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  1. irishengdave

    Construction joints

    I practiced in the british isles for 10 years and in vertical walls, we always just scabbled (exposed the aggregates) at the joint carried the rebar through and assumed it has the same shear capacity as a monolithic joint. I practice in N America (Canada) now and they always cast a shear key in...
  2. irishengdave

    Bond capacity of spiral duct in precast concrete connection deatail

    Dear Ingenuity, that's fantastic info, thanks very much for your help.
  3. irishengdave

    Bond capacity of spiral duct in precast concrete connection deatail

    I'm designing a connection in Precast concrete. Does anyone have any published values of bond capacity for steel spiral ducts cast into concrete?
  4. irishengdave

    Strengthening an Existing Hollowcore Plank Roof System

    #6 is the only practical option! it might crack the topping over the support but you can grout it up if it's an issue. Just add enough beams until you get the capacity in shear and moment you need. Putting in frp or adding rebar will magnify moment capacity but beware as it will increase the...
  5. irishengdave

    Tension Reinforcing in Auger Cast Piles

    It's technically an anchor as a column is normally in compression. Check the dev. Length as you're using a high yield bar. Are you using couplers in the pile for the central bar? I don't use them in cases where corrosion is a risk. If the threads on the coupler degenerate over time you will...
  6. irishengdave

    Concrete curing of Foundations

    Assuming 30mpa concrete and normal compaction equipment, 3 days should give you about 15mpa strength. Plenty of capacity. Ask for 3 day cylinder results before compaction.
  7. irishengdave

    Saw-Cuts In Precast Concrete Topping

    I hope you're not using the topping as a diaphragm for lateral loads? Saw cutting it will kill the concrete shear capacity. I've never seen this done before. I'd imagine the plank will restrain shrinkage in the topping. Ask the contractor why they want to do this.
  8. irishengdave

    QUICK ESTIMATE FOR SWAY DEFLECTION IN A MULTISTOREY STEEL MOMENT FRAME

    OK using Dave Atkins method above I checked it against an SFRAME analysis model. A two storey frame with three bays. Bay width 6m and storey height 3m. Assuming beams and columns of equal stiffness rotation at beam-column joints will magnify Column displacements By a factor of 2.25 approx...
  9. irishengdave

    QUICK ESTIMATE FOR SWAY DEFLECTION IN A MULTISTOREY STEEL MOMENT FRAME

    Great idea, The beams will magnify the displacement though. I will model a typical frame on computer, assuming equal stiffness of members for comparison. That will give me an idea of the magnification factor. I'll report back. Thanks.
  10. irishengdave

    QUICK ESTIMATE FOR SWAY DEFLECTION IN A MULTISTOREY STEEL MOMENT FRAME

    I'm preparing for the IStructE Chartered member examination in January. I'm looking for a very "quick and dirty" way of estimating the sway deflection under wind load in a steel building moment frame. Typical building bay width is 6 to 8 m and storey height 3 to 4 m. Could be any number of bays...
  11. irishengdave

    Pipe Pile Plugged and Cored Conditions questions

    Sliderule, not at all its a legitimate question.. I need a way of calculating the target depth of the pile before the job goes to site. We are talking about a very large contract with many piles. To do it in the field you would need to know whether a true plug has fully mobilized, which would...
  12. irishengdave

    Pipe Pile Plugged and Cored Conditions questions

    Hi There, I am researching how to determine the axial capacity of open ended tubular piles in primarily cohesive material. The methods I have read about say you should check the plugged and unplugged conditions. 1. The plugged capacity = Outer skin resistance + Base resistance of a closed...
  13. irishengdave

    Grout Problem

    Attached is a picture of a grouted baseplate. Our site rep is telling me the edges of the grout (microsil) are crumbling and have a honeycombed appearance. It can be broken up in your hand quite easily. Any ideas about what happened? I don't know if the strength has been compromised or...
  14. irishengdave

    Overturning of footing with uplift

    Mike, The one in the direction of the shear will govern, no need to check in the opposite direction. Its a hypothetical example, The FOS in a real world problem would be normally 1.5 or greater (depending on the level of uncertainty of the applied load, surcharge effects etc...)
  15. irishengdave

    Overturning of footing with uplift

    OK I think Im getting it now, The eccentricity will cause the footing to rotate in the opposite direction of the overturning, thus reducing the overturning. If you check OT including the uplift in the overturning calc. the end result is the same as reducing the direct downwards pressur. You...
  16. irishengdave

    Overturning of footing with uplift

    Well, the result ends up being the same, but it is incorrect to say you don't include it." Say the uplift is moved so its 1/2 m from the edge to the right. Now the uplift still cancels out the downwards load. By your argument, If you take it as a moment @ the edge that gives you 100 kNm...
  17. irishengdave

    Overturning of footing with uplift

    Mike, In my sketch, I think the uplift cancels out the downward load, so the O/T=200 kNm. I don't think you should take moments of the uplift times the distance to edge of footing as an overturning moment, it just reduces or cancels out the downwards load on the footing, correct?
  18. irishengdave

    Overturning of footing with uplift

    Thanks BA What if the uplift is eccentric, say 1/2 meter from the right end of footing. How do you calculate the overturning moment and what is it?
  19. irishengdave

    Overturning of footing with uplift

    Trying to upload sketchhttp://files.engineering.com/getfile.aspx?folder=2d43cc47-fc60-459f-804f-2b92fd1876d1&file=OT.pdf
  20. irishengdave

    Overturning of footing with uplift

    Cant't get the upload function to work, tries several times.

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