Integrated Buildings & Structures

I just completed a design on turnbuckles in compression! I did a 3/8 inch bolt with 6 inch open body. It turned out to be a major research project because there is no literature on turnbuckles in compression! I had a client who put turnbuckles in compression with seismic loading. It took 44 pages of calculations with trial and error until I had a solution that made sense. All the literature said no compression, but turnbuckles can take about 20% of their maximum tensile strength! The maximum tensile strength was 5000 pounds with WLL of 1000 pounds. I determined it could take approximately 1000 pounds in compression with a factor of safety of approximately FS=2.0-1.60 WLL= 500-612 pounds in compression! I saw a compression test on YOU Tube with a 3/16 inch bolt and 4 inch open body! The bolts buckled at 240 pounds!

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Gary Cooper P.E., M.ASCE
Roy UT
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Hi,

The issue I would have with it is the failure mode.  Buckling is a sudden, unpredictable failure.

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Sarah Halsey P.E., M.ASCE
New York NY
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The manufacturer is not likely to assign a load rating for compression on a turnbuckle.  The quality of the components is controlled by the manufacturer and there is no way of knowing whether your test results would be consistent with hundreds or thousands of trials.  Is the retrofit cost to reinforce the as-built condition really cost prohibitive to the owner?

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Chad Morrison P.E., F.ASCE
Professional Engineer
Greenville RI
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That is very interesting! Sounds like a very thorough analysis.I think it would be great to conduct a few tests of various sizes to prove the calculations, if an opportunity arises. 

Thanks for posting. 

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Jeffrey Walkley P.E., S.E., M.ASCE
Vice President
Michael J Walkley, PA
Towson MD
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Any time I've used a turnbuckle it was in a tension only member, so I understand why there is no or limited published data on compression. I was always taught that "you can't push a rope", and as these devices are almost exclusively used for long, slender members it would be interesting to know the type of applications whereby you need to have a turnbuckle in compression.

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David Kennicutt, PE (NY), M.ASCE
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