Patent Document

[0001]    This is a continuation of patent application Ser. No. 09/388,695 filed Sep. 2, 1999.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to devices and methods used for supporting equipment on the rooftops of buildings or in similar locations. In particular aspects, the invention is directed to support systems for telecommunications equipment, heating and cooling equipment and the like.  
           [0004]    2. Description of the Related Art  
           [0005]    Modem commercial buildings normally mount most of their auxiliary equipment on the roof of the building. This auxiliary equipment includes telecommunications equipment, antennas, waveguides, ice bridges, heating and cooling equipment, ductwork and piping. Currently, telecommunications enclosures and materials are being installed on the roofs of new buildings as well as being retrofitted onto older buildings. In some instances, this equipment is mounted on the ground or another support surface.  
           [0006]    A number of commercially-available support systems are currently used or known to mount the auxiliary equipment on roofs or other locations. Most often, however, make-shift supports are created out of pieces of angle iron that are secured by screws or other fasteners to the rooftop. A problem with conventional support systems is that the fasteners damage the rooftop. Further, as a building roof is exposed over time to rain, snow, wind and extreme temperature variations, the support systems tend to damage the roof even more as the hard and sharp edges of angle iron pieces or wood cut into the rooftop.  
           [0007]    A further drawback is that currently known support systems are not easily installed on uneven roofs or roofs where the elements have caused differential settlement. When settlement occurs, the support platform can become unstable, and weight from the supported equipment can become concentrated in a few areas. To address the problem, shims can be fabricated on-site to shore up a portion of the support system and level it out. However, the shims are often made of cut pieces of wood, such as plywood or lumber. These cut pieces typically have relatively sharp corners and edges that can also cut into the roofing material over time, thus damaging the roof and creating the potential for leaks.  
           [0008]    Even without differential settlement, conventional support systems do not always distribute the load of the supported equipment evenly across the rooftop. Instead, the load may be concentrated onto just a few support members, thereby resulting in eventual failure of the rooftop in those areas.  
           [0009]    A further drawback of conventional, particularly makeshift, rooftop support systems is that they are typically not designed to resist specific wind loads. Those systems that are constructed to resist design wind loads do so by securing the support system to the rooftop or to the structure of the building. If the support system is under-designed, the supported equipment may blow over or become torn loose from its support system during high winds. As over-designed support system may be costly and excessively heavy.  
           [0010]    It would be an improvement to have systems and methods that address the problems of the prior art.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention provides improved equipment support systems. In described embodiments, modular platforms are constructed that provide an equipment support portion with lateral walkways and work areas. The platforms have a skeletal frame that supports a plurality of grates to form the work area. The frame of the platforms also has a number of support legs with circular bases at their lower ends to rest upon the roof or other support surface. The circular bases distribute the load of the supported equipment evenly upon the roof so that specific spots are not overloaded. Outriggers may be removably added to the platform to increase the dimensions of the platform thereby making the platform and supported equipment less prone to overturning from wind loading. Methods are described for providing a support platform designed to resist a specific design wind load.  
           [0012]    In some preferred embodiments, one or more of the support legs of the platforms are adjustable in length, to allow portions of the platform to be adjusted for differential settlement of the roof.  
           [0013]    The support platforms of the present invention provide a number of additional operational advantages not found in conventional systems. These include the presence of walkway and work areas adjacent the equipment support section of the platform, access space beneath the platform and the rooftop for the running of cables, piping or the like, and drainage and air flow through the platform.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a plan view of an exemplary support platform constructed in accordance with the present invention.  
         [0015]    [0015]FIGS. 2 and 3 are side and isometric views, respectively, of the platform shown in FIG. 1.  
         [0016]    [0016]FIG. 4 is a partially exploded view of the platform shown in FIGS.  1 - 3 .  
         [0017]    [0017]FIG. 5 illustrates the platform of FIGS.  1 - 4  having structures supported thereupon.  
