Two methods of truncating the transaction logs for a database for SQL Server 2008 or newer:

Perform a backup to the nul device, essentially a "black hole":

BACKUP LOG [databaseName] TO DISK = 'nul:'

Temporarily set the recovery model to SIMPLE, then shrink the transaction log:

ALTER DATABASE databaseName SET RECOVERY SIMPLEDBCC SHRINKFILE('databaseName_log', 0, TRUNCATEONLY)ALTER DATABASE databaseName SET RECOVERY FULL

WARNING: truncating the transaction log without a backup may result in data loss in case of a database failure!

EDIT (26/05/2015):

You could attempt the backup/shrink routine without changing the recovery mode, but this will most likely onl  ...