Members of the Development Authority of Cobb County gave their final approval Thursday to the issuance of nearly $56.9 million in bonds to allow Georgia Tech to expand operations on part of Marietta’s Lockheed Martin campus. The Atlanta-based university had sought the bonds to buy 32 acres on the northern portion of Lockheed’s property adjacent to Dobbins Air Reserve Base and the Georgia Tech Research Institute, an applied research arm of the school. The funds will also go toward construction, renovations, and equipment at four existing buildings on the site to provide additional research space.