Abstract:
A building frame resistant to earthquakes, gale-force wind loads, fire, insects and rot includes a peripheral frame wall constructed of square or rectangular steel tubing. Side wall frame modules bolted together along adjacent edges, and end wall modules bolted together along adjacent edges and to the ends of the connected side wall modules form the peripheral frame wall. Diagonal bracing is built into selected side and end wall modules as required for the desired degree of wind resistance. Trusses made of various size tube such as 2×3 inch rectangular steel tubing for supporting a roof on the peripheral wall, are assembled and welded in a welding shop and the prefabricated trusses and wall modules are trucked to the building site. Multiple stones may be erected and fastened together, and the building frame is secured to a foundation or slab by attaching to anchor bolts or plates.

Description:
[0001]    This invention relates to improved building frames constructed from prefabricated frame modules, and buildings constructed from such frames, and more particularly to fire and insect resistant buildings that can be built with multiple stories, resistant to wind, impact and seismic damage and with interior and exterior walls that are isolated from the support frames to enhance thermal and acoustical values. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional building practice for residence housing and small commercial buildings has in the past relied primarily on wood frame construction in which the building frame is constructed on site from framing lumber cut to fit piece-by-piece individually. It is a labor-intensive process and demands considerable skill from the carpenters to produce a structure that has level floors, perfectly upright walls, square corners and plumb door and window openings. Even when the building frame is constructed with the requisite care and skill, it can become skewed by warping of the lumber, especially modern low grade lumber produced on tree farms with hybrid fast-growth trees. 
         [0003]    Although conventional wood frame buildings require very little equipment for construction, they have become quite costly to build. The labor component of the cost is substantial, partly because of the wages that must be paid for the laborious process of constructing the frame, and partly because of the many government mandated extra costs such as workman&#39;s compensation and liability insurance, social security payments, medical insurance premiums, and the host of reports that must be made to the Government by employers. Accordingly, employers now seek to minimize their work force by whatever means is available to minimize these burdensome costs. 
         [0004]    Steel frame construction, usually referred to as “red iron” construction, is commonly used on commercial buildings because of its greater strength, fire resistance and architectural design flexibility. The parts of such a steel frame are typically cut and drilled to order in accordance with the architect&#39;s plans, then trucked to the building site and assembled piece-by-piece with the use of a portable crane. The building can be made precisely and as strong as needed, but the cost is relatively high because of the costly materials and the skilled crew and expensive equipment need to assemble the building. It is a construction technique generally considered unsuitable for single family residence building because the cost is high and the building walls are substantially thicker than those made using standard frame construction, so standard door and window units do not fit properly and must be modified with special trim that rarely produces the desired aesthetic appearance. 
         [0005]    Earthquake damage is becoming a matter of increasing concern among homeowners because of the publicity given to damage and loss of life in recent earthquakes in the U.S. and abroad. Earthquake preparedness stories and advice abound, but an underlying unresolved concern is that conventional wood frame homes in the past were not built to tolerate the effects of an earthquake, neither in its ultimate load-bearing capability nor its post-quake serviceability limits. Modern building codes attempt to address this concern, but the measures they require add to the already high cost of a new home and may not always provide significantly improved resistance to earthquake damage, particularly with respect to after-quake serviceability. 
         [0006]    Fire often follows an earthquake, as happened in the disastrous Kobe earthquake of 1994, and of course fire is a major threat to homes independent of earthquake. When fire breaks out in a conventional home, the wood frame fuels the fire and reduces the chances of successfully extinguishing it before the entire structure is destroyed. The major life saving advance in the recent past is the fire alarm which detects the fire and alerts the occupants that a fire has started so they may escape before burning up with the house, but significant improvements to the fire resistance of the home itself that would retard the spread of the fire would be desirable. 
         [0007]    The other major catastrophic threat to homes is wind. Wind loads on wood frame homes have destroyed many homes, primarily because the roof is usually attached so weakly to the walls that the combination of lift, exerted upward on the roof by the Bernoulli effect of the wind flowing over the roof, and pressure under the eves tending to lift the roof off the walls, wrenches the roof off the walls and allows the wind to carry the roof away like a big umbrella. Without the roof, the walls of the house collapse readily under the wind load, completing the total destruction of the house. 
