Vibration serviceability of hybrid CLT-steel composite floors based on experimental and numerical investigations using random walk models

Cross-laminated timber (CLT) floors often encounter vibration issues when employed in large spans bearing heavy loads, and the enhancement of their vibration performance frequently centres around achieving composite action. This study delves into the effectiveness of hybrid CLT-steel composite floors as potential substitutes for traditional, long-span CLT floors. A parametric model was developed using OpenSeesPy and validated with prior vibration experimental tests on hybrid and pure CLT floors. It was then employed in examining the sensitivities of the floors to various excitation scenarios via an integrated random walk model used to generate random dynamic responses. Two extreme boundary conditions: pinned-pinned and clamped- clamped, were also simulated to investigate the limits of the vibration response of the hybrid composite floor. The chosen metrics for assessment comprised fundamental frequency, vibration dose value, peak acceleration and velocity, response factor, as well as root-mean-square acceleration and velocity. These metrics were also juxtaposed against the predictions put forth by the new Eurocode 5 draft. Though the fundamental frequency of the much-stiffer hybrid composite floor was about thrice that of the bare CLT, the considerably lower damping of the former - about 60 % less, resulted in a comparable acceleration response with the CLT floor. Also, despite a 55% increase in fundamental frequency when the hybrid floor was simulated with clamped supports, the resulting serviceability metrics did not indicate a clear-cut performance improvement over the pinned boundary condition. The results highlight the leading influence of damping rather than bending stiffness and fundamental frequency on the serviceability metrics of hybrid CLT-steel composite floors.