Effect of end support restraints on vibration performance of cross laminated timber floors: An analytical approach

摘要

As an emerging building solution, cross-laminated timber (CLT) floors have been increasingly used in mass timber construction. The current vibration design of CLT floors is conservative due to the assumption of simple support conditions in the floor-to-wall connections. It is noted that end restraint occurs as a result of clamping action at the ends, arising from the gravity load applied by the structure above the floor and by the mechanical fasteners. Several attempts have been made to investigate the influence of end support restraints on CLT floor performance by using numerical modelling and experimental studies. Little research has been found to establish an analytical approach to characterize the effect of end support restraints. In this paper, the floor-to-wall connections are treated as elastically restrained edges against rotation to account for the effect of partial constraint. The end fixity factor was introduced to reflect the relative bending stiffness between CLT floor and elastic restraint at the edges. Then, end restraint coefficients were defined and analytical expressions were derived for the fundamental natural frequency and mid-span deflection under a concentrated load, respectively. By comparing with reported experimental data, the proposed design formula showed excellent agreement with test results. Test methods for determining fixity factors are discussed. It was found that the traditional static tests on end-support joints solely cannot provide accurate characterization of end-support fixity. The mid-span deflection of beam bending test combining with the derived analytical expression can be used to inversely determine fixity factors and excellent accuracy was achieved.