Study to Validate the Floor Vibration Design of a New Mass Timber Building

This study was undertaken by KPFF with a United States Forest Service Wood Innovations Grant. The purpose was to apply the floor vibration design procedures outlined in WoodWorks’ U.S. Mass Timber Floor Vibration Design Guide to a mass timber project—the University of Washington Health Sciences Education Building—and compare the predicted and actual levels of floor vibration. Although the study focused on footfall-induced vibrations, further study and calibration of the analysis principles described in the report could lead to analysis methods for other sources of mass timber floor vibrations, such as building mechanical equipment and vehicles driving on nearby roadways.

A distinguishing feature of the tested mass timber floor systems was the composite action created between structural steel floor beams, cross-laminated timber (CLT) floor panels, and cast-in-place concrete floor topping slab as shown in Figure 1. Composite action was achieved using conventional welded, headed, shear studs installed along the top flanges of the steel floor beams. Laboratory tests of two composite beams were carried out to explore the relative contributions of the beams, slabs, and CLT to the elastic stiffness of the composite section. Tests were also performed on isolated CLT panels to determine the orthogonal stiffness properties of the panels for use in computer models that were developed to calculate floor vibration response in accordance with the Guide.

Figure 1: Typical composite floor section