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RELATED APPLICATION  
   This application claims priority of U.S. Provisional Patent Application 60/225,337 filed Aug. 15, 2000, and is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The present invention is directed to composite column and beam framing members for use in building construction. More particularly, the present invention is directed to a composite column or beam and a method for its manufacture that has superior insulating and fire/heat resistance characteristics. 
   2. Reference to Related Art 
   It is well known that the steel beams and columns that are used as the structural framework of modem buildings are not fireproof. Indeed, when exposed to heat and fire, steel beams and columns will expand, warp and rapidly lose strength. To protect against this type of extreme structural damage as well as the ongoing effects of weather, modem building codes often require that a coating of protective material be applied to the exterior surface of a building&#39;s steel framework. These protective materials are typically classified as either fire-resistant materials (i.e. mineral wool, fiberglass or the like) or heat sink materials (e.g. gypsum board or cement plasters). However, additional types of thermal or weather insulation may also be thought of as protective materials. Either class of fire-protective material can, for a reasonable period of time (e.g., one to three hours), be designed to delay the heat from a fire from affecting the steel framework. 
   Reinforced concrete framing systems, either pour-in-place or precast/prefabricated systems, do offer some known advantages over steel framing systems in the area of fire protection. However, columns and beams constructed of reinforced concrete have the notable disadvantage of being larger and heavier than steel framing members with the same capacity. Additionally, reinforced concrete systems necessarily require the builder to use concrete forms as part of the construction process. The erection, installation and removal of those forms can add significant cost (in time and labor) to any construction project. 
   Composite beam and column framing members that combine steel and concrete represent a compromise between pure steel or concrete building framing systems and are known in the art. One example is U.S. Pat. No. 4,333,285, which discloses a concrete column encased in a unitary steel tube. The column is adapted to support a reinforced concrete beam that is sheathed in a steel shell. 
   U.S. Pat. No. 4,409,764 discusses the use of steel column and beam forms that include internal metal reinforcing skeletons. The forms are prepared at an off-site factory and subsequently erected at the building site. The steel forms are filled with concrete at the building site and remain in place as a permanent part of the building framework. 
   Finally, U.S. Pat. No. 5,678,375 discusses a building framework that includes a number of structural steel members that each has a hollow interior. The steel members have openings that permit the hollow interiors to be filled with concrete in conjunction with the construction of the building frame. 
   Composite columns and beams are generally stronger than concrete framing members of similar size and are lighter than steel framing members. However, composite framing members still suffer from an increased risk of damage as a result of exposure to heat and flame. Therefore, it would be beneficial to provide improved composite column and beam framing members that have superior insulating, thermal and/or fire resistance characteristics. 
   SUMMARY OF THE INVENTION  
   The present invention is directed to a composite column or beam framing member for use in building construction and a method of manufacturing the column or beam. Preferably, the composite framing member includes a pair of elongated shell members that have a length dimension that is greater than a width dimension. Each shell has one substantially open side that extends along the length of the shell and provides access to an interior channel that is defined by the walls of the shell. The shells are securable to each other along their open sides such that the interior channels of the shells cooperate to define a structural member having an interior volume. 
   Prior to being secured together, reinforcing bars are positioned throughout the interior channel as required by the user. Spacers or risers may also be positioned along the surface of the interior channel in order to maintain the reinforcing bars a predetermined distance from the interior surface of the channel. Additionally, the interior channel of at least one of the shell members may be coated with protective materials (i.e., insulation). The use of a protective material is most preferred when at least a portion of framing members of the present invention are exposed to the exterior of a building. Under such conditions, the use of a protective material on the internal surface(s) of the framing member (particularly those having exposed external surfaces) provides the framing member with an additional defense against condensation, corrosion, fire and heat. 
   Preferably, the composite structural member is erected (in the case of a column) or positioned (in the case of a beam) at the work site and filled with concrete according to the needs or requirements of the user. 
   A preferred method for constructing the composite framing members of the present invention includes a first step of providing a first and a second shell member. Each shell is elongated so as to have a length dimension that is greater than a width dimension and includes one substantially open side extending along the length dimension. The shells are preferably U- or L-shaped such that the walls of each shell define an interior channel. 
   In a second step, at least one spacing bar (e.g., a steel reinforcing rod) is secured along the interior surface of each shell. 
   In a third step, a protective material (i.e., thermal/weather insulation) is applied into the interior channel of at least one of the shells following the insertion of the at least one spacing bar into the interior channel of each shell. 
   In a fourth step, the first and second shells are secured together at least partially along their respective substantially open sides so that the interior channels of the first and second shell members cooperate to define either a hollow column or open beam having an interior volume. 
   In a fifth step, at least one reinforcing member is installed within the interior volume formed by the shells. 
   In a sixth step, the interior volume of the column or beam is filled with a filler material (e.g., concrete). 
