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Structural Task Force

Structural Task Force. Main areas for investigation Promote LRFD design methodology Develop load factors and load combinations for bus and insulator analysis (ASCE 113 covers load factors and combinations for structures and foundations)

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Structural Task Force

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  1. Structural Task Force • Main areas for investigation • Promote LRFD design methodology • Develop load factors and load combinations for bus and insulator analysis (ASCE 113 covers load factors and combinations for structures and foundations) • Use Aluminum Association Design Manual 2005 for LRFD aluminum bus design • Develop load factors and load combinations for bus and insulator analysis (ASCE 113 covers load factors and combinations for structures and foundations)

  2. Structural Task Force • Main areas for investigation • Determine consistent load reduction factors for insulators • Possibly address polymer insulators for bus support use • Possible copper bus LRFD criteria • Minor clean up issues • The remaining slides are based on particular chapter sections

  3. Structural Task Force • Chapter 10 Overview of mechanical design of bus structures • 10.2 General mechanical design procedure • Load factors and combinations hinted at but no guidance • LRFD vs. ASD • 10.2.1 Note 4 states that wet snow load guidance will be considered in next revision • 10.3.3 notes that a civil, structural or mechanical engineer is required for even simplified bus calculations

  4. Structural Task Force • Chapter 11 Loads on bus structure • If wet snow loads are to be presented they should be in chapter 11 • This chapter is otherwise up to date

  5. Structural Task Force • Chapter 12 Dimensional, strength, and other design considerations • 12.1.1, 12.1.2 and 12.1.3 are correct formulations for deflection of a single span (very rare real world configuration) • 12.1.4 gives verbal guidance for continuous bus span deflection; the equations from 1998 have been removed but the note that refers to the equations is still there.

  6. Structural Task Force • Chapter 12 Dimensional, strength, and other design considerations • 12.2 equation 78 is only true for circular bus cross sections, not angle, bar or integral web sections • 12.2.1 12.2.2 and 12.2.3 are correct formulations for bending stress of a single span (again, very rare real world configuration) • 12.2.4 correctly cautions that continuous bus is more complex and requires detailed analysis. The table from 1998 has been removed.

  7. Structural Task Force • Chapter 12 Dimensional, strength, and other design considerations • 12.3 cantilever forces on insulators • Table 18 (was table 5 in 1998) has some ambiguity in boundary condition definitions. Pinned support condition on any insulator is questionable. • Remainder of 12.3 is OK • 12.4 Strength of porcelain insulators • 12.4.1 Treats torsional and bending stress separately while acknowledging that they act concurrently

  8. Structural Task Force • Chapter 12 Dimensional, strength, and other design considerations • 12.4 Strength of porcelain insulators • 12.4.2 Proposes strength reduction factors for insulators (the inverse of K factors in previous editions) based on load type and stress type. 1998 edition was based on load type (as is RUS 1724E-300 2001) Insulator manufacturers and ANSI C29.7 base factors on stress type.

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