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    Structural / Serviceability

    Floor Vibration Check

    The natural frequency of a floor from its static deflection, and whether it sits far enough from the walking pace to avoid resonance. AISC Design Guide 11 uses exactly this relationship.

    Natural frequency6.29 HzLimit3.0 HzWalking pace1.6–2.2 Hz
    Natural frequency
    6.29 Hz
    Above the limit
    Limit
    3.0 Hz
    For this occupancy
    Walking pace
    1.6–2.2 Hz
    The forcing frequency
    Verdict
    Acceptable
    Frequency criterion
    Frequency from deflection
    Frequency f ≈ 0.18·√(g/Δ); keep it above 3 Hz for offices and 5 Hz for rhythmic activity.
    Frequency from deflection
    Deflection (mm)Frequency (Hz)
    48.90
    67.27
    86.29
    125.14
    164.45
    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Frequency against deflection
    Stiffer floors ring higher; the curve falls as the square root.
    Frequency against deflection0.0002.825.648.4611.2814.102 mm2 mm4 mm4 mm8 mm8 mm16 mm16 mm32 mm32 mmFloor Vibration Check
    Canonical equations
    The exact relationships implemented by this engine.

    f = 0.18·√(g/Δ) · AISC DG11, Δ in the same units as g.

    f ≈ 17.8/√Δ(mm) · The form used here.

    engineering methodology

    A clear path from inputs to results.

    The natural frequency of a floor from its static deflection, and whether it sits far enough from the walking pace to avoid resonance. AISC Design Guide 11 uses exactly this relationship.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Set static deflection under live load (mm).
    2. Set span (m).
    3. Set occupancy.
    4. Read the headline metrics, then check the table for the detail.

    The formula

    f=0.18⋅√(g/Δ)f = 0.18·√(g/Δ)

    Reference: AISC Design Guide 11 frequency criterion.

    Worked example

    At the default inputs

    Inputs
    • Static deflection under live load (mm): 8; Span (m): 8; Occupancy: office
    Calculation path
    1. 1

      Natural frequency: 6.29 Hz · Limit: 3.0 Hz · Walking pace: 1.6–2.2 Hz · Verdict: Acceptable

    Result

    Natural frequency: 6.29 Hz · Limit: 3.0 Hz · Walking pace: 1.6–2.2 Hz

    Interpreting the result

    8.0 mm of deflection gives 6.29 Hz, against a 3 Hz limit.

    Assumptions & limitations

    • First mode only.
    • Static deflection under live load, not total.

    Frequently asked questions

    Why 3 Hz?

    Walking paces sit at 1.6–2.2 Hz; keeping the floor above 3 Hz avoids the second harmonic.

    Is frequency enough?

    No — acceleration matters for sensitive occupancies, which needs the DG11 response calculation.

    Methodology last reviewed 2026-10-22. Results are informational and not financial or engineering advice — see our disclaimer.