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INSTRUCTORS:
Matthew Thomas, M.ASCE, PE
Dylan Madden, P.E.
Vainqueur Ndangi, P.E.
Vidhi R. Solanki, PhD
Purpose and Background
These presentations were recorded at the Electrical Transmission & Substation Structures Conference 2025.
Development of a VIV Analysis Process for Utility Structures (22 minutes)
This presentation introduces a simplified yet rigorous process for evaluating vortex-induced vibration (VIV) effects on utility structures such as davit arms and monopoles. Attendees will learn the fundamentals of VIV formation, the significance of reduced velocity, natural frequency, and damping ratios, and how these parameters influence dynamic amplification. The speaker outlines how offshore-industry codes, such as the DNV recommended practice, can be adapted for utility applications through targeted modifications grounded in engineering judgment. The procedure involves screening structural members for susceptibility, applying exception criteria to evaluate damping and Reynolds number effects, and designing mitigation strategies including stockbridge dampers. Several real-world examples illustrate how VIV can produce harmful cross-flow vibrations and how damping can significantly increase fatigue life.
Rethinking Conventional Insulator Bracket Design: Improved Designs using FEA (24 minutes)
This presentation examines how conventional insulator bracket designs can fall short when supporting modern high-strength station post insulators, especially under elevated fault duty conditions. The speaker walks through the limitations of traditional thin-plate, elevated brackets that often rely on overly simplified hand calculations for local bending and capacity checks. Using multiple real-world utility standard designs, the team compares hand-calculated stresses with detailed finite element analysis (FEA) to reveal discrepancies in load paths, localized bending, and plate overstress. Both linear elastic and nonlinear elastic-plastic FEA models are used to assess whether the brackets can withstand the full cantilever strength of the insulators. The findings show that some brackets do not converge under nonlinear analysis and exceed allowable stresses, prompting the development of a more robust built-up bracket design with stiffeners.
Effect of Seismic Interaction on Flexible Conductor Terminal Loads in an Interconnected Circuit Breaker-Disconnect Switch System (15 minutes)
This presentation explores shake-table testing and analytical modeling of interconnected substation equipment to better understand seismic load transfer through flexible conductors. Traditional seismic qualification methods evaluate equipment independently and account for conductor forces only heuristically, but recent testing reveals more nuanced behavior. The presenter reviews dynamic tests on catenary and height-differentiated configurations where terminal forces, slack conditions, and mode shapes were closely observed under earthquake excitation. Results show that even with zero slack, impact-like forces do not necessarily occur due to unexpectedly high damping in certain modes and strong participation of “together” modes. Analytical modal methods can accurately predict equipment base moments up to 0.8–1.0 g, with system linearity depending on conductor span and slack. The session highlights how these insights may support more accurate seismic evaluation approaches in the future, as well as the need for expanded datasets before modifying existing codes.
Benefits and Learning Outcomes
Upon completion of this course, you will be able to:
- Describe the fundamental mechanics of vortex-induced vibrations and their potential impact on utility structures.
- Explain how VIV screening, exception criteria, and damping-based mitigation strategies can be applied to evaluate and reduce vibration-related fatigue.
- Identify limitations of conventional insulator bracket designs when subjected to increased cantilever and fault-related loads.
- Discuss how finite element modeling can reveal critical load paths and inform improved bracket designs for utility structures.
- Describe how flexible conductors influence modal behavior and seismic load transfer between interconnected substation components.
- Explain how modal analysis can be used to predict terminal loads and identify conditions under which nonlinear or impact-like behavior may occur.
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]