Patent Publication Number: US-2020299951-A1

Title: Modular dome-like structure and voussoirs and keystone used to construct the dome-like structure

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a dome-like structure and, in particular, to a modular dome-like structure and voussoirs and keystone used to construct the dome-like structure. 
     Description of the Related Art 
     The advantages of using dome-like structures for emergency shelters are well known. Dome-like structures are resistant to high velocity winds and projectiles may glance off the dome-like structure minimizing the impact that the projectile has on the dome-like structure. United States Patent Application Publication No. 2003/0051418 which was published on Mar. 20, 2003 in the name of Crowder discloses a monolithic prefabricated dome-like structure that is wind and impact resistant. The pre-cast lightweight concrete dome-like structure is a blend of special aggregates and additives combined to resist the impacts of flying debris and extremes of weather. The curved exterior surface minimizes wind friction and deflects debris. It is however also desirable to provide a modular dome-like structure which may be used as an emergency shelter. 
     U.S. Pat. No. 7,458,186 which issued on Dec. 2, 2008 to Carter discloses a modular dome-like structure that may be used as an emergency shelter. The dome-like structure is constructed from a plurality of rectangular shaped blocks each having a rim and a trough molded therein. The rim has pins adjacent the corners of the blocks that engage apertures or holes of the fastening plates. Each fastening plate has four holes to enable it to snap together four blocks. Subsequent rows of blocks may have smaller dimensions so that the assembly curves inward forming the familiar domed shape of an igloo. Curved trapezoidal shaped blocks, also held together with fastening plates, are used to cap off the dome-like structure. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a modular dome-like structure and voussoirs and keystone used to construct the dome-like structure. 
     There is accordingly provided a modular dome-like structure comprising a semispheric wall. A lowermost course of the semispheric wall is constructed using a plurality of springers. An intermediate course of the semispheric wall is constructed using a plurality of a first voussoir type. A second to uppermost course of the semispheric wall is constructed using a plurality of a second voussoir type. An uppermost course and third to uppermost of the semispheric wall is constructed using a plurality of a third voussoir type. The modular dome-like structure may have a cap constructed using a plurality of fourth voussoir type and a keystone or the modular dome-like structure may have an oculus. The modular dome-like structure may further include a lateral opening in the semispheric wall. 
     A voussoir in an uppermost course of the semispheric wall may extend across substantially one-quarter of a first voussoir in the second to uppermost course of the semispheric wall and substantially three-quarters of a second voussoir in the second to uppermost course of the semispheric wall. A voussoir in a second to uppermost course of the semispheric wall may extend across substantially three voussoirs in a third to uppermost course of the semispheric wall. The lowermost course of the semispheric wall and the intermediate course of the semispheric wall may be laid in a stretcher bond. The may be a tension strip about the lowermost course of the semispheric wall 
     There is also provided a modular half dome-like structure comprising a half semispheric wall. A lowermost course of the half semispheric wall is constructed using a plurality of springers. An intermediate course of the half semispheric wall is constructed using a plurality of a first voussoir type. A second to uppermost course of the semispheric wall is constructed of a plurality of second voussoir type. An uppermost course and third to uppermost of the semispheric wall is constructed of a plurality of a third voussoir type. A half cap of the half semispheric wall is constructed using plurality of a fourth voussoir type and a keystone. The modular dome-like structure may further include a lateral opening in the half semispheric wall. 
     A voussoir in an uppermost course of the half semispheric wall may extend across substantially one-quarter of a first voussoir in the second to uppermost course of the half semispheric wall and substantially three-quarters of a second voussoir in the second to uppermost course of the half semispheric wall. A voussoir in a second to uppermost course of the half semispheric wall extends across substantially three voussoirs in a third to uppermost course of the half semispheric wall. The lowermost course of the half semispheric wall and the intermediate course of the half semispheric wall may be laid in a stretcher bond. 
     There is further provided a modular dome-like structure comprising an inner dome and an outer dome disposed about the inner dome. The modular dome-like structure may further include foam disposed between the inner dome and the outer dome. 
     There is still further provided a method of constructing a dome-like structure comprising: 
     constructing a lowermost course of a semispheric wall using a plurality of springers;
 
constructing an intermediate course of the semispheric wall using a plurality of a first voussoir type;
 
constructing a second to uppermost course of the semispheric wall using a plurality of a second voussoir type; and
 
constructing an uppermost course and third to uppermost of the semispheric wall using of a third voussoir type.
