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Recent content by MichSt

  1. MichSt

    Bridge Design Consulting Fees

    Make a detailed task list (part of your scope of work). Estimate hours for each task and apply rates. Add costs for services your firm does not provide (e.g. survey, geotech, traffic, etc.). Use 10% of construction cost, mentioned above, as a check. That said, if it's a local agency job that...
  2. MichSt

    Drilling into Precast Concrete Box Culvert

    Next time require inserts cast in the box for the contractor's forming and platform needs. Grout holes after work is complete. This is standard practice for precast beam construction.
  3. MichSt

    Longitudinal Post-Tensioning in Precast Concrete Deck Panels

    I think a conventional negative moment design over the pier under factored loads at ultimate capacity would be warranted. It sounds like you need to increase your girder section over the pier to get your design to work out.
  4. MichSt

    virtis-superstructure definition at where skew angle changes

    I would use a girder-line analysis and model each beam individually in this case. I'm not sure how you could model that bridge as two separate superstructures since the superstructure is not discontinuous at the change in skew angles.
  5. MichSt

    Sheet Pile Driving - Low Headroom

    If you have enough room to drive with the timber decking removed, you could consider driving partial depth sheets under the beams that have little or no toe and design the adjacent sheeting toe and section to take the addition load from the sheets that are not toed in. You may need to use some...
  6. MichSt

    Effect of Concrete Overlay on Deck Rating

    Do you have a current inspection report for the bridge? IS the overlay currently debonded/spalled, etc? If not, I would agree with the state to rate it with the overlay included in the capacity. When/if it debonds the rating would be updated at that point. Just have your assumptions stated...
  7. MichSt

    RR Bridge Girder

    Mike - with direct fixation of the rails on the bridge steel, and even with a ballasted bridge deck, the RR's typically require a tight tie spacing with extra long ties near the bridge to help reduce differential deflection of the rails (or the bump if you will) at the bridge approach. Track...
  8. MichSt

    AASHTO LRFD Minimum Bending Reinforcement - Cracking Moment

    FYI.... http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w149.pdf
  9. MichSt

    P/S Strands in the top of a box beam?

    Why not thicken up your bottom flange a little bit and use two rows of bottom strands?
  10. MichSt

    Concrete Spalling to ends of pretensioned beams

    1. This problem is very common in Michigan where I work. Most of the older prestressed bridges are all simply supported with expansion joints above all the substructure units making the problem even worse. 2. Michigan Tech has done a recent study for Michigan DOT on the problem. See link...
  11. MichSt

    Pedestrian Bridge FE model boundary conditions

    If the two truss chords are braced together, wouldn’t one chord what to stretch and the opposite chord what to compress under lateral loading?? Similar to beam bending. Seems like the displacement of the two truss chords would cause the longitudinal reactions you are questioning at the fixed...
  12. MichSt

    Interesting Integral abutment behaviour

    Intersting...I can tell you the contractor's proposed solution to beam straightening: hook a dozer to each end and pull! In addition to dealing with the beams, I suspect they will have to cut anchor rods, or other conntections between the beams and substructure, and then reset and reattach the...
  13. MichSt

    Interesting Integral abutment behaviour

    Never seen or heard of anything like this. Wonder if the abutments are too stiff and not allowing thermal movements, causing internal compressive forces in the superstructure. Then once the deck was removed and not there to share some of the compressive loading, the girder turned into spaghetti.
  14. MichSt

    expansion joint vs continuity slab

    I agree with eliminating the deck joints due to future maintenance issues. That's pretty much standard practice now where practable, as mentioned above. If you're concerned with movement issues between your beam types, why not make all the spans prestressed??? What's the point of mixing your...
  15. MichSt

    Live load distribution factors

    Worst case would be one wheel line on a box, no?? Could compare that to the result you would get using Nb = 4 in the distribution equation.
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