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I'm looking to find the safest way to secure a 4x4 to act as a beam for rope-climbing. In the picture below, the "top" beam sits on-top of two 4x4 posts.

The rope will extend from the far right of the post, putting upward force against whatever join/fastener is selected when someone is climbing it.

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Most of the 4x4 fasteners I've seen are designed to secure a post vertically and not against the direction of force being applied here.

represton
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Numpty
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1 Answers1

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This can take a load of 1,950/1.6=1,289 pounds. Just make sure the cantilever length doesn't exceed it's back span. Make sure there's 2 installed on each post to beam connection.

For the horizontal force, install (1) Simpson A21 on the underside of the beam to the side of the post on the left and (2) Simpson A21 from the underside of the beam to the faces of the post on the right. Use (2) 0.148 x 1 1/2 nails for each of the clip connections.

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represton
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  • This is perfect, thank you so much! – Numpty May 06 '20 at 17:06
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    The loads are relatively short duration so this could be increased by 1.15 or 1.25 so the given numbers are conservative – Ack May 06 '20 at 17:25
  • Sure - thanks again. I noticed you used screws in the first edit and nails in the last edit. I'm assuming nails are the right way to go here? Same thing for the LCE bracket? – Numpty May 06 '20 at 17:32
  • I switched it from an A34 clip to A21 angle. I made the change so everything could fit within the width of the post. The fastener changed with the clip change. – represton May 06 '20 at 17:33
  • @Ack I don’t think you can increase the loads. Did you see Footnote #1 ? – Lee Sam May 06 '20 at 17:34
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    Yes use the nails prescribed in the table from the second image for the LCE4 bracket – represton May 06 '20 at 17:34
  • you can sub screws for nails, Simpson now has some too - Strong-Drive SD Connector screw – Ack May 06 '20 at 18:27
  • @LeeSam it's ok because I have not increased beyond 1.6 (160 (%) as shown in the table) but back up from 1.0 with the result in between in the range of 1.15 to 1.25. All these numbers are the load duration factor. Dividing by 1.6 takes the table loads down to 'normal', then, as I said, it can be bumped back up due to the shorter load duration. I'm not suggesting doing that, but was just noting that the results are conservative. Side notes, as a structural engineer I could supersede the footnotes if I wanted. And the load duration is from the code based on material design, not by Simpson. – Ack May 06 '20 at 18:33
  • @Ack So what you’re saying is that the OP could reduce the values that Simpson shows by 60% and then the OP could add your 15% to 25% back in. What help is that? – Lee Sam May 06 '20 at 20:22
  • @LeeSam Just the engineering side of things and if you pay close attention you'll note that I didn't say to do what you ask (as well stated that at least twice) but rather affirmed represton's answer where they correctly and necessarily reduced the table loads to a more appropriate level. It was then that I noted that there is additional capacity and so that this is a safe approach. Are you on the same page now? – Ack May 06 '20 at 23:16
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    NOTE: the angle bracket was added to the answer after I posted. That is NOT a safe approach. There is uplift on the beam ("putting upward force against whatever join/fastener is selected") and this bracket provides NO uplift resistance. Use the LCE4 – Ack May 06 '20 at 23:35