What is the free length of the compression flange?
Here is an example of a lateral support in the span of the beam, so the free length of the compression flange is 6 meters.
For beams without lateral support points in the midspan, L1 is the span; for the beams with lateral supporting points in the midspan, L1 is the distance between the lateral supporting points of the compression flange (the lateral support of the beam is considered as lateral support).