 
     The method of constructing a modular dome-like structure may further include constructing a cap using a fourth voussoir type and a keystone. The method of constructing a modular dome-like structure may include extending a voussoir in an uppermost course of the semispheric wall to across substantially one-quarter of a first voussoir in the second to uppermost course of the semispheric wall and substantially three-quarters of a second voussoir in the second to uppermost course of the semispheric wall. The method of constructing a modular dome-like structure may include extending a voussoir in a second to uppermost course of the semispheric wall across substantially three voussoirs in a third to uppermost course. The method of constructing a modular dome-like structure may include laying the lowermost course of the semispheric wall and the intermediate course of the semispheric wall in a stretcher bond. The method of constructing a modular dome-like structure may further include coupling a voussoir in a lower course to a voussoir in an upper course with a tension strap to apply tension to the voussoir in the upper course to maintain the voussoir in the upper course in a position. 
    
    
     
       BRIEF DESCRIPTIONS OF DRAWINGS 
       The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective, partially exploded view of a dome-like structure; 
         FIG. 2A  is a perspective view of a springer of the dome-like structure of  FIG. 1  showing an intrados surface of the springer; 
         FIG. 2B  is a perspective view of the springer of the dome-like structure of  FIG. 1  showing an extrados surface of the springer; 
         FIG. 2C  is an elevation view of the springer of the dome-like structure of  FIG. 1  showing an extrados surface of the springer; 
         FIG. 2D  is an elevation side view of the springer of the dome-like structure of  FIG. 1  showing an end surface of the springer; 
         FIG. 2E  is a top plan view of the springer of the dome-like structure of  FIG. 1  showing an upper load bearing surface of the springer; 
         FIG. 2F  is a bottom plan view of the springer of the dome-like structure of  FIG. 1  showing a lower load bearing surface of the springer; 
         FIG. 3A  is a perspective view of a first voussoir type of the dome-like structure of  FIG. 1  showing an intrados surface of the first embodiment of a voussoir; 
         FIG. 3B  is a perspective view of the first voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the first embodiment of a voussoir; 
         FIG. 3C  is an elevation view of the first voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the first embodiment of a voussoir; 
         FIG. 3D  is an elevation side view of the first voussoir type of the dome-like structure of  FIG. 1  showing an end surface of the first embodiment of a voussoir; 
         FIG. 3E  is a top plan view of the first voussoir type of the dome-like structure of  FIG. 1  showing an upper load bearing surface of the first embodiment of a voussoir; 
         FIG. 3F  is a bottom plan view of the first voussoir type of the dome-like structure of  FIG. 1  showing a lower load bearing surface of the first embodiment of a voussoir; 
         FIG. 4A  is a perspective view of a second voussoir type of the dome-like structure of  FIG. 1  showing an intrados surface of the second embodiment of a voussoir; 
         FIG. 4B  is a perspective view of the second voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the second embodiment of a voussoir; 
         FIG. 4C  is an elevation view of the second voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the second embodiment of a voussoir; 
         FIG. 4D  is an elevation side view of the second voussoir type of the dome-like structure of  FIG. 1  showing an end surface of the second embodiment of a voussoir; 
         FIG. 4E  is a top plan view of the second voussoir type of the dome-like structure of  FIG. 1  showing an upper load bearing surface of the second embodiment of a voussoir; 
         FIG. 4F  is a bottom plan view of the second voussoir type of the dome-like structure of  FIG. 1  showing a lower load bearing surface of the second embodiment of a voussoir; 
         FIG. 5A  is a perspective view of a third voussoir type of the dome-like structure of  FIG. 1  showing an intrados surface of the third embodiment of a voussoir; 
         FIG. 5B  is a perspective view of the third voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the third embodiment of a voussoir; 
         FIG. 5C  is an elevation view of the third voussoir type of the dome-like structure of  FIG. 1  showing an extrados surface of the third embodiment of a voussoir; 
         FIG. 5D  is an elevation side view of the third voussoir type of the dome-like structure of  FIG. 1  showing an end surface of the third embodiment of a voussoir; 