         [0018]    [0018]FIGS. 6 and 7 are plan and side views, respectively, of an exemplary support platform with modular outrigger portions added.  
         [0019]    [0019]FIGS. 8 and 9 illustrate an exemplary adjustable leg structure for use with platforms in accordance with the present invention.  
         [0020]    [0020]FIG. 10 is a block diagram illustrating the effect of weight forces upon an exemplary platform and supported load.  
         [0021]    [0021]FIG. 11 is a block diagram illustrating potential rotational motion of the platform and supported load in response to wind loading.  
         [0022]    [0022]FIG. 12 illustrates the relationship between the height and weight of the platform and supported load and the length of overhang needed to resist an overturning moment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    FIGS.  1 - 5 , illustrate an exemplary support platform  10  constructed in accordance with the present invention. The platform  10  is constructed of modular components that can be readily assembled and disassembled. The platform  10  has a central equipment support section  12  and a laterally-located areas  14  that serve as walkways and allow access to equipment supported on the equipment support section  12 . As FIG. 2 shows, the platform  10  is placed on a supporting surface  16  without being affixed to the supporting surface  16  by fasteners. The typical supporting surface  16  is the rooftop of a building.  
         [0024]    The platform  10  includes a skeletal supporting frame that is formed of metal frame members and tubular struts interconnected by bolt-and-nut assemblies or other connectors. The equipment support section  12  is formed by frame members  18  that are preferably sections of angle iron. It can be seen that the frame members  18  form a base to which equipment such as a telecommunications building can be affixed and supported atop. The base formed by the frame members  18  also defines openings  19  through which electrical cabling, piping or the like ( 21  in FIG. 5) can be disposed and interconnected with the supported equipment.  
         [0025]    Brackets  20 , visible in FIG. 5, extend from the frame members  18  so that the lateral walkway areas  14  can be reversably attached to the central support section  12 . The lateral walkway areas  14  include a number of horizontally-disposed supporting struts  22  that interconnect to the brackets  20 . The struts  22  are preferably tubular metal pieces, or box-beams, that have a square or rectangular cross-section. Metallic grates  24  are placed atop the supporting struts  22  and are affixed to them using clips of a type known in the art for affixing grating to a support member. The grates  24  are preferably rigid, metallic grids that define rectangular gaps  26  that permit drainage and air flow through the grate  24 . Drainage and airflow is particularly important since the equipment mounted upon the equipment support portion  12  is often telecommunications equipment or heating and cooling equipment that benefits from improved air circulation around the equipment and the prevention of flooding. The grids  24  are preferably constructed of a durable steel, iron or aluminum that is sufficiently sturdy to support the loads of the equipment to be mounted thereupon. The presence of the grids  24  allows airflow through the work areas  14  and around the supported equipment.  
         [0026]    A plurality of vertically-disposed support legs  28  extend downwardly from the equipment support portion  12  and the work areas  14 . The legs  28  may be simply box-beam sections or adjustable assemblies of the type which will be described shortly. The lower end of each leg  28  is seated within a substantially circular, load-distributing support base  30 . Support bases  30  are preferably of the type described in U.S. Pat. No. 5,816,554 entitled “Equipment Support Base” by Ronald G. McCracken, which is herein incorporated by reference. The bases  30  are lightweight and effectively distribute weight over the entire footprint of the base  30  so as to avoid unnecessarily localized stresses in the roof surface  16 . It is pointed out that neither the bases  30  nor other portions of the support platform  10  need to be secured to the roof  16  or to the structure of the building, thereby making installation of the platform  10  inexpensive and quick. Further, the structure of the rooftop  16  is not damaged by the use of fasteners. Although not shown, it is preferred that in rooftop applications, a slip sheet formed of roofing material or another suitable, durable material be placed between the base  30  and the roof surface  16 . The slip sheet will tend to hold the base in place and resist movement of the slip sheet with respect to the roof surface  16 .  
