The given in the first column of Table 4.3-3 identifies items relevant to properties or results “Level” associated with that level. Items related to story drift (presented later in this chapter) are identified at the relevant of the building because these quantities represent the deformations between levels. “Story” Table 4.3-3 includes a mass computed for Level G of the building. This mass is associated with an extremely stiff story (the basement level) and is dynamically excited by the earthquake in very high frequency modes of response. As shown later, this mass is not included in equivalent lateral force computations, and can complicate modal response spectrum and modal response history analysis. Table 4.3-1. Area weights contributing to masses on diaphragms (See Fig. 4.3-5) Mass Source Area A Area B Area C Area D Area E Slab and Deck (psf) 50 75 50 75 75 Structure (psf) 20 20 20 20 50 Ceiling and Mechanical (psf) 15 15 15 15 15 Partition (psf) 10 10 0 0 10 Roofing (psf) 0 0 15 15 0 Special (psf) 0 0 0 60 25 Total (psf) 95 120 100 185 175 Table 4.3-2. Line weights contributing to masses on diaphragms (See Fig. 4.3-5) Mass Source Line 1 Line 2 Line 3 Line 4 Line 5 From Story Above (plf) 60.0 93.8 93.8 93.8 135.0 From Story Below (plf) 93.8 93.8 0.0 135.0 1,350.0 Total (plf) 153.8 187.6 93.8 228.8 1,485.0 Figure 4.3-5. Key diagram for computation of floor weights
The given “Level” in the first column of Table 4.3-3 identifies items relevant to properties or results associated with that level. Items related to story drift (presented later in this chapter) are identified at the relevant “Story” of the building because these quantities represent the deformations between levels. Table 4.3-3 includes a mass computed for Level G of the building. This mass is associated with an extremely stiff story (the basement level) and is dynamically excited by the earthquake in very high frequency modes of response. As shown later, this mass is not included in equivalent lateral force computations, and can complicate modal response spectrum and modal response history analysis. Table 4.3-1. Area weights contributing to masses on diaphragms (See Fig. 4.3-5) Mass Source Area A Area B Area C Area D Area E Slab and Deck (psf) Structure (psf) Ceiling and Mechanical (psf) Partition (psf) Roofing (psf) Special (psf) Total (psf) 50 20 15 10 0 0 95 75 20 15 10 0 0 120 50 20 15 0 15 0 100 75 20 15 0 15 60 185 75 50 15 10 0 25 175 Table 4.3-2. Line weights contributing to masses on diaphragms (See Fig. 4.3-5) Mass Source Line 1 Line 2 Line 3 Line 4 Line 5 From Story Above (plf) From Story Below (plf) Total (plf) 60.0 93.8 153.8 93.8 93.8 187.6 93.8 0.0 93.8 93.8 135.0 228.8 135.0 1,350.0 1,485.0 Figure 4.3-5. Key diagram for computation of floor weights
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