Patent Publication Number: US-2013227897-A1

Title: Truss-Based Monopole Support Structure

Description:
CROSS-REFERENCE RELATED TO APPLICATION 
     This application claims priority under 35 U.S.C. §119, based on U.S. Provisional Patent Application No. 61/605,534, filed Mar. 1, 2012, the disclosure of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of monopole structures, and more particularly to support systems associated with such structures. 
     Monopole structures may be employed for housing or supporting elements such as antennae and other communications equipment, signage, high voltage transmission wires, or lighting in an elevated position. Such structures often include a long, hollow pole structure connected to an underlying surface such as a concrete pad formed in the ground. Such monopole structures are typically subjected to wind or other types of forces along their length, which may cause the structure to bend or sway. These forces create a moment about the base termination, which in turn stresses the base termination location and can lead to fatigue and eventual failure of the base termination material. 
     Conventional monopole structures are often rigidly connected to the ground via direct embedment, or via concrete base plates, via concrete encased anchor bolts, or via drilled, concrete filled caissons. Unfortunately, each of these support structures can be expensive and can raise environment concerns. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a isometric view of a portion of a monopole support structure consistent with embodiment described herein; 
         FIG. 1B  is an expanded isometric view of the monopole and support structure of  FIG. 1 ; 
         FIG. 2  is a side view of an exemplary truss element of  FIG. 1A ; 
         FIG. 3  is a top view of the monopole and support structure of  FIG. 1B ; and 
         FIG. 4  is an isometric view of an exemplary helical pier usable with the support structure of  FIGS. 1A-3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
     Consistent with implementations described herein, a number of truss-based support structures may be used to structurally connect a tubular monopole to a number of helical piers embedded within an environment surface. As described below, each truss-based support structure may be coupled to the monopole via pin or bolt-based assemblies, thereby allowing the support assembly to adapt to variations in installation parameters, such as angle of inclination of the embedded piers. In contrast to existing monopole support systems using concrete base plates, concrete encased anchor bolts, or via drilled, concrete filled caissons, the described system may be employed in environments that are not conducive to the use of concrete or that are not conducive to the impact caused by driving conventional piers or piles. In addition, the described embodiments may be used to remediate or supplement existing monopole support structures with minimal environmental impact. 
       FIG. 1A  is an isometric view of a portion of a support structure  100  for supporting a tubular monopole  105  consistent with an embodiment described herein. Tubular monopole  105  may include a substantially cylindrical or frusto-conical configuration. In some implementations, monopole  105  may be formed of tubular steel or similar material.  FIG. 1B  is an isometric view of tubular monopole  105  showing an overall length of monopole  105 . In some implementations, as shown in  FIGS. 1A and 1B , monopole  105  may include a multi-sided configuration, such as a 12-sided (dodecagon) configuration, comprising 12 sides, each having a same width and an angle of approximately 15° relative to each adjacent side. 
     In addition, as shown in  FIG. 1B , monopole  105  may have an extended length relative to its diameter, such length suitable for a given application. For example, a monopole for supporting high voltage power lines may be approximately 117 feet long, while a monopole for supporting a traffic signal may be approximately 20-30 feet long. Embodiments described herein are suitable for monopole  105  having any particular length. 
     Consistent with implementations described herein, monopole support structure  100  may include a plurality of truss assemblies  110 - 1  to  110 - 4  (collectively referred to as “truss assemblies  110 ” and individually as “truss assembly  110 ”) depicted in isometric view in  FIG. 1A , one of which is shown in side view in  FIG. 2 . In an exemplary implementation, monopole support structure  100  may include four truss assemblies  110  spaced equidistantly about a perimeter of monopole  105 , e.g., at 90° intervals relative to each other. In other implementations, more or fewer truss assemblies  110  may be used.  FIG. 2  is a side view of one of truss assemblies  110  and  FIG. 3  is a top view of monopole support system  100 . Consistent numbering is used throughout, where appropriate. 
