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Recent content by wiktor

  1. wiktor

    When does a cantilever concrete beam become classified as a deep beam?

    The beams formulas become invalid when span to depth ratio exceed 7:1, so for a cantilever it's 3.5:1
  2. wiktor

    Cracks on pier cap

    The craks are apparently a structural (shear) due to almost complete lack of shear reiforcement in the pile cap. The #4 stirrups at 30" o.c. look inadequate. Applying expoxy filler is pointless, as this is cosmetic repair only. [u]Are the same cracks at the other face of the plie cap?
  3. wiktor

    Bridge design software for steel superstructure

    "Multiframe" currently own by Bentley is back on the market. It's easy to use and allows for quick modeling of complex structures.
  4. wiktor

    Miami Beach, Champlain Towers South apartment building collapse

    Some of the most important drawings are conveniently missing - the piling plan, type of the piles used (looks like "Franki" piles), diameter, and the most important the location and exact composition of the foundations - the beams listed suggest that some of the columns were supported by them...
  5. wiktor

    Miami Beach, Champlain Towers South apartment building collapse

    The sudden collapse of relatively new RC concrete frame building is unusual. As the failure appears to be related to the crushing of one or more concrete columns at the garage level the plausible reason is salt weathering of concrete. Concrete spalling due to the corrosion of rebars should be...
  6. wiktor

    Mexico City subway overpass collapses, killing at least 23 and injuring dozens

    The composite action of precast decks is actually quite simple - holes in the precast planks where the shear studs are located, filled with HS grout. The quality of the fill in between planks is critical, as these shall be done extremely well. To avoid locking DL in the steel the span shall be...
  7. wiktor

    Mexico City subway overpass collapses, killing at least 23 and injuring dozens

    The shop welds in a railway bridge shall be grinded smooth and x-rayed - so much for good workmanship. Any irregularity in the tension elements acts as a stress riser The smaller top flange was due to assumed composite action of precasted deck. With the deteriorated joint that was not the...
  8. wiktor

    Mexico City subway overpass collapses, killing at least 23 and injuring dozens

    The failure was sudden, so definitely it was fatigue cracking of the butt weld across the bottom flange - category E' by AASHTO ( 2.5 ksi constant amplitude fatigue threshold). Anyway, although shop welding of the elements of the railway bridge is permitted in controlled environment and with the...
  9. wiktor

    Sounding Bridge Deck for Repairs

    I did some soundings years ago with mixed results. It helps to find the areas delaminated, but it only allows for performing repairs immediately required, while leaving already corroding areas undetected. Measuring and mapping the electro potential of the top rebars could be helpful, as the...
  10. wiktor

    Miami Pedestrian Bridge, Part XIV

    Hi Hookie66 & FYE, I 100% agree that there are few examples of RC or PRC trusses used as bridges, and definitely none with deck and canopy used as top and bottom chords. So, the bridge was definitely a novel structure, designed using wrong code, with the initial S.F. close to 1.3-1.35 at...
  11. wiktor

    Varying length PS girders

    @Mike There will be no issue with the design - the decks on the PC bulb tees are designed as a hinged slab, so some extra reinforcement in the slabs would be required - but the increase of the spans will be gradual. With the hinged slab approach, the issue of the uplift in the acute corner is...
  12. wiktor

    Bridge Engineering

    AASHTO may have some reference, but typical seals shall be durometer 60. To convert to the Young modulus use these formulas: https://en.wikipedia.org/wiki/Shore_durometer In typical bridge design these forces are disregarded, as their magnitude is irrelevant to the...
  13. wiktor

    The Roosevelt Bridge, Stuart, FL

    This bridge, as I recall,have both internal and external tendons, so some addition or replacement of tendons is more than feasible, without replacing the span - I do not think that it will take more that two weeks to fix the bridge - FL DOT has replaced some tendons in other bridges in the past...
  14. wiktor

    The Roosevelt Bridge, Stuart, FL

    @
  15. wiktor

    The Roosevelt Bridge, Stuart, FL

    The locations of the cracks at the segments' joints may indicate corrosion of the "stiff" reinforcement located too close to the segment edge, causing the spalling. Unfortunately I do not have the drawings of the bridge anymore, but some years ago these were used as a guide to design similar...
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