Inaccurate Self Weight of Concrete on Columns

Hello,

I have designed a breasting dolphin for vessels completely in Staad.pro with a concrete cap (3.5' thick) and steel pipe piles. I created the concrete slab using plate meshing and have assigned self weight to all members, but it doesn't seem like the Fy reaction forces from the self weight at the end of the pipe piles are correct. I'm getting reaction forces as low as 1 kip, but I figured the reactions should be more considering it should include the self weight from the concrete and from the pipe itself. I believe all properties have been assigned correctly. Is there a reason for this, perhaps based on geometry? Please see my attached file.

New Design.std

  • I did not get any 1 Kip reaction at any of the supports. Some supports got much more load than some others which is understandable as your structure is not supported symmetrically. Here are the support reactions I am getting for load case 1

    Here are a few other points that I noted. You pile cap seem to be 6.5 ft thick as opposed to the 3.5 ft that you mentioned. Just wanted to make sure you are aware. Also for the dummy member please do not use zero for the ZD value (member 300). Use something small like say 0.1 ft. You already have the density set to 0 so you are not going to get any weight due to the member anyway.

    You may want to split the member 300 into segments at each node of the plate mesh so that connectivity is established at every node. Now the beam is just connected to the end nodes of the cap. In your model the piles are connected at single points to the pile cap. In case you develop stress concentrations at these nodes you may want to distribute the load by adding a few dummy elements radially coming out of these nodes and connecting those to the adjacent nodes of the plate mesh. 

    I hope this helps.