Patent Document

FIELD OF THE INVENTION 
       [0001]    The present invention relates to underground disaster shelters and, in particular, to improved structural elements therefore. 
       BACKGROUND 
       [0002]    In spite of a large amount of misinformation which has been presented to the public, there is convincing scientific and technical information available that it is possible for most people to survive a full scale exchange of nuclear, biological, or chemical weapons, or disaster caused by an industrial accident, provided that proper advance preparations are made. 
         [0003]    It is acknowledged that there would be little incentive for an individual to survive such a nuclear holocaust or biological disaster if, as a result, all life on earth were doomed to extinction or marginal existence. However, the National Academy of Sciences (NAS) has produced extensive reports on the atmospheric effects from various war scenarios, which contradict the likelihood any such idea. In reality, therefore, the question today is not whether persons can survive nuclear, biological, and chemical warfare or disaster agents, but whether people have the will and determination to prepare for survival. 
         [0004]    A number of underground disaster shelters have been developed in preparation of such a disaster. The ability of such a shelter to adequately protect one or more individuals depends on many factors, such as its equipment to provide the shelterists with fresh, uncontaminated air; its ability to dispose of and store waste; its food stocks; and of course, the integrity of the shelter itself. The shelter needs to be strong enough to withstand not only extreme above ground external forces, such as nuclear or High Altitude Electromagnetic Pulse (HEMP) weapons, and inter-earth forces, such as earthquakes, but also the everyday force of the weight of earth above the shelter, and to withstand these forces without corrosion or other degradation of shelter materials. 
         [0005]    Electromagnetic Pulse (EMP) is created by nuclear weapons detonated at altitudes of 40+ miles above ground. HEMP damage electrical and electronic circuits by inducing voltages and currents that they are not designed to withstand. EMP induces large voltage and current transients on electrical conductors such as antennas and wires as well as conductive tracks on electronic circuit boards. When EMP pulses enter a system through a path designed to gather electromagnetic energy, such as an antenna, they are said to have entered through the front door. In contrast, when they enter through an unplanned path, such as cracks, seems, trailing wires or conduits, they have entered through the back door. The efficiency of the energy transfer from pulse to system depends upon the frequency compatibility between the pulse and the entry path and on the conductivity of the material. In general, sophisticated integrated circuits with short signal paths are susceptible to high frequency pulses while large electrical systems, such as commercial power characterized by long transmission lines, are vulnerable to low frequency EMP. It follows that a broadband EMP weapon threatens a greater number of systems than a narrowband weapon, though the power requirement for a broadband weapon is much higher. Regardless of how EMP enters a system, it damages components simply by overloading them. 
         [0006]    An EMP is composed of three components. The first (E1) is a high frequency (1 mHz-1 gHz) free-field energy pulse with a rise time of a few billionths of a second. This component disrupts or damages electronics-based control systems, sensors, communications systems, computers, and similar devices. The second component (E2) is a medium frequency pulse, similar to lightning, that follows E1 by a few millionths of a second. The E2 component is not particularly dangerous to electronics, especially those hardened against lightning, except when the E1 pulse damages surge protection circuitry first. The third component is a relatively low frequency (3-30 Hz) slower rising pulse that follows E2 by a couple thousandths of a second and creates disruptive currents in long transmission lines. The sequence of E1, E2, and E3 is important, because each causes damage building on the preceding pulse. 
         [0007]    Several underground shelter systems exist including several of the inventor&#39;s. These include the inventor&#39;s disaster shelters disclosed in U.S. Pat. Nos. 6,438,907 and 6,385,919, and U.S. patent application Ser. No. 11/373,431. Although each of these disaster shelters is an excellent structure, still stronger structures and structures capable of withstanding EMPs for disaster shelters are desirable. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention includes extruded hexoid ribs with convex half-hexagon cross-sections, a shelter substructure, extruded hexoid shelters, and a shelter with a copper mesh infused hull. 
         [0009]    The first rib of the present invention is a half-hexoid rib. The half-hexoid rib may be a single piece forming a 180° half-hexoid arch, but preferably spans only 90° so that two first ribs are required to form an entire half-hexoid arch. Having noted the possibility of the half-hexoid rib being a single piece forming a full half-hexoid arch, hereinafter, “first rib” refers to the preferred rib that spans only 90°, or half of a half-hexoid arch, and “arch” refers to the sealed combination of two first ribs that spans the full 180°. 
