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  • 1.  Crack width check with seismic load combinations?

    Posted 02-21-2020 09:59 AM
     I am working on this project in a seismic zone and was wondering if it is required by the code to check crack widths in concrete under the seismic load combinations following LRFD. I am following ACI 224 code for crack check.

    Rocio Rodriguez P.E., M.ASCE
    Structural Engineer
    Orlando FL

  • 2.  RE: Crack width check with seismic load combinations?

    Posted 02-22-2020 10:19 AM
    I would say for extreme event limit state such as seismic events, the structure as a whole and its components need to be checked to resist collapse due to extreme events.  Crack widths need to be investigated at  service limit states.

    Gergis William Ph.D., P.E., F.ASCE
    Morgantown WV

  • 3.  RE: Crack width check with seismic load combinations?

    Posted 02-22-2020 04:32 PM
    Dear Mr. Rodriguez,
    I believe checking crack width would be part of Serviceability Limit State (stress limitation, aesthetics, drainage, deflection, creep, vibrations, reinforcement corrosion, watertightness) using load factors of 1.0 unless you are conducting a special limit state analsyis. The reinforcement tensile stress limitation rules at SLS in ACI 318 (e.g limiting fs to 2/3 of fy) along with minimum reinforcement ratio and maximum reinforcement spacing rules are intended to limit crack widths without having to calculate them directly. 

    See ASCE 7-10 Commentary Appendix C - Serviceability Considerations for load combinations (mostly for static loads) used to check SLS. Load combinations may include wind to check drift but I can't think of a situation where they would include seismic loads (maybe for critical tank structures??).

    Hope this is helpful :)

    Robert Yates P.E., M.ASCE
    Senior Civil Engineer
    ROY Structural and Materials Engineering
    Roseville, CA