The goal post frame normally uses a very large, trussed portal frame spanning parallel to the open edge.
The goal post frame usually supports trusses or beams running orthogonally and that carry the roof cladding.
The Ajax Stadium in Amsterdam is a special case since it is in effect two pairs of trussed goal post frames
In the short direction the spanning truss is curved upwards and supports the track that allows centre portion of the roof to be retracted
The stands at Liverpool FC's Anfield stadium and the San Siro also use a goal post frame structure.
The vertical legs of the frame are set back on two sides which gives more scope for use of the corners but means that the secondary structure cantilevers towards the playing area.
In Milan the San Siro stadium is a very readable structure with long span box truss supported on concrete columns, around which spiral circulation routes are wrapped.