Modeling Vertical Cables in SAP2000

[bigrod223399]

I'm looking to model vertical/angled cables in SAP2000 that support individual, freely-hanging thin shell elements. Has anyone done this before? Most examples I see are for horizontal cables. Which "Cable Type" should I be using in this scenario? The options are:

[li]Minimum tension at I-End[/li]

[li]Minimum tension at J-End[/li]

[li]Tension at I-End[/li]

[li]Tension at J-End[/li]

[li]Horizontal tension component[/li]

[li]Maximum vertical sag[/li]

[li]Low-point vertical sag[/li]

[li]Undeformed length[/li]

I've been trying a few of them out and the only one that seems to give any type of valid result is the "Maximum vertical sag" option, where I just specify it to be very very low to simulate a vertical cable. However, this doesn't seem correct and I'd appreciate any insight. Should I just switch to frame elements w/ moment releases at each end? Thanks.

 

[TLHS]

Do you need to use an actual cable element? If it's actually vertical, or close to vertical where there is zero or negligible load from self weight normal to the axis of the rope then the sag effects are not significant.

 

[bigrod223399]

Do you need to use an actual cable element? If it's actually vertical, or close to vertical where there is zero or negligible load from self weight normal to the axis of the rope then the sag effects are not significant.

The only reason I went down the cable element path is because when I used frame elements, the deformed shape did not look correct (the cables began sagging but the hanging load did not displace along with them like I'd expect), but when I used cable elements it looked much more realistic and the load moved with the cables. It seemed when using frame elements, that the hanging loads were frozen in space when they should have deformed due to gravity.

 

[dhengr]

Bigrod223399:
Use a 1 sq.inch area round stl. bar (rad. = .564”) in place of the cables, with pinned ends (ball joints), no end moments, in any direction. Thus, bar forces show bar stresses by inspection, and provide elongations pretty easily. You said they were vertical or nearly vert., so sag or self weight bending and deflection should be very small. Then, for cable analysis and design just use the above forces, and adjust the cable extensions/elongations a little bit. Remember, wire rope (cable) has two elongation components, a fairly std. elastic stretch (δ = PL/AE) and a mechanical stretch due to the way it is manufactured, and tightens or loosens under tension load. Then, the translation/movement of the panels consists of two items: a rigid body translation due to the cable length changes in space; and a superimposed deflection due normal plate/shell bending and deflection.