Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. andrews2

    Finding Effective Wind Area for C&C

    Previous replies are correct, you need a pressure that is specific to each component, not a single value for the whole building. If your question is what value to provide on your drawings for others to use in the design of non-structural components and attachments, then it is best to provide a...
  2. andrews2

    Seismic Story Drift Combination

    You seem to be missing some information. The separation needs to be sized for relative movement between the structures, so you need the seismic drift of both structures. You need to use the SRSS as stipulated in ASCE 7 12.12.3 like driftLimiter stated, but you should be using the drift of the...
  3. andrews2

    Redundancy ASCE 7 - 17 Clause 12.3.4

    1. This condition needs to be met for every beam-to-column connection, not just a randomly selected beam or the most highly stressed one. You need to pin the ends of each beam, one at a time, and make sure that there is not a strength reduction of 33% or an extreme torsional irregularity for...
  4. andrews2

    ACI 9.7.6.4.1 - Compression Bar Confinement

    I would say you do not need to meet the requirements of this section. If you do not need and are not counting on the compression in these bars to provide extra strength, I don't see any reason to provide confinement for them. In my opinion, this provision is more applicable to a beam with...
  5. andrews2

    Concrete beam loaded at the bottom?

    rapt, I agree that loads on concrete beams are intended to be applied to the top of the member, but where have you read that this is the case for steel beams? Loading steel beams from the bottom is actually better (Although not usually practical) because it helps to stabilize against lateral...
  6. andrews2

    Concrete beam loaded at the bottom?

    He could be referring to how concrete has a lower strength when tension is applied in the transverse direction. If you apply tension to concrete (Like the bottom fibers of a simple span beam) then pulling an anchor out of the bottom of the beam may be easier. His concern may be that if a...
  7. andrews2

    Stress Analysis Help

    If I had a scenario like this, I would work it backwards. Based on the point load, span, yield strength, and plate thickness I would determine what the REQUIRED plate width would be and then decide if I was comfortable with assuming the point load distributes itself over that width. If the...
  8. andrews2

    Risk Category IV vs Roof Live Load Reduction

    Live load reduction is based on tributary area and (In the case of roof live loads) slope. Live load reduction is not affected by the risk category of your building.
  9. andrews2

    Mean Roof Height vs modeling in RAM

    Flexible is probably a fair assumption then. Forces to the frames would be correct, but drifts and moments caused by those forces still aren't accurate if the column heights are not correct.
  10. andrews2

    Mean Roof Height vs modeling in RAM

    For generation of wind loads, this is slightly conservative as you say. However this will not accurately capture the behavior of your building. Frames/walls on the left are shorter than those on the right and will therefore be stiffer and take a greater portion of the load, but RAM will not...
  11. andrews2

    Overturning bearing pressure with uplift present

    I believe any time I've used the reduction from 12.13.4 it's been for general stability in an overturning spread footing, not for bearing. Although, I suppose with the wording being "Overturning effects" you can probably justify this as reducing bearing pressure as well. The increase in...
  12. andrews2

    Overturning bearing pressure with uplift present

    What is your allowable bearing? With the numbers you show I get about 2500 psf with a 6'x6' footing (Excluding any weight from the concrete wall). Since allowable bearing pressure is often controlled by long term settlement, geotechnical engineers will sometimes allow you to increase your...
  13. andrews2

    Steel structure base fixity (theoretical)

    I see. This is on me for misunderstanding your question. I thought you were asking about assumptions that may have been made for existing structures. To answer your actual question, I think human909 said it best. Nothing is truly "pinned" and nothing is truly "fixed" and there are probably...
  14. andrews2

    Steel structure base fixity (theoretical)

    It all comes down to what design assumptions you make and making sure you design your structure to accommodate those assumptions. If you design your structure to have a fixed base, then you should design the base to be rigid and provide the fixity you are counting on. If you design the base as...
  15. andrews2

    ACI 318-19 Moment of Inertia Change

    Yes I don't see a problem using 0.35Ig if you're also providing an amount steel that you feel comfortable will provide an appropriate corresponding Icr value. I worry some are not as thoughtful as you and use the 0.35Ig value without a second thought about what the actual cracked or effective...
  16. andrews2

    ACI 318-19 Moment of Inertia Change

    Similar to the new shear equations, I imagine this change will receive a lot of industry push back and might be changing again in the next code cycle. The new moment of inertia equation just hasn't been talked about as much yet. This isn't a slight change either. In the cases I've seen, it...
  17. andrews2

    Unbraced length input

    I'm going to assume that L33 correlates to buckling about the strong axis and L22 correlates to buckling about the weak axis. If I have that backwards, be sure to flip. The roof deck will prevent lateral translation of the top flange and compression buckling about the weak axis. Strong axis...
  18. andrews2

    Calculation of Punching Shear Control Perimeter Eccentricity

    It is done using the exact method you describe in your original post. [Area of the right section (b+d) x it's distance from the left edge (b+d/2) + Area of the top and bottom section (2*(b+d/2)) x their distance from the left edge ((b+d/2)/2)] / [Total area (b+d) + 2*(b+d/2)] - column...
  19. andrews2

    Coefficient of Friction

    This is true, so why do you feel the need to create your own load combinations and apply an even greater factor of safety? The factor of safety is partially to account for uncertainty, but we can already say with absolute certainty that the dead load will not be two values at the same time as...
  20. andrews2

    Coefficient of Friction

    "Factor the dead load up for calculating sliding force, and factor it down for calculating resistance." I disagree. There's no load combination that uses different factors for the same load type in different directions (except seismic). You should just use your typical service level load...

Part and Inventory Search

Back
Top