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| Weight of Threaded Rod |
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| Someone:
--- Quote from: CatalinaWOW on March 11, 2020, 10:14:38 pm ---You clearly don't understand the mechanics well enough to trust your calculations, though calculations provided by others here show large margins to your needs. But the calculations done here don't include the strength of your anchor or any loads due to shock, misalignment or anything else and also seem to presume that the load is shared evenly among the four hangers. --- End quote --- I'll disagree about the value of the calculations presented so far, as they aren't even taking into account "rule of thumb" factors for the obvious (and still not mentioned) realities. This is non-trivial and just listing the half dozen or so confounding realities that need to be considered won't help as someone who can't see those immediately likely lacks the skills to calculate them adequately. Mechanical engineering, actually quite hard to do properly. Mechanical trades use codified tables/rules of thumb, but still require significant training to use them appropriately. |
| bostonman:
The calculations provided above is a slap in the face. I made it too complicated and didn't see that 'PSI' is as simple as: lbs / in^2 When multiplied by the area of the rod (0.11 in^2 in this case), the in^2 cancel and you're left with lbs. Sometimes I over think things so much that I confuse myself. To answer the questions everyone has. I went over this design with the mechanical engineers at work (I'm on the electronics side) to the point that one created a computer model to simulate bowing and stuff. So the design is as follows: all the wood is slightly over 1" thick (I think about 1 and 3/16" - but labeled as 1.5"). The bookcase will have five shelves with sides (and a dado for each shelf) and open back. It will be about 45" wide, 12" spacing between shelves, and 11.25" deep. Two threaded rods will go through each shelf with a washer underneath each shelf. From the computer model, the best is location for the rods is somewhere around 8" from each side (I have it noted somewhere - but going with 8" for purposes of discussion). So one threaded rod on each side, both being an equal 8" from the sides. As for suspending, the threaded rods will go through the ceiling and into the attic where a 4" x 4" will be laid across about five joists. These joists are located on the load baring wall, so all the weight is transferred down to the basement steel posts. Most likely I'll put two or four screws into the wall just to keep the bookcase from pulling away from the wall (or shacking). Hardware will be 70,000 psi stainless steel threaded rod, standard nuts, oversized washers under each shelf, and some aluminum plates (I have some spare pieces of aluminum) for washers on the 4x4. I oversized everything. All the books I currently own weigh approximately 250lbs and doubt I'll add the same size large textbooks in the future (or even add another 100 or so books to make an additional 250lbs). In any case, I'm stating that the total weight (minus wood weight) will be 500lbs. Without looking at notes, I think 5/16" threaded rod is good for 2300lbs, so two will hold 4600lbs. This 2300lbs is using 30,000psi as a safety margin (i.e. yield????). |
| Someone:
--- Quote from: bostonman on March 12, 2020, 02:03:19 am ---As for suspending, the threaded rods will go through the ceiling and into the attic where a 4" x 4" will be laid across about five joists. These joists are located on the load baring wall, so all the weight is transferred down to the basement steel posts. Most likely I'll put two or four screws into the wall just to keep the bookcase from pulling away from the wall (or shacking). Hardware will be 70,000 psi stainless steel threaded rod, standard nuts, oversized washers under each shelf, and some aluminum plates (I have some spare pieces of aluminum) for washers on the 4x4. I oversized everything. All the books I currently own weigh approximately 250lbs and doubt I'll add the same size large textbooks in the future (or even add another 100 or so books to make an additional 250lbs). In any case, I'm stating that the total weight (minus wood weight) will be 500lbs. Without looking at notes, I think 5/16" threaded rod is good for 2300lbs, so two will hold 4600lbs. This 2300lbs is using 30,000psi as a safety margin (i.e. yield????). --- End quote --- Your 3/8" design was undersized even for unreasonably slim safety margins, 5/16" is going in the wrong direction. Looking at the rod diameter alone is like planning to tow a 747 with a Cessna because the tow rope is technically adequate. Just the point loads you plan on the joists are enough to need more detail about the existing structure and its design. |
| bostonman:
--- Quote ---Your 3/8" design was undersized even for unreasonably slim safety margins, 5/16" is going in the wrong direction. --- End quote --- I meant that even 5/16" is more than enough and I'm probably going with 3/8". What do you mean 3/8" is undersized, but then you stated the rod can pull a 747? |
| langwadt:
--- Quote from: calzap on March 11, 2020, 11:56:41 pm ---Tensile strength of rod material is only a starting point. If you think about it, the holding strength of a rod threaded into a nut or sleeve is dependent on the number of threads engaged and the shear strength of threads from core of the rod and from shell of the nut. It was failure to fully account for this that led to the infamous Hyatt Regency Hotel disaster in Kansas City in 1981 (google it). --- End quote --- in that case it none of that failed, it was the box sections that connected the rods that were not build correctly |
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