Four aspects influencing the vibration characteristics of steel member supported
floors were investigated. The four aspects are: 1) the number of tee-beams effective in resisting
a heel-drop impact for steel joist and steel beam-concrete slab floors, 2) the effective
moment of inertia of steel joist and joist-girder members, 3) the ability of joist seats to
provide composite behavior between the supporting member and overlying slab, and 4) the
effects of extending and restraining the bottom chords of joist members.
A new equation was developed to predict the number of effective tee-beams. The
proposed equation is recommended to replace the two current equations. The proposed
equation is a regression equation based on the results of a finite element analysis of 240 floor
systems and is considered to be more accurate than the current equations.
Next, a study was undertaken to determine the relationship between the span-to depth
ratio of a joist or joist-girder member and it's effective moment of inertia. Twenty five
joists and joist-girders were modeled and analyzed using the finite element method and
their effective stiffnesses calculated. The effective stiffness of each member was plotted
against the respective span-to-depth ratio. A linear regression line was then fit to the data to
mathematically represent the trend.
Finally, a vibration test floor was constructed to investigate the joist seat behavior
and extended bottom chords. Finite element models were developed and analyzed and frequency
and stiffness tests were performed to evaluate the floor's behavior. Conclusions
were then drawn and recommendations made concerning the joist seat behavior and the effects
of extending joist bottom chords.
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