Charles Davis Nov 29, 2015:

Cheers, James. That's the key to it, I think. I was about to add another reference, this time from Spain, in which D.O. is explicitly identified as Director de Obra:

"Las funciones del Director de Obra (DO) que fundamentalmente afectan a sus relaciones con el Contratista, son las siguientes:"

and is also used a number of times (see pp. 11-14) as la DO, interspersed with la Dirección de Obra.
http://www.aytonavalmoral.es/documentos/perfilcontratante/DO...

James Arthur Williamson (asker) Nov 29, 2015:

Thanks Charles, quite obvious really. I was looking for another aspect of the floor slabs similar to expansion joints but you are quite right: "conjuntamente" refers to "analizar", not "juntas de trabajo".