Soil Bearing pressure cals for footing design 1

[ak.t]

Hi all,
Anybody done Footing design using PROKON? I could not understand the calculation made by PROKON for ULS & SLS bearing pressure. It does not match with my manual cals. I just want to make sure whether my input in PROKON is right or not?

Thank you,

Prokon Input & output. Also here why the SLS pressure is greater than ULS pressure?

Support Reaction & Moments for load combination from Staad
[img [URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1581512490/tips/stadre_xgf1v6.png[/URL]

 

[JLNJ]

Post your hand calcs so we can see where the disagreements are. You should easily be able to get the same results by hand, but you need to know what PROKON is doing in the black box.

A few things to consider:
- Footings and piers with nearly 100% offset do not act like "normal" footings. To make this work you will likely need to transmit moment from the pier to the footing in your long direction. (For typical isolated footings no pier-to-footing moment transfer is necessary.) I don't know if or how PROKON handles this. You should figure this out before relying on PROKON.
- If you don't or can't tolerate moment in the pier, then your effective footing length is just 3(pier size)/2, and soil pressures will be quite large. This may be actually how your footing acts, no matter what PROKON tells you.
- This type of arrangement is very sensitive to dead and live load proportions. Service loading may appear to give more favorable results. An engineer with good judgment needs to decide if this is appropriate.
- You need the soil DL to draw the resultant away from the pier toward the middle of the footing. This can be a tenuous assumption.
- Settlement calcs (and therefore bearing capacity values) are not as straightforward for a footing constantly loaded eccentrically as for a concentrically loaded footing.

 

[ak.t]

KIndly find this manual cals. Thank u.