A short column is said to depend on material strength only. But you know deflection still occurs. It may be negligible, but I'm computing the corresponding strain of concrete at mid-height with respect to the upper and lower region. If concrete fails at a strain of 0.003 at mid-height. What formula do you use to compute for the strain at the upper region. I'd like to compare them. Please see color diagram of the strains attached herewith.
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Short Column Deflection
- Thread starter kylelo
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paddingtongreen
Structural
Guys, you are at cross purposes. JAE, he has an equal eccentricity of the reaction at the base. This does not need an external equalizing moment - no horizontal reactions.
If pinned/pinned JAE is correct when you draw in the horizontal reactions required to make ΣM=0 for the free body.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
If pinned/pinned JAE is correct when you draw in the horizontal reactions required to make ΣM=0 for the free body.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
In the sketch provided, both ends may be considered pinned. Each end has an applied moment of Pn*e. Neglecting deflection, the moment is constant for the full length of column.
The first order deflection at midspan is M.L2/8EI but this provides a variable moment over the height of column, so at mid-height, the moment is Pn(e + δ). But because the moment has increased, the deflection also must be increased, so the moment must be amplified to account for increased deflection.
If the load is sustained over a long period of time, concrete creeps and further increases deflection, again amplifying the magnitude of the moment at mid-height. The exact amount of this amplification is dependent on several factors but can be estimated for purposes of design and is given in the applicable concrete code.
BA
The first order deflection at midspan is M.L2/8EI but this provides a variable moment over the height of column, so at mid-height, the moment is Pn(e + δ). But because the moment has increased, the deflection also must be increased, so the moment must be amplified to account for increased deflection.
If the load is sustained over a long period of time, concrete creeps and further increases deflection, again amplifying the magnitude of the moment at mid-height. The exact amount of this amplification is dependent on several factors but can be estimated for purposes of design and is given in the applicable concrete code.
BA
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