Low-frequency vibration of a timber joist floor section connected by metal screws: experimental validation of FEM models

The structural dynamics of a timber floor junction (six pieces of chipboard plate screwed to a single timber joist) have been investigated experimentally in a frequency range up to 200Hz. Experimental Modal Analysis (EMA), transfer mobilities and velocity level ratios between the chipboard walking surface and the joist were measured with 12 or 24 screw connections between the joist and the chipboard. These experimental data were used to validate Finite Element (FE) models that focussed on the interaction between the chipboard and the joist due to the screws. The aim is to develop validated FE models for timber floors that can be used to assess heavy impacts (such as the rubber ball impact source) and act as a reference for the future development of TSEA models for lightweight structures. The screws were modelled using both rigid connections and springs. For the latter, each point connection was modelled by four springs with stiffness (three coordinate directions and one rotational direction), with model updating using a Deep Neural Network (DNN). A comparison of mode frequencies and mode shapes from EMA and FEM will be made along with forced vibration of the structure.