Tapered Beam-Column with non-prismatic elements for Electrical Transmission Structure Supports

Abstract

This invention uses a hybrid of latticed steel and tapered tubular steel technologies. Namely, latticed steel and tapered tubular steel pole technology, to provide a more economical structural support with the advantages of each. It utilizes latticed steel hot-rolled angles for bracing elements and cold formed steel plate for main leg elements. The tapered geometry of the leg elements provides a more optimum utilization of material by the use of a non-prismatic (tapered) element profile. This element consists of a bent plate shape profile that varies in structural section modulus vertically along the height of the structure which optimizes the use of steel material to resist the applied structural loads. The arms include an invention that allows for post-tensioning and thereby provides deflection control and/or the ability to modify the natural frequencies of vibration to mitigate vortex induced vibrations caused by wind. The main support elements in the arms are developed using plates formed into angle shapes that provide inherent gusset plate material to accommodate the bracing bolted connections without the need for separate gusset plates. The direct embedded portion of the structural design allows for transverse passive soil pressures to be collected by trapezoidal plates and resisted by the grillage superstructure. A transition section is subpart of the embedded structure portion and accommodates multiple structure heights as a standard foundation system.

1 . A method of using cold-formed non-prismatic steel plate for leg and main load carrying elements in a structural support for electrical power transmission structures. Utilizing these elements, structural resistance can be more optimally provided minimizing structure weight and associated cost. Load resistance is provided with variable section modulus with increased height taking advantage of tapered topology, and non-prismatic shape geometry reducing weight and cost. 
     
     
         2 . A method of using hot rolled or cold-formed steel angle elements as bracing elements in a topology that optimizes structure weight and fabrication. By positioning successive structural elements with inclination angles varying along the tapered geometry of the mast, identical length elements are achieved minimizing fabrication costs for high volume fabrication. End connections are identical and variations to necessitate consistent multiple end bolt spacing is accommodated with gage line variations on the main leg of  claim 1 . Said bracing is utilized in a single or in a cross brace configuration depending on load demand. Said bracing is either standard bracing, collocated at nodal points for all bracing planes, or for staggered bracing whereby out-of-plane bracing points lie at non-coincident locations. 
     
     
         3 . A method of adjusting the deflection, and/or structural natural frequencies and mode shapes of the loaded or unloaded arm, the post-tension adjustment allows for pre-load or post-load adjustments to counteract vertical deflection or to counteract aeolian or vortex-induced-vibration (VIV). By way of adjusting the relative positions of the tension elements along an arm configuration, the lengths of the tension elements are reduced or increased allowing for vertical movements at the end of the arm where the insulators are attached and changes in the natural frequencies and mode shapes associated with the arm. When the upper tension elements are translated inward, along their threaded rod, and the lower internal tension elements are translated outward, along their threaded rod, the length from the upper arm connection to end of the arm is reduced, moving the arm vertically positive (up) and changing its natural frequencies and dominant modes of vibration. 
     
     
         4 . A method of providing optimum weight by integration of gusset plate functionality into the steel elements of  claim 1 . By providing for additional steel plate material where it is needed, that is an integral part of the main load-carrying element, multiple bolt connections that are typically required for load transfer at truss bracing points are integrally provided by the main load-carrying element. 
     
     
         5 . A method of using structural steel elements as a system of structure support identified in  claim 1  and  claim 2  for resisting the reactions using a combination of steel angles with bracing elements and trapezoidal plate elements whereby transverse passive soil pressures are collected by the trapezoidal plates and resisted by the grillage superstructure. A transition section is part of the embedded structure portion and accommodates multiple structure heights as a standard foundation. Construction access is available for backfill compaction exteriorly and interiorly and this increases the foundation capacity as compared to direct embedded tubular steel poles.