Patent Abstract:
A floor system for a building that includes primary and secondary structural supports, a grid attached to the supports, and a plurality of panels removably mounted in the grid to provide access to the space below the panels and the grid. The floor system replaces conventional permanent structural floors, and provides ready access to the underlying space, which would otherwise be inaccessible in a conventional floor.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 09/887,772, filed Jun. 21, 2001, now pending, which application is incorporated herein by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to floor structures, and more specifically to a floor assembly having removable access panels supported on a grid that is supported on a plurality of primary and secondary structural supports. 
   2. Description of the Related Art 
   The increase in the use of computers, communication devices, and other electronic hardware has placed new demands on building designers. Users desire a large number of outlets for access to electrical power and communication signals, and they need the ability to change the location of such outlets on a regular, sometimes frequent basis. Power and data outlets have been located in, or under, a floor, typically in removable floor sections elevated above the original floor by supports. Two typical types of elevated floors are the pedestal floor and the low-profile floor. 
   The pedestal access floor has pedestals that consist of metal rods with a base plate at one end and a supporting plate on the other that supports removable horizontal panels, thus forming a raised floor structure. The metal rods are height adjustable and rest on a conventional solid floor deck. The solid floor deck may be made of wood, concrete, or a combination of metal deck and a deck may be made of wood, concrete, or a combination of metal deck and a concrete topping slab. The rods are arranged in a grid, typically square. The rods and plates support removable floor sections. The height of the rods is typically about 12 to 18 inches and can be adjusted to a desired height prior to installing the floor sections. Electrical power and data cables are laid between the solid floor deck and the underside of the floor sections. The cables penetrate the floor sections at a desired location to suit the user&#39;s needs. The penetrations may consist only of openings for cables, or may be junction boxes, similar to common electrical wall outlets. The penetrations may accommodate power wires, or signal cables such as cable television, speaker wire, computer networks, etc. In some designs, the space between the floor deck and the elevated floor sections is configured to enable the distribution of conditioned air through grilles and/or registers located in selected floor sections. A flooring system of the type described above is disclosed in U.S. Pat. No. 3,396,501, issued to D. L. Tate on Aug. 13, 1968. 
   There is a labor premium involved in having to locate and install the foregoing pedestal system. The pedestals must be braced to meet seismic code, further increasing labor and cost. Moreover, the pedestals increase ceiling height requirements, and ultimately the height of the building, which increases the area of the exterior envelope, thereby increasing not only construction costs but also operating costs due to heat loss. If the pedestal access floor is only used in parts of a building, ramps or structural accommodations must be made for the changes in floor elevation. As users re-route electrical cables below the access floor, the pedestals may present an impediment in pulling cables to a new location. The access floor also represents another step in the construction schedule. The acoustical properties of this system are poor. The floor sections are usually relatively thin and rigid and transmit sound both horizontally and vertically. 
   A second type of elevated floor is a low-profile design, which may be roughly 2½ inches to 4 inches high. This design does not use pedestals to raise and support the floor sections, but rather relies on “feet” at the corners of the sections to create the space above the solid floor deck and below the underside of the panel. The panels, with low “feet,” rest directly on the floor deck. This low-profile design is less costly than the pedestal floor, but still impacts the cost of a traditionally designed floor in a building because it requires the use of a solid floor deck. The problem of elevation changes between the existing conventional floor and accessible floor also remains. 
   There are also disadvantages to the low-profile floor compared to the pedestal floor. The space below the low-profile sections is not deep enough to be used to supply air. The resulting floor is not as stable, in either the horizontal or vertical dimension, as the pedestal access floor described above. Since the sections are not fastened to the floor deck, they can move when cable is being pulled and re-routed. It also increases the floor-to-floor height of the building, and thus the construction and operating costs. In general, the smaller distance between the solid floor deck and the surface of the floor sections decreases the flexibility of the low-profile floor. Both types require an underlying solid floor deck for support and to provide structural stability to the exterior building. 
