Complex sentence: SEC Ltd had identified the need for a new arena designed specifically for large scale performance events ranging from rock concerts to children's shows, although the main reason for the building is due to the lack of a dedicated high capacity indoor events space in Glasgow.
Split into simpler sentences: SEC Ltd had identified the need for a new arena, specifically designed for large scale performance events, ranging from rock concerts to children's shows. Although, the main reason for the building was due to the lack of a high capacity indoor events space in Glasgow.