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INSTRUCTORS:
Tony Cunha, P.E.
Kory Rankin
Jason W. Kilgore, PE, SE
F. Elliott Thaxton, PE
Purpose and Background
These presentations were recorded at the Electrical Transmission & Substation Structures Conference 2025.
Historical Procedures for Angle Member Compression Design (21 minutes)
This presentation explores the evolution of compression design procedures for steel angle members in lattice transmission towers. Before 1991, no unified standard existed, resulting in dozens of competing methods with varying assumptions and safety factors. The presenter revisits early research efforts, from R.D. Coombs’ 1916 investigations to the development of ASCE Manual Practice 52, and highlights how member end conditions, material properties, and local buckling behavior influenced these differing approaches. The talk visualizes over 70 historic equations to reveal discrepancies in allowable compressive stresses and design philosophies. Attendees will gain perspective on how today’s ASCE 10 provisions developed through a century of iterative learning. The presentation closes by linking these insights to practical evaluation of existing towers still in service today.
Structural Reliability Targets for Steel Transmission Poles – A Modest Proposal (20 minutes)
This session introduces reliability-based design (RBD) principles for steel transmission poles and discusses how they differ from traditional prescriptive approaches. The presenter outlines the fundamentals of structural reliability, probability of failure, reliability index (ß), and performance-based targets, and connects these to practical calibration efforts across codes such as ASCE 7 and ASCE 74. Drawing on decades of literature and case studies, he presents proposed reliability targets for steel poles and demonstrates how RBD can balance safety, redundancy, and cost-effectiveness. The presentation highlights both benefits and challenges of implementation, including computational demands, data collection, and code alignment. Attendees will come away with a clear understanding of how reliability targets can improve consistency and reduce unnecessary conservatism in pole design.
Real Life Jenga: Verifying The Safety of In-Service Lattice Towers During Repair and Strengthening Efforts (24 minutes)
This presentation delves into the engineering analysis, field evaluation, and safety considerations involved in repairing or strengthening existing lattice transmission towers. The presenters describe methodologies for assessing aging towers, many exceeding 100 years in service, while maintaining structural integrity and worker safety. The session covers investigation techniques, modeling levels (from conservative to comprehensive FEA), and decision-making between reinforcement and replacement. Real-world examples illustrate issues such as buried corrosion, impact damage, member replacement, and supplemental bracing. The speakers also emphasize construction safety, fall protection, and the role of field validation in ensuring that repairs meet both engineering and operational requirements.
Benefits and Learning Outcomes
Upon completion of this course, you will be able to:
- Describe how early design procedures for angle member compression evolved before modern standards.
- Identify the key factors, end conditions, material strength, and local buckling, that influence discrepancies in compression design results.
- Explain the concept of structural reliability and its role in performance-based design for transmission poles.
- Discuss how reliability-based design can improve consistency, safety, and efficiency compared to traditional prescriptive methods.
- List common damage types and safety considerations when repairing or strengthening existing lattice towers.
- Describe the analytical and procedural methods used to verify tower stability during in-service modification work.
Assessment of Learning Outcomes
Students' achievement of the learning outcomes will be assessed via a short post-test assessment (true-false, multiple choice, and/or fill in the blank questions).
Who Should Attend?
- Utility Engineers
- Structural Engineers
- Consulting Engineers
- Contractors
- Suppliers & Manufacturers
- Researchers & Educators
How to Earn Your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short post-test and receive a passing score of 70% or higher within 1 year of purchasing the course.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]