   In addition, the acoustical characteristics of both common types of elevated floors are typically very poor. They tend to transmit noise to a degree that makes them impractical for use in many environments. 
   Another type of accessible floor is disclosed in U.S. Pat. No. 3,583,121, issued to D. L. Tate on Jun. 8, 1971. This system includes two layers of bar joists laid one on top of the other at right angles thereto. Panels laid over the upper layer may be configured to be removable, to provide access to space underneath. One disadvantage of this system is the height of the two layers of joists and the added height this imparts to a building. Additionally, the joists must be laid at least as closely together as the width of the panels. The resulting weight and depth of the system is too great to be practical except where particularly heavy loads are imposed on the floor. Also, the joists have to be welded at each intersection greatly increasing field labor costs. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the invention, a floor assembly for a building is provided, the floor assembly having a plurality of primary structural building members, a plurality of spaced-apart secondary structural building members spanning the primary building members, a support grid on the top surfaces of the secondary building members, and a plurality of panels mounted on the support grid to form the floor, with each of the panels individually removable from the support grid to provide access to the space beneath. 
   According to an alternative embodiment of the invention, a floor assembly is provided that includes a plurality of longitudinal structural supports, a grid assembly, an attachment system attaching the grid assembly to the upper surface of each of the longitudinal structural supports and configured to enable adjustment in the position of the grid assembly relative to the longitudinal structural supports, and a plurality of panels, the bottom portion of the panels configured to be received into openings in the grid, and the top portion configured to bear against a top surface of the grid assembly. 
   According to another embodiment of the invention, a floor system is provided, that includes a prefabricated floor section. The floor section comprises a plurality of support rails positioned a selected distance apart, each having a pair of spaced apart angle members with spacers positioned between the angle members. The support rails are configured to extend between two secondary structural members of a building. The floor section also includes a plurality of cross rails, each spanning between adjacent pairs of support rails, the support rails and cross rails together defining, between adjacent pairs of support rails and adjacent pairs of cross rails, a plurality of apertures, with each aperture configured to receive a removable floor panel. 
   In accordance with another embodiment of the invention, a building is provided that includes a plurality of primary structural building members, a plurality of spaced-apart secondary structural building members spanning the primary building members, a support grid affixed to the top surfaces of the secondary building members and configured to receive panels, an attachment system attaching the support grid to the top surface of each of the secondary structural building members and configured to enable adjustment in the position of the support grid relative to the secondary structural building members, and a plurality of panels received in the support grid to form a floor, each of the panels individually detachable from the support grid to provide access to the space between the secondary structural building members. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       FIG. 1  shows an isometric view of a section of the floor system formed in accordance with one embodiment of the present invention; 
       FIG. 2  shows a detail of a structural support grid element of a floor system formed in accordance with another embodiment of the present invention; 
       FIG. 3  is a cross-sectional view taken along line III-III of a portion of the floor system of  FIG. 1 ; 
       FIG. 4  is a cross-sectional illustration of an alternative embodiment of the floor system of  FIG. 3  taken along line IV-IV; 
       FIG. 5  is a plan view of a floor system according to another embodiment of the invention; 
       FIG. 6  is a plan view of a floor system according to an alternative embodiment of the invention; 
       FIG. 7  is an isometric view of a further embodiment of a floor system of the present invention; 
       FIG. 8  is an isometric view of a floor system illustrating an alternative embodiment of the present invention; 
       FIG. 9  is a partially exploded view of a flooring system according to another embodiment of the invention; 
       FIG. 10  is a more detailed view of the system of the embodiment of  FIG. 9 ; 
       FIG. 11  shows a detailed view of a feature of the embodiment of  FIG. 9 ; 
       FIG. 12  is a cross sectional view of the portion of  FIG. 10  indicated at lines XII-XII; 
       FIG. 13  is a partial cut-away plan view of the system of  FIG. 9 ; 
       FIG. 14  is a cross sectional view of the portion of  FIG. 9  indicated at lines XIV-XIV; and 
       FIG. 15  is a cross sectional view of the portion of  FIG. 9  indicated at lines XV-XV. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The structurally integrated accessible floor system, hereinafter referred to as the floor system, is designated generally as  100 , and is shown isometrically in  FIG. 1 . 
