Basis of T-Beam effective width
Basis of T-Beam effective width
(OP)
I was wondering, why is the T-beam effective width a function of the span length? or to be more precise for relevant codes a function of the points of contraflexure for sagging bending moments.
Hope someone could help
Hope someone could help






RE: Basis of T-Beam effective width
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Basis of T-Beam effective width
RE: Basis of T-Beam effective width
RE: Basis of T-Beam effective width
Regardless, it was not my intent to suggest that the effective flange width provisions were based on strut and tie analyses. Rather, I was merely suggesting the use of strut and tie visualization as a device for understanding the need for a span based limit on effective flange width.
The code provision would seem to imply a load spread of about 1:4. For comparison, other code provisions (walls) in ACI imply load spread of 1:2 and, were strut and tie methods to be used in earnest, one could conceivably bump that up to around 1:1.5.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Basis of T-Beam effective width
And we always thought your answers were based on deep thinking theory!
It is due to the fact that the compression stress in the slab drops off as you move away from the web due to shear lag. The effective width is an attempt to define a width over which the stress assuming constant stress over the flange width would give a reasonable estimate of this drop off. It is related to span length (and distance between points of contra-flexure) in many codes because the dispersion width will be greater in a longer span length. Those rules are based on UDL's however. For major concentrated loads it should be related to the distance from the maximum +ve moment point to the point of contra-flexure of the concentrated load is not at mid span.
RE: Basis of T-Beam effective width
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.