Abstract:
The modular anti-ballistic shelter system includes two end units and, optionally, additional middle units for a wider structure. End and middle units may also stack atop each other for multi-story structures. Each unit is configured to comply with both ISO standards for size and weight, and with the U.S. Department of State Certification Standard for Forced Entry and Ballistic Resistance of Structural Systems. Each exterior wall of each end unit and each middle unit is reinforced with wall studs that penetrate the unit&#39;s structural framework of beams and frames. Even though these wall studs are welded into place, penetration of the wall studs into the beams and frames ensures acceptable blast, ballistic, and forced entry resistance even if the welds are flawed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation-in-part and claims the benefit of U.S. patent application Ser. No. 15/461,226 filed Mar. 16, 2017, and U.S. patent application Ser. No. 13/886,248 filed May 2, 2013, which claims the benefit of U.S. Provisional Application No. 61/641,877 filed May 2, 2012. The above applications are incorporated by reference herein in their entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    The invention described herein was made by an employee of the United States Government and may be manufactured and used by the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. 
     
    
     FIELD OF INVENTION 
       [0003]    This invention relates to the field of armor and more specifically to construction of armored structures which comply with both ISO and State Department Standards. 
       BACKGROUND OF THE INVENTION 
       [0004]    The U.S. Army Corps of Engineers (USACE) currently uses shipping containers as components for transportable shelters to protect troops from ballistics and explosives. This system is known in the art as a Hardened Alternative Trailer System (HATS). 
         [0005]    The HATS structures must comply with the U.S. Department of State Certification Standard for Forced Entry and Ballistic Resistance of Structural Systems, SDSTD01.01, without exceeding stringent ISO weight and dimensional specifications. USACE has conducted considerable laboratory research to develop a HATS shelter which concurrently meets most standards. U.S. patent application Ser. No. 13/886,248 (the &#39;248 Application) teaches precise specifications developed by the government to meet ISO Standard No. 668:2013 for twenty-foot structures. 
         [0006]    At present, over four hundred structures having the specifications taught in the &#39;248 Application have been fielded “in theater.” At a cost of several hundred thousand USD per structure, this technology represents investment in the range of $100,000,000 to the U.S. government. However, these structures are limited to no more than twenty feet in length, and no more than 8 feet wide or 8.6 feet high, which can restrict the utility of the structures. 
         [0007]    To address this problem, USACE conducted extensive research and testing to develop precise specifications for forty foot structures. These extensive specifications are taught in co-pending U.S. patent application Ser. No. 15/461,226 filed Mar. 16, 2017. 
         [0008]    However, there is a continuing unmet need for considerably larger structures with much greater width and height than are permitted under current ISO standards. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    A modular anti-ballistic shelter system incorporates multiples end units. Each end unit includes a base assembly, a top assembly, first and second end wall assemblies, and a sidewall assembly. 
         [0010]    The base assembly includes channeled floor/roof support beams extending between floor girders and connected to floor/roof support beams. A floor connects to the floor girders. One of the floor girders has stud apertures spaced 16 inches apart at center. 
         [0011]    Each of the channeled floor/roof support beams has a length of 9.59375 feet, a width of 3 inches, a height of 2 inches, and a weight of 7.1 lbs. per foot of length. Each of the floor girders has a length of 39.125 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. Each of the floor/roof support beams has a length of 7.125 feet and a hollow structural cross-section of 3 by 3 by 5/16 inches. The floor has dimensions of 39.5 feet by 7.395833 feet. 
         [0012]    The top assembly includes channeled floor/roof support beams extending between a top girder and a top main girder and connected to floor/roof support beams. A roof connects to and is located above the top girder and the top main girder, while an interior roof connects to and is located below the top girder and the top main girder. The top girder has stud apertures spaced 16 inches apart at center. 
         [0013]    The top girder has a length of 39.833 feet and a hollow structural cross-section of 5 by 3 by ½ inches. The top main girder has a length of 39.125 feet and a hollow structural cross-section of 9 by 5 by ¼ inches. The roof has dimensions of 39.95833 feet by 7.95833 feet. The interior roof has dimensions of 39.20833 feet by 7.125 feet. 
         [0014]    The first end wall assembly includes two ISO right freight container corner fittings and two ISO left freight container corner fittings, with a bottom frame and a top frame connecting the two ISO right freight container corner fittings to the two ISO left freight container corner fittings. Corner columns connect the two ISO right freight container corner fittings and the two ISO left freight container corner fittings. Exterior and interior plates connect to the bottom frame, the top frame, and the corner columns. The bottom frame and the top frame have stud apertures, with wall studs extending through the stud apertures into the bottom frame and the top frame. 
