ASCE Codes and Standards

Oct. 19, 2016
ASCE’s Electrical Transmission Structures committee has been busy improving the tools used for transmission, distribution and substation structural design.

While most Americans have been focused on the NFL, Netflix and Adele, a couple of hundred engineering professionals have been giving up their evenings and weekends to improve the tools we use for transmission, distribution and substation structural design. For the past year, I have had the good fortune to serve as chairman of ASCE’s Electrical Transmission Structures committee. As I’ve traveled to meetings and conferences, I have seen several seemingly subtle yet monumental shifts in our industry.

First, many of the faces that made up the core group who developed standards and manuals of practice (MoPs) are no longer in attendance. The good news is the remaining veterans are providing leadership and mentoring for the cadre of mid-career and younger engineers who now fill committee rosters.

Secondly, these new faces bring a noticeable increase in the level of enthusiasm and energy to the work of each committee. These new members, although generally less experienced than their predecessors, make up for it by listening to colleagues, researching past practices and technical papers, and quickly reaching consensus on best practices.

Finally, the current committee work has a distinctive grassroots feel. Much of the development or revisions to the standards and MoPs are the result of initiatives identified by practitioners across our industry. For example, these initiatives — guided by senior leaders — will result in ASCE being able to publish one new MoP for the design of wood pole structures and completely rewrite the MoP for transmission line structural loading, which also includes a draft pre-standard. These documents are long overdue and provide significant enhancements to the tools engineers use in daily practice.

The updates on the following three MoPs highlight the important work currently in progress:

•  Guidelines for Wood Pole Structures for Electrical Transmission Lines. “This document will change the way wood poles are designed,” said James McGuire, chair of the task committee for this MoP. “No longer will wood pole design be based upon a single point load at the top of the pole. Instead, loads will be applied in the same rigorous fashion as done for steel and concrete structures.” McGuire also identified the actual design of wood pole foundations as a significant enhancement over the current rule of thumb of 10% plus 2 ft (0.6 m). This document will be published in 2017.

•  ASCE-104 Recommended Practice for Fiber-Reinforced Polymer Products for Overhead Utility Line Structures. This MoP contains much more than design guidance. Manufacturing, testing, quality assurance, assembly, erection and field testing are all addressed. The ultimate goal is to evolve a standard for all types of utility structures including communications, traffic and lighting. Galen Fecht, the chair of the task committee for ASCE MoP 104 reported, “The publication of MoP 104 in 2003 dramatically increased the understanding, acceptance and subsequent use of fiber-reinforced polymer (FRP) products. Since then, the utility-focused FRP industry has matured tremendously, particularly in the areas of hardware compatibility and structural design. The most significant addition to this document is improved guidance on the deflection performance of FRP poles. This is particularly important when determining deflection limits for FRP poles to achieve a service equivalency with traditional grid infrastructure materials.” This document also will be published in 2017.

•  ASCE-74 Guidelines for Electrical Transmission Line Structural Loading. This MoP has been a mainstay for the design of transmission line structures for more than 30 years. The fourth edition is currently in development. Although only providing guidelines, this document is used as the basis for design of transmission structures throughout the U.S. and in many places around the world. Frank Agnew, chair of the task committee for ASCE MoP 74, recalled, “Once we started to incorporate the new wind and ice maps, the committee members really pushed for a total rewrite to incorporate new material and some fresh thinking into what everyone agrees is already an excellent design guide.”

Agnew added the most significant difference users will notice is a change from a 50-year return period basis for design to a 100-year return period basis for extreme wind and extreme ice with concurrent wind load cases. The most significant potential long-term impact of the fourth edition may be the inclusion of a draft pre-standard on minimum design loads for electrical transmission line facilities. This draft pre-standard is presented to address an anticipated future need for a loading standard for transmission structures. ASCE MoP 74 is set to publish in 2017.

I am pleased to report the effort that has gone into these and other standards and MoPs has not gone unnoticed by the thousands of engineers, designers and managers who perfect their craft on a daily basis designing efficient, safe and reliable transmission, distribution and substation facilities. 

Ronald J. Carrington is a project director at POWER Engineers Inc. and chair of the ASCE Electrical Transmission Structures committee. He is a registered professional engineer.

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