         [0010]    The first rib is a modification of a conventional elliptical rib. Instead of a standard elliptical curve, the first rib has been pushed out or extruded at the sides, making the structure slightly more square or rectangle. The inventor has blended several radii into a fillet blend radius so that the bottom part of the first rib is almost a vertical wall, but is still curved. How far the sides are extruded is further guided by superimposing a half-hexagon over a standard half-ellipse, where the half-hexagon is half of a hexagon with all 120° angles, and a longest distance between opposite vertices equal to the major axis of the half-ellipse. The extruded shape of the arch is made by beginning and ending at the same points as the standard half-elliptical shape, reaching the same maximum height of the half-ellipse between those points, but connecting the curve to intersect with the half-hexagon&#39;s vertices, rather than following the curve of the half-ellipse. The fillet blend produces the desired shape. As its shape is guided by a half-hexagon, but is smooth and without flat surfaces or points, we call this shape a “half-hexoid” shape. Pushing or extruding the wall out so that it is almost vertical provides much more room within the shelter structure of which the first rib is a part. Preventing it from being extruded all the way to vertical so that the wall is still curved, however, ensures that there are no tensile loads on the wall and places the structure in buckling mode. The half-hexoid arch, formed by two first ribs, uses only slightly more material than a conventional half-elliptical arch, but is much stronger and provides much more usable space within the shelter structure of which the arch is a part. 
         [0011]    The first rib includes a base end and a top end. The base end will attach to a base, which is a part of the substructure of the shelter structure, discussed below. The top end is at the height of the first rib and is where two first ribs will be sealed to form a half-hexoid arch. The preferred arch has a horizontal span, where half of the span is approximately 1.1 to 1.5 times that of the vertical height. To be specific, the floor between the base ends of the arch, which is the span, is about 52 feet wide, and the distance between the floor and the ceiling halfway between the base ends is about 20 feet high, which is the height. 
         [0012]    The second rib of the present invention is a full hexoid rib. The second rib of the present invention is therefore the equivalent of four first ribs together to form an entire extruded hexoid shape that is all one piece. The second rib has the same modified elliptical/hexagonal hybrid shape as the first rib in that the classic elliptical shape has been pushed out using a hexagon as guidance to create almost vertical sides, but has all curved surfaces. The second rib therefore also creates much more room within its shape as compared to a non-extruded ellipse, but is also stronger. The preferred second rib has a horizontal span of 14 feet and a vertical total height of 11 feet. As the floor within the second rib is not necessarily positioned at the halfway point of the total height of the second rib, however, the ceiling is preferably approximately 8⅓ feet tall. 
         [0013]    The first and second ribs have a cross-section that is shaped like a convex half-hexagon that has no flat surfaces. The convex half-hexagon cross-sectional shape and the extruded elliptical/hexoid shape of the overall rib make for a very strong structure. As with the overall hexoid shape, the lack of flat surfaces of the convex half-hexagon cross-section of the ribs means that all of the earth loads on the rib surfaces are compressive, rather than tensile. The curved surfaces of the convex half-hexagon cross-section of the ribs are curved just enough to prevent “snap through” or inward bending. As this is a fairly high threshold, the curves are fairly broad. As such, minimal extra material is required to form the convex half-hexagon cross-section, as compared to an actual half-hexagon cross-section with flat sides. The convex half-hexagon cross-section of the preferred first rib is 12 feet wide, which is about ¼ the span of the arch, which is preferably 52 feet, as discussed above. Although the preferred cross-sectional width of the first rib is 12 feet, the width may be between 12 and 16 feet. The convex half-hexagon cross-section of the preferred second rib is 4 feet, which is about ¼ the span of the second rib, which is preferably 14 feet, as discussed above. The ratio of cross-section width to span is preferably between 0.22 and 0.31. 
         [0014]    The convex half-hexagon cross-section of the first and second ribs preferably includes a base flange extending outwardly from the bottom of either side of the cross-section. A lip flange preferably extends perpendicularly upward from the base flange. The lip flanges of adjacent ribs are designed to meet and be sealed to one another so as to adjoin the adjacent ribs. The sealing is achieved with a firm ethylene propylene diene monomer (EPDM) rubber gasket and bolts. This sealing is used along the length of adjacent ribs at the lip flanges. It is also used to secure the tops of first ribs to form an arch. 
