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Hi all:
Was wondering if any of you have had experience with flitch plates added to an existing 3-ply, 2×8 beam to change span from 7 feet to 14 feet (remove column at 7′ position) ? Size of hardware, spacing of same, staggered or double row, thickness and lengths of flitch plate(s) and material (angle, channel or flatbar), etc. ?
Please don’t just tell me to see an engineer. I’ve inquired of a couple and they wanted $350-$500 just to come look, with no guarantees a design could be done which wasn’t to combersome to install without a 12 man rigging crew. If you know of design can be used (ie personnal experience), then I’ll draw it up and bring in the engineer to stamp his/her approval on it.
Thanks,
Cadman
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load please
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Cadman:
You really should see an engineer. Provide a scale drawing showing location, size, spacing of all contributing framing members, pictures would help-shouldn't take more than an hour of his/her time (unless there are some unusual features to your design). The more info you provide, the less questions your engineer will have.
I also assume that the existing beam runs
b continuous
over the middle support.
*Hi Mark,Here's the complete (I think) Scenario:Split level house, Exterior (poured concrete) Foundation size = 24' x 42' x 8"Main support beam = 3 ply 2x8 running total of 42', supported at both ends (3-1/2" bearing within frame work of knee wall on each end), and along length with 5 lally columns,(each col. has a 3/16" thk x 5" x 7" top plate), floor joists are 2x8's, 16 o.c. and over lap on top (about 3-1/2"). Joists are tied to single rim joist at other end.I live in Massachusetts wfere the code is 40LL/10DL. By my figures, (please correct me if I'm making false assumptions or using wrong formula[s]), total load at section of beam to be "flitched" = 50 PSF x 24' x 14' (**) = 16,800 lbs. Since beam normally supports half the load, uniform load on beam = 8,400# (Find load/inch =) 8,400# / 14' / 12" = 50 lbs./inch. (**) {actually 13.92' [14.5' - (3.5" [gable end]) -3.5" [half length of column top plate])] } Smax=k((wr^2)/t^2)= .5(50x49)/.25[2)1/4" thk plates (2x.25 = .5; .5^2 = .25]) = 4,900 . . . (what ???) . . . I can no further as I don't know what to do from here, or the properties of the two 1/4" steel plates are. Not being a structural engineer, (but having had about 5 years of steel detailing/design experience in prior jobs), I "feel it in my bones", (however I don't want to end up with any broken bones if it all collapses), I will have the proper support required to remove the column.My proposal:Prior to removing the first column from the gable end of the beam, I intend to add two (2) 1/4" thk x 7" Wide x 14'-6" long, steel flitch plates, one (1) to each side of existing beam and bolted through with 1/2-13 x 6" bolts, (with flat and lock washers on each side), in thirty-five (35) places as follows:1-1/2" in from each edge and 3" in from end, 12" o/c staggered spacing.At each end would be a four (4) hole pattern (6" x 4"). Same pattern would be used on centerline of column to be removed. (All hardware to be tightened prior to removal of column.) ?? Torque ??The plates will start at the gable end of the main beam and extend about 6" past the second column. I then plan to box-in the assembly with 1x10's on each side, suspended from the floor joists. I also plan to box-in the column, (square to the finished width of the boxed in beam).To further enhance support, I can increase bearing support inside of the column "box", (floor to bottom of beam). I can also "pilaster" the gable end by adding supports off of the top of the exposed foundation, (about 4" wide, fluctuates due to forms & seams, etc.), lessening the span even more, thus lessening the load as well.I apologize for being long winded, but thought the more info you had, the better. Any help or direction will be greatly appreciated.Thank you in advance.
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Cadman. See pages 44-46 Flitch Beam,in Principles of Timber Design for Architects & Builders, by Halpern & Bible, published by John Wiley & Sons.GeneL.
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Hi Fred,
Your assumption is correct. I'll e-mail a quick sketch of what I'm trying to accomplish.
Thanks for your response.