         [0008]    Termite and carpenter ant damage to wood frame homes is a major form of damage, costing many millions of dollars per year. Although the damage done by insects is rarely life threatening, it is actually more extensive in total than the combined effects of wind and earthquake, and it is an ever-present danger in many parts of the country. 
         [0009]    These and other problems with wood-frame construction have made the insurance costs for new buildings, particularly for multi-story residential construction such as apartment and nursing home construction, increasingly expensive. 
         [0010]    Thus, there has existed an increasing need for a home building frame design that would enable the inexpensive construction of homes that are highly tolerant of the effects of earthquakes, do not support combustion, are capable of withstanding high winds, are immune to damage from insects, and can use standard building components such as door and window units. Such a building frame concept would be even more commercially valuable if it were possible to erect the building in a short time with a small crew and without heavy equipment, and the frame could be adapted to produce buildings of attractive building styles desired locally. Such a building frame is disclosed in U.S. Pat. No. 6,003,280 issued to Orie Wells on Dec. 21, 1999, and in U.S. Pat. No. 6,460,297 issued to Delton J. Bonds on Oct. 8, 2002, both of which are assigned to the assignee of this application. However, numerous improvements were found to be desirable in the building frame system shown in those patents for improved design flexibility, fabrication economy, ease of assembly and improved structural strength and resistance to adverse environmental conditions. Multi-story construction with concrete floors flush with top of frame and linked together by rebar extending through holes in the interior wall frames or by joists attached to support the floor and to structurally link the opposed walls to provide in-plane shear transfer and diaphragm continuity in and through the entire wall frame, and frames stacked vertically and bolted together w/o crushing the frame members would improve the structural strength of the building frame, and frame modules insulated from interior furring channels would improve the sound and thermal insulation of the interior and external walls of the building. These and other improvements would make the building system disclosed in these two patents even more desirable. 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, these and other features of the invention are attained an improved building frame, ideally suited for single story and low multi-story buildings, that can be assembled rapidly at the building site by bolting together a multiplicity of unitary metal frame modules that have been pre-fabricated off site. The frame for the building is made from a multiplicity of wall modules attached edge-to-edge to form a peripheral wall frame for the building frame. The wall modules are unitary rectangular frames made of square, round or rectangular structural steel tubing. Several different wall module designs can be used, including one having a top tube, two upright tubes, and a bottom tube, welded at four corners of the module and having internal braces for strengthening and stiffening. Light gauge furring channels are attached to each side of the wall frames, interior and exterior with screws. Isolator tape is positioned between the wall frame and the interior furring channels that are attached to the frame. The isolator tape minimizes thermal and acoustic metal-to-metal conduction across the wall frame and the interior furring by creating a separation between adjacent metal surfaces of approximately ⅛″. Interior and exterior finishing materials are fastened directly over the interior and exterior furring. Insulation fills the space between the exterior siding and the interior furring channels. 
         [0012]    Rim track can be attached to the wall frames, spaced below the top of the wall frame, to support floor joists. The rim track is a C-shaped channel with a top and bottom flange projecting outward of the peripheral building frame. The ends of the floor joists are fitted into the rim track between the top and bottom flanges and are attached to the rim track by right-angle brackets that are attached, by screws or welding, to the rim track and to the joist web. The attachment of the floor joists in this way provides in-plane shear transfer and diaphragm continuity in and through the entire wall frame. Metal decking is supported on the joists. Rebar may be inserted through holes in the top tubes of the peripheral wall frame to provide additional tensile coupling between opposite walls of the building. A concrete floor is poured on the metal deck flush with the top of the building frame, thereby allowing the top of the wall frames to be used as a screed when the concrete deck is being poured and leveled, and producing a floor that is flush with the top of the wall frame. The rebar links adjacent concrete floor panels and provides in-plane shear transfer and diaphragm continuity in and through the entire wall frame. 