         [0015]    The first and second ribs are preferably made using a polyester resin with between 65 and 75% glass content, and preferably approximately 70%. As glass bends, and resin is stiff, the inventor has found that using 70% glass in resin results in the desired flexibility and resilience profile for the laminate. The designated glass content also makes the laminate fire resistant. The preferred process used to mold the ribs is called the vacuum infusion process. With this process, all the glass is laid down in full thickness, a bag is placed over the entire rib, a full vacuum is drawn on the glass over the mold, and then the polyester resin is sucked into the laminate. Whether or not the vacuum infusion process is used to mold the ribs, it is preferred that an inner layer of the ribs contain a fine copper mesh. The preferred copper mesh has at least 12 strands per inch, is preferably 16 mesh solid copper, and is typically used for electromagnetic fields and RF frequencies. The copper mesh is preferably approximately 0.060 inches from the inside surface of the shelter hull. The copper mesh is between 0.75 and 0.85 inches from the inside surface of the shelter hull, and preferably 0.80 inches. Although a copper mesh EMP shield is presented herein specifically with respect to the shelter structures formed by the first and second ribs of the present invention, it is understood that the inclusion of copper mesh in the hull of any disaster shelter structure as an EMP shield is considered part of the present invention. 
         [0016]    The first ribs of the present invention are designed for use with the substructure of the present invention. The substructure of the present invention is a substructure for the shelter structure of the present invention that is formed of the first ribs of the present invention. In its most basic form, the substructure of the present invention includes at least one composite, precast base or precast concrete that is resin coated. It is an advantage to have precast bases as less construction must be done in the field. The base includes two pedestals, each of which has a top, a bottom, a height between the top and bottom, and an inner and outer side. At least the tops of the pedestals are coated in fiberglass. The tops of the pedestals are sized and equipped to affix the base ends of first ribs of the present invention. Holes are preferably drilled into the pedestals so that expanding anchor bolts may be used to secure the base ends of the first ribs to the pedestals. The inner sides of the pedestals face toward the inside of the shelter structure. The outer sides of the pedestals face away from the inside of the shelter structure. 
         [0017]    It is preferred that the inner sides of the tops of the pedestals include a lip on which a fiberglass corrugated floor segment may rest. The fiberglass corrugated floor segment is preferably made of two equally sized floor panels. The floor panels are bolted together with gaskets and all seams along and between the floor panels and the pedestals are sealed with a flexible sealant to create a gas tight foundation and floor. This gas tight surface prevents radon and methane gas, commonly found in underground structures, from entering the shelter. When more than one base is used, there are ¼ inch spaces between adjacent pedestals. During ground shock, as each arch has a designated base, and each base is separated by ¼ inch, arches are somewhat isolated and therefore have more room to articulate. A recess is formed under the floor based on the height of the pedestals. This recess can be used to house air ducts, plumbing, electrical lines, and sump pumps, and other shelter infrastructure. 
         [0018]    In its most basic form, the half-hexoid shelter structure of the present invention includes at least two first ribs of the present invention, a substructure of the present invention, and two end panels. The end panels are sized and dimensioned to mate with the first ribs. The end panels seal along the lip flanges of the first ribs&#39; cross-sections, just as adjacent first ribs are sealed to one another. 
         [0019]    In its most basic form, the hexoid shelter structure of the present invention includes one or more second ribs and two end panels. In hexoid shelters including more than one second rib, the second ribs are sealed together along the lip flanges of the adjacent second ribs&#39; cross-sections. The end panels are sized and dimensioned to mate with the second ribs. The end panels seal along the lip flanges of the second ribs&#39; cross-sections, just as adjacent second ribs are sealed to one another. 
         [0020]    Therefore it is an aspect of the present invention to provide ribs of a shelter structure that include a half-hexoid or hexoid shape. 
         [0021]    It is a further aspect of the present invention to provide ribs with a cross-section with a convex half-hexagon shape. 
         [0022]    It is a further aspect of the present invention to provide a disaster shelter that is stronger than its prior art counterparts. 
         [0023]    It is a further aspect of the present invention to provide a superior shelter substructure including a gas tight floor and a recess beneath the gas tight floor for housing shelter infrastructure. 
         [0024]    It is a further aspect of the present invention to provide a precast composite base having significant advantages over prior art fiberglass and concrete bases. 
