Hello forum,
I have built a large mat foundation with dead and operating loads in the x, y and z directions. I have entered the y-direction loads negatively to reflect a downward force. The mat foundation is supported with piles. I used the pile position table under the pile layout leaf to place my piles. When I analyze the model, my pile reactions do not equal the downward force which is being applied to them. Does anyone have any ideas on what I might be doing wrong? I can get into more detail if anyone might have any ideas on this boondoggle. Thanks!!
JP
It is not possible to comment on your query without going through the file. Will you please let me know whether the pile reaction obtained is higher or lower than the applied load?
Have you modelled this in STAAD.Pro or STAAD.Foundation? It appears from your description that you are using STAAD.Foundation. It is highly possible that the springs resembling the soil supports are taking some of the loads. However, it would not be possible to comment without looking at the actual file. You may upload your file here. Better still, if you log in a service ticket with the technical support group.
Sudip Narayan Choudhury
Thank you for your responses. The model was done in STAAD Foundations. The applied loads are larger than the pile reactions. I analyzed the model with and without the soil subgrade modulus and got unfavorable results. An example of this is a point load of 29.25 Kips downward direction allowable strength primary dead load which is supported by two piles. The two piles get a reaction of 2.4 and 1.2 respectively. I have run many different variations and cannot find an answer.
What I am feeling that most of the load is passing on to earth below the raft in lieu of that to the pile. Only pile cap would be able to transfer the total load to the pile not the raft. Sudip is requested to throw some more light in the matter.
I took out the spring from the soil so that should not account into the load distribution (I think). I created a mat foundation with user defined piles, I was not able to create a pile cap with a mat foundation as am dealing with existing piles as well as new piles. The spacing of them is not uniform. I am wondering if my problem has something to do with mat/pile/load y-elevations.