   Primary framing members  102  are provided, which can be formed as integral parts of metal frame type buildings. Secondary framing members, such as joists  104  are connected to the primary framing members  102 . According to one embodiment of the invention, a structural support grid  106  is then formed bearing on the secondary framing members  104 . The grid  106  is configured to receive removable floor panels  108  in the openings  110  formed by the grid  106 . 
   The grid  106  is configured to span across the secondary framing members  104  such that a plurality of floor panels  108  are supported by the grid between each secondary framing member  104 , without the need for support by a secondary framing member for each floor panel  108 . For example, the grid  106  is shown in  FIG. 1  spanning across a distance D between two secondary framing members  104  while supporting the width of three panels  108  in that same distance. This is in contrast to conventional removable flooring systems, in which each removable panel is generally supported by a grid having a leg, post, or pedestal at each corner of each panel. 
   The removable floor panels  108  are of a uniform size to allow interchangeability, and they may be provided with terminals or hookups  112  for electrical power and communication access, and with vents or registers  114  for ventilation. 
   For the sake of convenience and clarity, one type of power terminal  112  is shown in  FIG. 1 . However, it will be obvious to those skilled in the art that a wide variety of terminals may be used, including standard 110 volt sockets, coaxial cable terminals, fiber optical connections, heavy duty power terminals, T2 connectors, etc. A user may further choose to provide an opening in the panel to enable the passage of cable without the use of a terminal. These and other options are considered to be within the scope of the invention. 
   By the same token, a wide variety of means to transmit air and gas may be used in place of the vent  114 , including compressed air hookups, vacuum lines, fans, directionally adjustable vents, filters, emergency gas evacuation systems, compressed oxygen, CO 2 , propane, nitrogen, etc. 
     FIG. 1  also shows optional panels  116  attached to metal channels  118 , which are in turn affixed to the underside of the secondary framing members. These panels  116  are ideally constructed of material that resists fire, thus forming a fire block. The panels  116  isolate one story of a building from the next, establishing fire protection, which may be required by many building codes. The panels  116  attached to the underside of the secondary framing members enclose the space between the secondary framing members. This enclosed space may be employed as a plenum for HVAC. This can result in a financial savings, because ductwork is reduced or eliminated. Partitions may be used within this space to permit discreet sections of the floor system to pressurize for use as a plenum. 
   Referring next to  FIG. 2 , shown therein is a section of one embodiment of the structural support grid  106 . According to this embodiment, the structural support grid comprises L-shaped rail members  202  affixed in back-to-back relationship to T-shaped joint nodes  200  to form supports for the removable floor panels. The nodes and rail members are standardized to permit interchangeability. 
   It is to be understood that the rail members may have many different cross-sectional shapes and node configurations. For example, some alternative cross-sectional shapes include channel, “T”, and square. 
     FIG. 3  shows the floor system  100  in cross-section taken along lines III-III in  FIG. 1 . The removable floor panel  108  has a plurality of layers, including a top layer  300 , which is configured according to the requirements of the particular application and may have a carpeted surface or a tile surface. Alternatively, the top surface  326  may be formed using chemically resistive materials for use in a lab or other caustic environments. The top layer  300  and a bottom layer  306  are designed to provide structural stiffness to the panel  108  and are configured according to the structural and weight bearing requirements of the particular application. Fire retardant layers  304  may also be structural and are composed of fire resistant materials such as gypsum, or other appropriate material, and serve to inhibit the passage of fire from one side of the panel  108  to the other. An insulation layer  302  provides thermal and acoustic insulation, and may be slightly oversized to provide a friction fit in the grid. 
