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  1. ronster

    Wind uplift on roof deck

    I have no problem determining the wind loads on the roof. I was looking for guidance in how other engineers detailed the condition and/or guidance how the wind load is applied to roof. ASCE7-05 is the applicable design standard, The wind force is P=Qh(GCp-GCpi). I am in a 110 psf, exposure...
  2. ronster

    Wind uplift on roof deck

    Sorry for the double negative in the last post. Kindly omit one "not" as you read it.
  3. ronster

    Wind uplift on roof deck

    Bagman I am not talking about a deck over open space but rather a placing decking on sleepers over a flat roof to an enclosed space. I do not believe that roof overhang uplifts forces would not apply to this situation.
  4. ronster

    Wind uplift on roof deck

    But what is the uplift force? Any internal uplift force will be resisted by the roof joists below but how do you calculate the uplift suction force on the deck from the wind blowing accross the roof? You need this info to be able to design the fastners which are not that simple to flash and...
  5. ronster

    Wind uplift on roof deck

    I design many oceanfront homes in hurricane areas. Architects often specify wood roof decks placed on sleepers over the flat roof areas (1/4"/ft pitch to drain). In the past the wood decking and sleepers would be installed like pallets so that they could be removed to allow for cleaning and...
  6. ronster

    Column Eccentricity

    Yummm cake, I admit that I do eat my cake when I have it. Yes I I do make rationalizations but I do not change them to suite me. The connection is assumed pinned but with enough stiffnes to transfer the shear accross a 3" plate. Is this an absolute truth? Of course not but it is close...
  7. ronster

    Column Eccentricity

    Dave once again you get it and others just get perturbed. To look at a connection as a cantilever is just not correct. There is a beam attached to the connection that is not free to rotate, it is supported at its other end and there for the joint rotation is limited by the beam stiffness. The...
  8. ronster

    Super Long Span (Steel Trusses)

    Unless you have rigid stucture on one side (such as a reinforced concrete wall) then I would not count on coming up with a connection that will allow the end of the truss to move 4 inches without the top of column or spandrel beam moving and taking a large lateral force. That is why i said good...
  9. ronster

    Timber-Concrete Moisture Barrier

    Assuming it is a slab on grade and has the potential to get damp then I would not allow the joists to be glued to the slab and all lumber should be pressure treated. While not the easiest way to skin a cat there is nothing wrong with your detail. The detail can be simplified by using...
  10. ronster

    Column Eccentricity

    For the condition that you describe, I do not design the column for any moment as the beam on the opposite side will resist any induced moment that may occur. Any moment in the column would be negligable. I will use a 3" eccentricity from the face of the column when a beam is framed into only...
  11. ronster

    Steel roof deck with bar joists chord force transfer

    Thanks for your replies. How do you calculate the shear transfer force to the chord remains my question. Is it (2 x chord force/length of the chord) or would VQ/It apply? The building was recently erected and when I went out to look at it, the transfer of the shear force to the chord accross...
  12. ronster

    Steel roof deck with bar joists chord force transfer

    I have a one story 50' X 86' building with 22 ga type roof deck on steel bar joists at 5'-6" o/c and spanning 50 feet. I designed the metal deck roof deck diaphragm and it can tranfer the lateral loads to the shear walls on each end. My chord force for the diaphragm is 4.2 kips. I am using...
  13. ronster

    Super Long Span (Steel Trusses)

    If you use a scissor truss on a 250 ft span you are going to have a large horizontal deflection or lateral outward force to deal with and only a cantilevered wall or column to hold it back. Good luck with that. Also, while South Florida does not have earthquake loads, you may find yourself...
  14. ronster

    OLD WOOD BUILDING IN NJ

    2x10 roof joists spanning 17 feet will have little or no additonal capacity above the flat roof snow load. I would strengthen any portion of the roof that has additional load being added. A common bending value for lumber of that time would be 1250psi for Doug Fir. You can increase that by...
  15. ronster

    partially enclosed vs enclosed

    Design as enclosed, the overhead door should be designed to handle the wind load so it does not blow out.
  16. ronster

    Existing Beam - Added Shear Capacity

    I'm not clear on two things. Do you have drawings showing the stirrup spacing decreasing at the ends of the concrete beam. Reinforcing the mid span only of beam for shear when everything else works is not very common. How is the infill framing for the proposed opening attached to the concrete...
  17. ronster

    Existing Beam - Added Shear Capacity

    When you checked the design of the beam did you take into account the 8" slab on top and design it as a T beam or just check it as a 12"x16" beam? If you checked it as a T beam and it still does not work then I would add a steel channel for the full length on one or both sides as required. I...
  18. ronster

    Steel beam question

    You have a WF12x27 or WF12x31. Field dimensions of old steel beams tend to be slightly higher than book dimensions due to to rust scale and painting. I would conservatevly assume a WF12x27. You can take wire brush to the beam and use a micrometer to try to get a more accurate measurement.
  19. ronster

    determing grade of steel

    In response to "A36 is still used in most industrial settings. I just finished a project that used 30 to 40 tons of A36." You may have specified the W sections as A36 but if you look at the mill certs for the steel supplied then I'm pretty sure you will find it to be grade 50 steel.
  20. ronster

    What is the section modulus of 3/8" A36 steel plate

    Feel the need to clear up of few things stated here: I'm in agreement with HgTX, what is the question. Someone posting as a structural engineer better know how to calculate the section modulus of a rectangular plate. 3/4" diameter A325 bolts are not used in a flitch beam. A307 carriage bolts...

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