         [0015]    The bottom frame has a length of 6.9270833 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. The top frame has a length of 6.9270833 feet and a hollow structural cross-section of 5 by 3 by ⅜ inches. Each of the corner columns has a height of 9.166 feet and a hollow structural cross-section of 5 by 5 by ⅜ inches. Each of the wall studs has a height of 9.166 feet and a hollow structural cross-section of 3 by 2 by ¼ inches. The exterior plate has dimensions of 7.125 feet by 8.270833 feet. The interior plate has dimensions of 7.125 feet by 8.270833 feet. 
         [0016]    The second end wall assembly includes two ISO right freight container corner fittings and two ISO left freight container corner fittings, with a bottom frame end and a top frame end connecting the two ISO right freight container corner fittings to the two ISO left freight container corner fittings. Corner columns connect the two ISO right freight container corner fittings and the two ISO left freight container corner fittings. Exterior and interior end walls connect to the bottom frame end, the top frame end, and the corner columns. The bottom frame end and the top frame end have stud apertures, with wall studs extending through the stud apertures into the bottom frame end and the top frame end. 
         [0017]    The bottom frame end has a length of 7.125 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. The top frame end has a length of 6.9270833 feet and a hollow structural cross-section of 5 by 3 by ½ inches. The exterior end wall has dimensions of 7.125 feet by 8.270833 feet. The interior end wall has dimensions of 7.125 feet by 8.25 feet. 
         [0018]    The sidewall assembly includes exterior and interior sidewalls connected to one of the floor girders and the top girder, with wall studs extending into the top girder and one of the floor girders through the stud apertures in the top girder and one of the floor girders. The exterior sidewall has dimensions of 39.125 feet by 8.25 feet, while the interior sidewall has dimensions of 39.125 feet by 8.25 feet. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING(S) 
         [0019]      FIGS. 1-49  illustrate the components of an exemplary embodiment of an end unit for a modular anti-ballistic shelter system. 
           [0020]      FIG. 1  illustrates the end unit including a base assembly, a top assembly, an endwall assembly with door, an endwall assembly with window, and a sidewall assembly with windows. 
           [0021]      FIG. 2  illustrates the base assembly including floor girders, floor/roof support beams, channeled floor/roof support beams, and floor. 
           [0022]      FIGS. 3 and 4  illustrate floor girders. 
           [0023]      FIG. 5  illustrates the floor/roof support beam. 
           [0024]      FIG. 6  illustrates the channeled floor/roof support beam. 
           [0025]      FIG. 7  illustrates the floor. 
           [0026]      FIG. 8  illustrates base assembly welds. 
           [0027]      FIG. 9  illustrates the top assembly including floor/roof support beams, channeled floor/roof support beams, top girder, top main girder, roof, and interior roof. 
           [0028]      FIG. 10  illustrates the top girder. 
           [0029]      FIG. 11  illustrates the top main girder. 
           [0030]      FIG. 12  illustrates the roof. 
           [0031]      FIG. 13  illustrates the interior roof. 
           [0032]      FIG. 14  illustrates the top assembly welds. 
           [0033]      FIG. 15  illustrates the end wall assembly with door, including ISO right freight container corner fitting, ISO left freight container corner fitting, door frame assembly, bottom frame for middle door, corner column, top frame for middle door, wall stud, exterior plate for middle door, and interior plate for middle door. 
           [0034]      FIG. 16  illustrates a cross section of end wall assembly with door. 
           [0035]      FIG. 17  illustrates the ISO right freight container corner fitting. 
           [0036]      FIG. 18  illustrates the ISO left freight container corner fitting. 
           [0037]      FIGS. 19-20  illustrate door frame assembly, vertical door frame, and door header. 
           [0038]      FIG. 22  illustrates the door frame assembly welds. 
           [0039]      FIG. 23  illustrates the bottom frame for middle door. 
           [0040]      FIG. 24  illustrates the corner column. 
           [0041]      FIG. 25  illustrates the top frame for middle door. 
           [0042]      FIG. 26  illustrates the wall stud. 
           [0043]      FIG. 27  illustrates the exterior plate for middle door. 
           [0044]      FIG. 28  illustrates the interior plate for middle door. 
           [0045]      FIG. 29-31  illustrate the end wall with door welds. 
           [0046]      FIG. 32  illustrates the end wall assembly with window, including bottom frame end, top frame end, wall studs, bottom jack studs, top jack studs, exterior end wall, interior end wall, and window frame assembly. 
           [0047]      FIG. 33  illustrates the bottom frame end. 
           [0048]      FIG. 34  illustrates the top frame end. 
