Turnbuckle Capacity 1

[structuralaggie]

If the threads of the rod at least extend through the turnbuckle, is it safe to assume the tensile capacity of the rod will control design? By inspection it appears that the turnbuckle body has more steel than the rod. If not, are there published design values for these things? Thanks.

 

[UcfSE]

Check out AISC 13th edition manual, Table 15-5 page 15-16. It contains dimensions, weights and capacities of turnbuckles. This is also in the AISC 9th edition on page 4-149.

 

[structuralaggie]

Thanks. I don't have the newest edtion, but it is in AISC LRFD third edition too.

 

[RARWOOD]

It is my experience that turnbuckle strength is less than the tension capacity of threaded rod. I think that you will find that the puplished working load for turnbuckles that accept 3/4 diam. thrd. rod is 5.2 kips.

In the past I spoke with a supplier of turnbuckles who no longer publishes loads because they felt the published loads used in the past were not reliable.

When I want to develop the full capacity of A307 threaded rod I use sleeve nuts. Sleeve nuts are just long nuts. I've used sleeve nuts threaded for 3/4" diameter rod that have been up to 12" long. The sleve nuts can be threaded with both right hand and left hand threads so that the threaded rod can be pretensioned by turning the sleeve nut.

Some suppiers do stock sleeve nuts but in many cases they are custom made. Turn around time in the past was 7 days or less. If you are using high strength rod it will probably take a lot longer to obtain the required sleeve nuts.

Two companies you can check with for more information are Coupling Nut Supply in Wisconsin and Cleveland City Forge in Cleveland, Ohio.

 

[structuralaggie]

From table 15-5, the service load would be 13.0/1.5, or 8.7 kips, right? (I have the LRFD manual and is says to divide by 1.5 for service loads). At any rate, yes, the rod will be stronger than the connection.

I didn't know that table was in the AISC manual. I am always finding more stuff in there.

How long do the threads need to be to develop the allowable load of the turnbuckle? From another thread I read the full legth of the threads in the turnbuckle was sufficient.

 

[RARWOOD]

Good question! I have been told, with bolts as long as the threads are fully engaged in a the nut that the fully capacity of the bolt will be developed.

I have also been told that atleast two threads must extended past the nut. This guideline may be more for inspection then strength, I don't know.

I deal almost totally in wood design so the question is really not much of a concern.

 

[UcfSE]

I would make sure all the threads on the rod are engaged.