CLT shear wall
A stacked cross-laminated timber shear wall of equal rocking panels with the prescribed nailed angle connectors, by SDPWS 2021 Appendix B, story by story from the top: connector shear, panel shear, hold-down strength and deformation, compression zone, deflection and drift. The default is the wall of FEMA P-2192-V1, Chapter 6. SDPWS 2021 Appendix B and 4.6 were read against this module on 2026-11-08; the Commentary equations (C-B.2 to C-B.5) are not in the copy on file and follow FEMA's use of them.
Inputs of the CLT shear wall #
- System. Cross-laminated timber shear walls, h/bs from 2 to 4, R, Ω, Cd of 3, 3, 3; or high aspect ratio panels only, h/bs of 4, with 4, 3, 4 (ASCE 7-22 Table 12.2-1). R is not used here: forces are entered. Cd is.
- Panels. Panel length bs and the number in the wall; every story has the same panels.
- Stories, top first, up to 6. F at strength level, added at the top of that story. wD and wL on the panel; FEMA enters each story's own load, not the accumulation. Connectors at the bottom of a panel (the top matches), hold-downs at each end, what it bears on.
- Added to h. FEMA's text writes the panel height, but its Tables 6-6 to 6-8 only come out with the 6.875 in. floor panel above added for stories with a floor over them. So it's an input, prefilled as those tables: 0 reads h as the equation writes it, and gives less overturning. Your call.
- CLT panel. Thickness (at least 3.5 in., B.3.1), the layers along the height, G, Ft, Fc. In-plane Fv(tv), EIeff and GAeff are from the panel's report and the SDPWS Commentary for your panel length; they're prefilled for the example's 4 ft 9 in. panel, so change them with the panel length.
- Hold-downs. Position, capacity and deformation from the device's report, at the design method's level; the factor of B.3.4, 2.0 for seismic (B.3.4 permits 1.5 for wind; the prefilled 2.0 is on the safe side); the end of the panel developing them, 1 ft in the example.
- Compression bearing. Floor panel Fc⊥, thickness and E across the grain. End grain bearing takes 0.75 Fc unless on stiff metal.
- Add the gravity of the stories above to the compression. On by default, off in FEMA's tables. The load from the panels above reaches this end panel too, so the default is the longer zone; the hold-down never counts it, which is the conservative side there.
- Ie, allowable drift. 0.025 is the example's case, ASCE 7-22 Table 12.12-1: risk category II, four stories or less, finishes that accommodate drift.
Auto-design varies the connectors per panel and the hold-downs at each end, top story first, then more connectors if deflection asks for them. Panels, the device and loads stay yours.
Checks performed #
| Check | Basis |
|---|---|
| Panel aspect ratio, each story: 2 to 4, or 4 for high aspect panels | SDPWS 2021 B.3.1, B.3.7 |
| Panel thickness at least 3.5 in.; at least two connectors at the top and bottom of each panel | SDPWS 2021 B.3.1, B.3.2 |
| Wall height at most 65 ft, seismic | ASCE 7-22 Table 12.2-1 |
| Connector shear: vs = n × 2,605 CG / bs (Eq. B-2), then 0.5 or vn / 2.8 for seismic, 0.8 or vn / 2.0 for wind | SDPWS 2021 B.5, B.6; the factors of 4.1.4.1 and 4.1.4.2, which B.3.4 names |
| Panel in-plane shear, and enough that the nails govern | NDS 2024 Table 10.3.1 |
| Hold-down strength at the entered factor (2.0 seismic, 1.5 permitted for wind) times the connectors' design capacity, accumulating down | SDPWS 2021 B.3.4 item 3; Commentary Eq. C-B.2 as FEMA uses it |
| Hold-down deformation at most 0.185 in. per story under strength forces | SDPWS 2021 B.3.4 item 2 |
| Panel tension over the length developing the hold-downs | NDS 2024 Table 10.3.1 |
| Compression zone within the end panel | SDPWS 2021 B.3.5; Commentary Eqs. C-B.3 to C-B.5 as FEMA uses them |
| Deflection against drift limit × h × Ie / Cd | SDPWS 2021 B.4, Eq. B-1 (h the panel height), ASCE 7-22 12.8.6 |
Limitations of the CLT shear wall #
- Walls not meeting Appendix B (the R = 1.5 route of SDPWS 4.6.3.2) are not covered, nor are diaphragms.
- Stated in a note, not checked: moisture content under 16 %, platform construction, connectors within 12 in. of each panel end, the anchorage designed for the connectors' concurrent tension and shear, and B.3.6 load path connections.
- Not checked: the panel's column stability, net sections at holes and cuts, row and group tear-out at the hold-downs, screws of the device. Use the CLT panel type for the panel in compression.
- One panel length per wall. Panels of different lengths or a wall set up at "T" intersections are not modelled.
- Appendix B applies to wind as well as seismic (4.6.3.2). B.6 and 4.6.3.1 send the design values to 4.1.1, the general requirements; the factors used are those of 4.1.4, which B.3.4 names for the hold-down: an interpretation, stated here.
- EIeff and GAeff aren't calculated; PRG 320 and SDPWS Commentary C-B.4 aren't on hand.
- Connector layout is by count: drawings do not place them.
Verification examples #
Verification status: 55 values compared in 7 examples (6 published, 1 hand calculations from the cited equations): 51 within tolerance, 4 recorded deviations. Code basis: partial. Only some provisions were read in the target edition; the rest rests on older editions, examples or summaries.
FEMA P-2192-V1, Chapter 6, pp. 229-246: Tables 6-4 to 6-9 by strength design, with the compression option off as FEMA has it. Differences, plainly:
- Table 6-9's shear and total at stories 2 and 1 follow the height plus the floor panel, where Eq. B-1 says panel height. ILX uses panel height: 0.319 and 0.338 in. against 0.33 and 0.35. That is about 0.01 in. on the low side of the printed value; recorded as a deviation.
- FEMA's printing has small slips, not differences in method: 20,849 plf where its factors multiply to 20,952; 17,687 and 17,678 lb for one device; 35,540 for 34,540 lb on p. 237.
Allowable stress design and wind have no published example: hand calculations. Appendix B was read on 2026-11-08; PRG 320 and the Commentary were not.