   It will be understood that the composition of the removable floor panels will vary according to the requirements of a particular application and will in part be dictated by the anticipated environment, the required load carrying capacity, the desired appearance, the anticipated degree of noise control, local building and fire codes, and other factors. 
   Although the removable floor panels  108  bear against the structural support grid  106 , panel fasteners  310  may be used to positively attach the panels  108  to the structural support grid  106 . In the embodiment shown in  FIG. 3 , the panel fasteners  310  comprise threaded fasteners that pass from a lower surface of the structural support grid  106  into an opening in a lower surface of the removable panel  108  via an opening  311  in the rail member  202  of the structural support grid  106 . The opening  311  is oversized in relation to the threaded fastener  310  to enable adjustment in the position of the removable panel  108  relative to the structural support grid  106 . The threads of the threaded fastener  310  engage the removable panel and a hexagonal head of the fastener  310  bears against the lower surface  324  of the support grid  106 , drawing the removable panel tight against the structural support grid  106 . Thus, in this embodiment access to the panel fasteners  310  is from beneath the structural support grid  106 . 
   A leveling unit  308  is provided to control a vertical distance  320  between the structural support grid  106  and the secondary framing members  104 .  FIG. 3  shows one of a plurality of similar units that comprise the leveling system, which functions as described below. 
   As shown in  FIG. 3 , the leveling unit  308  includes a threaded rod  312  attached to a support plate  314  that bears against an upper surface  322  of the secondary framing member  104 . The threaded rod  312  passes through a lift plate  316  via an opening in the lift plate  316 , with the lift plate  316  bearing upward against the lower surface  324  of the structural support grid  106 . The rod  312  is slideably received in an opening  307  formed in the grid  106 . A pair of jam nuts  318  on the threaded rod supports the lift plate  316 . The position of the jam nuts  318  on the threaded rod determines the distance  320  between the upper surface  322  of the secondary framing member  104  and the lower surface  324  of the structural support grid  106 . 
   By adjusting each of the plurality of units of the leveling system, the bearing surface  326  of the floor system  100  can be leveled, even if the upper surfaces  322  of the secondary framing members are not level. 
   In another embodiment of the invention, leveling devices that are functionally similar to the leveling unit  308  described above may be employed between an upper surface  120  (shown in  FIG. 1 ) of the primary framing members  102  and the part  105  of the secondary framing members  104  that bears against the primary framing members. By adjusting the vertical distance between the primary and secondary framing members, the level of the structural support grid  106  can be controlled. 
   Other methods of controlling the vertical distance (not shown) between the primary and secondary framing members  102 ,  104 , or between the structural support grid  106  and the secondary framing members  104  will be obvious to those skilled in the art. These methods include the use of wedges, shims, threaded devices that are accessed from above the floor system, automatic or remotely adjustable devices, etc., all of which are deemed to be within the scope of the invention. 
     FIG. 4  is a cross-sectional view of a floor system  100 , taken along line IV-IV, and shows an alternative embodiment of the removable panel  108 . In this embodiment, a flexible gasket  400  is affixed to the top edge  412  of each panel  108 ,  109 . The gaskets  400  of adjoining panels  108 ,  109  press against each other, providing a seal between the removable panels  108 ,  109 . The seal may be employed to prevent spills from leaking through the floor system. In applications where spills of caustic or dangerous fluids might be anticipated, the composition of the gasket  400  is chosen to be resistant to the particular classes of substances in use. Multiple or interlocking gaskets may also be employed to provide a more secure seal. Alternatively, a single gasket may be wedged between the adjoining panels  108 ,  109  after they are installed on the structural support grid  106 . The gasket  400  may also be used in applications where it is desirable to control the movement of air or other gasses from one side of the floor system to the other. 
