huangyhg

erection of cable bracing
hello all,
does anyone have any idea what the requirements are for the tensioning of cable braces in the walls and roofs of a metal building? intuitively, i know that the cables need to the taut so that they are immediately engaged when loaded, but i can't find a specification that seems to address this. i have looked in the mbma and in the ubc to no avail.
any help would be appreciated.
thanks in advance,
js.
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tia/eia standard which is the structural standards for steel antenna towers and antenna supporting structures recommends that guy cables be tensioned to 10% of their published breaking strength with upper and lower limits of 15 and 8 percent respectively. (reference section 10.2).
this might be a start.
also note that the tension force in a tension only brace is reduced when the force is compresive. it is usual to provide sufficient tension so that the brace does not go slack under normal loading conditions but only under the extreme design loads.
i would think the only requirement would be to to maintain tension prior to any lateral movement. ie, design so that when compression loads are applied to the structure, the cable still has tension in it. that way, it doesn't have to move to take up any slack.
aisc's steel design guide series #10, "erection bracing of low-rise structural steel buildings", provides some guidance that you can use. see page 29 for max. drape (per caltrans falsework manual) and then eq 5-4 for how to calculate the cable preload value.
advice from j19 sounds good to me. here is a link to the caltrans falsework manual (free .pdf download). take a look at the pages beginning on 4-40.

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