say I have a beam start from 20" on one end and go to 10" on the other end, what depth should I use to go into the CL calculation?

Using 20 is apparently conservative and OK, but is there any explicit rule for that?

@billkirkham  @heblomgren  @johnlawson

There are very limited design guidelines or resources available for practitioners. The current design equations in the CLT Handbook (Canada or US versions) are limited to floors with rigid supports (walls), and the U.S. Mass Timber Floor Vibration Design Guide is basically a literature review of CLT handbook method and other response-based methods developed for concrete and steel floors, without any verifications against data.

The challenges in vibration serviceability design for timber structures are twofold: predicting dynamic properties and responses and establishing suitable design or performance criteria. Due to the inhomogeneous material properties, orthotropic elastic constants, and construction details with discontinuity and semi-rigid connections, accurately predicting the dynamic properties and responses of timber structures under footfall or wind excitations can be complex. Moreover, human perception of vibration can be highly subjective, influenced by environmental conditions and psychological and physiological aspects. The latter one is even more challenging.

To address this gap, the only way is to create a database, which consists of both the physical data of the floor and occupants' subjective ratings (post-occupancy evaluation). With the database, we can do all kinds of analysis and develop design guidelines tailored for mass timber floor systems. 

Please share your thoughts and discussion.