     As shown, each truss assembly  110  may include an angled brace element  112 , a horizontal brace element  114 , joint elements  116 ,  118 , and  120 , mounting brackets  122  and  124 , pier bracket  126 , and cross members  128  and  130 . Truss assemblies  110  are configured for securing to monopole  105  and a number of helical piers  148 - 1  to  148 - 4  (collectively referred to as “helical piers  148 ” and individually as “helical pier  148 ”). As described in additional detail below, helical piers  148  may include a substantially cylindrical body having a number of helical blade-like elements projecting therefrom. Helical piers  148  are capable of being drilled into a support surface, such as the ground to support a structure attached thereto. In some instances, a number of helical piers  148  may be linked together to allow driving of the piers  148  to significant depths within the Earth, such as depths of 10 to 60 or more feet. Exemplary helical piers  148  for use in the manner described herein may have lengths of 26 feet, shaft diameters of approximately eight inches, and blade diameters of approximately 24 inches. However, other dimensions may be used, depending on the specific application. Though helical piers are shown, it is understood that the system may include a variety of different micropile and pier systems. 
     Angled brace element  112  may include one or more structural elements configured to provide a rigid and supportive connection between monopole  105  and pier bracket  126  via joint elements  116  and  118 . As described in additional detail below, pier bracket  126  may be coupled to helical pier  148  (one of which is shown schematically in  FIG. 4 ). As shown in  FIG. 1A , in one embodiment, angled brace element  112  includes two lengths of angle steel (denoted as elements  112 - a  and  112 - b  in  FIG. 1A ) joined (e.g., welded) to opposing portions of joint elements  116  and  118 . The two lengths of angle steel  112 - a  and  112 - b  may be joined to each other (e.g., welded) along their lengths for extra support and rigidity. In other embodiments, other types of steel (or other rigid material) may be used, such as hollow structural section (HSS) steel, tubular steel, etc. For example, eight-sided tubular steel may be used for brace elements  112  and  114  and/or cross members  128 / 130 . 
     A length of angled brace element  112  (shown as “L 1 ” in  FIG. 2 ) may be determined based on a positioning of helical piers  148  relative to monopole  105 , such that a desired angle may be maintained with respect to horizontal. For example, an angle of 45° may be desired for angled brace element  112  with respect to horizontal upon coupling with monopole  105 . However, it should be noted that deviations from this angle may be possible due to the adjustable nature of joint mounting brackets  122  and  124 , and pier bracket  126 , described in detail below. 
     Horizontal brace element  114  may include additional structural elements to provide a rigid and supportive connection between monopole  105  and pier bracket  126  via joint elements  118  and  120 . As shown in  FIG. 1A , in one embodiment, horizontal brace element  114  may include two lengths of angle steel (denoted as elements  114 - a  and  114 - b  in  FIG. 1A ) joined (e.g., welded) to opposing portions of joint elements  118  and  120 . In other embodiments, other types of steel (or other rigid material) may be used, such as HSS steel, tubular steel, etc. As with horizontal brace element  112 , a length of horizontal brace element  114  (shown as “L 2 ” in  FIG. 2 ) may also be determined based on a positioning of helical piers  148  relative to monopole  105 . 
     As shown in  FIG. 2 , joint elements  116  and  118  may be secured, such as via welding, to opposing ends of angled brace element  112 . In one embodiment, joint elements  116  and  118  may be formed of steel or another rigid material. Joint element  116  may be secured to an upper end of angled brace element  112  and may have a four or five-sided configuration having a mounting aperture  127  formed therethrough. As described in detail below, mounting aperture  127  may align with a corresponding hole  129  in mounting bracket  122  upon assembly of truss assembly  110  to monopole  105 . 
     Although not shown in the Figures, an upper portion of joint element  116  may include an angled or curved configuration, thereby allowing joint element  116  and angled brace element  112  to pivot or move with respect to monopole  105  following assembly. 