           [0049]      FIG. 35  illustrates the window frame assembly. 
           [0050]      FIG. 36  illustrates the horizontal window frame. 
           [0051]      FIG. 37  illustrates the vertical window frame. 
           [0052]      FIG. 38  illustrates the vertical window molding. 
           [0053]      FIG. 39  illustrates the horizontal window molding. 
           [0054]      FIG. 40  illustrates the window frame assembly welds. 
           [0055]      FIG. 41  illustrates the bottom jack stud. 
           [0056]      FIG. 42  illustrates the top jack stud. 
           [0057]      FIG. 43  illustrates the exterior end wall. 
           [0058]      FIG. 44  illustrates the interior end wall. 
           [0059]      FIG. 45  illustrates a cross section of the end wall assembly with window. 
           [0060]      FIG. 46  illustrates the sidewall assembly with windows, window frame assemblies, wall studs, bottom jack studs, top jack studs, interior sidewall, and exterior sidewall. 
           [0061]      FIG. 47  illustrates the interior sidewall with punchouts. 
           [0062]      FIG. 48  illustrates the exterior sidewall with cutouts. 
           [0063]      FIG. 49  illustrates the sidewall assembly with windows welds. 
           [0064]      FIGS. 50-69  illustrate the components of an exemplary embodiment of an optional middle unit for the modular anti-ballistic shelter system. 
           [0065]      FIG. 50  illustrates an optional middle unit including a middle base assembly, a middle top assembly, and end walls without openings. 
           [0066]      FIG. 51  illustrates the middle base assembly including floor girders, channeled floor/roof support beams, middle floor/roof support beams, and middle floor.  FIG. 52  illustrates the floor girder. 
           [0067]      FIG. 53  illustrates the channeled floor/roof support beam. 
           [0068]      FIG. 54  illustrates the middle floor/roof support beam. 
           [0069]      FIG. 55  illustrates the middle floor. 
           [0070]      FIG. 56  illustrates the middle base assembly welds. 
           [0071]      FIG. 57  illustrates the middle top assembly, including middle top main girders, channeled floor/roof support beams, middle floor/roof support beams, roof, and middle interior roof. 
           [0072]      FIG. 58  illustrates the middle top main girder. 
           [0073]      FIG. 59  illustrates the roof. 
           [0074]      FIG. 60  illustrates the middle interior roof. 
           [0075]      FIG. 61  illustrates the middle top assembly welds. 
           [0076]      FIG. 62  illustrates the middle end wall assembly without openings, including top end beam, bottom end beam, wall stud, middle corner column, interior end plate, exterior end plate, ISO right freight container corner fittings, and ISO left freight container corner fittings. 
           [0077]      FIG. 63  illustrates the top end beam. 
           [0078]      FIG. 64  illustrates the bottom end beam. 
           [0079]      FIG. 65  illustrates the wall stud. 
           [0080]      FIG. 66  illustrates the middle corner column. 
           [0081]      FIG. 67  illustrates the interior end plate. 
           [0082]      FIG. 68  illustrates the exterior end plate. 
           [0083]      FIG. 69  illustrates the endwall welds. 
           [0084]      FIGS. 70 a   - 72  illustrate the components of an exemplary embodiment of modular anti-ballistic shelter system. 
           [0085]      FIGS. 73 a -73 c    illustrate a flowchart of an exemplary method for making the end unit for the modular anti-ballistic shelter system. 
       
    
    
     TERMS OF ART 
       [0086]    As used herein, the term “hollow structural cross-section” refers to a measurement of a hollow member including a first dimension, a second dimension, and a wall thickness. 
         [0087]    As used herein, the term “inches apart at center” refers to the distance between the centers of spaced structures. 
         [0088]    As used herein, the term “ISO freight container corner fitting” refers to a cast metal fitting forming the corner of a structure, having a hollow interior and at least one elongated aperture allowing insertion of the mobile portion of a twistlock. 
         [0089]    As used herein, the term “twistlock” refers to a two- or three-portion connector, wherein at least one mobile portion of the connector may be inserted into an elongated aperture in a structure and rotated to prevent removal of the mobile portion from the elongated aperture and separation of the connector from the structure. 
         [0090]    As used herein, the term “welding interface” refers to a joint created by welding to or more pieces of metal together. 
         [0091]    As used herein, the term “welding scaffold” refers to a removable frame work used to hold the components of a welded structure in place during fabrication. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0092]      FIGS. 1-49  illustrate the components of an exemplary embodiment of end unit  200  for modular anti-ballistic shelter system  100 .  FIG. 1  illustrates end unit  200  including base assembly  10 , top assembly  20 , endwall assembly  30  with door, endwall assembly  40  with window, and sidewall assembly  60  with windows. End unit  200  has a weight of approximately 43,786 lbs. 
