Patent Publication Number: US-6341456-B1

Title: Long-span in-situ concrete structures and method for constructing the same

Description:
TECHNICAL FIELD 
     The invention herein resides generally in the art of concrete building structures. More particularly, the present invention relates to spans across long distances, utilizing in-situ forms. Specifically, the present invention relates to a structure that facilitates stressing of concrete spans. This is accomplished by installing cables into a form and then placing them under tension against cast-in-place concrete or an external form support. Next, the concrete is poured into the form around the cables. Once the concrete has set, the tension in the cable is released for transfer into the span. 
     BACKGROUND ART 
     There are two commonly-used methods for forming long-span concrete structures such as bridges, parking decks, building floors, structures within stadiums, and the like. These structures may be made by either using pre-cast pieces which are manufactured offsite, and then transported to the construction site and assembled. Alternatively, these structures can be manufactured by building the forms on site, pouring concrete into the forms and then removing the forms. 
     The pre-cast method utilizes standard or special forms which receive concrete or other structural building-type material. After an appropriate curing time, the form is opened and the piece is removed. Reinforcing members may be included in the form if desired. Utilizing such forms allows the manufacturer to efficiently build a large number of building components to a particular specification depending upon end-use. Although this method is effective, there are high costs involved in shipping and erecting the pre-cast pieces. Additionally, the cost of craning the large weight of pre-cast pieces into place adds significant extra cost to high-rise structures. 
     The other common method for forming long-span concrete structures is where the forms are assembled on site with the desired reinforcing structure. In some instances, significant site preparations are required. Next, the concrete is poured into the form, and after it has set, the forms are removed. This method is also costly inasmuch as the site must be properly prepared to accommodate the form and supporting structure and then the supporting structure must be torn down, cleaned and removed or reinstalled after completion of the concrete pour and setting thereof. Forming the concrete members in place is quite expensive for highly-engineered structures such as bridges, stadiums, and high-rise structures. 
     Although these known methods are effective in providing high-quality building structures, it is submitted that their cost is excessive and somewhat time-consuming in preparation. Moreover, the concrete is ultimately exposed to the elements which contributes to the deterioration of the entire structure. Current construction methods do not adequately provide a reliable and easy low-cost way to build long-span concrete structures. Nor do current methods provide protection to the concrete material after it has set. 
     DISCLOSURE OF INVENTION 
     In light of the foregoing, it is a first aspect of the present invention to provide a long-span in-situ concrete structure and method for constructing the same. 
     It is another aspect of the present invention to provide a long-span concrete structure extending between supporting structures such as beams, walls, piers, and the like. 
     It is a further aspect of the present invention to provide for the in-situ forming of long-span structures, as set forth above, which are assembled on site, are cost effective to assemble, and provides significant protection from natural elements upon completion of the construction. 
     It is yet another aspect of the present invention to provide a long-span concrete structure, as set forth above, in which a form support extends between and is coupled to the supporting structures. 
     It is still another aspect of the present invention to provide a long-span structure, as set forth above, which utilizes a form hanger that is frictionally assembled to the form support along the length thereof between the supporting structures. 
     It is still a further aspect of the present invention to provide a long-span structure, as set forth above, to suspend a beam form from the form hangers along the entire length of the form support between the supporting structures. 
     It is an additional aspect of the present invention to provide a long-span structure, as set forth above, to employ a form support positioned between the form support and the bottom of the beam form to maintain medial spacing between the form support and the beam form. 
     It is still yet another aspect of the present invention to provide a long-span structure, as set forth above, in which a deck form is assembled onto the top of the beam forms and supported thereby so as to receive concrete material within the beam form and on the deck so as to form the span between the supporting structures. 
     It is yet another aspect of the present invention to provide a long-span structure, as set forth above, wherein a deformed cable conduit is carried by the beam form and is capable of carrying a cable. The cable conduit precludes entry of the concrete material into the conduit during the assembly of the long-span structure. The conduit may be a single, double, or a plurality of tubes so as to allow for receipt of a cable in each one. 
     It is yet a further aspect of the present invention to provide a long-span structure, as set forth above, wherein the cable received within the conduit is tensioned or pre-stressed a predetermined amount against the previously poured and set concrete and whereupon concrete material is filled into the conduit. After setting of the concrete within the conduit, the tension applied to the cables is released so as to transfer the pre-stress from the cable to the initially poured concrete. 
