Abstract
Impact hammer tests and analyses by finite element method were conducted to demonstrate the effects of support condition and uneven distributed load on the vertical dynamic characteristics of light frame joist floors with 3.64m-long-span and from 0.91m to 7.82m-wide joist floor consisted of 2" by 8" dimension lumbers and 15 mm-thick plywood subfloor.
The results indicate, i) Support condition slightly affects the natural frequencies when the width/span ratios exceed 2; ii) In addition to the mass-ratio of human-load, both the placement and the stand position of persons onto the joist floor give influence on the damping factor of 1st natural frequency; iii) The joist subjected to uneven distributed load generates locally deformed vibrational mode and also determines the 1st natural frequency of the joist floor; iv) Finite element analysis employed the appropriate models is effective to predict the natural frequencies and mode shapes of joist floor subjected to uneven distributed load.