     FIG. 4  also shows an alternative embodiment of the panel fasteners. Here, the panel fastener  410  is accessed with a tool (not shown) that is inserted from above the surface of the floor system into the center of the joint node  200 . The panel fastener  410  is rotated approximately 45°. Fastener blades  408  rotate from positions in slots (not shown) in the joint node  200  into slots in the corners of the removable panels  406 , locking them in place. 
   Other locking devices and systems will be evident to those skilled in the art and are considered to be within the scope of the invention. Such devices include those employing cam-type fasteners, devices that are accessible from the surface of the removable floor panels, devices that latch automatically when the removable floor panels are emplaced, etc. 
   Depending upon the height and local requirements, some buildings include devices or methods of construction that provide earthquake resistance. In conventional construction methods a solid floor deck functions as a diaphragm, which is resistant to dimensional stresses. 
   According to one embodiment of the invention, and as illustrated in  FIG. 5 , the structural support grid  106  is attached orthogonally, relative to the primary  102  and secondary  104  framing members. Diagonal stays  501  are employed to brace and provide the requisite stability to the structure. The stays  500  are attached directly to the primary columns  502  of a building and pass underneath the floor structure  500 . 
     FIG. 6  shows floor structure  600  according to an alternative embodiment of the invention, in which the structural support grid  106  is oriented diagonally, relative to the primary  102  and secondary  104  framing members. In this embodiment, the structural support grid  106  itself forms the diagonal bracing that reinforces the building structure. 
   In a further embodiment of the invention, and as shown in  FIG. 7 , repositionable walls  702  may be employed as part of the structurally integrated accessible floor system  700 . These repositionable walls may consist of floor to ceiling room dividers, which may be assembled on site, as shown in  FIG. 7 , or prefabricated and installed as individual units, or alternatively they may be prefabricated cubicle dividers of the type common in office environments. The repositionable walls  702  are affixed directly to the structural support grid  104 . Partial floor panels  108   a  may be cut to the necessary size at the site, using conventional methods, or may be manufactured in common dimensions. By affixing the walls  702  to the grid  106  and employing partial floor panels, acoustical isolation is enhanced and the structural stability of the walls  702  is improved. 
   Electrical components in the walls  702 , such as light switches, thermostats, power connections etc, may be wired directly through the bottom of the walls via harnesses (not shown) that can be connected to cables and connectors underneath the floor panels  108 . This is a significant advantage, especially in the case of cubicle dividers, over the methods currently in use, because conventional cubicle dividers must bring power into open areas and may involve complex interconnections between the dividers, and power drops from ceilings. Other methods include the use of wireless technology for switches and controls. Such technology has the advantage that it doesn&#39;t require any wiring connections in the walls. 
     FIG. 8  illustrates an alternative embodiment  800  of the invention in which structural support rails  802  are employed. The rails  802  span the secondary framing members  104  and support the removable floor panels  108  on two sides. The floor panels  108  of this embodiment are configured to span the structural support rails  802 . 
   Another embodiment of the invention is described with reference to  FIGS. 9-15 . A floor system  900  is shown in  FIG. 9  as part of a building structure. The system  900  includes a prefabricated floor section  902  having a first plurality of support rails  904 . Each of the support rails  904  includes a pair of spaced-apart angle members running the full length of the section  902 . Cross-support rails  906  are positioned at regular intervals between the support rails  904 , each adjacent pair of support rails  904  and cross-support rails  906  forming an opening configured to receive a removable floor panel  908  therein. 
   The prefabricated floor section  902  is configured to span secondary framing members  909  of the structure. Connectors  910  are affixed to an upper surface of the secondary framing members  909  in a regularly spaced relationship, corresponding to the spacing of the support rails  904  of the prefabricated section  902 . The connectors  910  may be affixed to the upper surface of the secondary framing member  909  by any appropriate method, including welding, bolting, etc.  FIG. 10  shows each connector  910  as comprising a pair of angle sections in a spaced-apart relationship. It will be understood that the connector  910  may be formed from a single T-shaped member or some other structure that provides the necessary spacing and support for the support rail  904 . The spaced-apart angle members  905  of each support rail  904  engage the connector  910  to provide positive contact between the prefabricated section  902  and the secondary framing member  909 . The support rails  904  may be affixed to the connectors  910  by a known method such as welding or bolting. Alternatively, some of the support rails  904  of the prefabricated section  902  may be affixed to their respective fasteners  910 , while others of the support rails  904  may be allowed to rest directly on the connector  910  without being positively affixed thereto. The connectors  910  may be preaffixed to the secondary framing member  909  prior to erection of the structure. For example, the secondary support member  909  may have the connectors  910  affixed thereto at a fabricating plant prior to shipment to a construction site. 
