huangyhg

resistance factor for structural cable.
i am designing a cable stayed roof canopy and will be using astm a586 galvanized structural cables which have published "breaking strengths".
i have done my analysis using lrfd but am unable to find any information on the correct resistance factor to use with this product.
does anyone know the appropriate factors or where i can find them?

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haydenwse,
i don't know if there is anything published. the only thing that i would point to is the aisc with tension members - that is structural steel so it might be argued that it doesn't apply to stay cables.
if it were developed in a code, the φ factor would be based upon the variability of the material properties and of the actual diameter....and anything else that affects the strength capacity. this is then balanced with the load factors to create a probability of failure that is calibrated to other designs such as steel flexure, shear, concrete flexure, etc. (at least this is the concept of reliability design).
if you can find out that the variability of the yield or ultimate strength is less than the variability of a992 or a36 steel, then a φ equal to what aisc requires for tension
actually there is this publication available at the asce website -
structural applications of steel cables for buildings
asce standard no. asce 19-96
whether it includes lrfd methods and a φ factor i don't know.
i preserve a copy of the information given to the ingenieros de caminos, canales y puertos (the structural and civil engineer of always in spain) when making their course on cables for structural behaviour (got it from my brother, who is a iccp). the 4 tomes or so
are copies of very bad quality, with drawings inside making one to think is seeing information of the thirties. well, home is burdened by tons of stuff and have it in some closed cabinet that i don't attempt to open but say 3 times a year, on the stuff over there. but i remember well that safety factors of even over 9 were there for cables.
i don't think such safety factors are required by now... if everything that apples get taken into account.
tensile stress
bidimensional compression
stress concentration
loss of section, corrossion
embrittlement
change of mechanical properties over time
bending on the cable for curvatures not big respect the size of cable and wire, size effects
fatigue, effect of friction at the seat
and some others that may appear consulting some text or thinking a bit more.
i would apply 1.6 to 2.2 safety factor after applying everything above and whatever other thing may be in my sight. if not, i would stick to higher values.
the cozy ways would be that the fabricators would provide information on the safe values at factored or service level with their fittings targeted to specific application. yet even if they have may not be providing.

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