         [0093]      FIG. 2  illustrates base assembly  10  including floor girders  11 , floor/roof support beams  12 , channeled floor/roof support beams  13 , and floor  14 . Base assembly  10  has a weight of approximately 6,900 lbs. 
         [0094]      FIGS. 3 and 4  illustrate floor girders  11 , which have a length of 39.125 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. As seen in  FIG. 4 , floor girder  11  may include multiple stud apertures  15  spaced apart 16 inches apart at center. This critical dimension provides optimum structural integrity to any assembly utilizing stud apertures  15  without increasing weight to the point that it violates ISO standards. FIG.  5  illustrates floor/roof support beam  12 , which has a length of 7.125 feet and a hollow structural cross-section of 3 by 3 by 5/16 inches.  FIG. 6  illustrates channeled floor/roof support beam  13 , which has a length of 9.59375 feet, a width of 3 inches, a height of 2 inches, and a weight of 7.1 lbs. per foot of length.  FIG. 7  illustrates floor  14 , which has dimensions of 39.5 feet by 7.395833 feet.  FIG. 8  illustrates base assembly  10  welds. 
         [0095]      FIG. 9  illustrates top assembly  20  including floor/roof support beams  12 , channeled floor/roof support beams  13 , top girder  21 , top main girder  22 , roof  23 , and interior roof  24 . Top assembly  20  has a weight of approximately 13,719 lbs. 
         [0096]      FIG. 10  illustrates top girder  21 , which has a length of 39.833 feet and a hollow structural cross-section of 5 by 3 by ½ inches. Top girder  21  includes multiple stud apertures  15  spaced apart 16 inches apart at center.  FIG. 11  illustrates top main girder  22 , which has a length of 39.125 feet and a hollow structural cross-section of 9 by 5 by ¼ inches.  FIG. 12  illustrates roof  23 , which has dimensions of 39.95833 feet by 7.95833 feet.  FIG. 13  illustrates interior roof  24 , which has dimensions of 39.20833 feet by 7.125 feet.  FIG. 14  illustrates top assembly  20  welds. 
         [0097]      FIG. 15  illustrates end wall assembly  30  with door, including ISO right freight container corner fitting  31 , ISO left freight container corner fitting  32 , door frame assembly  33 , bottom frame  34  for middle door, corner column  35 , top frame  36  for middle door, wall studs  37 , exterior plate  38  for middle door, and interior plate  39  for middle door. In the exemplary embodiment, end wall assembly  30  with door has a weight of approximately 5,472 lbs. 
         [0098]    Exterior plate for middle door  38  and interior plate for middle door  39  are made from sheets of steel 0.0625 inches to 1 inch thick. Thicker sheets (0.5 inches to 1 inch thick) may be used for end units  200  which will see deployment in areas where more protection may be needed. In embodiments without openings in an endwall assembly, additional wall studs  37  may be added, and exterior end plate  38  and interior plate  39  have neither punchouts nor cutouts for insertion of door frame assembly  33 . 
         [0099]      FIG. 16  illustrates a cross section of end wall assembly  30  with door.  FIG. 17  illustrates ISO right freight container corner fitting  31 .  FIG. 18  illustrates ISO left freight container corner fitting  32 .  FIG. 19  illustrates door frame assembly  33 , which includes two vertical door frames  33   a  and one door header  33   b . Door frame assembly  33  has a height of 7.25 feet and a width of 3.84375.  FIG. 20  illustrates vertical door frame  33   a , which has a height of 7 feet and a hollow structural cross-section of 8 by 3 by ¼ inches.  FIG. 21  illustrates door header  33   b , which has a length of 3.84375 feet and a hollow structural cross-section of 8 by 3 by ¼ inches  FIG. 22  illustrates door frame assembly  33  welds.  FIG. 23  illustrates bottom frame  34  for middle door, which has a length of 6.9270833 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. Bottom frame  34  for middle door includes multiple stud apertures  15 .  FIG. 24  illustrates corner column  35 , which has a height of 9.166 feet and a hollow structural cross-section of 5 by 5 by ⅜ inches.  FIG. 25  illustrates top frame  36  for middle door, which has a length of 6.9270833 feet and a hollow structural cross-section of 5 by 3 by ⅜ inches. Top frame for middle door  36  includes multiple stud apertures  15 . 
