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  1. mchen96

    Retaining wall reinforcement

    It's easier on the contractor, particularly when bending the rebar by hand, since the tolerance for L-shaped bars is not as restrictive as for U shaped bars. When bending a U bar, the bottom part must have the exact width required, or there will be cover issues (if the bottom part is too wide)...
  2. mchen96

    CONCRETE BRIDGE DESIGN STANDARDS

    Ok... I've never seen something like that. Talk about building on the edge... The country matters a lot since it will state which code applies to your region. I'll post some general answers below; however, it's important to remember that some (or all) of these things may or may not apply in...
  3. mchen96

    Finite Element Analysis

    For a one-off (if you're just looking to check a requirement and will double check with hand-calcs), you could look into Code-Aster + Salome for windows. It's not particularly easy to use nor is it very intuitive and has a tough learning curve, but it is trustworthy (if it's good enough for...
  4. mchen96

    Shell Elements as Slabs

    Shells do work fine, but you have to be consistent in you assumptions. Right now, you are modeling two completely different (but both equally constructable) structures. When you use area loads, you are implying that the shell does not carry any load at all. (All loads are carried by the...
  5. mchen96

    Cracking moment larger than moment of resistance?

    You're not mentioning what is the applicable code for your project. If you´re using ACI 318, the minimum reinforcement provision usually ensures that the section´s ultimate flexural capacity is greater than the cracking moment of the section. However, your situation (having a cracking moment...
  6. mchen96

    Pile Driving Design (Hand Calculation) Example

    FHWA also makes very complete guides (including design examples). Search for NHI-16-009, NHI-16-010, and NHI-16-064 (Volumes 1,2, and 3).
  7. mchen96

    Steel Box Girder Design

    As said above, FHWA Steel Bridge Design Handbook will likely be helpful. I've linked the updated manual below. https://www.fhwa.dot.gov/bridge/steel/pubs/hif16002/ Depending on your application, fatigue may or may not be an issue, but otherwise their resources should be useful.
  8. mchen96

    Retaining Walls: Drainage

    Need? It doesn´t need one. But you probably want it: If I had a situation in which drains were unacceptable, I'd make sure that the wall could take the hydrostatic pressure of water accumulating behind the wall(which would result in a much thicker and more expensive wall). The lack of a heel...
  9. mchen96

    Rebar Anchorage

    Retired13, Yea, you're right, my bad. They did remove the reinforcement clause for hooks for ACI 318-19. Interestingly enough, though, that clause still exists on the 2017 AASHTO LRFD specification.
  10. mchen96

    Rebar Anchorage

    It is still there(assuming you don't need fy for seismic). See 25.4.10.1
  11. mchen96

    Rebar Anchorage

    Sort of. What you are proposing on the diagram is not valid. If you don't have the hook development length, you can't make the hook larger to compensate and call it a day; the concrete will crush in the bend or the hook may pull out. That being said, (if you go by ACI 318-19 only; previous...
  12. mchen96

    Foundation Over Foundation

    I also vote for lowering the higher foundation. For something like this, I'd probably combine both footings into a single, larger rectangular one. Having one footing on top of another just seems like asking for trouble. Besides the fact that differential settlements could be a problem, the...
  13. mchen96

    Shallow foundations: distribution of soil pressure with Eurocodes

    I'm not familiar with the Eurocode, so please keep in mind that my responses will be as per US code. First, soil behavior is more "plastic" at the ULS, while it exhibits a more linear behavior in the SLS. That is why the load distribution assumptions changes between both limit states. While I...
  14. mchen96

    Deflection in a 12" sch 40 pipe (with internal pipe supports) problem

    I would only consider the outer pipe. I don't think those "donuts" will be able to transfer the horizontal shear required for the section to act compositely unless they are very thick or stiffened. In any case, the major contribution to resistance would have come from the outer pipe, anyways.
  15. mchen96

    Anchoring Rebar - Welded to Anchor Bars or Bearing Plates

    Do keep in mind that the corbel is not dimensioned in that drawing, so perhaps my sense of scale might be off. With all due respect, hook development for a #5 (at least based on the ACI equations) is not met (at least, not without going into curved bar nodes and the likes). If a strut and tie...
  16. mchen96

    Anchoring Rebar - Welded to Anchor Bars or Bearing Plates

    @ HotRod10 I'm not sure I'm a fan of that detail since ACI 318M-14 16.5.6.3 explicitly requires the bar to be developed by (a) a weld to a transverse bar, (b) the rebar bent in a horizontal loop, or (c) some other means of anchorage that develops fy. The commentary, in particular, advises...
  17. mchen96

    Anchoring Rebar - Welded to Anchor Bars or Bearing Plates

    Hi, Is there any rational design method for anchoring bars by welding them onto horizontal anchor bars and/or bearing plates? Alternatively, is there any good design reference that anyone could recommend? We know it obviously works (else corbels would be failing everywhere), but I'm searching...
  18. mchen96

    Effective Buckling Length for Top and Bottom chord

    I would argue both are important (if it acts as an arch and not as a curved beam). The distance between diagonals will control local buckling of a section within the arch. The 40 meter arch will control global buckling of the whole arch.
  19. mchen96

    Truss Bridge Stringer Secondary Stresses

    @rb1957 They will be pieces 1 truss frame bay long, connected to each floorbeam by a double angle shear connector. @Lomarandil I do believe having the stringers with one end slotted and using slip critical bolts whose slip resistance is enough to brace the floorbeam but slips when the tension...
  20. mchen96

    Truss Bridge Stringer Secondary Stresses

    We would usually go for steel girders as well, but there is very little clearance for this particular bridge, which is why a through truss bridge is the only viable choice. For the same reasons (low clearance), having a single continuous stringer is not possible in this scenario, which is why...

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