Cadman
*Hi Gene,Been an admirerer (sp?) of yours for years. Read your book about super insulated homes many times, cover to cover, looking for ideas for various home improvements.Would this book be available at a Library, or, without violating copywrite laws, could you paraphrase or send an excerpt ?Thanks for your input,Cadman
*Hi Fred,I just shot off an e-mail to you with a sketch. Also futher information can be gleened from the post I sent to Mark.Thanks again, Cadman
*Cad,I agree with FredL... and I am an Engineer. The channel is much more efficient in resisting bending stresses because there is more steel at the top and bottom of the section (greater moment of inertia). Will be easier to come by etc. etc. etc.
*Cadman, Flitch plates are typically designed to be sandwiched between two wood beams and bolted together. What your trying to do is some what the opposite. Does'nt mean it is wrong. Make sure you have full bearing. why not put up temp support walls and replace beam with properly sized beam by an engineer.
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I like the idea of replacing the beam. An used 8" wide flange steel beam can be had pretty cheaply(look up the flange thickness in a chart from one of Parker and Ambroses' Simplified engineering for Builders and Architect books to size it correctly for your load). You would have to trim the lally column and have it welded but it sounds doable. If you remove the live load while you do it you really shouldn't have too much load.
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All you "ENGINEERS" may be in a little over your heads on this one,
send me a copy. I need the following info:
existing footing size of exterior wall and lolly pads.
soil conditions under footings.
ground water location below slab.
sectional view of structure.
all walls above resting on present beam.
all point loads and location on beam.
any large hot tubs etc.
roof area onto beam.
location of roof ridge beam.
vertical height you would allow for the new steel.
your stated loads are to light and are missing
additional loadings for your structure.
you are doubling the existing loading on the adjacent
lolly and this must be addressed.
your bolting might work as stated.
send all the above and what ever else you have
......Ray. Fiore..PE
*All you "ENGINEERS" may be in a little over your heads on this on, send me a copy. I need the following info:existing footing size of exterior wall and lolly pads.soil conditions under footings.ground water location below slab.sectional view of structure.all walls above resting on present beam.all point loads and location on beam.any large hot tubs etc.roof area onto beam.location of roof ridge beam.vertical height you would allow for the new steel.your stated loads are to light and are missingadditional loadings for your structure.you are doubling the existing loading on the adjacentlolly and this must be addressed.your bolting might wok as stated.send all the above and what ever else you have......Ray. Fiore..PE
*hey folks,For any and all who are interested, &/or contacted me, I've attached a drawing of plate, where they are to go, floorplan etc. Still open to suggestions ! Will let all know results when taken to the inspector's office.Thanks for all the help given thus far ~CadmanPS See attached:
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Cadman,
I've just recenly done a job very similar to what you propose. My span was 14'3" with the same roof loads, but with two floors above. By your drawing it seems you are carrying one floor and the roof. I did the load calcs and drawings myself and had a PE do the calcs again and sign-off the drawings. He also detailed the bolting and various connections. He charged me $150. (Well worth it!!) I used a W6X25 because I needed it fully recessed, but the PE also gave me the option of using two C7X9.8's. The two channels seem like a good idea for your application. They are much lighter(~140lbs each.) than a W or S beam and stiffer than a plate. In my case the PE spec'd 1/2" bolts, staggered, 12" OC for attachment, and that the posts should rest on 2'x2'x1' conc. footings. Another concern might be exactly where the splices are in the existing beam, unless you go with a channel that can carry the load alone. In any case it is certainly worthwhile to have a PE review your plans. I know that I have restated what other posters have already said but I hope my recent experience is of some use.
BTW, I installed all 400lbs. of my beam by
myself using a simple 2x4 frame ...no 12 man rigging crew ;-) Let me know if you go that route.
Jerry
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Hi all:
Was wondering if any of you have had experience with flitch plates added to an existing 3-ply, 2x8 beam to change span from 7 feet to 14 feet (remove column at 7' position) ? Size of hardware, spacing of same, staggered or double row, thickness and lengths of flitch plate(s) and material (angle, channel or flatbar), etc. ?
Please don't just tell me to see an engineer. I've inquired of a couple and they wanted $350-$500 just to come look, with no guarantees a design could be done which wasn't to combersome to install without a 12 man rigging crew. If you know of design can be used (ie personnal experience), then I'll draw it up and bring in the engineer to stamp his/her approval on it.
Thanks,
Cadman