     It is still yet a further aspect of the present invention, as set forth above, to provide mating hooks on the form hangers and the beam forms to assist in their assembly and wherein the beam forms are made of a plastic or polymeric material which protects the concrete after it has taken a set. 
     In a variation of the present invention, it is another aspect to provide the beam forms with side supports between the supporting structures. 
     It is another aspect of the present invention, as above, to configure the side supports such that they are braced to each other to maintain proper spacing therebetween and assist in carrying the beam forms. 
     It is still another aspect of the present invention, as above, to provide a tension plate at each end of the beam form to assist in tensioning cables placed in the beam form against the side supports, prior to receipt of concrete therein. 
     It is yet another aspect of the present invention, as above, to position the form support horizontally in the beam form and provide pegs vertically extending from the form. After the setting of the concrete within the form, the tension applied to the cables is released so as to transfer the stress from the cables to the span. 
     The foregoing and other aspects of the present invention, which shall become apparent as the detailed description proceeds, are achieved by a long-span concrete structure extending between supporting structures, comprising at least one form support extending between the support structures, and at least one beam form carried by the support structures and partially enclosing the corresponding form support, wherein concrete is receivable in said beam form to form the long-span concrete structure. 
     The present invention also provides a long-span structure formed in-situ and extending between supporting structures, comprising at least one form support extending between the supporting structures, wherein each end of said form support includes a bearing plate coupled to the adjacent supporting structure, a plurality of form hangers frictionally engaging said form supports, each said form hanger having upwardly extending hooks, and a beam form carried by said plurality of form hangers and extending the length of each said form support, each said beam form having opposed side walls connected by a bottom to form a cavity, each sidewall having a downwardly extending hook mating with said upwardly extending hooks, wherein concrete is receivable at least in said beam form cavity to form the long-span structure. 
     The present invention further provides a method for constructing a long-span structure, comprising the steps of providing at least two supporting structures spaced a distance apart from each other, spanning said distance with at least one form support, supporting at least one beam form for each said form support and extending the entire length thereof, each said beam form having a cavity, and pouring concrete into said cavity to form the long-span structure across the distance. 
     These and other aspects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein: 
     FIG. 1 is an elevational view, in cross-section, of a long-span concrete structure; 
     FIG. 2 is an elevational view, in cross-section, of an alternative long-span concrete structure; 
     FIG. 3A is an elevational view of a beam form with a double-conduit; 
     FIG. 3B is an elevational view of a beam form with a triple-conduit; 
     FIG. 4 is a perspective view of a single supporting structure and form supports coupled thereto; 
     FIG. 5 is an elevational view of a form hanger according to the present invention; 
     FIG. 6 is an elevational view of a form spacer according to the present invention; 
     FIG. 7 is an elevational view of a beam form according to the present invention; 
     FIG. 8 is a side elevational view of a conduit disposable between the form spacer and the beam form; 
     FIG. 9 is an end view of the cable conduit; 
     FIG. 10 is an elevational view of a deck form according to the present invention; 
     FIG. 11 is a side view of the deck member according to the present invention; 
     FIG. 12 is a perspective view, partially fragmented, of an assembled long-span structure prior to receipt of concrete; 
     FIG. 13 is a cross-sectional view of a cable within a cable conduit; 
     FIG. 14 is a perspective view of a beam form with associated supporting structure; 
     FIG. 15 is a perspective view of a beam form with its supporting structure removed; and 
     FIG. 16 is a perspective view of a deck form installed upon the beam form. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring now to the drawings and more particularly to FIG. 1, it can be seen that a long-span concrete structure employed in the construction of bridges, building floors, and the like, is designated generally by the numeral  20 . Generally, the structure  20  includes a vertically-oriented form support  22  extending from or coupled to an existing or site-formed foundation or other support. The form support  22  could be a light-weight steel structure or a uniquely designed bar joist employing deformed bars. The form support  22  is of adequate structural strength to support itself and any concrete received therein. A form hanger  24  is snapped or pressed onto the form support  22  and is preferably of a plastic construction. A beam form  26  is suspended or carried by the form hanger  24  and in the preferred embodiment, is of a light-weight plastic construction. The beam forms may be made by either a pultrusion or extrusion process. The beam form  26  may be provided in sections and connected end-to-end so as to enclose the entire length of the form support  22 . Each beam form  26  provides a pair of opposed side walls  28  connected at respective ends by a bottom  30 . The side walls  28  and the bottom  30  form a beam cavity  32 . As best seen in FIG. 1, a form spacer  34  may be positioned between the bottom surface of the form support  22  and the bottom  30  so as to maintain the form support in a medial position between the side walls  28 . A deck  36  may be assembled onto the beam forms  26  while leaving the cavity  32  open so as to receive a structural material such as concrete  38  therein and upon the deck  36 . Upon curing of the concrete  38 , the long-span concrete structure is essentially complete. It will be appreciated that FIG. 1 shows only a single form support and beam form. Those skilled in the art will appreciate that multiple and substantially parallel form supports and beam forms may be employed depending upon the loads to be encountered by the long-span structure  20 . Moreover, the deck  36  is an optional component of the complete long-span structure. 