         [0100]      FIG. 26  illustrates wall stud  37 , which has a height of 9.166 feet and a hollow structural cross-section of 3 by 2 by ¼ inches. Wall studs  37  are inserted into stud apertures  15  and welded into place during assembly. Wall studs  37  provide critical anti-ballistic, -blast, and -forced entry properties.  FIG. 27  illustrates exterior plate  38  for middle door, which has dimensions of 7.125 feet by 8.270833 feet.  FIG. 28  illustrates interior plate  39  for middle door, which has dimensions of 7.125 feet by 8.270833 feet.  FIG. 29-31  illustrate end wall with door  30  welds. 
         [0101]      FIG. 32  illustrates end wall assembly  40  with window, including bottom frame end  41 , top frame end  42 , wall studs  37 , bottom jack studs  43 , top jack studs  44 , exterior end wall  45 , interior end wall  46 , and window frame assembly  50 . In the exemplary embodiment, end wall assembly  40  with window has a weight of approximately 3,507 lbs. 
         [0102]    In the exemplary embodiment, exterior end wall  45  and interior end wall  46  are made from sheets of steel 0.0625 inches to 1 inch thick. Thicker sheets (0.5 inches to 1 inch thick) may be used for end units  200  which will see deployment in areas where more protection may be needed. In embodiments without openings in an endwall assembly, wall studs  37  replace bottom jack studs  43  and top jack studs  44 , and exterior end wall  45  and interior end wall  46  have neither punchouts nor cutouts for insertion of window frame assembly  50 . 
         [0103]      FIG. 33  illustrates bottom frame end  41 , which has a length of 7.125 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. Bottom frame end  41  includes multiple stud apertures  15 .  FIG. 34  illustrates top frame end  42 , which has a length of 6.9270833 feet and a hollow structural cross-section of 5 by 3 by ½ inches. Top frame end  42  includes multiple stud apertures  15 . 
         [0104]      FIG. 35  illustrates window frame assembly  50 , which includes horizontal window frames  51 , vertical window frames,  52 , vertical window moldings  53 , and horizontal window moldings  54 .  FIG. 36  illustrates horizontal window frame  51 , which has a length of 2.4166 feet and a hollow structural cross-section of 3 by 2 by ¼ inches.  FIG. 37  illustrates vertical window frame  52 , which has a length of 2.4375 feet and a hollow structural cross-section of 3 by 2 by ¼ inches.  FIG. 38  illustrates vertical window molding  53 .  FIG. 39  illustrates horizontal window molding  54 .  FIG. 40  illustrates window frame assembly  50  welds. Window frame assembly  50  also includes glass  63  or another transparent material. 
         [0105]      FIG. 41  illustrates bottom jack stud  43 , which has a height of 3.9166 feet and a hollow structural cross-section of 3 by 2 by ¼ inches. Bottom jack studs  43  are inserted into stud apertures  15  and welded into place during assembly. Bottom jack studs  43 , similarly to wall studs  37 , provide critical anti-ballistic, -blast, and -forced entry properties for areas which include a window assembly  50 .  FIG. 42  illustrates top jack stud  44 , which has a height of 2.28125 feet and a hollow structural cross-section of 3 by 2 by ¼ inches. Top jack studs  44  are inserted into stud apertures  15  and welded into place during assembly. Top jack studs  44 , similarly to wall studs  37  and bottom jack studs  43 , provide critical anti-ballistic, -blast, and -forced entry properties.  FIG. 43  illustrates exterior end wall  46 , which has dimensions of 7.125 feet by 8.270833 feet.  FIG. 44  illustrates interior end wall  47 , which has dimensions of 7.125 feet by 8.25 feet.  FIG. 45  illustrates a cross section of end wall assembly  40  with window. 
         [0106]      FIG. 46  illustrates sidewall assembly  60  with windows, window frame assemblies  50 , wall studs  37 , bottom jack studs  43 , top jack studs  44 , interior sidewall  61  with punchouts, and exterior sidewall  62  with cutouts. In the exemplary embodiment, sidewall assembly  60  with windows has a weight of approximately 14,185 lbs. 
         [0107]    In the exemplary embodiment, interior sidewall  61  and exterior sidewall  62  are made from sheets of steel 0.0625 inches to 1 inch thick. Thicker sheets (0.5 inches to 1 inch thick) may be used for end units  200  which will see deployment in areas where more protection may be needed. In embodiments without openings in a sidewall assembly, wall studs  37  replace bottom jack studs  43  and top jack studs  44 , and interior and exterior sidewalls  61  and  62  have neither punchouts nor cutouts for insertion of window frame assembly  50 . 
         [0108]      FIG. 47  illustrates interior sidewall  61 , which has dimensions of 39.125 feet by 8.25 feet.  FIG. 48  illustrates exterior sidewall, which has dimensions of 39.125 feet by 8.25 feet.  FIG. 49  illustrates sidewall assembly  60  with windows welds. 