         FIG. 5E  is a top plan view of the third voussoir type of the dome-like structure of  FIG. 1  showing an upper load bearing surface of the third embodiment of a voussoir; 
         FIG. 5F  is a bottom plan view of the third voussoir type of the dome-like structure of  FIG. 1  showing a lower load bearing surface of the third embodiment of a voussoir; 
         FIG. 6A  is a perspective view of a fourth voussoir type of the dome-like structure of  FIG. 1  showing an upper load bearing surface of the third embodiment of the voussoir; 
         FIG. 6B  is a perspective view of the fourth voussoir type of the dome-like structure of  FIG. 1  showing a lower load bearing surface of the third embodiment of the voussoir; 
         FIG. 7  is a perspective view of a keystone of the dome-like structure of  FIG. 1 ; 
         FIG. 8  is a perspective view showing the construction of another dome-like structure; 
         FIG. 9  is a perspective view showing the constructed dome-like structure of  FIG. 8 ; 
         FIG. 10  is a sectional view of yet another dome-like structure comprising an inner dome and an outer dome; 
         FIG. 11  is a perspective view of still yet another dome-like structure comprising a floor and a lateral opening; 
         FIG. 12  is a bottom plan view of the dome-like structure of  FIG. 11 ; 
         FIG. 13  is a side, fragmentary view of the dome-like structure of  FIG. 11 ; 
         FIG. 14  is a perspective, partially exploded view of a half of a dome-like structure; 
         FIG. 15  is a perspective view of the half of the dome-like structure connected to an arched tunnel; and 
         FIG. 16  is a perspective view of two halves of a dome-like structure connected by an arched tunnel. 
     
    
    
     DESCRIPTIONS OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and first to  FIG. 1 , a dome-like structure  10  is shown. The dome-like structure  10  generally comprises a substantially semispheric wall  12  and a cap  14 . It will be understood by a person skilled in the art that the semispheric wall  12  by itself could also be considered a dome-like structure with an oculus  16 . In this example, the dome-like structure is also provided with an outwardly extending arched structure  11  which serves as an entrance/exit. 
     The semispheric wall  12  includes a plurality of courses  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  and  32 . Voussoirs in the courses are generally laid in a stretcher bond with the exception of a second to uppermost course  30  in which each voussoir, for example voussoir  34 , is laid and extends across substantially three voussoirs, for example voussoirs  36 ,  37  and  38 , in a third to uppermost course  28 . Voussoirs in the second to uppermost course  30  and an uppermost course  32  are laid in a modified stretcher bond relative to one another in which a voussoir, for example voussoir  90 , in an uppermost course  32  extends across substantially one-quarter of a first voussoir  35  and substantially three-quarters of a second voussoir  34  in the second to uppermost course  30 . This results in a dome-like structure  10  not having continuous joint lines. 
     A lowermost course  18  of the semispheric wall  12  is constructed using springers, for example springer  40 , which is best shown in  FIGS. 2A to 2F . The springer  40  has an intrados surface  42  and an extrados surface  44 . The springer  40  also has an upper load bearing surface  46  and a lower load bearing surface  48 . The upper load bearing surface  46  has a slope α 1  between the intrados surface  42  and the extrados surface  44  as best shown in  FIG. 2D . There are also protrusions  50  and  52  on the upper load bearing surface  46 . The protrusions  50  and  52  function as keys to interlock the springer with voussoirs in a second to lowermost course  20  of the semispheric wall  12 . In this example, the lower load bearing surface  48  has no slope or a substantially negligible slope  131  between the intrados surface  42  and the extrados surface  44 . In other examples, the springers may be on imposts. 
       FIGS. 3A to 3F  show a first voussoir type, for example a voussoir  60 , used to construct the dome-like structure  10  shown in  FIG. 1 . The voussoir  60  has an intrados surface  62  and an extrados surface  64 . The voussoir  60  also has an upper load bearing surface  66  and a lower load bearing surface  68 . The upper load bearing surface  66  has a slope α 2  between the intrados surface  62  and the extrados surface  64  as best shown in  FIG. 3D . There are also protrusions  70  and  72  on the upper load bearing surface  66 . The protrusions  70  and  72  function as keys to interlock the voussoir  60  with other voussoirs. The lower load bearing surface  68  has a slope β 2  between the intrados surface  62  and the extrados surface  64  as best shown in  FIG. 3D . There are also recesses  74  and  76  in the load bearing surface  68  which function as keyholes. 
