for skilled labor.  
      To provide a method of construction which reduces waste.  
      To provide a structural member with an outside which has improved characteristics for bonding veneer.  
      To provide a building material which can be stored with minimal storage area.  
      To provide pre-engineered building materials for use on a job site.  
      To provide a building material with a good bonding surface for natural and simulated finishing materials. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an illustration of a concrete rib panel.  
       FIG. 2  is a cross sectional view of the concrete rib panel of  FIG. 1  across the line  2 - 2 .  
       FIG. 3  is a cross sectional view of the concrete rib panel of  FIG. 1  across the line  3 - 3 .  
       FIG. 4  is an illustration of a connector and spacer system.  
       FIG. 5  is an exploded view showing a method of building a structural member with the concrete rib panel system.  
       FIG. 6  is an illustration of a gripping connector and spacer system.  
       FIG. 7  is an illustration of a gripping connector with two rib panels. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  is an illustration of a concrete rib panel  100 . A system of ribs  10  is shown on all sides of the concrete rib panel  100 . In the preferred embodiment, the concrete rib panel  100  has only one transverse rib  12 , but the panel may be made with two ribs such that the ribs cross in the middle of the panel, or more ribs. One purpose of the ribs  10  is to reduce the weight of the overall panel, while providing strength to the panel. The panel also has a section between the ribs  20 .  
       FIGS. 2 and 3  shows cross sectional views of the concrete rib panel  100  along the lines  2 - 2  and  3 - 3  respectively. In the preferred embodiment the length of the concrete rib panel  100 , as the section shown in  FIG. 3 , is 48 inches, the height, as the section shown in  FIG. 2 , is 24 inches. In the preferred embodiment the thickness of the ribs  10 , as shown in  FIG. 2 , is two inches, and the thickness of the sections  20 , is one inch. The thickness of the ribs  10  and the sections  20  can be varied and still meet the objects of the invention, for instance the rib sections can be made thicker to add more structural support in the panels without adding significant weight. In the preferred embodiment, the width of the transverse rib  12  is four inches, and the width of the outside ribs,  10 , are two inches. The number, width, and thickness of the ribs can be varied to produce a lightweight concrete rib panel.  
      According to the preferred embodiment the weight of the lightweight concrete is less than about 90 lbs/cubic foot. Concrete may be mixed to produce a lighter weight concrete. The panel described as a 24 inch by 48 inch panel contains one cubic foot of concrete, and will weight less than about 90 lbs. Another embodiment of the invention has face of the panel which is 24 inches by 96 inches, and will weigh less than 180 lbs., preferably less than 160 lbs. This is still small enough to be handled with out the use of lifting equipment if desired, and conforms to masonry standards. Other sizes, such as a 32 inch by 64 inch panel, may also be used in accordance with the present invention.  
       FIG. 4  shows a connector system  200  according to the preferred embodiment. the system  200  has a threaded rod,  202 , two large nuts,  210 , a small nut or tie  212 , and a spacer,  220 . In the preferred embodiment the spacer is shaped in a tube, but it may be shaped as a hollow box, or any other shape which will allow the bolt to pass through between two concrete rib panels. The present invention is not limited to the connector described in the preferred embodiment, but any connector know to those skilled in the construction trade, such as those shown in U.S. Pat. No. 6,722,099, may also be used in accordance to the present invention. The manner in which the connector system works with the concrete rib panel system is discussed in more details below.  
      Referring to  FIG. 5 , an exploded view of a method of building structural members with the concrete rib panel system is shown. The method of building a structural member according to the preferred method of the present system is to build the wall on a poured foundation,  512 , which has j-bolts,  514 . The j-bolts,  514 , are used to attach a frame system,  520 , to the foundation. The frame system,  520 , can be made from any material suitable for aligning the structural member, and only needs to provide minimal support while the structural member is being formed. According to the preferred method, the frame system is made from crossing metal c-frames and attached with bolts. It is noted that although the frame system,  520 , is shown attached in a manner to contact the outer side of the structural member, the frame system,  520 , may be set up in a manner to contact the inner side of the structural member, or between the panels. The methods of anchoring and support known to those skilled in the construction trades may be used to attach the panels to the frame.  
      With the Frame system,  520 , attached to the foundation,  512 , a first set of concrete rib panels,  120 , is attached to the frame system,  520 , using the connector system  200 . The bottom panel,  122 , of the first set of rib panels,  120 , is set in place and bolted at the bottom to the frame system,  520 . The threaded rod,  202 , is attached to the frame system,  520 , using a large nut,  210  just above the bottom panel,  122 . A small nut or tie,  212  is then used to hold the concrete rib panel,  100 , in place. A second panel,  124 , is placed on top of the bottom panel,  122 , and another connector  200 , is used just above the second panel,  124 , to hold the panel in place as the bottom panel was held in place. The small nut or tie between the bottom and second panels, ( 122 ,  124 ) may be removed after the second panel,  124 , is placed because the weight of the second panel  124  will hold the bottom panel,  122 , in place. The process of putting panels on top of other panels is repeated to the desired height of the structural member, attaching the first set of concrete rib panels  120  to the frame system,  520 . According to the preferred method a small indent is formed on the top and bottom of each panel where the connector system is used so that the threaded rod,  202 , passes through the first set of concrete rib panels,  120 , and the edges of the concrete rib panels are in near continuous contact. It is not necessary according to the preferred method to use mortar between the top of the bottom panel,  122 , and the bottom of the second panel,  124 , or between the bottom and top of any of the panels. Mortar may, however, be used between the panels.  
