Seismic Base Shear for Residential Building in SDC D per ASCE 7-22

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Seismic Base Shear for Residential Building in SDC D per ASCE 7-22

Summary: Calculate seismic base shear and vertical force distribution for a two-story wood light-frame residence in SDC D per ASCE 7-22 §12.8. Free structural…

Overview

Calculate seismic base shear and vertical force distribution for a two-story wood light-frame residence in SDC D per ASCE 7-22 §12.8. Free structural design software with ASCE 7 load combination calculator.

Problem statement

A two-story residential building in SDC D has 80 kip total seismic weight (40 kip per floor, 10 ft story height each). Wood light-frame with R = 6.5 (Table 12.2-1, Light-frame wood walls). Site Class D. hn = Σhx = 20 ft. Table 12.8-2 structure type for wood: "All other structural systems", Ct=0.02, x=0.75. Determine base shear V and vertical distribution Fx per ASCE 7-22 §12.8.

Workflow in StructSuite

StructSuite's free structural design software. Step 1: enter Level, wx (lb), hx (ft) for each story. hn = Σhx used in Period step. Step 4: select Table 12.2-1 row (e.g., id 16 wood light-frame); Table 12.8-2 row auto-selects for Ta. Step 5: hn and Ct, x read-only. Step 6: Cs and V. Step 7: Fx, Vx distribution.

Design considerations (excerpt)

Weight W (Σwx) drives base shear directly: V = Cs×W. Height hn (Σhx) drives period Ta = Ct×hn^x—taller buildings have longer periods. Longer T can reduce Cs when SD1-controlled (upper bound Cs ≤ SD1/(T×R/Ie)). For two-story residential, 40 kip/floor (35–50 psf) typical; 10 ft story height common. Weight at roof (snow, mechanical) affects Fx distribution.

SDS and SD1 from USGS or site-specific study. Site Class D (stiff soil) is default; Class E or F (soft soil) amplifies ground motion—SDS/SD1 can increase 30–50%. Higher SDS = higher base shear. SDC D typically SDS 0.5–1.5g, SD1 0.2–0.6g. Coastal CA, Pacific Northwest, central US have high values.

Ie (Importance Factor) from Table 1.5-2:…

Related terms

  • StructSuite
  • structural engineering
  • design example
  • seismic
  • ASCE 7-22
  • residential base shear

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