   Spacers  922  are positioned and affixed between the spaced apart angle members  905  of each of the support rails  904 . The spacers  922  maintain the spaced apart relationship of the angle members  905  in the embodiment shown, the spacer is illustrated as a section of square rod positioned between the angle members  905 .  FIGS. 10-12  show the spacers  922  having threaded holes passing therethrough, and positioned in locations corresponding to the positions of the crossrails  906 . 
   The prefabricated section  902  includes subfloor rails  912  affixed to the underside of the prefabricated section  902  at right angles to the support rails  904 . In the embodiment shown in  FIGS. 9-15 , the subfloor rails  912  comprise spaced-apart angle members  917  similar to those of the support rails  904 , with square spacers  915  affixed between the angle members  917 . The subfloor rails  912  run the entire width of the prefabricated section  902 , and are positioned such, that the subfloor rails  912  of adjoining prefabricated sections  902  meet in an end-to-end configuration. Splice plates  914  affixed between subfloor rails  912  of adjoining sections  902  join the subfloor rails of adjoining sections  902  together. By aligning and joining subfloor rails  912  of adjacent sections  902  together, correct positioning and spacing of adjacent prefabricated sections  902  is assured. Secondary crossrails  916  are positioned in a spaced apart relationship between adjacent sections  902  in positions corresponding to the crossrails  906  of the prefabricated floor sections  902  to provide support for removable floor panels  908  to be placed between adjacent prefabricated panels  902 . 
   Gaskets  924  of resilient or semi-resilient material are positioned between the floor panels  908 . The gaskets  924  may be configured to improve the sound dampening characteristics of the floor system  900 . The gaskets  924  may also be configured to provide a seal between adjacent floor panels  908 , configured to prevent the passage of liquids or gasses therethrough. They may be formed from material that is heat or fire resistant, to provide improved fire protection. In  FIG. 10 , the gasket  924  may be seen to have a modified T-shape in cross-section, with a lower portion sized and configured to fit snugly between the spaced apart angle members  905  of the support rails  904 , and the crossrails  906 . The gaskets further include flanges extending to the sides and configured to receive the upper portions  911  of the floor panels  908  thereon. An upwardly extending portion of the gasket  924  rises between two adjacent floor panels  908  to terminate at a height approximately flush with an upper surface of the floor panels. 
   As disclosed in previous embodiments of the invention, the removable floor panel  908  includes an upper portion  911  having dimensions that are greater than a lower portion  913 , such that, when a floor panel  908  is appropriately positioned between support rails  904  on two sides and crossrails  906  on two sides, the lower portion  913  of the panel  908  lies between the upright portions of the support rails  904  and crossrails  906 , while the upper portion  911  of the panel  908  extends over the support rails  904  and crossrails  906 . Typically, the floor panels  908  are configured to rest on the flanges of the gaskets  924 , with the upper surface of the support and cross rails  904 ,  906  bearing the weight of the panels  908  and any load thereon. Such an arrangement ensures a good seal between the panel  908  and the flange  924 . The lower portion  913  of the panels may comprise insulation and fire retardant material. The lower portion  913  of the floor panels  908  may be sized and configured to have a very snug fit in the space between the rails  904 ,  906  to provide maximum sound and temperature insulation and fire protection. 
