QConBridge computes self-weight dead load as the product of Ax and
Density, found in the Span Edit dialog. The Section Properties Calculator is an efficient
tool for computing Ax and Density. The Section Properties Calculator computes a
transformed area for Ax and an equivalent density for Slab on Beam sections.
The Section Properties Calculator incorrectly models Slab on Beam cross sections,
resulting in an equivalent density that is incorrect. This leads to an unconservative
estimate of dead load.
The Section Properties Calculator fails to account for the portion of the slab that
falls outside of the effective slab width as shown in the figure below. The neglected
portion of the slab is shown in red.
To correct for this deficiency, compute the "missing" equivalent density as
(Gross Slab Depth)*(Tributary Slab Width - Effective Slab Width)*(Density of Slab
Material).
Add this value to the Density for the composite cross section computed by the Section
Properties Calculator. |