Vibrations of cross-laminated timber floors

Abstract

© 2019, Journal Drvna Industrija. All rights reserved. This paper investigates the vibrations caused by human action of five-layer cross-laminated timber panels with a height of 14 cm. Analysis is made of three floor panels of identical height, but with different combinations of thicknesses of the laminas in cross-layers, varying their spans. The longitudinal layers of the panels have better physical and mechanical characteristics than transverse layers. The relevant criteria to be observed in floor construction at the designing stage are specified in order to ensure acceptable behavior regarding the dynamic load. Limit values are also given. As it is very difficult to determine the threshold of human acceptability, since vibrations that someone finds disturbing do not have to be disturbing for others, the relevant criteria used in the work has been chosen on the basis of the highest representation in the literature: Natural Frequency Limit, Unit Load Deflection Limit and the Combined Criterion. Calculation of the effective bending stiffness of the panel was performed using Gamma method, K-method and Kreuzinger analogy. The natural frequency of each panel was determined analytically, and so was the maximum deflection due to unit static force and the obtained results were compared with the values obtained by modal and static analysis in the Ansys software package. All the obtained data were compared with the valid criteria, and panels that meet the criteria in terms of the serviceability limit state were selected. The results showed that the analyzed floor panels of the span up to 4.5 m are acceptable in terms of adequate dynamic behavior related to human action according to all criteria. Also, the results showed that the Combined Criterion and the Unit Load Deflection Limit are significantly stricter due to the unit static force compared to the Natural Frequency Limit. If the minimum required natural frequency of the CLT panel were accepted with a value of 8 Hz, which corresponds to the milder recommendations in the available literature, the spans could go up to 6 m. On the basis of the obtained results, it can be concluded that in the design of floor structures, in addition to static stability, an adequate dynamic response to the initiative caused by everyday human activities must be provided. The results also show that the analyzed floor CLT panels can be very successfully applied in the floor constructions of residential and commercial buildings, provided that the required dynamic calculations are made.