         [0109]      FIGS. 50-69  illustrate the components of an exemplary embodiment of optional middle unit  300  for modular anti-ballistic shelter system  100 . While only two end units  200  are necessary for system  100 , in certain embodiments, a user may insert one or more middle units  300  between end units  200  to provide additional space in system  100 . Broadly, middle units  300  are similar to end units  200 , but lack sidewall assembly  60  and any attendant structures.  FIG. 50  illustrates optional middle unit  300  including middle base assembly  70 , middle top assembly  80 , and end walls  90  without openings. Middle unit  300  has a weight of approximately 27,485 lbs. 
         [0110]      FIG. 51  illustrates middle base assembly  70  including floor girders  11 , channeled floor/roof support beams  13 , middle floor/roof support beams  71 , and middle floor  72 . Middle base assembly  70  has a weight of approximately 7,130 lbs. 
         [0111]      FIG. 52  illustrates floor girder  11 .  FIG. 53  illustrates channeled floor/roof support beam  13 .  FIG. 54  illustrates middle floor/roof support beam  71 , which has a length of 7.11979166 feet and a hollow structural cross-section of 3 by 3 by 5/16 inches.  FIG. 55  illustrates middle floor  72 , which has dimensions of 39.20833 feet by 7.953125 feet.  FIG. 56  illustrates middle base assembly  70  welds. 
         [0112]      FIG. 57  illustrates middle top assembly  80 , including middle top main girders  81 , channeled floor/roof support beams  13 , middle floor/roof support beams  71 , middle roof  82 , and middle interior roof  83 . Middle top assembly  80  has a weight of approximately 13,750 lbs. 
         [0113]      FIG. 58  illustrates middle top main girder  81 , which has a length of 39.125 feet and a hollow structural cross-section of 9 by 5 by ¼ inches.  FIG. 59  illustrates middle roof  82 , which has dimensions of 39.95833 feet by 7.953125 feet.  FIG. 60  illustrates middle interior roof  83 , which has dimensions of 39.20833 feet by 7.953125 feet.  FIG. 61  illustrates middle top assembly  80  welds. 
         [0114]      FIG. 62  illustrates middle end wall assembly  90  without openings, including top end beam  91 , bottom end beam  92 , wall studs  37 , middle corner column  93 , interior end plate  94 , exterior end plate  95 , ISO right freight container corner fitting  31 , and ISO left freight container corner fitting  32 . Each middle end wall assembly  90  without openings has a weight of approximately 3,301 lbs. 
         [0115]      FIG. 63  illustrates top end beam  91 , which has a length of 6.9375 feet and a hollow structural cross-section of 5 by 3 by ½ inches. Top end beam  91  includes multiple stud apertures  15  spaced apart 12.25 inches to 16 inches apart at center.  FIG. 64  illustrates bottom end beam  92 , which has a length of 7.125 feet and a hollow structural cross-section of 10 by 5 by ⅜ inches. Bottom end beam  92  includes multiple stud apertures  15  spaced apart 12.25 inches to 16 inches apart at center.  FIG. 65  illustrates wall stud  37 .  FIG. 66  illustrates middle corner column  93 , which has a height of 8.72395833 feet and a hollow structural cross-section of 5 by 5 by ⅜ inches.  FIG. 67  illustrates interior end plate  94 , which has dimensions of 8.27604166 feet by 7.125 feet.  FIG. 68  illustrates exterior end plate  95 , which has dimensions of 8.27604166 feet by 7.125 feet.  FIG. 69  illustrates endwall  90  welds. 
         [0116]    Wall studs  37  are welded into place using weld type A. Each weld type A is a fillet weld 3 inches long and 0.25 inches wide located at an interface between hollow wall stud  37  and whatever hollow member stud aperture  15  is located in. Because wall studs  37  extend through stud apertures  15  into a hollow member, even if a weld attaching wall studs  37  is defective or fails, end unit  200  and/or middle unit  300  maintains sufficient structural integrity to resist ballistic, blast and/or forced entry threats. The engagement and attachment between wall studs  37  and stud apertures  15  is sufficiently strong, even without a structural quality weld attaching wall studs  37 , to provide end unit  200  and/or middle unit  300  with suitable blast, ballistic and forced entry protection performance. 
