Modelling of thin constrained layer damping treatment applied to composite floor beams

Abstract

The Vibration Serviceability Limit State (VSLS) due to human dynamic loading is increasingly becoming the sizing criterion for long-span composite floors. To meet this requirement, structural designers usually tend to increase the stiffness or the mass of the floor. This paper studies a damping technology applicable to these floors since the design stage for improving their dynamic behaviour by increasing their damping capacity and avoiding thus over-sizing the floor structure to meet the VSLS. The studied technology is based on a Constrained Layer Damping (CLD) treatment made of a thin viscoelastic (VE) layer integrated between the concrete slab and the steel profile of the floor, along a percentage of the beam length near the supports. Thus, this paper proposes a simplified Finite Element (FE) approach to model this treatment based on using simple SPRING elements for the VE layer and a corrected version of the modal strain energy method for damping estimation, avoiding thus the use of complex modal analysis. The proposed approach is used to assess the additional damping ratio provided by the CLD treatment. The accuracy of this approach has been validated by comparing it with detailed FE models and widely accepted analytical formulations considering different percentages of the beams’ length treated with CLD. Finally, an application example has been performed with CLD-treated and untreated single-spanning composite floors, showing: i) CLD-treated floors have a better dynamic performance, and ii) CLD technology enables reducing the amount of steel needed to design lightweight floors especially sensitive to vibration.