Question

Could you help me understand what this option does? The default value as per in manual is very small. I am using a value of 0.01, and the model works better. 

Answer

Out-of-straightness is an imperfection intentionally added to structural members. We assume that the member is not a straight line between its two ends, and this way, the model may be more realistic, especially if the weight of the structures is not considered during the analysis. If the model weight is already applied in the load sequence as the first load case, out-of-straightness may not be necessary. However, sometimes, we need this imperfection to model construction imperfections accurately. It's important to note that adding out-of-straightness increases the likelihood of buckling.