A $9 million office complex is being planned for Olney, a town in Montgomery County at the center of a triangle formed by the metropolitan areas of Frederick, Baltimore and Washington.

The three-story building is being developed by Woodfield Partnership of Olney and will be constructed on slightly more than 5 acres to the west of Georgia Avenue just north of Route 108, in what many consider the heart of Olney. Construction is expected to begin in 1989.

Building design and preliminary planning of the project are nearing completion, said Louis J. Iaquinta, a general partner for Woodfield. Iaquinta estimates that the complex will employ 300 to 350 people.

According to Iaquinta, demographics indicate that Olney is ready for a major new office complex because of the rapid growth of its business and residential population.

"Olney is a dynamic community with a high concentration of well-educated residents who earn substantial incomes in professional and technical careers," Iaquinta said.

The 82,000-square-foot office building, designed by Ward/Hall Associates of Fairfax, will have a three-story atrium leading to a glass-domed rotunda. Interior balconies on the upper levels will have views of the rotunda.

"The atrium and the glass-domed rotunda will be the building's artistic signature," Iaquinta said.

The building will be built on a campuslike setting and will have a brick facade in the tradition of colonial architecture used in many commercial and residential properties in Olney, Iaquinta said.

Ninety percent of the building will be devoted to office space for high-technology and professional businesses. The rest of the space will be for service-oriented businesses. IKO Real Estate Inc., the agency in charge of Woodfield's real estate transaction, has announced plans to occupy the building.

The developer envisions a health club or day care facility in the building, but said that more needs to be known about the needs of the tenants before a decision is reached.

In other developments in commercial realty: Integrated Systems Analysts Inc., a defense contractor, leased 51,000 square feet at Shirlington Gateway, I-395 and Shirlington Road, Alexandria, from Weissberg Corp. Julien J. Studley was the leasing agent.

Advanced Biotechnologies Inc., an international biotechnology company, leased 26,909 square feet at RiversPark II, 9108 Guilford Rd., Columbia, from McCormick Properties Inc. Long & Foster was the leasing agent.