   Other embodiments of the invention may include panels configured to bear against lower portions of the support and cross rails, or may even be configured to fit entirely between the support and cross rails, with no part of the panel extending over the rails. 
   As shown in  FIGS. 10 through 12 , the floor panels  908  may be affixed in position by threaded fasteners  918  that engage threads in the opening  930  of the spacer  922  of the support rails  904 . The floor panel  908  includes a fastener recess  919  at each corner thereof. The fastener recess  919  defines a shoulder  928 , against which a head of the threaded fastener  918  bears to maintain the floor panel  908  in position. A fastener  918  is provided at each corner of the floor panel  908 , and each fastener  918  bears against the shoulders  928  of four adjoining removable panels  908 . A fastener recess cap  920  is configured to fit in the fastener recesses  919  of four adjoining floor panels  908 , and to cover the respective fastener  918 . 
   As is most easily visible in  FIGS. 10 ,  14 , and  15 , the floor system  900  includes deck support rails  934 , running generally parallel to the subfloor rails  912 , and the secondary framing member  909 . The deck support rails  934  include threaded spacers  938 , similar to the spacers  922  of the support rails  904 . Threaded rods  926  engage the threaded spacers  915  of the subfloor rails  912  at a first end and the threaded spacers  938  of the deck support rails  934  at a second end, supporting the deck support rails  934  a selected distance beneath the section  902 . Corrugated decking  932 , of a type commonly used in commercial construction to support concrete flooring, may be placed between deck support rails  934 . The corrugated decking  932  provides a barrier between floors, and it may be used as part of a plenum enclosure for HVAC. 
   Lighting fixtures, fire control sprinklers, and other utilities for the space beneath the floor system  900  of  FIGS. 9-15 , such as a lower floor of the structure, may be affixed to the corrugated decking  932  or to the deck support rails  934 . Fire resistant paneling such as gypsum board may also be affixed to the underside of the corrugated decking  936 , or to the deck support rails  934 . 
   In manufacturing and assembling the floor system  900 , much of the system may be prefabricated and assembled prior to assembly in a structure. For example, the floor section  902  shown in  FIG. 9  is an 8′×8′ prefabricated section, having 2′×2′ floor panels  908  installed therein. The prefabricated floor section  902  may include temporary removable panels  908 , which can be left in place until completion of construction at which time the temporary panels  908  are replaced with finished panels. Use of temporary floor panels  908  prevents damage to the finished panels during construction, and allows construction workers, painters, and finishers to work in floored spaces without the requirement of providing protection for finished flooring. When the temporary panels are removed, they may be reused in subsequent projects, thus providing additional savings to the manufacturer. 
   In assembling such a floor system, the secondary framing members  909  are provided with the connectors  910  pre-attached. Each section is lifted into place by a hoist or crane, and lowered onto the connectors  910 . Because of the configuration of the connectors  910  and the support rails  904 , the floor section  902  is provided with positive positioning in the X-axis. As may be seen in  FIG. 9 , each connector  910  provides positioning for a support rail  904  from each of two adjoining panels  902  in an end-to-end configuration. By drawing the support rails  904  of a section  902  tightly against the ends of the support rails  904  of a previously installed section  902 , positive positioning in the Y-axis may be assured. After the section  902  is correctly positioned in the X- and Y-axes, the section is leveled through the use of shims or jacks, to bring the section into correct position in the Z-axis. When the section is correctly positioned in the Z-axis, the support rails  904  of the section  902  are affixed to the connectors  910 , to lock them permanently in position. This may be achieved by any of several known methods, including welding in place, the use of bolts passing through the support rails  904  and the connectors  910 , or any other acceptable method of attachment. Next, splice plates  914  are affixed in position between subfloor rails  912  of adjoining sections  902 , secondary crossrails  916  are then positioned and affixed to adjoining sections  902 , and removable floor panels  908  are placed in the spaces created thereby, between adjoining sections  902 . Threaded fasteners  918  and fastener recess caps  920  are installed as necessary to secure the removable floor panels  908 . From underneath the floor panels  902 , threaded rods  926  are affixed to the threaded spacers  915  of the subfloor rails  912 , and to the threaded spacers  938  of the deck support rails  934 . Corrugated decking  932  is then laid between the deck support rails  934  to enclose a space under the floor system  900 . 