     A similar long-span concrete structure can also be seen in FIG.  2  and is designated generally by the numeral  40 . The only significant difference between the structure  40  shown in FIG.  2  and the structure  20  shown in FIG. 1 is the inclusion of a deformed cable conduit  42  employed in place of the form spacer  34 . The cable conduit  42  provides an opening for receiving a cable  44  which may be employed as a tensioning device to increase the strength of the long-span concrete structure. Particular details of tensioning the entire structure through the use of the cable conduit  42  and the cable  44  is discussed in further detail below. 
     Where additional strength is required to be imparted to the long-span concrete structure, variations of the beam form  26  may be employed. These variations are best seen in FIGS. 3A and 3B, which show an alternative beam form designated generally by the numeral  50 . The form  50  includes opposed side walls  52  from which extend shoulders  54 . The shoulders  54  provide a sloping angle so as to allow rain and snow to be deflected off the beam form  50 . More importantly, the indentations formed by the shoulders  54  remove unneeded weight from the finished span. Sloping of the shoulder minimizes the potential for cracks at the corners. Extending further and down from the shoulders  54  are arm sides  56  which are connected to one another by a bottom  58 . As seen in FIG. 3A, a double conduit construction is designated generally by the numeral  60 . The conduit  60  includes a pair of side-by-side tubes  62  which are interconnected by a web member  64 . Both of the tubes  62  receive a cable  66  which may be tensioned by the method to be discussed below. FIG. 3B presents another alternative construction wherein three individual conduits are disposed or carried by the bottom of the beam form  50 . The three conduits may be solitary conduit members  68  or may be side-by-side conduits constructed with interconnecting web members as shown in FIG.  3 A. It will be appreciated by those skilled in the art that any number of conduits may be included within the beam form and that they may be incorporated into various positions as required by the loads anticipated to be applied to the structure. 
     Referring now to FIGS. 4-12, the assembly of a long-span concrete structure is described in detail. In particular, a pier or other similar supporting structure is designated generally by the numeral  70 . As seen in FIG. 4, only one supporting structure  70  is shown, but it will be appreciated by those skilled in the art that a similar supporting structure supports the opposite end of the form supports  22 . Each supporting structure  70  includes at least a top surface  72  and end walls  74 . 
     A form support  22  is positioned or coupled to the structure  70 . The form support  22  is either carried or attached during formation or after completion of the structure. It will be appreciated by those skilled in the art that the structure  70  may be a pre-existing structure or that it may be formed in conjunction with use of the long-span concrete structure disclosed herein. The form support  22  may be in the form of a bar joist, I-beam, T-beam, or any other similar supporting steel structure. In the present instance, a bar joist is shown which has a compression bar  76  with a structural bar  78  extending to a deform bar  80 . As is known by those skilled in the art, the compression bar  76  provides compression reinforcement in the completed concrete member and is shaped to receive the form hanger  24 . Other usual structural shapes for the compression bar  76  include, but are not limited to, a channel, an angle, or I-beam construction. The structural bar  78  serves as a web member to support and provide horizontal sheer reinforcement in the finished concrete structure. The deform bar  80  serves as a tensile member in the form support  22  and also as tensile reinforcement in the completed concrete structure. Further, the form support  22  may be provided with a camber or slight arc between the supporting structures. The form support  22  may include a bearing plate  82  which extends from the compression bar  76  at each end so as to be carried by the supporting structure  70  in a manner well known in the art. 
     As best seen in FIGS. 4 and 5, the form hangers  24  are strategically placed along the length of the compression bar  76 . The form hangers are preferably made of a light-weight plastic material similar to that used for the beam form  26 . The form hanger  24  includes a plate  86  with downwardly extending ends  88 . A hook  90  extends upwardly from each end  88  and wherein the hook  90  is reinforced by support members  92  extending between the hook and the plate  86 . The support members  92  form channels  94  which conform to the shape of the compression bar  76 . As such, the form hangers are easily connected to the form support  22 . 
