Primary Load Carrying Subsystem : Structure tying column tops together and supporting deck levels. This structure may consist of either trusses, box girders, plate girders or a combination thereof. (RP 2T)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}