   Therefore, the framing members of the present invention include reinforced concrete columns and beams surrounded by steel shells. The shells impart greater structural strength and integrity than the reinforced concrete columns and beams could alone. Furthermore, the concrete core of the framing member, which is aided by the use of a coating of protective material, functions as a heat sink, absorbing heat and allowing the entire framing member a longer structural life than it would have if the steel or concrete were used alone. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     The invention will now be described in more detail with reference being made to the accompanying drawings in which: 
       FIG. 1  is a perspective view of a preferred embodiment of the composite column or beam framing members constructed in accordance with the present invention; 
       FIG. 2  is a planar end view of a shell for use in constructing a column in accordance with the present invention; 
       FIG. 3  is a planar end view of a column according to a preferred embodiment of the present invention; 
       FIG. 4  is a planar end view of a shell for use in constructing a beam in accordance with the present invention; 
       FIG. 5  is a planar end view of a beam according to a preferred embodiment of the present invention; 
       FIG. 6  is a planar end view of a shell for use in constructing a beam in accordance with an alternative embodiment of the present invention; 
       FIG. 7  is a planar end view of a beam according to an alternative embodiment of the present invention; and 
       FIG. 8  is a diagrammatic view of a method for manufacturing a composite framing member in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
   Referring now to  FIG. 1 , there is shown in accordance with the present invention, a composite column and beam framing member system  10  for use in building construction. The framing system  10  includes column  12  and beam  14  framing members. Preferably, the column  12  has a first  16  and a second  18  elongated shell that each have a generally U-shaped appearance. The beam  14  includes a first  20  and a second  22  elongated shell that each have a generally L-shaped appearance. At least one reinforcing member  24  is secured within an interior of each shell  16 ,  18 ,  20 ,  22 . A coating of protective material  26  is also applied on the interior surface of at least one of the shells  16 ,  18 ,  20 ,  22 . The shells  16 ,  18 ,  20 ,  22  are preferably secured together and filled with a filler material  23  to form the column  12  and beam  14  structures of the present invention. 
   Referring now to  FIGS. 1 ,  2  and  3 , there is shown a column  12  constructed in accordance with the present invention. Preferably, the column  12  of the present invention includes a first  16  and a second  18  elongated shell member. Each shell member includes a base portion  30  and a pair of sidewalls  32 ,  34  that combine to provide the shells  16 ,  18  with a generally U-shaped appearance and form an interior channel  36 . Flanges  38  extend inwardly toward the channel  36  from each sidewall  32 ,  34  and, as discussed below, are used in securing the shells  16 ,  18  together. Preferably, the shells are constructed of steel. However, it will be appreciated that other materials such as metal alloys or other known construction materials may also be used. 
   Still referring to  FIGS. 1 ,  2  and  3 , at least one reinforcing member  24  is secured within the interior channels  36  of each shell  16 ,  18 . Preferably, the reinforcing member  24  is a steel reinforcing rod or the like. The reinforcing member  24  is preferably welded onto spacing bars  27  that are welded to the base  30  of each shell  16 ,  18 . Alternatively, the reinforcing members may be secured or positioned upon a spacer  40  that is secured to the base  30  and extends upwardly from the base  30  a predetermined distance. 
   Following installation of the spacing bars  27 , a coating of protective material  26  is applied to the surface  37  of the interior channel  36  of at least one of the shells  16 ,  18 . The use of a protective material is most preferred when at least a portion of framing members of the present invention are exposed to the exterior of a building. Under such conditions, the use of a protective material on the internal surface(s) of the framing member (particularly those having exposed external surfaces) provides the framing member with an additional defense against condensation, corrosion, fire and heat. 
   Preferably, the protective material  26  is a known insulation material, such as weather insulation, a fire-resistant material (e.g., mineral wool or fiberglass), a heat sink material (e.g., gypsum board or cement plasters) or other type of thermal insulation material. Notably, coating the surface  37  of the interior channel  36  of at least one of the shells  16 ,  18  with the protective material  26  during the fabrication of the column  12  removes or limits the need to apply insulation to the column  12  in the field and provides the column  12  with superior insulative or fire/heat resistance characteristics. 
   Still referring to  FIGS. 1 ,  2  and  3 , preferably, the shells  16 ,  18  are secured together along their respective flanges  38  by welding or similar process. Securing of the shells along the open sides of the interior channel  36  provides the column  12  with a generally open, or hollow, interior that defines an interior volume  39 . Following erection of the column  12  at a construction site, at least one reinforcing member  24  may be disposed into the interior volume  39  formed by the shells  16 ,  18 . Finally, the interior volume  39  is filled with a filler material  23  that provides increased structural characteristics to the column. Preferably, the filler material  23  is concrete. However, other types of filler materials  23  may also be used according to the needs of the user. 
