Wood floor vibration
Walking vibration of a one-way wood joist floor (sawn joists, I-joists or floor trusses) against the criterion you choose. US and metric units.
- Live load deflection: limit L/Δ.
- Onysko / CCMC: the 1 kN point-load deflection.
- Hu and Chui (FPInnovations): the frequency-deflection ratio.
- Frequency: an optional minimum.
Only the APA L/480 basis is from a document on disk. The Onysko and Hu-Chui criteria and the frequency minimum are built from knowledge and marked "to confirm against the code text".
Inputs of the floor #
- Joists:
- sawn lumber (species, grade, size; E from Supplement Table 4A or 4B); or
- I-joists or floor trusses, with the EI of one joist from the manufacturer's evaluation report.
- Span: simple span.
- Spacing: joist spacing.
- Floor weight: the actual dead load for the frequency, not the design value.
- Live load: for the deflection.
- Vibration criterion: your choice.
- Onysko / CCMC: the deflection under 1 kN (225 lb) at midspan must not exceed 8 / L^1.3 mm (L in m) and 2 mm.
- Hu and Chui: f1 / d1^0.44 ≥ 18.7, with f1 in Hz and d1 the 1 kN deflection in mm.
- Deflection only.
- Share of a point load on one joist: your judgment. 1.0 is a joist alone. About 0.3 to 0.5 applies where glued sheathing, bridging or strongbacks spread the load. The published methods take the floor system from tests and their own load-sharing models, which this calculation does not reproduce.
- Live load deflection limit: L/480, the APA Performance Rated I-Joist basis for better floor performance (APA Z725H), or L/360 (IBC Table 1604.3).
- Minimum frequency: optional; 15 Hz is commonly recommended.
Auto-design (editor toolbar) varies the sawn joist size and the spacing (only the spacing for I-joists and trusses). Objective: the least wood per foot of floor.
Checks performed #
| Check | Basis |
|---|---|
| Live load deflection | 5wL⁴/(384EI) against L/limit |
| 1 kN deflection | k P L³/(48EI), with k the load share, against min(8/L^1.3, 2) mm (Onysko / CCMC) |
| Frequency-deflection | f1 = (π/2L²)√(EI g/w) with the floor weight on one joist; f1/d1^0.44 against 18.7 (Hu and Chui) |
| Frequency | f1 against your minimum (optional; otherwise reported) |
The drawings are a framing plan of a bay (the joists, the spacing and span, the 1 kN load) and the joist section.
Limitations #
- Criteria from knowledge: the Onysko and Hu-Chui criteria and their constants are to be confirmed against their sources (Onysko 1985 and the CCMC / NBC span tables; Hu and Chui 2004, FPInnovations).
- Load sharing: the share of a point load is your input, not the methods' own models.
- Not covered:
- two-way action;
- composite toppings and finishes;
- continuous joists;
- damping;
- the AISC Design Guide 11 method (the steel floor vibration type);
- I-joist shear deflection beyond the entered EI.
- Strength: the joists' strength is checked in the wood beam or I-joist calculation.
Verification examples #
Verification status: 8 values compared in 4 examples (1 published, 3 hand calculations from the cited equations): 8 within tolerance, 0 recorded deviations. Thin: only 1 published example. Code basis: not yet recorded for this module.
The default deflection limit is APA's published L/480 basis. Everything else is a hand calculation with the criteria as built:
- a 2x10 Douglas Fir-Larch No. 2 floor: deflection, 1 kN deflection, Onysko limit, frequency and the Hu-Chui ratio;
- an I-joist with its entered EI.
No published wood floor vibration example is on disk. The FPInnovations and CCMC documents are listed as needed.