prestressing timber structural members with cables
 

prestressing timber structural members with cables
i'm working on a project which requires the use of pretensioned cables attached to wooden girders. does anyone have any recommendations on how to anchor these cables, or how to (inexpensively) pull the wires to tension them. to give an idea of the scale of the project, 12 foot girders made of several 2 x 10's must carry a cable tension of about 4500 lbs. any advice would be much appreciated.
turnbuckles?
turnbuckles will work with the scale of your project. you will likely lose a good amount of pretension to creep in the wood, you may want to plan a periodic check of the cable tension. what do others think, is checking the torque on the turn buckle a reliable enough method to check the rod tension (assuming you are well below yield, say .25fy)? this question has come up around my office.
turnbuckles...sounds like a broken record.
riggers often use a cable tensioner - like a turn buckle but it is specifically designed to pre-tension cables - hold them while clamping w/o losing tension. they use them on tall towers, antennaes, etc.
any good cable supplier should be able to help