Does anyone know why the ends of the bottom chord of my truss fails when it has double angle section L75x75x6 LD, while when I use the single angle section L75x75x6, it passes? as per the output, the members fail in flexure compression and tension (eq. H2-1). I just wonder why it fails when it has larger section and the critical load for its failure is from upward windload.Attached is the staad file for reference.
WMF-ROOF_REVISED JULY 11.std