The president of George Hyman Construction Co. has doubled his shares of American Security Corp. stock with a purchase that gives him approximately 6 percent ownership of the holding company for Washington's second-largest bank.

A. James Clark, a member of the board of directors of American Security Corp. who has been associated with the bank for about 10 years, bought approximately 100,000 shares of the bank stock Jan. 26 for an estimated $3.9 million, raising his holdings to 194,000 shares.

The purchase apparently makes Clark the second-largest holder of American Security stock. Various funds operated for the benefit of members of the International Brotherhood of Electrical Workers hold more than 200,000 shares.

The stock purchase comes at a time when banking in the District of Columbia is fomenting, with former Washington Star publisher Joseph L. Allbritton attempting to gain control of Riggs National Bank in an unfriendly takeover -- a phenomenon on the rise in banking. It also comes at a time when investors are eyeing bank stock with increased enthusiasm because of the possibility of interstate branching.

But Clark said his stock purchase reflected no new motivation. "I've always been a large stockholder. I've been accumulating stock for years," Clark said yesterday. He said he had not paid attention to what percentage of stock he now holds nor to his ranking among stockholders.

"It's strictly an investment," said Clark, who bought the stock for himself and as a custodian. Some of Clark's stock is registered in the names of corporations in which Clark owns a majority interest. Clark Enterprises Inc. is the parent company of George Hyman Construction Co. [TEXT OMMITTED FROM SOURCE]

Clark "has been a very key, strong director of the bank," said National Bank of Washington Chairman Luther Hodges.

"Hyman is probably the most successful company in that industry in the Free World, and they're cash rich," said Patrick Ryan, an investment analyst with Johnston, Lemon & Co.

American Security Corp. was formed in 1957 as a successor to an earlier bank. In 1980 the bank had operating income of $24.4 million. Assets at year end topped $2.7 billion, loans were $1.5 billion and deposits were $2.1 billion.

George Hyman Construction Co., which Clark heads, is a privately held Washington area firm that had more than $300 million in contracts in 1977. The company operates all over the nation in both heavy and commercial construction.