         [0025]    It is a further aspect of the present invention to provide a rib, arch, and therefore hull of a shelter structure including an inner layer including copper mesh, thus protecting the shelter structure from EMPs. 
         [0026]    These aspects of the present invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective view of a first rib of the present invention. 
           [0028]      FIG. 2  is a front view of a prior art elliptical arch for a disaster shelter. 
           [0029]      FIG. 3  is a front view of a half-hexoid arch of the present invention. 
           [0030]      FIG. 4  is a diagram of how the half-hexoid shape of the ribs of the present invention is defined. 
           [0031]      FIG. 5A  is a cross-sectional view of a rib of the present invention. 
           [0032]      FIG. 5B  is cross-sectional view of several ribs of the present invention. 
           [0033]      FIG. 6  is a perspective view of a disaster shelter structure of the present invention using first ribs. 
           [0034]      FIG. 7  is a cutaway view of a prior art disaster shelter. 
           [0035]      FIG. 8  is a cutaway view of a disaster shelter structure of the present invention using second ribs. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Referring first to  FIG. 1 , a perspective view of a first rib  10  of the present invention is provided. First rib  10  has a half-hexoid shape  16 , a top end  20 , and a base end  18 . The top end  20  is where the first rib  10  will be sealed with another first rib  10  to form an arch  12  of a shelter structure  14 , shown in  FIG. 3 . The base end  18  is securely attached to the top  46  of a pedestal  44 , which is part of the base  42 , indicated in  FIG. 3 , for example. The pedestal  44  also has a bottom  48 , not visible in this view but understood to be the opposite side of the top  46 , shown, and facing down toward the earth. The pedestal  44  has an inner side  52  that faces toward the inside of the shelter structure  14 , and an outer side  54  that faces away from the shelter structure  14 . The inner and outer sides  52 ,  54  are shown more clearly in  FIG. 3 . The top  46  of the pedestal  44  includes a lip  62 , on which a floor segment  64  will rest, as shown in  3 . The cross-section  30  of the rib  10  is visible at the top end  20  of the rib  10 . The cross-section  30  has a convex half-hexagon shape  32 , as discussed below with reference to  FIGS. 5A and 5B . 
         [0037]    The ribs of the present invention, whether first ribs  10 , shown in  FIG. 1 , for example, or second ribs  80 , shown in  FIG. 8 , for example, are made using a polyester resin with approximately 70% glass content. The preferred process used to mold the ribs is called the vacuum infusion process. With this process, all the glass is laid down in full thickness, a bag is placed over the entire rib, a full vacuum is drawn on the glass over the mold, and then the polyester resin is sucked into the laminate. This results in a bubble free very dense and very strong resilient laminate with E values more than twice that of structural hand-lay-up laminates. In addition, this is a closed molding process so that employees are not exposed to volatile organic compounds. Alternatively, the first and second ribs  10 ,  80  may be made of concrete. 
         [0038]    Now referring to  FIGS. 2 and 3 , front views of a prior art arch for a disaster shelter and a half-hexoid shelter structure  14  of the present invention are provided respectively.  FIG. 2  shows a prior art elliptical arch. This arch is one piece, and its front view is either half-round or half-paraboloid, with the elliptical arch meeting the foundation at the neutral axis.  FIG. 3  shows an arch  12  of the present invention, made up of two first ribs  10  of the present invention sealed at the top end  20  of the first ribs  10 . The half-hexoid arch  12  in  FIG. 3  is similar to the prior art arch in  FIG. 2 , but the elliptical shape of  FIG. 2  has been pushed out to form the extruded elliptical/half-hexoid shape  16  of  FIG. 3 . This shape is explained in more detail with reference to  FIG. 4 . Each first rib  10  has a horizontal span  22  of fifty-two feet and a vertical height  24  of twenty feet. The dashed line in  FIG. 3  indicates the shape of a prior art elliptical arch, as in  FIG. 2 . 