         [0117]      FIGS. 70 a   - 72  illustrate the components of an exemplary embodiment of modular anti-ballistic shelter system  100 .  FIG. 70 a    illustrates an exemplary embodiment incorporating two middle units  300  between two end units  200 , for a “4×1” system  100 .  FIG. 70 b    illustrates an exemplary embodiment incorporating two end units  200  stacked atop another two end units  200 , for a “2×2” system  100 . Still other embodiments may use more or fewer middle units  300 , such as a “2×1” system  100  using only two end units or a “4×2” system  100 , which would use four end units  200  and four middle units  300 . 
         [0118]    System  100  includes at least one footer  110  embedded in the ground below end unit  200  and/or middle unit  300 . Footer  110  is a concrete platform  111  having at least one metal protrusion  112  extending therefrom. Footer  110  extends below first or second end wall assembly  30  or  40  from one ISO freight container corner fitting  31  or  32  to another ISO freight container corner fitting  31  or  32 . This enables connection of metal protrusion  112  to ISO freight container corner fitting  31  or  32 . Certain embodiments use multiple footers  111  below a single end unit  200  or middle unit  300 , or use a single footer  111  with multiple metal protrusions  112  beneath one or more end units  200  and/or middle units  300 . 
         [0119]    In certain embodiments, footer  110  has a rectangular or trapezoidal cross-section. In certain embodiments, metal protrusion  112  is a cone-shaped steel protrusion extending through an aperture in ISO freight container corner fitting  31  or  32 . In other embodiments, metal protrusion  112  is a vertical twistlock  120  extending through an aperture in ISO freight container corner fitting  31  or  32 . 
         [0120]    In system  100 , a user may connect a first end unit  200  to a second end unit  200  or a middle unit  300  by a plurality of horizontal twistlocks  125 , such as a double-sided twistlock. Horizontal twistlocks  125  extend between ISO right freight container corner fittings  31  and ISO left freight container corner fittings  32  to horizontally connect an end unit  200  to another end unit  200 , an end unit  200  to a middle unit  300 , or a middle unit  300  to another middle unit  300 . Horizontal twistlocks  125  have the same configuration as vertical twistlocks  120 , but are oriented along a horizontal axis instead of a vertical axis. 
         [0121]    In system  100 , a user may stack an end unit  200  or a middle unit  300  onto another end unit  200  or another middle unit  300  by a plurality of vertical twistlocks  120 , such as a double-sided twistlock. Vertical twistlocks  120  extend between ISO right freight container corner fittings  31  or ISO left freight container corner fittings  32  to vertically connect an end unit  200  or a middle unit  300  onto another end unit  200  or another middle unit  300 . 
         [0122]    Obviously, systems  100  with two end units  200  connect the end units  200  at their respective sides opposite each end unit&#39;s  200  sidewall assembly  60 . Systems  100  with two end units  200  and one or more middle units  300  connect the end units  200  to middle unit(s)  300  at their respective sides opposite each end unit&#39;s  200  side wall  22 . To avoid a weak point at the join, and to prevent precipitation from leaking into end units  200  or middle units  300 , a ballistic seal  130  extends along the seams between end units  200  and middle units  300 . Such a ballistic seal  130  also protects the joins between stacked end units  200  and middle units  300 , as can be seen in  FIG. 70   b.    
         [0123]    Ballistic seal  130  includes a first layer  131  of metal, a second layer  132  of waterproof polymer, and a third layer  133  of metal. In the exemplary embodiment, the metal is steel and the waterproof polymer is neoprene. Corner columns  35 , top main girders  22 , middle top main girders  81 , floor girders  11 , bottom frames  34 , top frames  36 , bottom frame end  41 , and/or top frame ends  42  of adjoining end units  200  and/or middle units  300  are located between second layer  132  and third layer  133 . A plurality of threaded rods  134  extends from first layer  131 , passes through second layer  132 , and protrudes through third layer  133 . A plurality of fasteners  135 , such as nuts or clamps, prevent threaded rods  134  from retracting from third layer  133 , keeping corner columns  35 , top main girders  22 , middle top main girders  81 , floor girders  11 , bottom frames  34 , top frames  36 , bottom frame end  41 , and/or top frame ends  42  secured between second layer  132  and third layer  133 . 
         [0124]      FIGS. 73 a -73 c    illustrate a flowchart of an exemplary method  400  for making end unit  200  for modular anti-ballistic shelter system  100 . 
         [0125]    In step  402 , method  400  removably connects 4 ISO right freight container corner fittings  31  to a welding scaffold. 
         [0126]    In step  404 , method  400  removably connects 4 ISO left freight container corner fittings  32  to the welding scaffold. Each ISO left freight container corner fitting  32  is located directly opposite a corresponding ISO right freight container corner fitting  31 . 
         [0127]    In step  406 , method  400  welds a corner column  35  between each pair of ISO right freight container corner fittings  31  and each pair of ISO left freight container corner fittings  32 . 