      After the first set of concrete rib panels,  120 , are aligned and attached to the frame system,  520 , the spacers,  220 , can be added to the connector system,  200 . In the preferred embodiment, the spacers,  220 , contact the rib sections,  10 , of the panels,  100 , and create a space between the first set of panels,  120 , and a second set of panels,  140 .  
      According to the preferred method, before the second set of panels,  140 , is attached, reinforcement,  530 , is attached to the foundation. The reinforcement,  530 , can be attached before the frame system,  520  is set up, and before the first set of panels,  120 , is attached. The reinforcement,  530 , can be attached so that at least one single continuous piece of reinforcement is attached to the foundation and can be used to anchor the roof. According to the preferred method, utilities can be installed in the within the structural member before the second set of panels,  140 , is attached. The conduit for utilities may include, but need not be limited to, electrical conduit, water piping, heating conduit, gas piping, and cable conduit. The utilities can easily be inspected for compliance with design plans and building codes before the second set of panels,  140  is attached. The preferred method of construction provides better quality control than block construction because the conduits and panels can be corrected if an inspection shows errors.  
      Before the second set of panels,  140 , is attached, foam, or other filler may be added to the structural member where poured concrete is not needed for structural support. The filler may be formed in columns such that the resulting concrete grout will form pillars between the first and second set of panels,  120 , and  140 , in the locations where the reinforcement,  530 , is placed. This method may reduce cost with less concrete material needed to form the structural members.  
      To facilitate the entry and exit of utilities from the structural member, holes may be cut in the second set of panels,  140 , in a panel section between the ribs,  20 . It is possible to form some of the panels with holes for the utilities so that the panels will not need to be cut.  
      An alternative embodiment of a gripping connector,  600 , is shown in  FIG. 6 . The gripping connector may be attached to the frame system,  520 , at one end with a nut,  610 , and a threaded rod,  602 . The gripping connector,  600 , may have a spacer,  620 , and a gripping element,  630 . As shown in  FIG. 7 , the gripping element,  630 , is attached to the end of the threaded rod,  602 . The gripping element,  630 , includes a threaded piece,  632 , which causes the grippers,  634 , to open or close when the threaded rod,  602 , is turned. The gripping element shown in  FIG. 6  and  FIG. 7  is for illustration and not limitation. Other gripping elements, or anchoring elements known to those skilled in the trades of construction may be used in the present invention.  
      When a gripping connector,  630 , is used, the concrete rib panel,  150 , may have a rib,  16 , which has a lip,  18  that extends towards the section,  20 . The embodiment of the invention which includes the gripping connector,  630 , and concrete rib panels with a lip,  150 , have the advantage that no connector is needed on the outer side of the structural member,  155 . An advantage of this design is that the concrete grout will interlock with the lip,  18  when the concrete grout cures.  
      The outer side of the structural member,  155  may be formed with a design, or finish including, but not limited to: high quality natural stone; a wood veneer; synthetic veneer; simulated shingles; or simulated siding. In this way construction costs may be reduced with a finished side of a structural member which needs no patching or finishing work once the structural member is completed. In the preferred embodiment the lightweight concrete has characteristics which allow veneer bonding to the outer side of the panels. In the alternative embodiment the outer side of the structural member,  155 , with a finish or design, may be on the interior or exterior of the finished structure.  
      Referring again to  FIG. 5 , the second set of panels,  140 , is put in place using the connector system,  200 , shown in  FIG. 4 , or the gripping connector,  600 , shown in  FIG. 6 . Once the second set of panels,  140 , is secured using the nut,  210 , or the gripping element,  630 , the structural member is prepared for concrete grout. According to the preferred embodiment, the concrete rib panels, connected to the connectors and the frame system will be able to withstand the lateral pressure of at least eight feet of concrete grout. Some of the prior art systems are not able to withstand this pressure so the grout is poured in part of a structural member, and allowed to cure at least in part. The present invention provides savings in cost and time as the full height of a structural member can be poured at one time.  
      When the concrete grout is cured a bond is formed between the surface of the cured concrete grout and the surface of the lightweight concrete rib panel. According to the preferred embodiment, the bond formed is a permanent bond with a minimum strength of 80 lbs/sq. inch.  
      Once the grout is cured the frame system,  520 , threaded rod,  202 , and nuts,  210 , can be removed and used again. If any of the pieces are damaged they can easily be recycled. This an advantage over the prior art of using concrete forms which wear out and cannot easily be recycled.  
      The method of the present invention is not limited to building structural members, but may be used in decorative walls and walls which are not part of a building, such as, but not limited to concrete fencing walls. The method is also useful in reinforcing existing walls or structural members. At times it is not possible or practical to remove existing structural members of a building which needs reinforcement. In this case the present invention may be used as described above except that the method may be preformed using only one set of panels,  120 . The method may be performed without using the temporary frame system,  520 , if the building structure can act as a frame system. The panels may be anchored to the building using one or two sets of panels. The method of reinforcing a building may be done without the use of concrete grout providing the additional structural support. If one set of panels is used, and it is desirable to pour concrete, then the area between the one set of panels and the building may be filled with concrete grout. The panels may be used above or below grade. It is not necessary for a structural member, completed according to the present invention, to have uniform thickness, but may have varying thickness.  
      While the principles of the invention have been made clear in illustrative embodiments and methods, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components used in the practice of the invention, and otherwise, which are particularly adapted to specific environments and operative requirements without departing from those principles. The appended claims are intended to cover and embrace any and all such modifications, within the limits only of the true spirit and scope of the invention. The drawings are not intended to be to scale, but are used only to assist in understanding of the principles of the invention.