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  1. onsiteeng

    Design of partial fixity connections

    Hi All, We have been reviewing a steel building where the designer has used partial fixity to reduce the moments in the beam. Magically! the partial fixity negative moment at the ends of the beam exactly matches the positive moment at midspan and therefore the lightest possible steel section can...
  2. onsiteeng

    Using steel wire mesh as ground

    I have done a bit more reading and I think the Electrical Engineer has specified a Ufer grounding system. He basically has specified the following. 1)continuos 4/) copper wire placed in the slab just inside the perimeter of the building(125' x 150ft) so the cable is about 350ft long. 2)"Bond...
  3. onsiteeng

    Using steel wire mesh as ground

    Thanks for the replies above. So I mentioned using the Ufer to my electrical Engineer and got this reply "Not in this case. NEC also does not apply. We have to have ground per the transformer section to ensure equipotential bonding and no possibility of electrocuting anyone. What you do not...
  4. onsiteeng

    Using steel wire mesh as ground

    Hi There, First let me state I am a Structural Engineer so not up date on the electrical requirements for grounding. We have a warehouse building that is being built on slab on grade which has steel mesh through out the slab. The mesh comes in 5'x10' segments and is tied together with galvanised...
  5. onsiteeng

    Composite Slab Cracking under forklift load

    Thanks All, They actually applied an epoxy coating to the traffic area to try and repair the floor which you can see in the photo(light grey). There was so much movement in this slab that it completely debonded and ripped up. I agree that possible complete slab replacement may be the only...
  6. onsiteeng

    Composite Slab Cracking under forklift load

    Good Day, We have a client whose composite slab has been compromised by the wheel action of a forklift(8000lb loaded- approximate 3000lb on front small hard plastic wheels). The slab is 3" CFD with 1.5" cover over the deck. The deck spans 5ft onto I beams. There does not appear to be mesh in the...
  7. onsiteeng

    Pile Capacities

    Hi All, On a recent marine piling project the depth from the water surface to the mudline was around 40ft. They used a ICE 28B vibratory hammer to set the open pipe piles(100T design load capacity). The hammer plus the 110ft 24" Diameter 1/2" thick pile sank 15ft through sand/silt under its own...
  8. onsiteeng

    Concrete walls - Load distribution to foundations

    engrbon, Thanks for your help. We removed the piles and put in supports. One issue we found was the walls had been drawn across the supports and not from support to support. This made the wall span to the end supports and applied very littleload to the interior supports. Drawing them as piers...
  9. onsiteeng

    Concrete walls - Load distribution to foundations

    Yes, our modeller was using them to depict the piles. Not 100% sure why as the walls over the piled supports are at least 20ft tall and are very stiff. I may get them to remove the grade beams and just add the three pinned supports.
  10. onsiteeng

    Concrete walls - Load distribution to foundations

    For our piled foundations design we typically use drive steel piles driven to the tonage specified based on working loads. Given the large safety factor incorporated in the actual placement of the pile and applied by the geotechnical engineer it is more likely that the piles will be a rigid...
  11. onsiteeng

    Concrete walls - Load distribution to foundations

    Yes but why opposing forces in the supports holding up a wall that is supposedly a monolithic element.
  12. onsiteeng

    Concrete walls - Load distribution to foundations

    Here are the support reactions. We do not understand the opposing lateral forces under the walls. http://files.engineering.com/getfile.aspx?folder=b3de658c-205e-46ce-8b74-38c8a630613d&file=Support_Reactions.bmp
  13. onsiteeng

    Concrete walls - Load distribution to foundations

    I have attached the actual wall elevation from etabs. Slightly differebnt from what I described(trying to keep it simple). See attachments. Our modeller has modelled the piles with short columns on grade beams...
  14. onsiteeng

    Concrete walls - Load distribution to foundations

    We are designing a 12 story building in etabs using a system of shear walls and one and two way concrete slabs. In most cases the walls are 50ft long until we get to the parking garage where a 30ft hole is punched through. The walls on each side of the opening are 10ft long and 12 inches thick...

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