         [0128]    In step  408 , method  400  welds bottom frame  34  between an ISO left freight container corner fitting  32  and a corresponding ISO right freight container corner fitting  31 , and welds bottom frame end  41  between another ISO left freight container corner fitting  32  and another corresponding ISO right freight container corner fitting  31 . Bottom frame end  41  is parallel to bottom frame for middle door  34 . 
         [0129]    In step  410 , method  400  welds one floor girder  11  between an ISO left freight container corner fitting  32  and a corresponding ISO right freight container corner fitting  31 , and welds another floor girder  11  between another ISO left freight container corner fitting  32  and another corresponding ISO right freight container corner fitting  31 . Floor girders  11  are parallel to each other, and perpendicular to bottom frames  34  and  41 . 
         [0130]    In step  412 , method  400  welds floor  14  to floor girders  11  and bottom frames  34  and  41 . 
         [0131]    In step  414 , method  400  inserts wall studs  37  into stud apertures  15  in one floor girder  11  and bottom frames  34  and  41 . 
         [0132]    In step  416 , method  400  welds wall studs  37  to one floor girder  11  and bottom frames  34  and  41 . 
         [0133]    In optional step  418 , method  400  inserts bottom jack studs  43  into stud apertures  15  in one floor girder  11  and bottom frame end  41 . 
         [0134]    In optional step  420 , method  400  welds bottom jack studs  43  to one floor girder  11  and bottom frame end  41 . 
         [0135]    In step  422 , method  400  inserts the wall studs  37  of step  414  into stud apertures  15  in top girder  21 , top frame  36 , and top frame end  42 . 
         [0136]    In step  424 , method  400  welds wall studs  37  to top girder  21 , top frame  36 , and top frame end  42 . 
         [0137]    In optional step  426 , method  400  inserts top jack studs  44  into stud apertures  15  in top girder  21  and top frame end  42 . 
         [0138]    In optional step  428 , method  400  welds top jack studs  44  to top girder  21  and top frame end  42 . 
         [0139]    In step  430 , method  400  welds top frame  36  between an ISO left freight container corner fitting  32  and a corresponding ISO right freight container corner fitting  31 , and welds top frame end  42  between another ISO left freight container corner fitting  32  and another corresponding ISO right freight container corner fitting  31 . Top frame end  42  is parallel to top frame for middle door  36 . 
         [0140]    In step  432 , method  400  welds top girder  21  between an ISO left freight container corner fitting  32  and a corresponding ISO right freight container corner fitting  31 , and welds top main girder  22  between another ISO left freight container corner fitting  32  and another corresponding ISO right freight container corner fitting  31 . Top and top main girders  21  and  22  are parallel to each other, and perpendicular to top frames  36  and  42 . 
         [0141]    In step  434 , method  400  welds roof  23  and interior roof  24  to the floor/roof support beams  12 , channeled floor/roof support beams  13 , top girder  21 , and top main girder  22  of top assembly  20 . 
         [0142]    In step  436 , method  400  welds exterior plate  38  and interior plate  39  to bottom frame  34 , corner columns  35 , and top frame for middle door  36  of end wall assembly with door  30 . 
         [0143]    In step  438 , method  400  welds exterior end wall  45  and interior end wall  46  to bottom frame end  41 , corner columns  35 , and top frame end  42  of end wall assembly with window  40 . 
         [0144]    In step  440 , method  200  welds an exterior sidewall  62  and an interior sidewall  61  to a floor girder  11 , a top girder  21 , and two corner columns  35 . 
         [0145]    In optional step  442 , method  400  welds window frame assembly  50  into endwall assembly  40  or sidewall assembly  60 . 
         [0146]    In optional step  444 , method  400  welds door frame assembly  33  into endwall assembly  30  or sidewall assembly  60 . 
         [0147]    When fabricated, each end unit  200  and each middle unit  300  conform to ISO standards for shipping containers, having outer dimensions of 40 feet long, 8 feet wide, and 8.5 feet tall, and a maximum weight of 66,139 lbs. When end units  200  and optional middle units  300  are assembled into modular anti-ballistic shelter system  100 , system  100  meets the U.S. Department of State Certification Standard for Forced Entry and Ballistic Resistance of Structural Systems, SDSTD01.01. 
         [0148]    It will be understood that many additional changes in the details, materials, procedures and arrangement of parts, which have been herein described and illustrated to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Moreover, the term “approximate” as used herein may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. 
         [0149]    It should be further understood that the drawings are not necessarily to scale; instead, emphasis has been placed upon illustrating the principles of the invention.