     As seen in FIG. 6, the form spacer  34 , which is positioned between form support  22  and the beam form  26 , includes a body  98  extending from a base  100 . Extending in a direction opposite the body  98 , the base  100  provides a series of tabs  102 . 
     Referring now to FIG. 7, it can be seen that the opposed walls  28  provide interior wall surfaces  104  that are connected to one another by an interior bottom  106 . A hook  108  extends downwardly from each of the interior wall surfaces  104  and mates with the downwardly extending hooks  90  provided by the form hanger  24 . It will be appreciated that the beam form is somewhat flexible at its bottom  30  so as to allow the hooks  108  to engage the hooks  90 . To ensure medial spacing of the deck form with respect to the form support, the bottom  30  provides upwardly extending nubs  112  which engage the tabs  102  provided by the form spacer  34 . 
     Referring now to FIGS. 8,  9 , and  12 , it can be seen that the conduit  42  may be employed in place of the spacer  34 . The conduit  42  is enclosed along its entire length and provided with a deformed structure. In particular, the conduit  42  has a ribbed wall  120  which has an outer rib  122  alternating with an inner rib  124 . The rib wall  120  forms a void  126  for receiving the cable  44 . The deformed structure of the conduit  42  may be provided in other manners such as a serpentine channel configuration, with horizontal and vertical ribs, or any other such protuberances for engaging the concrete poured into the cavity  32 . It will be appreciated that the conduit is enclosed so as to preclude entry of the concrete poured into the cavity  32  into the void  126 . Extending downwardly from the conduit  42  is a flange  128  which fits within the nubs  112 . In the preferred embodiment, the conduit  42  is placed along the bottom surface of the beam form  26  to maximize the strength of the finished span. 
     Referring now to FIGS. 10 and 11, it can be seen that the deck form  36  is a substantially corrugated member  132 . The corrugations provide added strength to the deck and ultimately to the long-span structure. The deck  36  may be provided with a chamfer end  134  and a notch  136  extending along an edge thereof. The notch  136  is sized to fit onto the side wall  28  so that the deck form  36  is held in place during assembly and pouring of the concrete. 
     Once the major components are assembled to one another, as best seen in FIG. 12, the concrete  38  is poured into the cavity  32  to fill the beam form  26  and then over the deck form  36 . Once the concrete  30  has set, the structure is ready for use. 
     In order to strengthen the structural integrity of the span and ensure maximum performance, a pre-stress may be applied to the entire structure. This is accomplished by first directing the tension cable  44  through the cable conduit  42 . The cable  44  is typically provided as rebar or other deformed structure which allows for bonding to concrete material. After the rebar or cable  44  is directed through the conduit  42 , one end of the cable is secured or held at one supporting structure  70  and the other end of the cable is pulled or tensioned by a tensioning device. As best seen in FIG. 13, an access hole  140  is provided through the supporting structure  70 . A tension device  142  then pulls on the cable and imparts a tension or pre-stress. Concrete with the desired structural properties is then pumped into the hole  140  through the structure  70  and into the cable conduit  42  so that it is completely filled. The solidified concrete engages both the cable  44  and the inner and outer ribs  122  and  124 . In other words, there is a mechanical engagement between the concrete and cable deformations and between the concrete and the inner and outer ribs. After the concrete has set within the cable conduit  42 , the tensioning device  142  releases the stress applied to the cable  44  and the tension is then transferred to the beam form  26 , the deck form  36  and the attached concrete material. 
     It is apparent then from the above description of the structural components and method of assembling the components, that the long-span concrete structure disclosed herein provides numerous benefits. Primarily the concrete structures allow for on-site construction of a long-span at a low-cost. By employing hanging forms to form the beams of the structure, shipping of heavy pre-cast beams is eliminated. Moreover, this method eliminates the need for preparing a site and the need to build a supporting structure on the site. Yet another advantage of the present invention is the formation of a void in the initial construction or assembly of the span and wherein this void is later employed to impart a pre-stress to the entire structure and thereby, strengthen the complete assembly. Accordingly, a low-cost long-span concrete structure is easily manufactured using the components and techniques of this structure. 
