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INSTRUCTORS:
Wesley J. Oliphant, P.E.
Ricky A. Cribbs
Shaojie Wu, Ph.D., S.E., P.E.
Angelo Fabri
Purpose and Background
These presentations were recorded at the Electrical Transmission & Substation Structures Conference 2025.
Evaluating the Load Transfer Mechanism of Telescoping, Friction Fit “Slip Splices” in Multi-sided Tubular Steel Poles (22 minutes)
This presentation investigates the real behavior of telescoping slip-splice connections—the most common joint in modern tubular steel transmission poles. Using historic EPRI data, finite element analysis (FEA), and comparative testing, the study evaluates how load transfers between overlapping inner and outer pole sections. The speakers discuss the evolution of the ASCE 48 guidance and the importance of overlap-to-diameter ratios (L/D) in determining performance. Results highlight local buckling mechanisms, frictional effects, and the influence of geometric slenderness on stability. Attendees will gain insight into the stress interactions within the joint, moment transfer behavior, and recommendations for future study and design refinement.
Toward Structural Design of Slip-Joint Connections for Tapered Steel Transmission Pole Structures with Polygonal Tubular Cross-Sections (20 minutes)
This session presents a proposed analytical approach for the structural design of slip-joint connections in tapered, polygonal transmission poles. Building on earlier testing and research, the method incorporates the effects of section slenderness, hoop stress, and contact pressure to allow more flexible and accurate design beyond the standard ASCE 48 provisions. The study also draws comparisons with similar grouted connections in offshore wind turbine monopiles to better understand stress distributions and frictional behavior between inner and outer sections. By linking failure modes with mathematical modeling, the research offers a foundation for calculating both demand and capacity using plate buckling theory. The presentation highlights how this framework can improve prediction accuracy and provide engineers with a more adaptable design tool.
Real vs. Theoretical Behavior of Transmission Poles Under Load Tests (18 minutes)
This presentation compares full-scale load test results of a 230 kV transmission pole against predictions from PLS-Pole and ANSYS finite element models. Conducted at Brahmetal’s structural testing station in Brazil, the study assessed real-world deflections, stresses, and connection behaviors to validate analytical assumptions. The test incorporated non-linear geometric and frictional contact effects to simulate realistic conditions for slip-joint and base-plate connections. Results revealed close agreement between measured and modeled behaviors, with differences under 3%, confirming the reliability of current analysis software. Attendees will learn how empirical testing can calibrate friction coefficients and improve accuracy in predictive structural modeling.
Benefits and Learning Outcomes
Upon completion of this course, you will be able to:
- Explain the load transfer mechanisms and critical stress patterns in telescoping slip-splice connections.
- Identify how geometric factors such as overlap length (L/D ratio) and wall slenderness influence buckling and failure modes.
- Describe the key stress mechanisms and failure modes influencing slip-joint connection behavior in tapered tubular poles.
- Discuss how plate buckling theory and frictional contact principles can be used to design slip joints with varying slenderness ratios.
- Explain how full-scale testing validates analytical models of transmission poles under horizontal loading.
- Identify key differences between theoretical FEA modeling and observed structural performance in real-world pole tests.
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]