         [0039]    The arch  12  shown in  FIG. 3  sits upon a substructure  40 . The substructure  40  includes a base  42 , floor segments  64 , a recess  66 , and a plastic liner  67 . The base  42  consists of a number of pedestals  44 . The base ends  18  of the first ribs  10  are attached to the pedestals  44 . Each pedestal  44  includes an inner side  52  and an outer side  54 , as described above with reference to  FIG. 1 . Each pedestal has a height  50 , a top  46 , a bottom  48 , and a lip  62  on the inner side  52  of the top  46 . For every arch  12  in a shelter structure  14 , the base  42  includes two pedestals  44  positioned on either side of the arch  12 . Adjacent pedestals  44  supporting adjacent ribs  12  include a ¼ inch space  68  between them, indicated in  FIG. 6 . 
         [0040]    Base  42  is precast concrete or made of composite. This is opposed to current, prior art bases made of fiberglass. Fiberglass is used at least on the tops  46  of pedestals  44 , however, so as to create a gas tight surface, preventing radon and methane gas, commonly found in underground structures, from entering the shelter structure  14 . The floor segments  64 , shown in  FIG. 3 , are made of corrugated fiberglass or precast concrete. Floor segments  64  are made of two floor panels that meet in the middle of the floor. Floor segments  64  may be supported by piers  65 . When the floor segments  64  are in position resting on lips  62  of pedestals  44 , they are bolted together with gaskets, and all seams and gaps are sealed with a flexible sealant to create a gas tight foundation and floor. The recess  66  of the substructure  40  is defined by the floor segments  64  and the height  50  of the pedestals  44 . This recess  66  is a crawl space that allows for important shelter infrastructure such as sewer lift stations, air ducts, plumbing, electrical lines, and sump pumps. A plastic liner  67  is placed at the bottom of recess  66  between bottoms  48  of pedestals  44  as an additional vapor barrier between the earth and the substructure  40 . The plastic liner  67  also makes it easier and dryer for a person to crawl in the recess  66  when necessary. 
         [0041]    The ¼ inch spaces  68  between the bases  42 , shown most clearly in  FIG. 6 , allow water to enter into this recess  66 . Making the bases  42  watertight would place a large uniform load on the floor. Specifically, for the preferred shelter structure  14  made of first ribs  10 , the floor might be thirty feet below the ground. Making bases  42  watertight under these circumstances, by resisting hydrostatic pressure, the floor would see 13.2 psi, calculated from 30 ft*0.44 psi/ft. This would place a uniform load on the floor of 1,140,480 lbs, calculated from 50 ft span*12 ft*144 in 2 *13.2 psi. To support such a load would require a concrete slab many feet thick. As such, the inventor chose not to make the bases  42  watertight. The recess  66  created by the pedestals  44  and floor allows space for sump pumps that can pump water that has entered the recess up to the ground surface a long distance away. The bases  42  therefore do not need to be watertight. A thick slab of concrete under the structure is therefore avoided. This also allows for fast assembly in the field, as there is no need to wait for concrete to cure. 
         [0042]    Now referring to  FIG. 4 , an illustration of how the extruded elliptical shape of ribs  10 ,  80  is formed is provided. The extruded elliptical/half-hexoid shape  16  of arch  12  is shown. Dashed line  104  is a half-circle, which is a common shape for prior art shelter structures. Dashed line  101  is the half-elliptical shape also common in prior art shelter structures, and the shape that is extruded to get the half-hexoid shape  16  of the present invention. Half-hexagon  102  is superimposed over half-ellipse  101 . The hexagon of which the half-hexagon  102  is a half has all 120° angles. It is not a regular hexagon because its sides are not necessarily the same length. As shown, the longest distance between opposite vertices is equal to the major axis of the half-ellipse  101 . This distance also corresponds with the span  22  of arch  12 . Prior art half-ellipse  101  and half-hexoid shape  16  meet at top end  18 . Half-ellipse  101 , half-hexoid shape  16  of the present invention, and half-hexagon  102  all begin and end at right and left common end points  95 ,  96 . Instead of following the curve of half-ellipse  101 , however, half-hexoid  16  nearly intersects with right and left hexagon vertices  103 ,  105  on its way up to top end  18 . 
