Riggs National Bank has promoted Robert K. Ratcliff to vice president and manager of the bank's new West-bridge office. The bank's 25th branch, under construction at 26th and M Streets N.W., will open in the spring.

A native of West Virginia, Ratcliff began his banking career with the Riggs Federal Office in 1960 as an information clerk and teller. Elected to assistant cashier in 1968, he was promoted to assistant manager in 1973.

Also promoted were Pedro E. Areu and Henry A. Dudley Jr. from assistant vice presidents to vice presidents, both in the international department.

Areu has been with the bank since 1962. Dudley joined the bank as assistant vice president in 1977.

David C. Scott, chairman, president and chief executive of Allis-Chalmers Corp., has been elected to the board of directors of Martin Marietta Corp.

Scott has been associated with Allis-Chalmers since 1968 and previously with General Electric, where he advanced through various executive levels in engineering, manufacturing, finance and management.

Lelis J. Silverstone, vice president for the southeast region of Dean Witter Reynolds Inc. in Washington, D.C, has been elected chairman, and Harry M. Boyd, senior vice president and director of Interstate Securities Corp. in Charlotte, N.C., has been elected vice chairman of the District's No. 10 Committee of the National Association of Securities Dealers, Inc. (NASD)

Silverstone is a former financial columnist for the Washington Star, a member of the Washington Society of Investment Analysts and of the Meteopolitan Washington Board of Trade.

Boyd has been associated with Interstate Securities Corp. for 11 years.

Edward B. Burwell has been appointed vice president, transportation, for the Southern Railway System. He has been general manager of western lines since 1970.

Burwell joined Southern in 195i as a student apprentice. He was named superintendent at Birmingham, Ala., in 1960 and also served as superintendent at Hattiesburg, Miss., and Knoxville, Tenn.

David Anderson, president of Arlington-Fairfax Savings & Loan Association, has been voted to the board of directors of the U.S. League of Savings Association, He will representginia. Anderson also has been elected to serve a two-year term with the Savings and Loan Foundation. Anderson has been president of AFS since 1962 and chairman of the board since 1975.

John A. Roosevelt has been named a director of Steadman Security Corp., a Washington-based investment adisory firm. Roosevelt will supervise the firm's acquisition program for securing investment advisory contracts with other mutual funds.

Roosevelt is a senior vice president and director of Bache Halsey Stuart Shields Inc.