         [0013]    Some of the wall modules can be rectangular frames made of an upwardly opening bottom channel, a downwardly opening top channel, and large high load capacity upright rectangular structural steel tubing seated into the upwardly opening bottom channel and the downwardly opening top channel, and attached to the channels by welding or screw fasteners. The top channels can each include an inwardly extending flange that functions as a metal deck supporting ledger below the top surface of the channel for supporting a poured concrete floor, such that a concrete floor can be poured onto the metal decking to form a floor for a second or more story of said building. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention and its many attendant objects and advantages will become better understood upon reading the following description of the preferred embodiment in conjunction with the following drawings, wherein: 
           [0015]      FIG. 1  is a perspective view of a corner at one end of a two-story building frame made in accordance with this invention; 
           [0016]      FIG. 2  is a cross sectional elevation view from the inside of the building frame shown in  FIG. 1 ; 
           [0017]      FIG. 3  is a perspective view of a top story building frame wall module for use in buildings made in accordance with this invention; 
           [0018]      FIG. 3A  is an enlarged view of a small portion of the building frame wall module shown in  FIG. 3 ; 
           [0019]      FIG. 4  is an exploded perspective view of a portion of a frame module with an isolator tape between the frame and an interior furring channel; 
           [0020]      FIG. 5  is a sectional view of an isolator bushing and a fastening screw drilling into an interior furring channel fastened to a frame over and through an isolator tape; 
           [0021]      FIG. 6  is a sectional view of isolator bushings fastened to interior and exterior furring channels by screws which also fasten the channels to a frame over an isolator tape; 
           [0022]      FIG. 6A  is an enlarged sectional view of the circled area of  FIG. 6 , shown similar to  FIG. 5 , showing an isolator bushing in an interior furring channel, fastened to a frame over an isolator tape and illustrating the compression of the isolator bushing and its stand-off effect to prevent the crushing of the isolator tape; 
           [0023]      FIG. 7  is a perspective view of an interior furring channel attached to a wall frame module over an isolator tape with a Tec Screw, washer, and an isolator bushing; 
           [0024]      FIG. 8  is an elevation of a wall module supporting a pair of floor or roof joists to which are attached a metal deck on which a concrete floor or roof has beem poured, and also showing rebar extending through a hole in the top of the frame for linking adjacent concrete floor panels and providing in-plane shear transfer and diaphragm continuity in and through the entire frame assembly; 
           [0025]      FIG. 9  is a perspective view of a wall frame module in accordance with this invention showing large rectangular vertical tubes fastened in a bottom channel and a top channel with integral flanges for supporting a metal deck; 
           [0026]      FIGS. 10 and 11  are front and side elevations of a frame module like that shown in  FIG. 9 , but with interior and exterior furring channels attached; 
           [0027]      FIG. 11A  is an enlarged section of the circled portion of  FIG. 11 ; 
           [0028]      FIG. 12  is an elevation of a wall module assembly made with wall modules as shown in  FIGS. 10 and 11 , showing the vertical connection of two vertically adjacent modules; 
           [0029]      FIG. 13  is an elevation of a wall module assembly using a horizontal steel tube rather than a track assembly on the top plane of the module wall assembly; 
           [0030]      FIG. 14  is a perspective view of a wall module assembly, viewed from the inside, using metal decking in lieu of exterior furring for wind, impact and shear resistance; 
           [0031]      FIG. 14A  is a detailed view of the area A in  FIG. 14 ; 
           [0032]      FIG. 14B  is a detailed view of the area B in  FIG. 14 ; and 
           [0033]      FIG. 15  is a perspective view of a wall module assembly like the module shown in  FIG. 14 , but viewed from the outside; 
           [0034]      FIG. 15A  is a detailed view of the area A in  FIG. 15 ; 
           [0035]      FIG. 15B  is a detailed view of the area B in  FIG. 15 ; 
           [0036]      FIG. 16  is an elevation of a wall module, before attachment of the furring channels, showing internal X-bracing attached to reinforcing corner gussets welded into the corners of the wall module; and. 