   Referring now to  FIGS. 1 ,  4  and  5 , there is shown a beam  14  framing member constructed in accordance with the present invention. Preferably, the beam  14  includes a first  20  and a second shell  22  member. Each shell  20 ,  22  has a generally L-shaped appearance that is defined by a base  50  having a first flange  52  that extends upwardly from the base  50  and a sidewall  54  having a flange  56  that extends inwardly from the sidewall  54 . The base  50  and sidewall  54  of each shell  20 ,  22  form an interior channel  59 . Similar to the column  12  discussed above, at least one spacing bar  27  is secured to the interior surface  60  of the interior channel  59  of each shell  20 ,  22 . Thereafter, a coating of protective material  26  (as discussed above) is applied to the interior surface  60  of at least one of the shells  20 ,  22 . The shells  20 ,  22  of the beam  14  are preferably secured together by welding the flanges  56  of the sidewalls  54  of the shells  20 ,  22 . 
   Welding of the shells  20 ,  22  provides an elongated beam  14  framing member having a generally U-shaped appearance having an open interior defining an interior volume  62  that is accessible though an open side  64 . Following erection of the beam  14  at a construction site, the interior volume  62  of the beam  14  may be disposed with reinforcing members  24  and then filled with a filler material  23  (as discussed above) that provides increased structural characteristics to the beam  14 . 
   Referring now to  FIGS. 6 and 7 , there is shown an alternative embodiment of a beam  14 ′ framing member constructed in accordance with the present invention. Preferably, the beam  14 ′ includes a first  20 ′ and a second shell  22 ′ member. Each shell  20 ′,  22 ′ has a generally L-shaped appearance that is defined by a base  70 ,  71  having a first flange  72  that extends upwardly from the base  70  and a sidewall  74  having a flange  76  that extends inwardly from the sidewall  74 . The base  70  and sidewall  74  of each shell  20 ′,  22 ′ form an interior channel  77 . The base  70  of the first shell  20 ′ is preferably wider than the base  71  of the second shell  22 ′ such that a floor or roof system  110  may be adapted to abut against the first shell  20 ′ while being supported by the beam  14 ′. 
   At least one spacing bar  27  is secured to the surface  79  of the base  70  of each shell  20 ′,  22 ′. Alternatively, spacers  40  are provided along the surface  79  of at least one shell  20 ′,  22 ′ to support the span of the at least one reinforcing member  24  from one shell  20 ′ to the other shell  22 ′. Following insertion of the spacing bars  27 , a coating of protective material  26  (as discussed above) is applied to the interior surface of at least one of the shells  20 ′,  22 ′. The shells  20 ′,  22 ′ of the beam  14 ′ are then preferably secured by welding together the flanges  76  of the sidewalls  74  of the shells  20 ′,  22 ′. 
   Welding of the shells  20 ′,  22 ′ provides an elongated beam  14 ′ framing member having a generally U-shaped appearance having an open interior defining an interior volume  82  that is accessible though an open side  84 . Following erection of the beam  14 ′ at a construction site, the interior volume  82  of the beam  14 ′ may be disposed with reinforcing members  24  and then filled with a filler material  23  (as discussed above) that provides increased structural characteristics to the beam  14 ′. 
   Referring now to  FIG. 8 , there is shown a method  90  for constructing a framing member in accordance with the present invention. Preferably, the method for construction includes a first step  92  of providing a first and a second shell member, each shell being elongated so as to have a length dimension that is greater than a width dimension and including one substantially open side extending along said length dimension. Additionally, the walls of the shells preferably provide the shells with a generally U- or L-shape and define an interior channel in each shell. 
   In a second step  94 , at least one spacing bar  27  (e.g., a steel reinforcing rod) is positioned and secured to the interior surface of at least one of the shell members. 
   In a third step  96 , a protective material is applied into the interior channel of each shell. As discussed above, the protective material  26  is preferably a known insulation material, such as weather insulation material, a fire-resistant material (e.g., mineral wool or fiberglass), a heat sink material (e.g., gypsum board or cement plasters) or other type of thermal insulation material. 
   In a fourth step  98 , the first and second shells are secured together at least partially along their respective substantially open sides so that the interior channels of the first and second shell members cooperate to define a hollow column or open beam having an interior volume. 
   In a fifth step  100 , the interior volume of the column or beam is disposed with at least one reinforcing member  24 . 
   In a final step  102 , the interior volume of the column or beam is filled with a filler material (e.g., concrete). 
   Therefore, by the present invention there is provided composite column and beam frame members for use in building structures that combine the characteristics of steel and reinforced concrete with superior fire-resistant qualities. However, having discussed several embodiments of the present invention, various modifications thereof will be apparent to those skilled in the art and, accordingly, the scope of the present invention should be defined only by the appended claims and equivalents thereof.

Summary:
Composite framing members for use in building construction include reinforced concrete columns and beams surrounded by a pair of steel shells. A layer of protective material is applied to the interior surface of at least one shell prior to assembly of the shell to provide the final integrated framing member with superior insulating or fire resistance and survivability characteristics. Additionally, the steel shells impart greater structural strength and integrity than the reinforced concrete columns and beams could alone. Furthermore, the concrete cores, aided by the protective coating, function as a heat sink, absorbing heat and allowing the entire framing member a longer structural life that it would have if the steel or concrete were used alone.