         [0043]    Ellipse  130  is included in  FIG. 4  for purposes of illustration. The major axis of ellipse  130  has the same length as span  22  and the minor axis of ellipse  130  has the same length as height  24 . Half-hexoid shape  16  has a top section  107  on either side of top end  18  that approximately follows the curve of ellipse  130  until it nearly meets right and left hexagon vertices  103 ,  105 . This section of the half-hexoid shape  16  is the fillet blend section  109  where half-hexoid shape  16  turns downward away from ellipse  130  to more closely approximate the shape of half-hexagon  102 . Fillet blend section  109  is a curved section that uses a fillet blend radius that is a blend of several radii to form half-hexoid shape  16 . Side portion  111  is on either side between fillet blend section  109  and common end points  95 ,  96  and is also curved. As the half-hexoid shape  16  is guided by a half-hexagon, but is smooth and without flat surfaces or points, we call this shape a “half-hexoid” shape. It is understood that to get the shape used with second rib  80 , a similar procedure is used, but with a full ellipse, and a full hexagon. Corresponding structures for second rib  80  are labeled in  FIG. 8 . 
         [0044]    Now referring to  FIGS. 5A and 5B , cross-sectional views of first and second ribs  10 ,  80  of the present invention are provided. Earth above the ribs  10 ,  80  is indicated by cross hatching. The shape of the rib cross-section  30  is a convex half-hexagon  32 . In other words, the shape has three of six sides of a hexagon—two vertical curved walls  33  connected by one horizontal wall  35 —but where all walls  33 ,  35  are convex, or curved outward. The arch cross-section  30  also includes a base flange  36  extending outwardly from the bottom of each vertical wall  33 , and a lip flange  38  extending perpendicularly and upwardly from each base flange  36 . Adjacent ribs  10 ,  80  are sealed to one another along their respective lip flanges  38 . This design results in a stronger shape than prior art and uses only a small amount more material. 
         [0045]    Cross-section  30  of first rib  10  has a width  34  of twelve feet, which is about ¼ the span of arch  12 , which is preferably fifty-two feet, as discussed above. Cross-section  30  of second rib  80  has a width  34  of four feet, which is about ¼ the span of the second rib  80 , which is preferably fourteen feet, as discussed in more detail with respect to  FIG. 8  below. Having cross-section  30  be approximately ¼ of the span of arch  12  or second rib  80  has been shown to create an extremely strong structural element. The approximate ¼ ratio of cross-section width  34  to span is between 0.22 and  0.31. When referring to the vertical and horizontal walls 33, 35, we use the terms “vertical” and “horizontal” walls approximately. The vertical walls 33 are not perpendicular to the horizontal wall 35. In addition, neither the vertical walls 33, nor the horizontal wall 35 include any flat surfaces, as may be commonly implied by the terms “vertical” and “horizontal.” Because the vertical and horizontal walls 33, 35 do not include any flat surfaces, there are no tensile loads. As the earth loads put axial loads on the curved vertical wall 33, the thrust loads on the vertical wall 33 are resisted by the opposing and equal thrust loads from the adjacent vertical wall 33 so the shape is strong and stable. In this case, “adjacent” vertical walls 33 refer not to the two vertical walls 33 of a single cross-section 30, but to the closest vertical walls 33 of two cross-sections 30 of ribs 10, 80 that have been sealed together.    
         [0046]    Now referring to  FIG. 6 , a perspective view of a half-hexoid shelter structure  14  of the present invention is provided. Shelter structure  14  sits on substructure  40 , shown in  FIG. 3 , of which the outer sides  54  of the pedestals  44  of base  42  are visible. Base  42  also extends beneath the end panel  78  of shelter structure  14 . Although not visible, a ¼ inch space  68  exists between each pedestal  44  of base  42 . The shelter structure  14  shown includes eleven arches  12  and two end panels  78 , the second end panel  78  not being visible in this view, but understood to be opposite from the visible end panel  78 . It is understood that shelter structure  14  may include greater or less than eleven arches  12  in other embodiments. Each of the eleven arches  12  is made up of two first ribs  10  sealed at the top ends  20  of the first ribs  10 . The sealing is achieved with a firm EPDM rubber gasket and bolts. This sealing is also used along the length of adjacent arches  12  at the lip flanges  38 . Each arch  12  meets base  42  at the base ends  18  of first ribs  10 . Holes are drilled into the pedestals  44  so that expanding anchor bolts may be used to secure the base ends  18  of first ribs  10  to pedestals  44 . End panels  78  have a shape designed to match with the half-hexoid shape  16  of the first ribs  10 . 
