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  • 1.  Cable Rail Design

    Posted 08-05-2020 09:18 AM
    Guardrail design with cable infill is a not always as straightforward as it seems.

    There are 2 codes that apply to the design of the cable infill.  50 lbf applied to 1 square foot & restricting a 4" sphere to pass through.
    The code does draw a relate the force to the opening limit.

    What is your approach to design of cable rails?  Do you have any sources or references to share on the topic?

    Chad Morrison P.E., M.ASCE
    Professional Engineer
    Greenville RI

  • 2.  RE: Cable Rail Design

    Posted 08-06-2020 11:20 AM
    Wagner Companies has a spec that can help with some general information  https://wagnercompanies.com/resources/guide-specifications/ but you need to design the anchor tension to not allow sag or too much deflection when loaded (L/120). Wager recommends a minimum tension load of 150 lbs to 225 lbs but this will need to be verified by calculations.  That is per cable so the end posts will need to support the loading from each cable at this loading.  It is noted that with cable barriers, 4" spacing may not be the best since the cable will deflect more and the gap will go over 4" so vertical support at 4ft with 3-1/8" cable barrier spacing will help eliminate this https://www.viewrail.com/cable-railing/cable-railing-safety-code/ .  
    As far as calculations, Post Tensioning Manual has a chapter on barrier cable systems. While these numbers and examples are for car impact it can be used for residential loads as well.   ASCE7-10 4.5.1 load is 50 lbs on 12" by 12" area with 4" cable spacing that is a 3 cables or 16.67 lbs per cable located at the center of the span.

    Brian Warner P.E., M.ASCE
    McNeil Engineering
    Sandy UT