     Referring now to FIGS. 14-16, it can be seen that a variation of a long-span structure is designated generally by the numeral  200 . Assembly of the structure  200  requires the use of a wall, beam, or pier  202  at both ends of the structure, although only one is shown in FIG.  14 . It will be appreciated that the opposite end of the structure  200  is supported by a pier or other similar supporting structure at an appropriate height. A pair of I-beams  204  are supported by the pier  202  and function as side supports in a manner to be described below. The I-beams or other similar supporting structure function to support the weight of the forms and concrete and as axial members against which cables or the like are tensioned. Ideally, the supporting structure is strong in both bending and axial compression. A brace  206  is bolted to the underside of each I-beam  204  to support a later-installed form and to maintain position and spacing between the I-beams and to prevent lateral movement thereof during formation of the structure  200 . 
     A beam form, designated generally by the numeral  210 , is carried and supported by the I-beams  204  and brace  206 . Of course, more than one beam form  210 , each positioned end-to-end, may extend between the piers  202 . Although the beam form  210  is carried by the I-beams  204 , it will be appreciated that other structural shapes may be employed to support the beam form  210 . For example, a T-shaped beam, a rectangular flat plate, or a bar joist may be employed to support each side of the beam form  210 . Each beam form  210  has a pair of opposed sides  212  connected by a bottom  214 . The sides  212  and the bottom  214  form a cavity  216  which later receives concrete or other material. Each side  212  provides a top edge  218  that includes an inner side ledge  220  which extends inwardly toward the other side. Each side ledge  220  provides a ledge rim  222  which extends upwardly and is substantially parallel with the top edge  218 . 
     In the assembly of the structure  200 , at least one deformed cable  228 , such as reinforcing bar or “rebar,” runs over the entire length of the form  210  and rests on the bottom  214 . Of course, more than one cable  228  may be disposed within the beam form  210 . Next, a form support  230  is positioned in the beam form  210 . In particular, the form support  230  is horizontally oriented within the form  210  such that its edges are carried by the side ledge  220  and the ledge rim  222 . Positioning of the form support  230  in this manner maintains the spacing of the top portion of the structure  200  so that it does not deform or collapse during receipt of the concrete material. Prior to receipt of the concrete material, a tension plate  232  is positioned at each end of the structure  200 . The tension plate  232  is provided with a hole  234  corresponding to the number of cables  228  disposed within the form  210 . Also at this time, vertically oriented reinforcing bar pegs  236  may be installed within the beam form  210  at various locations along the length of the structure  200 . At this time and in a manner consistent with the method discussed above, the cables  228  are tensioned or tightened by pulling them outwardly and utilizing the tension plate  232  and the I-beams  204  as a stationary force. At this time, a cover  231  is placed upon the remaining open end portion of the beam form  210  that is not covered by the tension plate  232 . Concrete  238  is then poured into the beam form  210  so as to cover the cables  228  and the form support  230 . 
     After the concrete has set, the cover plate  231  and the tension plate  232  is removed and the stress within the cables  228  is imparted to the entire structure  200 . At this time, the I-beams  204  and brace  206  are removed from the completed beam form  210 . 
     Referring now to FIG. 16, it can be seen that a deck form, generally designated by the numeral  240 , is installed on the formed beam. Although only one formed beam is shown, it will be appreciated by those skilled in the art that any number of beams may be spanning the piers  202  as needed by the end use. The deck form  240  includes a plurality of channels  242  in a generally corrugated-type shape. The deck form  240  is also provided with a plurality of openings approximately every other channel and wherein the openings  246  are positioned over the top surface of the formed beam. As can be seen, the pegs  236  extend through the openings  246  and into the channels  242 . At this time, additional concrete material  238  is disposed onto the deck form  240  to surround and cover the pegs and proceed into the openings  246  and allowed to set. Alternatively, the deck form  240  could be provided to engage just the top edge of the forms. This would allow placement of the forms  240  before placement of the concrete. As such, the concrete could be poured all at once with or without the pegs  236 . 
     The structure  200  presented in FIGS. 14-16 has many of the same advantages as the long-span structures presented in the other figures. One additional benefit of the present structure is that it does not require the use of an additional conduit and can be completed without the need for additional pours of concrete. It will also be appreciated that the I-beams used to support the side of the formed beam may be employed as compression members during the tensioning of the cables  228 . 
     Thus, it can be seen that the objects of the invention have been satisfied by the structure and its method for use presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of true scope and breadth of the invention, reference should be made to the following claims.