         [0027]    It can be seen that, when constructed, the platform  10  provides a work and access area  14  proximate the equipment support portion  12 . Also, the fact that the platform  10  is raised above the supporting surface  16  of the roof provides space for the running of cabling, piping and the like  21  beneath the platform  10 . The cabling and piping can then be disposed through the openings  19  of the equipment support portion  12  and interconnected with the supported equipment  32 . As a result, needed cabling and piping is maintained out of the way of personnel located on the work and access areas  14  minimizing the chances that it will be inadvertently damaged.  
         [0028]    One or more support brackets  33  (one shown in FIG. 5) extend between and are affixed to adjacent bases  30  beneath the equipment support portion  12  and are used to support the piping, cabling and the like  21  above the support surface  16 . The support brackets  30  are preferably affixed to the bases  30  using lengths of all-thread that are threaded into matching recesses on the bases  30 . The construction and operation of brackets  33  is described in further detail in U.S. Pat. No. 5,816,554. It is also noted that other suitable support arrangements for pipes are described therein.  
         [0029]    [0029]FIGS. 6 and 7 depict an exemplary support platform  50  that has modular outrigger portions  52  attached that increase the resistance of the platform to wind loading against the sides of the equipment. The platform  50  is constructed in a similar manner as the platform  10  described earlier except that a number of struts  18  have been removed from the equipment support section  12 . The outrigger portions  52  provide further lateral support and stability to the platform  50 . If desired or needed, additional outrigger portions can be modularly affixed to one or more sides of the platform  50  in order to increase the resistance of the platform to overturning due to wind loads upon a mounted structure.  
         [0030]    It is further pointed out that differing sizes of modular platforms can be constructed to meet different wind resistance requirements. To do this, a design wind load is first selected or determined. The design wind load is a preselected wind velocity that the platform and supported equipment must resist so that moments imposed upon the structure do not result in overturning. The design wind load may vary according to geographical area and/or be based upon subjective factors. Most commonly, the design wind load is established by a local government or municipality. For example, a city might establish a building code that requires that equipment mounted on rooftops to withstand wind speeds of 90 MPH.  
         [0031]    The effective wind exposure area and the weight of the supported equipment are then determined. The effective wind exposure area of the supported equipment is related to the height of the supported structures  32 . The required length, or overhang, of the platform from its center point to a side can then be determined.  
         [0032]    Referring now to FIGS. 10, 11 and  12 , calculations used to determine a required amount of overhang for a platform are illustrated. FIG. 10 is a simplified block diagram depicting an exemplary platform  80 , which is of the type described previously for platforms  10  or  50 . The platform  80  has a load  82  disposed thereupon that is representative of the weighted load provided by supported equipment, such as equipment  32 . The total weight R T  (illustrated by the downward arrow in FIG. 10 is the combined weight of the load  82  and the platform  80 . Since the critical calculations for moments is about the corners  84 ,  86 ,  88  and  90  of the platform  80 , the total weight R T  will be considered to be distributed evenly at each of the corners of the platform  80  and transmitted to the supporting surface  16  (not shown in FIG. 10) at those points. The forces R 1 , R 2 , R 3  and R 4  are illustrative of these weight forces.  
         [0033]    As FIG. 11 illustrates, the platform  80  and supported load  82  can rotate in three directions. These three directions are illustrated, respectively, by (a) the lines  92  between corners  84  and  86  or corners  88  and  90 ; (b) the lines  94  between corners  84  and  90  or corners  86  and  88 ; and (c) a vertical axis  96 . In other words, the platform  80  could either rotate upon the support surface  16  around vertical axis  96  or else overturn along any of its four sides. It is the latter, overturning type rotation that is particularly of concern here.  