     The voussoir  60  shown in  FIGS. 3A to 3F  is used to construct the second to lowermost course  20  of the semispheric wall  12 . The slope β 2  of the lower load bearing surface  68  accordingly has substantially the same grade as the slope α 1  of the upper load bearing surface  46  of the springer  40 . This allows one of the protrusions  50  and  52  of the springer  40  to be received by one of the recesses  74  and  76  of the voussoir  60  when the springers and voussoirs are laid in a stretcher bond during the construction of the semispheric wall  12  of the dome-like structure  10 . A grade of the slope α 2  of the upper load bearing surface  66  of the voussoir  60  is steeper than the grade of the slope α 1  of the upper load bearing surface  46  of the springer  40 . This provides an arc to the semispheric wall  12 . 
     Referring back to  FIG. 1 , voussoirs substantially identical to the voussoir  60  are used to construct the second to lowermost course  20  of the semispheric wall  12 . Voussoirs substantially similar in configuration to the voussoir  60  are used to construct intermediate courses  22 ,  24 , and  26  of the semispheric wall  12 . However, voussoirs used to construct each successive one of the courses  22 ,  24 , and  26  have upper load bearing surfaces and lower load bearing surfaces with slopes of increasingly steeper grades. This provides an arc to the semispheric wall  12 . A slope of an upper load bearing surface of a voussoir in a course, for example the course  22 , has substantially the same grade as a slope of a lower load bearing surface of a voussoir in the successive course  24 . This facilitates interlocking of the voussoirs during the construction of the semispheric wall  12 . 
     Voussoirs used to construct the second to uppermost course  30  of the semispheric wall are a second voussoir type used to construct the dome-like structure  10 .  FIGS. 4A to 4F  show the voussoir  34  used to construct the second to uppermost course  30  of the semispheric wall  12  in greater detail. The voussoir  34  has an intrados surface  210  and an extrados surface  212 . The voussoir  34  also has an upper load bearing surface  214  and a lower load bearing surface  216 . The upper load bearing surface  214  has a slope α 3  between the intrados surface  210  and the extrados surface  212  as best shown in  FIG. 4D . There are also protrusions  230 ,  232  and  234  on the upper load bearing surface  214 . The protrusions  230 ,  232  and  234  function as keys to interlock the voussoir  34  with voussoirs in the uppermost course  32  of the semispheric wall  12 . A center one of the protrusions  230  is an entire key while outer ones of the protrusions  232  and  234  are each half of a key. This allows a voussoir in an uppermost course to extend across substantially one-quarter of a first voussoir and substantially three-quarters of a second voussoir in the second to uppermost course. There are also recesses  240 ,  242  and  244  on the lower load bearing surface  216 . The recesses  240 ,  242  and  244  function as keyholes to interlock the voussoir  34  with voussoirs the third to uppermost course  28  of the semispheric wall  12 . A center one of the recesses  240  is an entire keyhole while outer ones of the recesses  242  and  244  are half a keyhole. This allows a voussoir in the second to uppermost course to extend across substantially three voussoirs in a third to uppermost course. 
     Voussoirs used to construct the third to uppermost course  28  and uppermost course  32  of the semispheric wall are a third voussoir type used to construct the dome-like structure  10 .  FIGS. 5A to 5F  show the voussoir  90  used to construct the uppermost course  32  of the semispheric wall  12  in greater detail. The voussoir  90  has an intrados surface  92  and an extrados surface  94 . The voussoir  90  also has an upper load bearing surface  96  and a lower load bearing surface  98 . The upper load bearing surface  96  has a slope α 3  between the intrados surface  92  and the extrados surface  94  as best shown in  FIG. 5D . There is also a protrusion  100  on the upper load bearing surface  96 . The protrusion  100  functions as a key to interlock the voussoir  60  with other voussoirs. The lower load bearing surface  98  has a slope β 3  between the intrados surface  92  and the extrados surface  94  as best shown in  FIG. 5D . There are also recesses  104  and  106  in the load bearing surface  98  which function as keyholes. Voussoirs, for example the voussoirs  36 ,  37  and  38 , used to construct the third to uppermost course  28  of the semispheric wall  12  are substantially similar in configuration to the voussoir  90 . However, the upper load bearing surface and the lower load bearing surface of the voussoir  90  have slopes with a steeper grade than slopes of the upper load bearing surfaces and the lower load bearing surfaces of the voussoirs  36 ,  37  and  38 . This provides an arc to the semispheric wall  12 . 