     Mounting bracket  122  may be formed of one or more rigid elements and may be secured to an outside surface of monopole  105 . In one embodiment, mounting bracket  122  may include a pair of bracket members  123  and a mounting plate  125 . This embodiment may also be referred to as a “doubler”. Bracket members  123  may be secured (e.g., welded, bolted, etc.) to mounting plate  125 , such that bracket members  123  extend substantially perpendicularly from mounting plate  125 . In addition, bracket members  123  may be spaced parallel from each other by a width substantially similar to a thickness of joint element  116 , thereby enabling the end of joint element  116  to be received between bracket members  123 . In implementations in which monopole  105  comprises a dodecagon or other multi-faceted or multi-sided configuration, mounting plate  123  may include an angled or beveled surface, thereby allowing mounting plate to conform to an outer configuration of monopole  105 . By providing a doubler configuration for supporting angled brace element  112 , through plates extending through monopole  105  may be unnecessary, thereby increasing the ease of assembly and reducing both the cost and complexity of monopole support system  100 . 
     As shown in  FIG. 2 , during assembly of truss assembly  110 , the exposed end of joint element  116  may be inserted between bracket members  123 , and aperture  127  in joint element  116  may be aligned with hole  129  in bracket members  123 . A bolt or pin  134 , as shown in  FIG. 1A , may be received through aperture  127  and hole  129  and may be secured via nut  135 , as shown in  FIG. 3 . By providing a bolt on assembly for truss assembly  110 , field installation is made possible without requiring welding, thereby increasing the speed and efficiency with which the installation may be made. 
     Joint element  118  may be secured to a lower end of angled brace element  112  and may include a joint portion  136  and a flange portion  138 . As shown, joint portion  136  may be further configured to secure to a first end  140  of horizontal brace element  114  in addition to the lower end of angled brace element  112 . More specifically, horizontal brace element  114  and angled brace element  112  may be fixed to joint element  118  in a desired relative angle, such as a 45° angle. In addition, as shown in  FIG. 1A , flange portion  138  may extend substantially perpendicularly from a lower end of joint portion  136  and may form a base for receiving pier bracket  126 . In one embodiment, a width of flange portion  138  may be slightly larger than an outside diameter or maximum outer dimension of pier bracket  126 . Pier bracket  126  may be fixed to flange portion  138  via welding, for example. In other embodiments, pier bracket  126  may be co-formed with joint element  118  (e.g., via casting, molding, etc.). 
     As described briefly above, joint element  120  may be secured to a second end  142  of horizontal brace element  114 . Joint element  120  may include a four or five-sided configuration having a mounting aperture  144  formed therethrough, as shown in  FIG. 2 . As described in detail below, mounting aperture  144  may align with a corresponding hole  145  in mounting bracket  124  upon assembly of truss assembly  110  to monopole  105 . 
     Mounting bracket  124  may be formed substantially similar to mounting bracket  122  and may be formed from one or more rigid elements secured to an outside surface of monopole  105 . For example, mounting bracket  124  may include bracket members  123  and mounting plate  125 . As shown in  FIG. 1A , mounting bracket  124  may be vertically aligned with mounting bracket  122 . 
     During assembly of truss assembly  110 , the exposed end of joint element  120  may be inserted between bracket members  123 , and aperture  144  in joint element  120  may be aligned with hole  145  in bracket members  123 . Bolt  134  is received within aperture  144  and hole  145  and may be secured via nut  135 . 
     Cross members  128  and  130  may be formed of a rigid material and may have lengths dictated by a desired geometry of truss assembly  110 . For example, cross member  128  may have a length (shown as “L 3 ” in  FIG. 2 ) configured to provide a vertical (e.g., 90° relative to horizontal brace element  114 ) interconnect between an intermediate portion of angled brace element  112  and an intermediate portion of horizontal brace element  114 . Similarly, cross member  130  may have a length (shown as “L 4 ” in  FIG. 2 ) configured to provide an angled (e.g., approx. 45° relative to horizontal brace element  114 ) interconnect between the intermediate portion of angled brace element  112  and an end of horizontal brace element  114 . In other implementations, alternative geometry may be used, including additional cross members, different angles, etc. In some embodiments, as shown in  FIG. 1A , one or more of cross members  128  and  130  may be formed of more than one member (e.g., two, paired members, etc.). 