         [0034]    When a wind load (shown in FIGS. 11 and 12 as F W ), is applied to the load  82  and platform  80 , the load generally acts upon them in a direction that is parallel to the supporting surface  16 . The wind load F W  normally acts perpendicular to the largest frontal area of the equipment load  82 . For the purposes of conservative estimation, it is presumed that the wind load F W  acts at the upper end  97  of the load  82 , thereby inducing a maximum turning moment M ( 98  in FIG. 12) about the opposite edge  100  of the platform  80 . The moment M is defined by the following equation:  
       M   =       (       F     W                  ×   H     )     -     (       R   T     ×     Length of Overhang       )                             
 
         [0035]    where H is the height of, or vertical distance to, the upper end  97  of the load  82  from the support surface  16 , and the Length of Overhang is the distance from a central point of the platform  80  to the edge  98  of the platform  80 .  
         [0036]    When the moment calculated by this equation is a negative number, the platform  80  and load  82  will remain stable against the force of the wind F W . Conversely, if the moment calculated is positive, the platform  80  and  82  will likely overturn. It can be seen that as the Length of Overhang is increased, the value of M will decrease, thus increasing the stability of the platform  80 .  
         [0037]    Given the relationship above, the equation can be solved for the required length of overhang using the following equation:  
       L   =       [       (       F   W     ×   H     )     -   M     ]     /     R   T                             
 
         [0038]    by inserting a positive number for the moment M. This type of analysis for overturning moments M and the required Length of Overhang should be performed for each of the four faces of the platform  80  and load  82 .  
         [0039]    Once the required Lengths of Overhang have been determined, a proper sized platform can be constructed on a roof surface, or other support surface, by adding enough outriggers to each side of a platform to ensure that the platform will not overturn in any direction. As the platform is disposed on the support surface in this manner, the legs  28  of the platform are disposed within the load-distributing bases  30 . The supported equipment  32  is then secured to the equipment support portion  12 .  
         [0040]    When constructed, platforms of the present invention preferably provide a convenient work and access area that is laterally located to, and may surround, the equipment  32 . Also, the fact that the platforms are raised above the surface  16  of the roof provides space for the running of cabling and the like beneath the platforms.  
         [0041]    The modular nature of the support system permits suitable platforms to be assembled or disassembled quickly and easily. Further, the modular nature of the support system permits suitable platforms of various sizes and configurations to be packaged and shipped as needed.  
         [0042]    Platforms constructed in accordance with the present invention can be provided with adjustable legs when required or desired for uneven rooftop surfaces. Referring to FIGS. 8 and 9, an exemplary adjustable assembly  60  is shown that may be used as one or more of the legs  28  for the platforms. Lower box section  62  is shaped and sized to fit within the central opening of a support base  30 . The adjustable leg assembly  60  further includes a strut  64  with a closed bottom end  66 . Although not shown, it will be understood that the upper end of the strut  64  is affixed to a portion of a platform. The bottom end  66  has a threaded hole (not visible) through which a threaded shank  68  is disposed. The threaded shank  68  is fixedly mounted to a platform  70  atop the box section  62 . By rotating the box section  62  and platform  70 , the threaded shank  68  is screwed into or out of the bottom end  66  of the strut thereby moving the box section  62  closer to (as in FIG. 9) or further away from (FIG. 8) the strut  64 . In this way, the length of the leg assembly  64  is adjusted. A nut  72  is retained on the threaded shank  68  and may be rotated downward to be brought into contact with the bottom end  66  after adjustment to lock the adjustable assembly  66  at the length chosen. It is noted that a portion of the strut  64  is cutaway (at  74 ) to provide access to the nut  72 .  
         [0043]    Adjustment of the length of one or more adjustable leg assemblies  60  may be necessary to account for settlement of portions of the roof surface  16 . Also, all of the legs  28  of a platform may be adjustable assemblies  60 , thereby allowing the height of the entire platform with respect to the roof  16  to be adjusted.  
         [0044]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes within departing from the scope of the invention.

Technology Category: e