         [0047]    Now referring to  FIGS. 7 and 8 , cutaway views of a prior art elliptical shelter  94  and a hexoid shelter structure  92  of the present invention are provided, respectively. Shelter structure  92  includes second rib  80 , which is has a full extruded elliptical/hexoid shape, and is one piece. Although not shown, hexoid shelter structure  92  would include end panels to match with the shape of second rib  80 . Second rib  80  has a convex half-hexagon cross-section  30  as described above with reference to  FIGS. 5A and 5B . Each shelter structure  94 ,  92  has a span  82  of seven feet and a total height  84  of 5.5 feet. 
         [0048]      FIG. 8  shows a front view of one second rib  80 . A preferred shelter structure  92  of the present invention includes ten adjoined second ribs  80 , where each second rib  80  has a cross-section width  34  of four feet on center, as discussed above with reference to  FIGS. 5A and 5B . This preferred shelter structure  92  has approximately 5600 cubic feet of volume and has 544 square feet of floor space. Prior art shelter structure  94  with its traditional elliptical shape and ten ribs four feet on center has approximately 4200 cubic feet of volume and  400  square feet of floor space. The hexoid shelter  92  of the present invention is therefore approximately 30% bigger than its prior art elliptical counterpart  94 , and is also approximately 30% stronger, while using only approximately 6% more material. Not only is there more space, but there is more usable space. Shelves  88 , for example, are much closer to the wall of the second rib  80  in present invention shelter  92 , thus minimizing the unusable space  90  between the wall and the shelves  88 . It is understood that although it is preferred for present invention shelter  92  to include ten second ribs  80 , some embodiments may include greater or fewer than ten second ribs  80 . Floor  121  is also shown. Floor  121  is preferably positioned within total height  84  so that the ceiling within hexoid shelter  92  is approximately 8⅓ feet tall. 
         [0049]    On the left of  FIG. 8  structural components pertaining to how hexoid shape  119  is formed are shown. It is understood that its formation corresponds to what is described above with reference to  FIG. 4 , but including upper and lower portions, or that which is described above with reference to the half-hexoid shape  16  and its mirror image below it. The full hexoid shape  119  includes the top portion  107 , upper side portion  111 , and upper fillet blend section  109 , as with the half-hexoid shape  16  shown in  FIG. 4 . The full hexoid shape  119  also includes bottom portion  113 , lower side portion  115 , and lower fillet blend portion  117 , which are the lower mirror images of the upper counterparts shared with half-hexoid shape  16 . Hexoid shape  119  is incorporated into second rib  80 , which is one integrated piece. When considering the ellipse  130  the curve of which the bottom portions  113  and upper portions  107  will approximately follow, it is understood that the minor axis of ellipse  130  will be half of the total height  84  indicated, and the major axis of ellipse  130  is span  82 . In other words, again hexoid shape  119  is equivalent to two half-hexoid shapes  16  as mirror images with the line of symmetry along span  22 / 82 . To envision ellipse  130  as a tool for approximating at least the bottom portions  113  and upper portions  107  of hexoid shape  119 , we would envision two ellipses  130  as mirror images, like a figure eight, with the line of symmetry along span  22 / 82 . Therefore half-hexoid shape  16  pertaining to a single first rib, as described above, has a top portion  107  beginning at top end  18 , a side portion  111  beginning at right or left end point  95 ,  96 , and a fillet blend section  109  between and connecting the top portion  107  and the side portion  111 . 
         [0050]    Full hexoid shape  119 , however, is the equivalent of four half-hexoid shapes  16 . Full hexoid shape  119  therefore has an left top portion, an upper left fillet blend section, and an upper left side portion in the upper left quadrant of the shape; a right top portion, an upper right fillet blend section, and an upper right side portion in the upper right quadrant of the shape; a left bottom portion, a lower left fillet blend section, and a lower left side portion in the lower left quadrant of the shape; and a right bottom portion, a lower right fillet blend section, and a lower right side portion in the lower right quadrant of the shape. Top end  18 , bottom end  132 , and right and left end points  95 ,  96  are also shown. The right and left top portions both begin at top end  18 . The upper right side portion and the lower right side portion both begin at right end point  95 . The upper left side portion and the lower left side portion both begin at left end point  96 . The right and left bottom portions both begin at bottom end  132 . 
