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 ASCE 113 MOP 2nd Edition Application of Seismic Forces on Insulators and Bus

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Dillon Curry's profile image
Dillon Curry posted 04-01-2025 05:44 PM

Hello! Within our workplace we are beginning to develop internal calculations utilizing the new 113 MOP. There is a question floating around the office around the exact interpretation and intent of section 3.1.7.11 - Seismic Demand on Other Components. The language in this section seems to imply that the use of Fp (Eqn. 3-36) would be used only to "design the component and anchorage to the support structure". Our interpretation is that this would be utilized either for analyzing bus strength, insulator strength, or the anchoring bolts from said insulator.

However, when you look at the Appendix A example A.1 a freebody diagram (Figure A-1) of seismic forces on the structure implies that it should be a combination of forces Fp (insulator seismic force) and Eh (structure member seismic force) utilized to perform seismic analysis on the structure as a whole. This seems to counter the language in 3.1.7.11.

In summary when looking a structure supporting a rigid insulator should we be utilizing Fp as applied to the insulator as a load on the structure or can the force Eh from Eqn. 3-11 be utilized to apply seismic loads on the structure from the insulator?

Tirza Austin's profile image
Tirza Austin posted 10-31-2025 02:04 PM

Thank you for posting your question on the Peer-to-Peer Standards Exchange. We noticed that an engineering colleague hasn’t responded yet, and we recognize how valuable timely input can be. In the meantime, you might find it helpful to explore Eaves (https://amplify.asce.org/eaves), our AI-powered assistant trained on ASCE AMPLIFY platform content—including ASCE 7, 41, 24, 73, and more.

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It’s a great way to get quick, standards-based guidance while continuing the conversation with your peers.

George Watson's profile image
George Watson posted 11-01-2025 05:43 PM

I was the editor of the 113 revision. I just got something in my eMail inbox about this question, and I will check with our committee members that worked on this section and get an answer. 

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