Seismic Anchorage of Structural Walls (ASCE 7)

Calculate the minimum seismic anchorage forces of structural walls as per ASCE 7 cl. 12.11

Input:

in
in
psf
g
ft
wall anchorage forces

Output:

  1. Definitions
    • Fp = Seismic Anchorage Force
    • htrib = Height of wall tributary to support or anchor
    • wtrib = Width of wall tributary to support or anchor
    • Wunit = Unit weight of wall (psf)
    • Wp = Tributary weight of wall (lb)
    • SDS = Design spectral acceleration at short periods (0.2sec)
    • Ie = Seismic importance factor
    • Lf = Span of the flexible diaphragm that provides support for the wall (ft)
    • ka = Amplification factor for diaphragm flexibility
  2. Determine weight of wall tributary to anchor or support
    • Wp = Wunit htrib wtrib = (250)(56)(12)/ (144 in²/ft²) = 1166.7 lb
  3. Determine minimum out-of-plane force
    • Fpo = 0.4 SDS Ie Wp > 0.1 Wp
    • Fpo = 0.4 (0.85) (1) (1166.7) > 0.1 (1166.7)
    • Fpo = 396.7 > 116.7
    • Fpo = 396.7 lb
  4. Determine minimum in-plane force
    • ka = 1.0 + Lf/100 < 2.0 = 1.0 + (10)/100 < 2.0 = 1.1
    • Fpi = 0.4 SDS ka Ie Wp > 0.2 Wp
    • Fpi = 0.4 (0.85) (1.1) (1) (1166.7) > 0.2 (1166.7)
    • Fpi = 436.3 > 233.3
    • Fpi = 436.3 lb

Notes: