Tension Only Members During Seafastening

[allisongibson]

Hi,

I am running a combined tow analysis with sea-fastening slings. I have static model which I have slings modeled in as tension only but with no section properties so they will not receive any load during the static case. I then have a dynamic model which I also model in tension only slings but this time with the appropriate section properties for a 2" sling. After I run the analysis I am getting compression in those tension only members.

Is this right? Or do I need to change something so that my combined output will show only tension slings.

 

[dhengr]

Allisongibson:
Towing it in the opposite direction would put the slings in tension, right? Come on, get on the stick and try being an engineer, or at least think like one. We can’t see it from here and have no idea what you are looking at or what analysis approach you are taking (most likely some software which isn’t being used properly). Can you even start to do this problem longhand so you have some idea of ballpark answers? You have to describe your problem so another engineer can start to understand what you are doing. You would be surprised at how a good, complete problem description, a little thought on your part, to provide enough dimensions, proper sketch proportions, member sizes and strengths, stiffnesses, etc., will bring help from experienced engineers, who have likely seen similar problems before. Reread your OP and imagine that you weren’t looking at your own drawings/problem, and ask yourself if you could picture what’s going on from your OP, what details are missing, what software is being used, or offer any meaningful advice.

 

[allisongibson]

dhengr:

I know that the slings should be in tension but for exsample when two are in tension the other two should be 0 not compression, like my SACS model was producing. Sorry I didn't suppoy enough information this is my first post and I am an EIT. Thanks for your advice. I figured it out. I had run gap element in my static case and dynamic case, but when I did the tow combined case I did not select the gap option.

 

[rb1957]

"no section properties" ? I'm surprised a model will run without all the properties ... perhaps you mean effectively no property (ie very small area) ? one thing, maybe trick the material property so that its effective in tension but ineffective in compression (very low, but not zero, Ec). it's possible that gaps are not allowed for dynamic analysis.

another day in paradise, or is paradise one day closer ?