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Calculation of allowable span lengths for CLT vibration uses the procedure in CSA O86 A.8.5.3.
The allowable vibration span is calculated as
lv <= 0.11 EIeff0.29 / m0.12
where EIeff is in N-m2 and m is the mass per square meter of the panel.
Multiple Spans
Although the equation is derived for simple spans, the allowable span is compared with the longest span on a multi-span member, as is allowed by Note 1.
Allowable Span Increases
In the Vibration Details dialog box, accessed from the Beam View or from Concept mode Joist Groups, you can enter a percentage span adjustment increase for manufacturers performance expectations as allowed by A.8.5.3 Note 3 and for multi-ply beams, whether to apply the 20% vibration span increase for non-structural elements from CSA O86 A.8.5.3.
Note that these are the only inputs pertaining to CLT in the Vibration dialog. All the other inputs, which are for joist vibration, are unavailable when designing a CLT member.
The allowable span is then increased by the largest of the performance increase or the non-structural element increase. Both increases are not applied simultaneously.
The non-structural element increase is not applied to spans greater than 8 m (26.25 feet in length) and will increase spans less than 8 m only as far as 8m.
A design note appears if either of these increases has been applied.