For the second time in less than three years, the nation's third-largest truck and trailer rental company reported that it has filed under Chapter 11 of the U.S. Bankruptcy Code. Jartran disclosed assets of $37 million and liabilities of $114 million when it filed for protection in the Miami branch of U.S. Bankruptcy Court. The Miami company blamed intense competition for the losses but did not elaborate. Jartran is a unit of Frank B. Hall & Co., an international insurance broker based in Briarcliff Manor, N.Y.