           [0037]      FIG. 16A  is a sectional side elevation along lines  16 A- 16 A in  FIG. 16 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Turning now to the drawings, wherein like reference numerals designate identical or corresponding parts, and more particularly to  FIGS. 1 and 2  thereof, one corner of a two-story building frame  20  is shown having a peripheral wall (shown only partially), the top edge of which would support a roof truss structure (not shown). The peripheral wall includes two end walls  22  (only one of which is shown in  FIG. 1 ) connected at their ends to ends of two side walls  26  (a portion of only one of which is shown in  FIG. 1 ). 
         [0039]    The end walls  22  and the side walls  26  are assembled from a plurality of wall modules  44 , one type of which is shown in  FIG. 3 , which are fabricated off site and trucked to the building site where they are bolted or welded together as the building frame, shown in  FIG. 1 . The modules  44  can be made quickly and economically in a welding shop from lengths of rectangular, square, or round metal tubing, welded together at precisely 90° corners so that the assembled building frame is perfectly true and square when joined together. All sizes of tubing can be used, with the most common sizes that are commercially available, 2″×2″ square steel tubing or 2″×3″ rectangular steel tubing having wall thickness selected according to the height, geometry, and designed load capacity of the building. Yield strength of about 50 KSI and a tensile strength of about 55 KSI are typical, but seismic, wind, snow and drift forces govern the engineering requirements in all areas. Naturally, other materials could be used, but the materials noted above are most commonly specified because they are widely available from many sources at low cost and in various wall thicknesses and dimensions for different strength requirements in accordance with the building height, design and load carrying requirements. The gauge and dimensions of the steel tubing is selected based on the strength requirements of the building frame and will normally be within the range of 5-18 gauge. 
         [0040]    Wall modules  44  may be made to a standard of exactly eight feet square, although the dimensions can conveniently be varied for different building designs if desired. The modules may be dimensioned to use standard interior wall board, such as that commonly sold in 4′×8′ or 4′×12′ panels, so the interior may be finished without extensive cutting of the wall board. 
         [0041]    It will be noted that the modules  44  are typically not all identical. As shown in  FIGS. 1 and 2 , some modules  44   a  have interior X-bracing  43  to contribute shear stiffness to the assembled peripheral wall. Other modules  44   b  have window openings  39 , and still other modules  44   c  have door openings  41 . The ability to provide the different modules with different architectural features allows great architectural flexibility to the design of the building frame in accordance with this invention. 
         [0042]    The modules are preferably welded together on a welding jig that holds the lengths of tubing at the desired 90° within about 2°, or preferably within about 1° tolerance. Care should be taken to tack weld the entire module before completely welding the junctions to avoid heat distortion of the assembly. GMAW (gas metal arc welding) welding has been found to produce clean welds that do not require de-slagging and also minimize heat input into the junction. If enough welding jigs are not available for the desired production rate, the first module may be made on the welding jig and the other identical modules may be made on top of the first as a pattern. 
         [0043]    The wall module  44  on shown in  FIG. 3  includes upper and bottom girt members  42   u  and  42   b , two upright end members  40  welded to the ends of the girt members  42   u &amp; b  and can include a center longitudinal girt member  45  welded between and spanning the end members  40 . Internal diagonal brace members  43  are attached to the corners of the module  44  to provide diaphragm stiffness to the module. 
         [0044]    As shown in detail in  FIG. 3 , an internal X shear brace is provided, having 45° braces  43  welded to and between opposite corners of the module frame  44 , or to corner gusset plates as shown in  FIG. 16 . The internal placement of the diagonal braces  43 , within the module frame  44 , defined by the two upright end members  40  and the upper and bottom girt members  42   u  and  42   b , ensures that light gauge elements, to be described below, can be attached to the inside and outside faces of the frame module  44  without special cutting or other costly operations. A third upright member  46  may be welded to the upper and lower girt members  42   u  and  42   b  midway between the two upright end members  40  at the intersection of the diagonal braces  43  for additional vertical load bearing capacity if the building design requires the additional strength. 