     Cross members  128  and  130  may be secured to angled and horizontal brace elements  112  and  114  via welding. In one embodiment, when brace elements  112  and  114  comprise pairs of structural elements (e.g., elements  112 - a / 112 - b  or  114 - a / 114 - b ), one of cross members  128  and  130  may be welded between each member in the pair and the other of cross members  128  and  130  may be welded outside of each member in the pair. For example, as shown in  FIG. 1A , one end of cross member  128  may be welded between the elements  112 - a  and  112 - b  of angled brace element  112  and the other end of cross member  128  may be welded between the elements  114 - a  and  114 - b  of horizontal brace element  114 . In this embodiment, the two members of cross member  130  may be welded to the outside of angled brace element  112  and horizontal brace element  114 . 
     As described briefly above, joint member  118  may be configured to support pier bracket  126 . As shown in  FIG. 1A , pier bracket  126  may comprise a substantially tubular member having an inside diameter substantially similar to an outside diameter of an exposed end  146  of helical pier  148 . Pier bracket  126  may include holes  149  for aligning with holes in an end of helical pier  148 , as described below. 
       FIG. 4  is an isometric view of one of helical piers  148 . As shown, helical pier  148  includes a shaft portion  150  and a number of auger or blade portions  152 . An operating end  154  of shaft portion  150  may include a pointed end for enabling pier  148  to more easily penetrate the Earth during installation. A retaining end  156  of shaft portion  150  may include retaining apertures  155 . Following insertion of helical pier  148  into the Earth to a desired or predetermined depth, retaining end  156  may project from the Earth by a set amount. As shown in  FIGS. 1A and 1B , helical piers  148  may be inserted into the Earth at locations radially aligned with mounting brackets  122  and  124 . Pier bracket  126  may be aligned with retaining end  156  and retaining apertures  155  may be aligned with holes  149  in pier bracket  126 . In some instances, it may be necessary to rotate helical pier  148  to bring apertures  155  into alignment with holes  149 . A pin  158  may be received through apertures  155  and holes  149  to secure pier bracket  126  to helical pier  148 . In other embodiments, pin  158  may be secured via other mechanisms, such as snap rings, nuts, clips, etc. 
     By providing pin or bolt-type securing of truss assemblies  110  to both monopole  105  and helical pier  148 , field assembly may be more easily managed. For example, it is not necessary for installers to weld items together in the field. Rather, pre-constructed truss assemblies  110  may be brought into the field and secured to monopole  105  and helical piers  148  using easily portable tools. 
     In some embodiments, as shown in  FIGS. 1A and 1B , an additional helical pier  148 - 5  may be mounted beneath a center of monopole  105 . For example, a pier bracket (not shown) similar to pier bracket  126  may be welded or otherwise secured to a center of the bottom of monopole  105 . During installation, helical pier  148 - 5  may be driven into a location corresponding to the center of monopole  105 . The helical pier  148 - 5  may be aligned with the center pier bracket and secured in a manner similar to that described above with respect to piers  148 - 1  to  148 - 4 . 
     In still other implementations, additional helical piers may be installed and secured to truss assemblies  110 . For example, one or more additional pier brackets may be secured to a bottom surface of horizontal brace element  114 . Additional helical piers may be driven corresponding to the locations of each additional pier bracket. The additional piers may be able to support longer monopoles having longer lengths or monopoles positioned in potentially less stable environments. As previously mentioned, though helical piers are shown in the embodiments, it is understood that the system may include a variety of different micropile and pier systems. 
     By providing a truss-based, helical pier monopole support system  100 , embodiments described herein may provide an efficient and environmentally sensitive alternative to existing monopole support systems. More particularly, helical piers may be driven into the ground surrounding a monopole with minimal environment impact. The above-described truss assemblies may be secured to both the helical piers and the monopole to provide an effective support system with minimal impact and cost. 
     The foregoing description of exemplary implementations provides illustration and description, but is not intended to be exhaustive or to limit the embodiments described herein to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the embodiments. 
     Although the invention has been described in detail above, it is expressly understood that it will be apparent to persons skilled in the relevant art that the invention may be modified without departing from the spirit of the invention. Various changes of form, design, or arrangement may be made to the invention without departing from the spirit and scope of the invention. Therefore, the above-mentioned description is to be considered exemplary, rather than limiting, and the true scope of the invention is that defined in the following claims. 
     No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.