         [0051]    The inner layer  26  of the ribs contains a fine solid copper mesh  28 , as indicated in  FIGS. 5A and 8 . The copper mesh  28  has at least twelve strands per inch, is preferably 16 mesh solid copper, and is typically used for electromagnetic fields and RF frequencies. The copper mesh  28  is approximately 0.060 inches from the inside surface  123  of the shelter hull, shown in  FIGS. 1 and 8 . The inclusion of the copper mesh  28  provides an EMP shield in the E1, E2, and E3 bands from an electromagnetic pulse weapon. The copper mesh  28  acts as a shield to the most dangerous portion of the EMP spectrum, which is 100-3000 MHz, and has an 80+ Db attenuation, not counting the 8.5 feet of earth cover over the shelter structure. Some prior art shelter structures use steel as an EMP shield. The copper mesh  28  is preferable to steel because it is 8.5 times more conductive, and does not corrode like steel resulting in a stable EMP shield over long periods of time with no deterioration and maintenance. In addition, it does not suffer the imminent corrosion of the welds, leading to holes in the welds, which break the Faraday cage envelope. Also, titanium dioxide is added to the resin to increase the conductivity of the polyester-resin laminate. With a thin layer of polyester on the inside of the copper mesh  28  facing the inside of the shelter  14 ,  92 , Mission Essential Equipment (MEE) are insulated from further damage if it is located against or near the shelter wall. The best Faraday cage or EMP shielded underground shelter has some form of copper shielding on the outside surface facing the EMP source with some type of insulator on the inside surface of the copper shield facing inside the shelter protecting the electronic equipment inside the shelter. The laminate used to manufacture the shelter hulls and entranceways is designed to meet MIL-STD-188-125-1. In addition, shelter structures  14 ,  92 , as well as the inventor&#39;s other structures, have been reviewed for an EMP Protection Analysis by a Certified Electromagnetic Compatibility Engineer and a Certified Electrostatic Discharge Control Engineer. 
         [0052]    The vacuum infused structural composite shelter hull and entranceway have a CPI (Copper Plastic Insulated) EMP Shield. Copper, with a conductivity of 60,000,000 Siemens/m is almost nine times more conductive than carbon steel which has a conductivity of 7,000,000 Siemens/m making it the strongest EMP shield used to protect military MEE. Unlike steel, copper shielding infused in the structural composite laminate is corrosion resistant so the level of EMP shielding does not deteriorate over time. It therefore does not require monthly maintenance and testing to be compliant with MIL-STD-188-125-1. The copper shield has a plastic layer facing the shelter interior to further protect the MEE that might be located near the shelter hull wall. The 20 psi external pressure resistance above the static earth load, with no earth arching, is constant over the first 150 years. The CPI Composite also forms a complete vapor barrier which provides a dry atmosphere when placed below ground. In addition, one of the greatest characteristics of the CPI Composite is its resiliency or ability to “remain intact” if overstressed. The inside of the shelter is smooth, curved, and white to create maximum brightness with minimal light. All of these facilities function without outside electricity through the use of an internal diesel generator, battery bank, and DC charger/AC inverter. The inside surface is easily cleaned with common detergents and is easily repaired and there is ample volume for food storage under the floor. 
         [0053]    All of the shelter structures described herein are shielded by the CPI Composite hull and entranceway. The radio antennas should not be connected to the radios prior to an EMP event. In military operations, where the radios need to be connected to the antennas and operational prior to an EMP event, backup radios need to be stored unconnected and kept in the shelter. The shelter structures of the present invention are designed to operate off grid with internal generators so they are not subject to EMP collected on the power grid. The power cable from the shelter to the dedicated well and the well water hose to the shelter are both underground and shielded. 
         [0054]    The half-hexoid shelter structure  14  and hexoid shelter structure  92 , shown in  FIGS. 3 and 8  respectively are well adapted for high external static and dynamic loads, such as earth. Many structures in many fields, such as siding and roofing materials, include ribs. Such ribs are very small, however, so that many ribs are used for each panel, and all the ribs have straight walls. These straight walled ribs are not adapted for high static loads. The tops of the shelter structures  14 ,  92  are convex. As shown in  FIGS. 3 and 5A , each rib  10 ,  80 , is curved across its entire length and depth. As such, the hulls of the shelter structures  14 ,  92  made of these ribs  10 ,  80  are not extrudable. As shown in  FIG. 6 , the shape of the end panels  78  also do not include flat surfaces, so that the end panels  78  are also designed to resist buckling loads. 
         [0055]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the description should not be limited to the description of the preferred versions contained herein.

Technology Category: 7