   The total height H of the floor system  900  (see  FIG. 14 ) above the surface of the secondary framing members is selected to be approximately equal to the height or thickness of a conventional steel and concrete floor of the type commonly used in hi-rise construction. In some cases a structure may include a combination of conventional flooring with the structurally-integrated flooring according to the principles of the invention. Because the heights are substantially equal, there is no requirement for ramps or height adjustment at transitions from one flooring to the other. 
   It will be understood that, while the embodiment of the invention described with reference to  FIGS. 9-15  is shown having particular selected dimensions, the dimensions of the sections  902 , the spacing of the rails  904 ,  906 ,  912 ,  916 , and  934 , the dimensions of the panels  908 , and other dimensions and parameters of the system are selectable according to the requirements of a given application, or preferences of the user. 
   In a conventional building, an elevated floor system of the type described in the background section of this document is installed on top of an existing floor. The elevated floor occupies a space above the floor, and is not part of the building structure. The accessible space provided by such an elevated floor is that space between the panels that form the surface of the elevated floor and the upper surface of the solid floor deck. In the structurally integrated accessible floor system of the embodiments of the invention described herein the solid floor deck is not needed. The removable panels provide access to the space beneath the grid and between the individual secondary framing members. In prior floor structures, this space is inaccessible and wasted. Because the structural support grid of the present invention spans the secondary framing members, the space beneath is unobstructed, providing simplified access for pulling cables, laying conduit, ducting, and pipe. The cost of the floor system disclosed herein is significantly mitigated by several factors. A conventional structural floor is not required, and the floor system is essentially the same height as a conventional structural floor, obviating the need for ramps in areas where conventional floors adjoin the floor system. Because the floor system does not add height per story to the final building structure, there will be a savings in building materials, and a savings in operating costs over those of a similar building using accessible floors according to the prior art. Also, because the space under the floor system is unencumbered by pedestals, feet, or other support devices, the floor system has improved flexibility and changeability. Pulling cable, laying conduit and pipe, and installing ducting are all simplified. The labor costs and down time costs are reduced during changeovers. This floor system would also allow the incorporation of, and relocation of, egress lighting in the floor system, as a part of the gasket systems, or the vertices of the panels, for example. The gaskets may also be configured to allow the passage of gas by incorporating perforations in the gaskets. 
   An additional cost savings over conventional construction methods is realized by the reduction in structural weight provided by the implementation of an embodiment of the invention. Flooring manufactured according to the principles of the invention has a per square foot weight of less than half that of conventional high-rise flooring. Such a weight savings can exceed 20 to 30 pounds per square foot, without reducing the weight bearing capacity of the floor. This savings translates to a reduction in the costs of bringing construction materials to a construction site, the costs of assembling a structure, the mass and cost of materials required to support a structure, and finally, affords the architect structural options that were heretofore unavailable due to the weight of the structure. 
   Advantages of the use of a sub floor space as a plenum for HVAC have been known previously. However, because of the inaccessibility of that space in conventionally constructed buildings, or the cost of conventional removable flooring systems, the associated effort and expense of employing sub floor spaces as plenums have outweighed the benefits, in most cases. With the implementation of the principles of the invention, the costs are much reduced. Sub floor spaces may be easily partitioned such that large areas of a floor may have pressurized, conditioned air, to be accessed as desired. Accordingly, ventilation may be inexpensively modified to suit varying needs and preferences, simply by exchanging floor panels with panels having the desired configuration. By the same token, return plenums having negative pressure may also be configured inexpensively. The need for expensive air ducting and channeling may be significantly reduced. All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. 
   From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Technology Classification (CPC): 4