     Referring back to  FIG. 1 , the cap  14  of the dome-like structure  10  includes a plurality of a fourth voussoir type, for example a voussoir  110 , used to construct the dome-like structure and a keystone  130 . The voussoir  110  is shown in greater detail in  FIGS. 6A and 6B . The voussoir  110  has an upper load bearing surface  112  and a lower load bearing surface  114 . There is a shoulder  116  on the upper load bearing surface  112 . The shoulder  116  extends outwardly from a first plurality of load bearing segments  118   a ,  118   b , and  118   c  to a second plurality of load bearing segments  120   a ,  120   b , and  120   c . The lower load bearing surface  114  has a plurality of load bearing segments  122   a ,  122   b  and  122   c . There is a respective one of recesses  124   a ,  124   b , and  124   c  in each of the load bearing segments  122   a ,  122   b  and  122   c . The keystone  130  is shown in greater detail in  FIG. 7  and has a head  132  and a stem  134 . There is a plurality of load bearing segments, for example load bearing segments  136   a  and  136   b , disposed about a periphery of the head  132 . There is also a plurality of load bearing segments, for example load bearing segments  138   a  and  138   b , disposed about a periphery of the stem  134 . 
     Referring again back to  FIG. 1 , during construction of the dome-like structure  10 , the recesses  124   a ,  124   b  and  124   c  receive a respective protrusion of a voussoir in the uppermost course  32  of the semispheric wall  12  to thereby interlock voussoirs used to construct the semispheric wall  12  with voussoirs used to construct the cap  14 . The keystone  130  is then set with the head  132  sitting on shoulders of the voussoirs used to construct the cap  14  and the stem  134  extending through an opening  126  defined by the voussoirs used to construct the cap  14 . The load bearing surfaces of the head  132  of the keystone  130 , for example load bearing segments  136   a  and  136   b  shown in  FIG. 7 , mate with corresponding ones of the first plurality of load bearing segments, for example load bearing segments  118   a ,  118   b  and  118   c  shown in  FIG. 6A , of the voussoir  110  used to construct the cap  14 . The load bearing surfaces of the stem  134  of the keystone  130 , for example load bearing segments  138   a  and  138   b  shown in  FIG. 7 , mate with corresponding ones of the second plurality of load bearing segments, for example load bearing segments  120   a ,  120   b , and  120   c  shown in  FIG. 6A , of the voussoir  110  used to construct the cap  14 . 
     The recesses and protrusions of the springers and voussoirs used to construct the dome-like structure  10  are similar to the recesses and protrusions of the voussoirs disclosed in U.S. Pat. No. 6,931,797 which issued on Aug. 23, 2005 to Drew and the full disclosure of which is incorporated herein by reference. However, it will be understood by a person skilled in the art that any suitable shape of recesses and protrusions may be used. The dome-like structure  10  may be used as an emergency shelter or for any other suitable purpose. 
       FIG. 8  shows another dome-like structure  310  being constructed. The dome-like structure  310  is generally constructed using springers, voussoirs, and a keystone similar in configuration to those used in the construction of the dome-like structure  10  shown in  FIG. 1 . Referring back to  FIG. 8 , the dome-like structure  310  also includes voussoirs, for example voussoirs  312  and  314 , which are provided with respective a hook  316  and  318  on extrados surfaces thereof. The hook  316  may be in a recess  320  in the extrados surface as shown for voussoir  312  or the hook  318  may be on the face of the extrados surface as shown for voussoir  314 . The hooks  316  and  318  may be used to couple the voussoirs  312  and  314  with a tension strap  322 . The tension strap  322  is anchored to the voussoir  312  in a lower course to maintain the voussoir  314  in an upper course in an offset placement as another voussoir  324  is being positioned in the upper course. It is possible to use a bridge  326  disposed between the voussoirs  312  and  314  to apply the appropriate tension. The tension strap may alternatively be used for reinforcement. 
