CAIRO, March 14 (Reuters) – Egypt’s Orascom Construction Industries (OCI) said BESIX Group, in which it has a 50 percent stake, has won a $1.3 billion contract to build a medical centre in Abu Dhabi in a joint venture with South Korea’s Samsung C&T. Belgian construction firm BESIX’s share of the contract is worth $780 million, or 60 percent, OCI said on Sunday, with the remainder of the work due …