Hello! Does anybody know how this formula is derived? I see the Mc/I form of the formula but can't seem to understand why the formula has a 4 in the numerator instead of a 6.
The value La x t^2 / 4 is the plastic section modulus Zx.
Using the value of 6 would be for an elastic section modulus Sx.
You are using LRFD with an ultimate limit state in weak axis bending.
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