What it calculates
Designs segmented and perforated wood shear walls to AWC SDPWS 2021 and NDS 2024 ASD. Enter wall geometry, sheathing, studs, and per-story lateral loads to get governing wind and seismic unit shear, chord tension and compression forces, and a check of your selected Simpson Strong-Tie holdown. Story shears link in through a Diaphragm Analysis.
Who uses this calculator
US structural engineers resisting wind and seismic story shears in light-frame wood buildings, designed to the current NDS 2024 and SDPWS 2021 ASD. Story shears link in from a Diaphragm Analysis that takes your wind and seismic results, so demands update as loads change. Segmented and perforated walls, single- or multi-story.
Blocked walls with 3/8 in or 7/16 in panels use the 15/32 in capacities allowed by footnote 2 of SDPWS Table 4.3A. This applies with studs at 16 in or less and 8d nails; unblocked walls keep their own tabulated values.
How it calculates
Lateral system and wall classification
The calculator treats the wall as either a segmented or a perforated shear wall. In the segmented method, only full-height segments without openings resist lateral load, and each segment needs a holdown at each end. In the perforated method, holdowns sit only at the wall ends. Capacity uses the sum of full-height sheathed segment lengths, multiplied by a shear capacity adjustment factor Co. Co depends on the wall area, the opening area and the full-height sheathed area, capped at 1.0.
Shear capacity per story
Each story's wind and seismic shear is checked against the story's allowable shear capacity:
- Segmented method: each segment's capacity uses its width and an aspect ratio factor. Segments above an h/b of 3.5 (blocked) or 2 (unblocked) are excluded. Story shear is shared between segments in proportion to their capacity.
- Perforated method: blocked segments with an h/b between 2 and 3.5 have their length reduced by 2b/h. Segments above 3.5 (blocked) or 2 (unblocked) count as zero length. The summed length is multiplied by Co, with nominal unit shear capped at 2,435 plf.
Nominal unit shear comes from the tabulated value for the selected wood structural panel sheathing and nail pattern, doubled when both sides are sheathed. It is adjusted for stud specific gravity and, for unblocked walls, for unblocked edges. Allowable capacity is nominal divided by 2.0 for wind and 2.8 for seismic. Seismic loads are assumed to already include wall self-weight; self-weight is counted only in the gravity loads.
Chord loads
The overturning moment at each segment generates tension and compression in the boundary chords. The moment arm is the segment length less the holdown offset you enter. For perforated walls it is the summed segment length less the offset, multiplied by Co. Chord tension is reduced by 0.6 times the dead-load restoring moment for wind, or (0.6 - 0.14 S_DS) times it for seismic. The full dead load on the panel counts toward that restoring moment. Chord compression adds only the gravity load tributary to the chord studs, with the rest carried by field studs. For multi-story walls, chord forces from upper stories are added at each lower story.
Chord tension design
Chord tension is checked on the net section of the boundary studs, allowing for the largest hole you enter. The reference tension value is adjusted for load duration, wet-service, temperature and size factors to NDS 2024.
Chord compression and bearing
Chord compression capacity is the lowest of three values. The first is gross-section capacity with the column stability factor, from strong-axis slenderness over the tallest story. The second is net-section crushing at the anchor hole. The third is bearing perpendicular to grain on the gross section.
Holdown check
Holdown design is optional. You select a Simpson Strong-Tie holdown (HDU, HDUE, HTT, DTT or LTTI), and the calculator reads its catalogue capacity for the stud species group. That capacity is checked against the maximum chord tension, which is net of the dead-load offset. The calculator also reports the minimum wood member size and the default number of stud plies for the selected holdown.
