Hi all Iam trying to analyse a combined footing using plate element in staad. I have modelled pedestals and applied load. But the bending moment profile is not matching with the theoritical calculations i.e., at support from the cantilever projection the cantilever moment is wl2/2 theoretically and it should be zero at the pedestal area but the plate moments are getting different and in midspan also the plate moments and shear stresses are entirely different. Please clarify
can some one respond for the query
Please attach the related model and illustrate with a screenshot what results are you getting and what results are you expecting.
FOOTINGS.std
Above are the attached images I'm expecting this type of bending behavior and shear but im not getting the behaviour in staad plate element. Please check
Few things to note here. The deflected shapes BMD, SFDs you have from theoretical calculations make an assumption that the foundation is rigid. In a FE analysis on the other hand, you are analyzing the mat as a flexible element. The soil is represented by springs and stiffness of the springs are not uniform at all points. So the soil reaction that your mat is subjected to is also not uniform. You may need to look at the value of the subgrade modulus. You have used 5000 kN/m2/m which seems low. Unless this is based on values that you got from your geotech, I would suggest trying higher values ( may be 30,000 kN/m2/m)
Ok but the bending moment profile has to change subjected to the base pressure I'm getting at that points. But that change in shear force and bending moment profile is not getting in the plate element modelling. At column face or pedestal face the moment has to be zero and it has to change the sign that is not reflecting