         [0045]    The X shear module  44  shown in  FIG. 3  may be used in the peripheral wall  20  ( FIG. 1 ) in all modules that do not have a window or door opening, to provide strength and stiffness in the plane of the wall section for resistance against deflection toward a parallelogram shape under wracking loads exerted by wind loads or lateral shaking during an earthquake. Because this invention can be used in buildings as high as ten stories, shear bracing is added for resistance to shear distortion as well as flexural distortion due to bending as a cantilever, so this strengthening minimizes not only threats to the safety of the occupants but also to the serviceability of the building after the windstorm or earthquake. 
         [0046]    Typical door and window wall modules  44   b  and  44   c , shown in  FIGS. 1 and 2 , do not normally include the diagonal shear bracing shown in the wall panel shown in  FIG. 3  because the assembled wall frame with one or more X shear bracing modules  44   a  as shown in  FIGS. 2 and 3  provides the shear stiffness for the entire wall. 
         [0047]    Light gauge elements are welded or screwed to the frame modules  44  for attachment of exterior siding and interior finishing such as wallboard, paneling or the like. The light gauge elements shown in  FIG. 3  include inside furring channels  60 , and exterior furring channels  62 . The inside channels  60  provide light gauge metal supports to which the interior wallboard can be attached by wallboard screws or the like. The interior sheet metal elements are typically about 22 gauge, on the order of 0.034″. The exterior sheet metal elements are typically about 20 gauge, on the order of 0.040″. These gauges provide the desired stiffness and ease of attaching to the tubing of the frame modules with self-drilling, self tapping fasteners while allowing ready penetration by drilling screws during attachment of the interior wallboard and exterior siding. 
         [0048]    To provide for improved thermal and sound insulation between the building frame module and the interior wall board, isolator tape  65  is positioned between the frame modules and the interior furring channels that are attached to the frame, as shown in  FIGS. 3A , and  4 - 7 . The isolator tape  65  minimizes thermal and acoustic metal-to-metal conduction across the wall frame and the interior furring by creating a separation between adjacent metal surfaces of approximately ⅛″-¼″. The isolator tape can be any material that provides thermal and acoustic insulation between the interior furring channels  60  and the frame modules  44 . One material that has worked well is “Econobarrier” supplied by American Micro Industries. Another is Model 4504 supplied by 3M. These are typically 2″×4″ rectangles of isolator tape about ⅜″ thick attached by pressure sensitive adhesive to the module frame, over which the interior furring channels  60  are attached to the module frame. 
         [0049]    For optimal thermal and acoustic insulation, the isolator tape  65  is normally a foamed material. To prevent the isolator tape from being crushed between the module frame and the interior furring channels  60 , which would reduce its insulating properties, an isolator bushing  70 , shown in  FIGS. 4-6A , can be utilized to provide a stand-off of the furring channel  60  from the module frame, and also to insulate the interior furring channels  60  from the screw  72  that holds the furring channels  60  to the module frame. The bushing, shown in  FIGS. 4 and 5 , is a hat-shaped item having a circular top flange  74  and a depending cylinder  76  made of damping thermoplastic material that will deform under load, but has sufficient stiffness to allow the screw  72  to hold the furring channel  60  firmly in place when the screw  72  is screwed into the module frame, as shown in  FIGS. 6 and 6A . 
         [0050]    As shown in  FIG. 5 , the depending cylinder  76  of the isolator bushing  70  fits through a hole  78  in the furring channel  60  and bears against the isolator tape  65 . The screw  72  extends through a central hole  80  in the isolator bushing  70 , and the screw head of the screw  72 , bearing against a washer  82 , compresses the isolator bushing against the module frame and distorts the depending cylinder  76  as shown in  FIG. 6A  to the extent that the furring channel  60  is held firmly at a stand-off position relative to the module frame such that the isolator tape is not compressed to the point that it loses its insulating value, and the furring channel  60  remains firmly held and spaced apart from the module frame by at least about ⅛″. 