     The dome-like structure  310  also includes voussoirs, for example voussoirs  328  and  330 , which are provide with respective channels  332  and  334  on the extrados surfaces thereof. The channels in voussoirs in adjacent courses are aligned to form continuous channels  336  and  338  on an exterior of the dome-like structure  310 . There may be hooks, for example hook  340 , in the channels to facilitate the running of a tension strap  342  in the channel  338  for exterior reinforcement as shown in  FIG. 10 . The dome-like structure  310  also includes voussoirs, for example voussoirs  344 , with an internal cavity  346  to facilitate the installation of electrical fixtures. 
       FIG. 10  shows a dome-like structure  410  which comprises an inner dome  412  and an outer dome  414 . The inner dome and the outer dome are constructed using springers, voussoirs, and a keystone similar in configuration to those used in the construction of the dome-like structure  10  shown in  FIG. 1 . Referring back to  FIG. 10 , there is a layer of foam  416  disposed between the inner dome  412  and the outer dome  414 . The foam  416  may be injected into a space between the inner dome  412  and the outer dome  414  prior to setting a keystone  418  of the outer dome  414 . The dome-like structure  410  may be suitable for storing explosives, for example, munitions  420  as the foam will absorb the shock of an explosion. 
       FIG. 11  shows a dome-like structure  510  comprising an arched lateral opening  512 . The dome-like structure  510  is constructed using springers and voussoirs similar in configuration to those used in the construction of the dome-like structure  10  shown in  FIG. 1 . Referring back to  FIG. 11 , the dome-like structure  510  may be used as a pizza oven or for any other suitable purpose. The dome-like structure  510  sits on a floor  514 . There is a tension strap  516  about a perimeter of the floor  514  which functions to keep the floor  514  in tension. The floor  514  is best shown in  FIGS. 12 and 13 . 
     Blocks, for example block  518 , used to construct an outermost ring of the floor  514  have protrusions  520  and  522  on an upper load bearing surface thereof and protrusion  526  and  528  on an inner lateral side thereof. The protrusions  520  and  522  on the upper load bearing of the block  518  functions as keys to engage a springer of the dome-like structure  510 . The protrusions  526  and  528  on the inner lateral side of the block  518  functions as keys to engage a recesses, e.g. keyholes, in an outer lateral side of a block  530  used construct a second to outermost ring of the floor  514 . Referring now to  FIG. 13 , the block  530  used to construct the second to outermost ring of the floor  514  also has a protrusion  532  on an inner later side thereof. The protrusion  532  on the inner lateral side of the block  530  functions as a key to engage a recesses in an outer lateral side of a block  534  used construct third to outermost ring of the floor  514 . The block  534  used to construct the third to outermost ring of the floor  514  has a protrusion  536  on an inner later side thereof. The protrusion  536  on the inner lateral side of the block  534  functions as a key to engage a recesses, e.g. keyhole, in an outer lateral side of a block  538  used construct fourth to outermost ring of the floor  514  which is thereby constructed from a plurality of inter-engaged rings of blocks. There is also an annular block  540  and cylindrical block  542  at the center of the floor  314  which complete the floor. There is also recess  544  in an outer lateral wall of the block  518  which receives the tension strip shown in  FIG. 9 . 
       FIG. 14  shows a partially constructed half dome-like structure  610  which may be used as an apse or vault or for any other suitable purpose. The half dome-like structure  610  is constructed using springers and voussoirs similar in configuration to those used in the construction of the dome-like structure  10  shown in  FIG. 1 . The keystone  612  of the half dome-like structure  610  is a half of the keystone used in the construction of the dome-like structure  10  shown in  FIG. 1 . The half dome-like structure  610  may be connected to an arched tunnel  614  as shown in  FIG. 15 . The arched tunnel  614  may be constructed as disclosed in U.S. Pat. No. 9,481,993 which issued on Nov. 1, 2016 to Drew and the full disclosure of which is incorporated herein by reference. Still alternatively, as shown in  FIG. 16 , the half dome-like structure  610  may be connected by the arched tunnel  614  to another half dome-like structure  616 . The structures shown in  FIGS. 14 to 16  may be used for any suitable purpose and may be provided with a quadrilateral opening  618 , which in this example functions as a door, or a stepped opening  620 , which in this example functions as a window. 
     It will be understood by a person skilled in the art that many of the details provided above are by way of example only, and are not intended to limit the scope of the invention which is to be determined with reference to the following claims.