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

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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?