         [0051]    The screw  72  is illustrated as a self-drilling, self-tapping screw, but other types of fasteners will also work where the particulars of the materials and labor economics so indicate. It should also be noted that the interior furring channel  60  illustrated in  FIG. 6  is a “skillet” channel rather than a more conventional “hat” channel. That is, it has only one attachment flange rather than the more conventional symmetrical two-flange “hat” shape. The skillet channel is less costly, lighter, easier and faster to install and presents a smaller heat conduction pathway from the module frame to the wall board, but hat channels can be used if off-setting circumstances indicate. 
         [0052]    The lower story wall modules  44  shown in  FIGS. 1 and 2  use the same basic welded tubing design described above in conjunction with  FIG. 3 . When the building is to be built with more than one story, the height of the modules may be increased to accommodate second and higher story floor joists  92 , shown in  FIGS. 1 and 2 , and also in  FIGS. 8 ,  12  and  13 . The floor joists  92  can be in the form of BCI joists, C-channel (as shown) or any other suitable form that is capable of supporting the floor load over the designed span. They are supported at their ends by a series of suitable joist hangers of known design (not shown), or by a rim track  56  that is welded to the wall module  44  as shown in  FIGS. 12 and 13 . The rim track  56  has upper and lower flanges  57 ,  58  projecting outward from a rim track web  55  toward the space spanned by the floor joists  92 , and the ends of the floor joists  92  are supported on the lower flange  58 . In addition, a series of joist attachment brackets  63  are attached to the rim track web  55  by screws or welding, and are attached to the ends of the floor joist web  59  by screws, as shown, or by welding. The hard attachment of the joists  92  between opposite walls of the building frame stiffens the frame against “oil can” diaphragm flexing of the side and end walls of the building frame and provides in-plane shear transfer and diaphragm continuity in and through the entire wall frame. Another floor joist support arrangement is to weld a bracket  90  to the module frame, as shown in  FIG. 8 , and to bolt the floor joists  92  to the bracket  90 . 
         [0053]    If a concrete floor is to be used, a metal deck  94  can be laid on and supported by the joists  92  and attached to the top of the upper flange  57 , as in  FIG. 13 , or to a supporting ledger  95  that is welded to the module frame uprights near the top, as shown in  FIG. 8 . As shown in  FIG. 13 , holes  96  can be drilled in the upper frame member  42   u  of the peripheral wall frame and rebar  98  inserted through the holes  96 . A concrete floor  100  is poured onto the metal decking, and the tops of the upper members  42   u  are used as a screed to level the concrete. The rebar  98  links adjacent concrete floor panels on opposite sides of the upper frame member  42   u  and provides in-plane shear transfer and diaphragm continuity in and through the entire wall frame, such that the concrete floor is flush with the top of the wall frame and provides structural diaphragm linkage for the floor across the entire floor surface of the building. 
         [0054]    Another type of frame module for building frame peripheral walls, and particularly for party and demising walls within and between the peripheral frame  22 ,  26 , can be made with module frames  110  shown in  FIGS. 9-12  in which the vertical members of the frame modules are large diameter square or rectangular tubes  115  set in and attached to top and bottom open channels  117  and  118 . The number of vertical tubes in a frame module is determined by the load carrying and span capacity of the building design. As shown in  FIG. 9 , the number of vertical tubes can be as few as three, leaving large areas unencumbered for window and door openings and the like. A central horizontal tube  120  can be welded between the vertical tubes  115  for support against bowing under load. 
         [0055]    As shown in  FIG. 12 , party and demising walls  22  can be made with wall modules which support an upper story floor directly on top of the modules of the next lower story. In the embodiment shown in  FIG. 12 , the upper story floor is made of a concrete slab  100  poured on a metal deck  94  supported atop joists  92  that are supported at their opposite ends in rim tracks  56  attached to the vertical tubes  115 , and by right angle brackets  63  attached between the rim tracks  56  and the joist  92 , as also shown in  FIG. 13 . 
         [0056]    The top channel  117  can be provided with integral flanges  95  to which a metal deck  94  can be attached, as shown in  FIG. 12 . The metal deck  94  is supported by joists  92  attached to flanges  90  secured to the vertical tubes  115 , similar to the structure shown in  FIG. 8  Although not shown in  FIG. 12 , holes may be drilled horizontally through the top of the vertical tubes  115  and the top channel  117  to receive reinforcing rebar, as in  FIG. 8  for the same purpose. 
         [0057]    As also shown in  FIG. 12 , another advantage of the frame module design shown in  FIG. 9  is the ability to attach the frame modules vertically together and fasten them with high tension fasteners, such as the bolt  130  shown in  FIG. 12  without taking care to prevent crushing the top and bottom abutting tubes  42  u&amp;b of the modules shown in  FIGS. 1-3 . 
         [0058]    A building frame module  140 , shown in  FIGS. 14-15B , uses the same rectangular or square tubes shown in  FIGS. 1-3 . The module  140  has interior furring channels  60  fastened to the top and bottom module tubes  42  u&amp;b, and to a center longitudinal girt member  45 , if there is one. A corrugated steel panel  144  is attached directly to the exterior face of the module, typically by the use of self-drilling, self-tapping screws  146 . The edges of the panel  144  can extend slightly beyond the upright end members  40  so they overlap on adjacent modules in the assembled building frame, and the junction of the steel panels  144  may be caulked to make the wall even more impermeable to wind-driven rain. A vapor barrier and exterior siding can be applied directly to the exterior surface of the panel for whatever finished appearance is desired. 
         [0059]    The steel panel  144  provides ballistic protection against penetration by wind driven objects, which is a serious problem in regions afflicted by the possibility of tornados, hurricanes and other destructive meteorological events. The panel  144  also increases the resistance to wind-driven rain penetration, thereby greatly reducing the chances of mold and mildew damage. The panel  144  provides greatly increased shear strength to the module and to the entire building frame wall, and can eliminate the need for the X-bracing  43  shown in  FIGS. 1-3 , although such X-bracing may be used if the additional shear strength is needed. 
         [0060]    The X-bracing shown in  FIGS. 16 and 16A  uses bracing tubes  150  and  152  that are slit at their ends and slip over gusset plates  155  welded into the corners of the module  160 . The gusset plates strengthen the corners of the module and the slit ends of the tubes can be welded to the gusset plates to provide a large length of weldment and a very strong connection. It is also a much easier weld to make. One of the diagonal tubes  150  extend completely corner-to-corner, and the other diagonal tube is in two parts, with straps  162  welded between the end of the two parts to complete the connection. This structure is very quick and easy to manufacture and provides high shear strength to the panel. It also provides a know failure mode, buckling of the diagonal bracing rather than failure of the module uprights, girt members, or corners, so the building remains serviceable even after failure and the design can be specifies with a high degree of certainty. 
         [0061]    The invention thus enables the low cost construction of a building with capabilities of meeting multiple design requirements without major redesign. In areas where heavy snow loads can be expected, the pitch angle of the trusses can be increased to any desired angle to increase the load bearing strength and the snow shedding capability of the roof. In earthquake prone areas, the diagonal shear panels give redundant load sharing capability. The roofing material may be selected for minimum weight to minimize the inertial forces so the house moves more like a rigid unit rather than a flexible vertical cantilever. This will minimize the damage to the building caused by differential movement of the foundation and the roof so that the building will remain serviceable after the earthquake. The metal frame building is inherently immune to attacks by termites and carpenter ants as well as mold and mildew, and is inherently resistant to fire damage. 
         [0062]    Obviously, numerous modifications and variations of the preferred embodiment described above are possible and will become apparent to those skilled in the art in light of this specification. Many functions and advantages are described for the preferred embodiment, but in some uses of the invention, not all of these functions and advantages would be needed. Therefore, I contemplate the use of the invention using fewer than the complete set of noted functions and advantages. Moreover, several species and embodiments of the invention are disclosed herein, but not all are specifically claimed, although all are covered by generic claims. Nevertheless, it is my intention that each and every one of these species and embodiments, and the equivalents thereof, be encompassed and protected within the scope of the following claims, and no dedication to the public is intended by virtue of the lack of claims specific to any individual species. Accordingly, I expressly intend that all these embodiments, species, modifications and variations, and the equivalents thereof, are to be considered within the spirit and scope of the invention as defined in the following claims, wherein I claim: